EP1725071A2

EP1725071A2 - Condenser microphone with air ventilation system

Info

Publication number: EP1725071A2
Application number: EP20050109505
Authority: EP
Inventors: Seung Taek Lee
Original assignee: Individual
Current assignee: Individual
Priority date: 2005-05-19
Filing date: 2005-10-13
Publication date: 2006-11-22
Also published as: KR20060119278A; CN1867206A; JP2006325177A

Abstract

The present invention relates to a condenser microphone including an internal air ventilation system. In accordance with the condenser microphone including an internal air ventilation system in accordance with an embodiment of the present invention wherein a facile adjustment of an acoustic characteristic of the condenser microphone is possible by adjusting a shape, dimension of the air ventilation system formed on each component.

Description

BACKGROUND OF THE INVENTION

FIELD OF THE INVENTION

The present invention relates to a condenser microphone including an internal air ventilation system.

DESCRIPTION OF PRIOR ART

As a technology develops, a size of electronic devices such as a cellular phone, telephone and a camcorder is reduced. In addition, a size of a condenser microphone which is an acoustic input component used for the electronic devices is also reduced. As shown in Fig. 1, a back type condenser microphone commonly used generally includes a casing 10 for defining an external shape and for providing a electrical path between a PCB 70 and a diaphragm 22, a vibrating plate 20 comprising the diaphragm 22 vibrating according to an acoustic pressure and a polar ring 24 for fixing the diaphragm 22 and for providing an electrical path between the diaphragm 22 and the casing 10, a back electret 50 for accumulating a charge and facing the diaphragm 22 to form a capacitor, a metal base ring 60 for providing an electrical path between the back electret 50 and the PCB 70, and an insulating base ring 40 for providing an electrical insulation between the metal base ring 60 and the casing 10. In case of a front type condenser microphone, positions of the vibrating plate 20 and the back electret 50 are interchanged.
However, in order to improve a sensitivity of the condenser microphone 100, an environment where the diaphragm 22 responses to the acoustic pressure sensitively must be provided. When a pressure of an outside air from which a sound flows in differs from a pressure of a chamber which is an internal space of the diaphragm 22, the diaphragm 22 does not response to the acoustic pressure sensitively. Therefore, in order to improve a sensitivity of the condenser microphone 100, a ventilation path connecting the air inside the chamber and the outside air should be provided to maintain the pressures of the outside air and the chamber substantially the same.
However, in accordance with the conventional condenser microphone, the ventilation path is formed by a method wherein exhausting the air in the chamber to outside through a gap between each component.
However, in accordance with the method, a case that the spacer ring 30 and the insulation base ring 40 are compressed together excessively, or a case that during a manufacturing process of the insulating base ring 40 and the metal base ring 60, an inner diameter of the insulating base ring 40 and an outer diameter of the metal base ring 60 may be almost the same although they are within a tolerable error range so that the both base rings 40 and 60 are adhered during assembly may occur. In this case, the ventilation path is isolated and the ventilation path cannot be secured inside the condenser microphone 100, resulting in a defect by degradation of a sensitivity of the condenser microphone. In order to prevent such defects, a degree of process precision of each component must be improved, resulting in a problem of an increase in manufacturing cost of components.
In addition, in case of the conventional condenser microphone 100, since the ventilation path formed between the air inside the chamber and the outside air is arbitrarily formed according to an assembly result, not by a precise design, an adjustment of a characteristic of the condenser microphone by a shrinkage or enlargement of the ventilation path is not possible.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a condenser microphone including an internal air ventilation system in accordance with the present invention further comprising the internal air ventilation system on the PCB, the insulation base ring, the metal base ring, the back electret, the spacer ring, the metal casing, the vibrating plate for smooth ventilation of air from the chamber of the condenser microphone to outside, thereby preventing a sensitivity defect induced by a closure of air ventilation path due to an excessive compression of components or faulty dimension of the components to achieve a standardization of a sensitivity characteristic of the condenser microphone.
It is an object of the present invention to provide a condenser microphone including an internal air ventilation system in accordance with an embodiment of the present invention wherein a facile adjustment of an acoustic characteristic of the condenser microphone is possible by adjusting a shape, dimension of the air ventilation system formed on each component.
It is an object of the present invention to provide a condenser microphone including an internal air ventilation system in accordance with an embodiments of the present invention wherein the air ventilation path inside the insulation base ring is secured and a pressure of the air inside the chamber is maintained same as an outside air by designing the outside diameters of the metal base ring and the back electret (the vibrating plate in case of the front type) being in contact with the inner sidewall of the insulation base ring to be smaller than the inside diameter of the insulation base ring, thereby improving the sensitivity characteristic.
It is an object of the present invention to provide a condenser microphone including an internal air ventilation system in accordance with an embodiments of the present invention wherein the air ventilation path inside the insulation base ring is secured and a pressure of the air inside the chamber is maintained same as an outside air by further comprising the groove such as the air ventilation slit on a portion of the inner sidewall of the insulation base ring even when the metal base ring and the back electret (the vibrating plate in case of the front type) which are in contact with the inner sidewall of the insulation base ring are adhered to the insulation base ring due to a manufacturing margin or a assembly margin, thereby improving the sensitivity characteristic.
It is an object of the present invention to provide a condenser microphone including an internal air ventilation system in accordance with an embodiments of the present invention wherein the air ventilation path inside the insulation base ring is secured and a pressure of the air inside the chamber is maintained same as an outside air by further comprising the groove such as the air ventilation slit on a portion of the outer sidewall of the metal base ring and the back electret (the vibrating plate in case of the front type) which are in contact with the inner sidewall of the insulation base ring even when the metal base ring and the back electret (the vibrating plate in case of the front type) which are in contact with the inner sidewall of the insulation base ring are adhered to the insulation base ring due to a manufacturing margin or a assembly margin, thereby improving the sensitivity characteristic.
It is an object of the present invention to provide a condenser microphone including an internal air ventilation system in accordance with an embodiments of the present invention wherein effectively a pressure of the air inside the chamber is maintained same as an outside air by further comprising additional internal air ventilation system between the metal casing and the insulation base ring to divide the ventilation path of the condenser microphone into inside and outside path, thereby improving the sensitivity characteristic.
It is an object of the present invention to provide a condenser microphone including an internal air ventilation system in accordance with an embodiments of the present invention wherein the air ventilation path inside the insulation base ring is secured and a pressure of the air inside the chamber is maintained same as an outside air by designing the outside diameters of the insulation base ring or insulation base ring and the vibrating plate (the back electret vibrating plate in case of the front type) being in contact with the inner sidewall of the metal casing to be smaller than the inside diameter of the metal casing, thereby improving the sensitivity characteristic.
It is an object of the present invention to provide a condenser microphone including an internal air ventilation system in accordance with an embodiments of the present invention wherein the air ventilation path inside the insulation base ring is secured and a pressure of the air inside the chamber is maintained same as an outside air by further comprising the groove such as the air ventilation slit on a portion of the inner sidewall of the metal casing even when the insulation base ring and the vibrating plate (the back electret in case of the front type) which are in contact with the inner sidewall of the metal casing are adhered to the metal casing due to a manufacturing margin or a assembly margin, thereby improving the sensitivity characteristic.
It is an object of the present invention to provide a condenser microphone including an internal air ventilation system in accordance with an embodiments of the present invention wherein the air ventilation path inside the insulation base ring is secured and a pressure of the air inside the chamber is maintained same as an outside air by further comprising the groove such as the air ventilation slit on a portion of the outer sidewall of the insulation base ring or the insulation base ring and the vibrating plate (the back electret in case of the front type) which are in contact with the inner sidewall of the metal casing even when the insulation base ring and the vibrating plate (the back electret in case of the front type) which are in contact with the inner sidewall of the metal casing are adhered to the metal casing due to a manufacturing margin or a assembly margin, thereby improving the sensitivity characteristic.
In order to achieve the above-described objects of the present invention, there is provided a condenser microphone including an internal air ventilation system, the condenser microphone comprising: a metal casing for enclosing an internal component of the condenser microphone, the metal casing having a first through-hole at a bottom portion thereof; a vibrating plate enclosed in the metal casing, the vibrating plate including a diaphragm vibrating according to an acoustic pressure and a polar ring attached below the diaphragm for maintaining a tension of the diaphragm and for providing a electrical connection between the metal casing and the diaphragm; a spacer ring disposed above the vibrating plate for electrically insulating an upper portion of the vibrating plate; an insulation base ring disposed above the spacer ring and inside the metal casing for electrically insulating an inner sidewall of the metal casing; an back electret disposed above the spacer ring and inside the insulation base ring to face the vibrating plate, the back electret being spaced apart from the vibrating plate by a predetermined distance, and including a second through-hole; a metal base ring disposed above the back electret and inside the insulation base ring for providing an electrical connection to the back electret; and a PCB disposed above the metal base ring and inside the metal casing to be electrically connected to the metal base ring and the metal casing through a bottom surface and an upper surface of the PCB, respectively, the PCB including a FET for converting the acoustic pressure being input through the vibrating plate to an electrical output and a terminal unit for providing the electrical output generated by the FET to a external circuit, wherein the PCB further comprises a first ventilation pattern disposed on a portion of a contacting surface with the metal base ring for exhausting an air inside an inner space defined by the back electret, the metal base ring and the PCB, wherein an outside diameter of the metal base ring is smaller than an inside diameter of the insulation base ring so that an air flown in through the first ventilation pattern is exhausted, wherein an outside diameter of the back electret is smaller than the inside diameter of the insulation base ring so that an air flown in through a gap between metal base ring and the insulation base ring is exhausted, wherein the insulation base ring is partially in contact with the spacer ring so that an air flown in through a gap between the back electret and the insulation base ring is exhausted, wherein an outside diameter of the vibrating plate is smaller than an inside diameter of the metal casing so that an air flown in through a gap between the spacer ring and the insulation base ring is exhausted, and wherein the metal casing further comprises a second ventilation pattern disposed on a portion of a contacting surface with the vibrating plate for exhausting an air so that an air flown in through a gap between the vibrating plate and the metal casing is exhausted.
In order to achieve the above-described objects of the present invention, there is provided a condenser microphone including an internal air ventilation system, the condenser microphone comprising: a metal casing for enclosing an internal component of the condenser microphone, the metal casing having a first through-hole at a bottom portion thereof; a vibrating plate enclosed in the metal casing, the vibrating plate including a diaphragm vibrating according to an acoustic pressure and a polar ring attached below the diaphragm for maintaining a tension of the diaphragm and for providing a electrical connection between the metal casing and the diaphragm; a spacer ring disposed above the vibrating plate for electrically insulating an upper portion of the vibrating plate; an insulation base ring disposed above the spacer ring and inside the metal casing for electrically insulating an inner sidewall of the metal casing; an back electret disposed above the spacer ring and inside the insulation base ring to face the vibrating plate, the back electret being spaced apart from the vibrating plate by a predetermined distance, and including a second through-hole; a metal base ring disposed above the back electret and inside the insulation base ring for providing an electrical connection to the back electret; and a PCB disposed above the metal base ring and inside the metal casing to be electrically connected to the metal base ring and the metal casing through a bottom surface and an upper surface of the PCB, respectively, the PCB including a FET for converting the acoustic pressure being input through the vibrating plate to an electrical output and a terminal unit for providing the electrical output generated by the FET to a external circuit, wherein the PCB further comprises a first ventilation pattern disposed on a portion of a contacting surface with the metal base ring for exhausting an air inside an inner space defined by the back electret, the metal base ring and the PCB, wherein a portion of an inside diameter of the insulation base ring is larger than an average inside diameter of the insulation base ring so that an air flown in through the first ventilation pattern is exhausted, wherein the insulation base ring is partially in contact with the spacer ring so that an air flown in through a gap between the back electret and the insulation base ring is exhausted, wherein an outside diameter of the vibrating plate is smaller than an inside diameter of the metal casing so that an air flown in through a gap between the spacer ring and the insulation base ring is exhausted, and wherein the metal casing further comprises a second ventilation pattern disposed on a portion of a contacting surface with the vibrating plate for exhausting an air so that an air flown in through a gap between the vibrating plate and the metal casing is exhausted.
In order to achieve the above-described objects of the present invention, there is provided a condenser microphone including an internal air ventilation system, the condenser microphone comprising: a metal casing for enclosing an internal component of the condenser microphone, the metal casing having a first through-hole at a bottom portion thereof; a vibrating plate enclosed in the metal casing, the vibrating plate including a diaphragm vibrating according to an acoustic pressure and a polar ring attached below the diaphragm for maintaining a tension of the diaphragm and for providing a electrical connection between the metal casing and the diaphragm; a spacer ring disposed above the vibrating plate for electrically insulating an upper portion of the vibrating plate; an insulation base ring disposed above the spacer ring and inside the metal casing for electrically insulating an inner sidewall of the metal casing; an back electret disposed above the spacer ring and inside the insulation base ring to face the vibrating plate, the back electret being spaced apart from the vibrating plate by a predetermined distance, and including a second through-hole; a metal base ring disposed above the back electret and inside the insulation base ring for providing an electrical connection to the back electret; and a PCB disposed above the metal base ring and inside the metal casing to be electrically connected to the metal base ring and the metal casing through a bottom surface and an upper surface of the PCB, respectively, the PCB including a FET for converting the acoustic pressure being input through the vibrating plate to an electrical output and a terminal unit for providing the electrical output generated by the FET to a external circuit, wherein the PCB further comprises a first ventilation pattern disposed on a portion of a contacting surface with the metal base ring for exhausting an air inside an inner space defined by the back electret, the metal base ring and the PCB, wherein a portion of an outside diameter of the metal base ring and a portion of an outside diameter of the back electret are smaller than an average outside diameter of the metal base ring and an average outside diameter of the back electret, respectively, so that an air flown in through the first ventilation pattern is exhausted, wherein the insulation base ring is partially in contact with the spacer ring so that an air flown in through a gap between the back electret and the insulation base ring is exhausted, wherein an outside diameter of the vibrating plate is smaller than an inside diameter of the metal casing so that an air flown in through a gap between the spacer ring and the insulation base ring is exhausted, and wherein the metal casing further comprises a second ventilation pattern disposed on a portion of a contacting surface with the vibrating plate for exhausting an air so that an air flown in through a gap between the vibrating plate and the metal casing is exhausted.
In order to achieve the above-described objects of the present invention, there is provided a condenser microphone including an internal air ventilation system, the condenser microphone comprising: a metal casing for enclosing an internal component of the condenser microphone, the metal casing having a first through-hole at a bottom portion thereof; a back electret having a second through-hole, the back electret being disposed at a bottom surface of the metal casing and being in electrical contact with the metal casing; a spacer ring disposed above the back electret for electrically insulating an upper portion of the back electret; an insulation base ring disposed above the spacer ring for electrically insulating an inner sidewall of the metal casing; a vibrating plate including a diaphragm disposed above the spacer ring and inside the insulation base ring and a polar ring attached to an upper portion of the diaphragm for maintaining a tension of the diaphragm, the diaphragm vibrating according to an acoustic pressure and the vibrating plate being spaced apart from the back electret by the spacer ring by a predetermined distance to face the back electret; a metal base ring disposed above the vibrating plate and inside the insulation base ring for providing an electrical connection to the vibrating plate; and a PCB disposed above the metal base ring and inside the metal casing to be electrically connected to the metal base ring and the metal casing through a bottom surface and an upper surface of the PCB, respectively, the PCB including a FET for converting the acoustic pressure being input through the vibrating plate to an electrical output and a terminal unit for providing the electrical output generated by the FET to a external circuit, wherein the PCB further comprises a first ventilation pattern disposed on a portion of a contacting surface with the metal base ring for exhausting an air inside an inner space defined by the vibrating plate, the metal base ring and the PCB, wherein an outside diameter of the metal base ring is smaller than an inside diameter of the insulation base ring so that an air flown in through the first ventilation pattern is exhausted, wherein an outside diameter of the vibrating plate is smaller than the inside diameter of the insulation base ring so that an air flown in through a gap between metal base ring and the insulation base ring is exhausted, wherein the insulation base ring is partially in contact with the spacer ring so that an air flown in through a gap between the vibrating plate and the insulation base ring is exhausted, wherein an outside diameter of the back electret is smaller than an inside diameter of the metal casing so that an air flown in through a gap between the spacer ring and the insulation base ring is exhausted, and wherein the metal casing further comprises a second ventilation pattern disposed on a portion of a contacting surface with the back electret for exhausting an air so that an air flown in through a gap between the back electret and the metal casing is exhausted.
In order to achieve the above-described objects of the present invention, there is provided a condenser microphone including an internal air ventilation system, the condenser microphone comprising: a metal casing for enclosing an internal component of the condenser microphone, the metal casing having a first through-hole at a bottom portion thereof; a back electret having a second through-hole, the back electret being disposed at a bottom surface of the metal casing and being in electrical contact with the metal casing; a spacer ring disposed above the back electret for electrically insulating an upper portion of the back electret; an insulation base ring disposed above the spacer ring for electrically insulating an inner sidewall of the metal casing; a vibrating plate including a diaphragm disposed above the spacer ring and inside the insulation base ring and a polar ring attached to an upper portion of the diaphragm for maintaining a tension of the diaphragm, the diaphragm vibrating according to an acoustic pressure and the vibrating plate being spaced apart from the back electret by the spacer ring by a predetermined distance to face the back electret; a metal base ring disposed above the vibrating plate and inside the insulation base ring for providing an electrical connection to the vibrating plate; and a PCB disposed above the metal base ring and inside the metal casing to be electrically connected to the metal base ring and the metal casing through a bottom surface and an upper surface of the PCB, respectively, the PCB including a FET for converting the acoustic pressure being input through the vibrating plate to an electrical output and a terminal unit for providing the electrical output generated by the FET to a external circuit, wherein the PCB further comprises a first ventilation pattern disposed on a portion of a contacting surface with the metal base ring for exhausting an air inside an inner space defined by the vibrating plate, the metal base ring and the PCB, wherein a portion of an inside diameter of the insulation base ring is larger than an average inside diameter of the insulation base ring so that an air flown in through the first ventilation pattern is exhausted, wherein the insulation base ring is partially in contact with the spacer ring so that an air flown in through a gap between the vibrating plate and the insulation base ring is exhausted, wherein an outside diameter of the back electret is smaller than an inside diameter of the metal casing so that an air flown in through a gap between the spacer ring and the insulation base ring is exhausted, and wherein the metal casing further comprises a second ventilation pattern disposed on a portion of a contacting surface with the back electret for exhausting an air so that an air flown in through a gap between the back electret and the metal casing is exhausted.
In order to achieve the above-described objects of the present invention, there is provided a condenser microphone including an internal air ventilation system, the condenser microphone comprising: a metal casing for enclosing an internal component of the condenser microphone, the metal casing having a first through-hole at a bottom portion thereof; a back electret having a second through-hole, the back electret being disposed at a bottom surface of the metal casing and being in electrical contact with the metal casing; a spacer ring disposed above the back electret for electrically insulating an upper portion of the back electret; an insulation base ring disposed above the spacer ring for electrically insulating an inner sidewall of the metal casing; a vibrating plate including a diaphragm disposed above the spacer ring and inside the insulation base ring and a polar ring attached to an upper portion of the diaphragm for maintaining a tension of the diaphragm, the diaphragm vibrating according to an acoustic pressure and the vibrating plate being spaced apart from the back electret by the spacer ring by a predetermined distance to face the back electret; a metal base ring disposed above the vibrating plate and inside the insulation base ring for providing an electrical connection to the vibrating plate; and a PCB disposed above the metal base ring and inside the metal casing to be electrically connected to the metal base ring and the metal casing through a bottom surface and an upper surface of the PCB, respectively, the PCB including a FET for converting the acoustic pressure being input through the vibrating plate to an electrical output and a terminal unit for providing the electrical output generated by the FET to a external circuit, wherein the PCB further comprises a first ventilation pattern disposed on a portion of a contacting surface with the metal base ring for exhausting an air inside an inner space defined by the vibrating plate, the metal base ring and the PCB, wherein a portion of an outside diameter of the metal base ring and a portion of an outside diameter of the back electret are larger than an average outside diameter of the metal base ring and an average outside diameter of the back electret, respectively, so that an air flown in through the first ventilation pattern is exhausted, wherein the insulation base ring is partially in contact with the spacer ring so that an air flown in through a gap between the vibrating plate and the insulation base ring is exhausted, wherein an outside diameter of the back electret is smaller than an inside diameter of the metal casing so that an air flown in through a gap between the spacer ring and the insulation base ring is exhausted, and wherein the metal casing further comprises a second ventilation pattern disposed on a portion of a contacting surface with the back electret for exhausting an air so that an air flown in through a gap between the back electret and the metal casing is exhausted.
In order to achieve the above-described objects of the present invention, there is provided a condenser microphone including an internal air ventilation system, the condenser microphone comprising: a metal casing for enclosing an internal component of the condenser microphone, the metal casing having a first through-hole at a bottom portion thereof; an insulation base ring disposed at a bottom portion of the metal casing for electrically insulating an inner sidewall of the metal casing; a vibrating plate including a diaphragm disposed at the bottom portion of the metal casing and inside the insulation base ring and a polar ring attached below the diaphragm for maintaining a tension of the diaphragm, the diaphragm vibrating according to an acoustic pressure and the polar ring providing an electrical contact between the metal casing and the diaphragm; a spacer ring disposed above the vibrating plate and inside the insulation base ring for electrically insulating an upper portion of the vibrating plate; a back electret having a second through-hole, the back electret being disposed above the spacer ring and inside the insulation base ring to face the vibrating plate, the back electret being spaced apart from the vibrating plate by the spacer ring by a predetermined distance; a metal base ring disposed above the back electret and inside the insulation base ring for providing an electrical connection to the back electret; and a PCB disposed above the metal base ring and inside the metal casing to be electrically connected to the metal casing through an upper surface of the PCB, the PCB including a FET for converting the acoustic pressure being input through the vibrating plate to an electrical output and a terminal unit for providing the electrical output generated by the FET to a external circuit, wherein the PCB further comprises a first ventilation pattern disposed on a portion of a contacting surface with the metal base ring for exhausting an air inside an inner space defined by the back electret, the metal base ring and the PCB, wherein a portion of outside diameters of the metal base ring, the back electret, the spacer ring and the vibrating plate are smaller than an inside diameter of the insulation base ring, and wherein the metal casing further comprises a second ventilation pattern disposed on a portion of a contacting surface with the vibrating plate for exhausting an air so that an air flown in through a gap between the vibrating plate and the metal casing is exhausted.
In order to achieve the above-described objects of the present invention, there is provided a condenser microphone including an internal air ventilation system, the condenser microphone comprising: a metal casing for enclosing an internal component of the condenser microphone, the metal casing having a first through-hole at a bottom portion thereof; an insulation base ring disposed at a bottom portion of the metal casing for electrically insulating an inner sidewall of the metal casing; a vibrating plate including a diaphragm disposed at the bottom portion of the metal casing and inside the insulation base ring and a polar ring attached below the diaphragm for maintaining a tension of the diaphragm, the diaphragm vibrating according to an acoustic pressure and the polar ring providing an electrical contact between the metal casing and the diaphragm; a spacer ring disposed above the vibrating plate and inside the insulation base ring for electrically insulating an upper portion of the vibrating plate; a back electret having a second through-hole, the back electret being disposed above the spacer ring and inside the insulation base ring to face the vibrating plate, the back electret being spaced apart from the vibrating plate by the spacer ring by a predetermined distance; a metal base ring disposed above the back electret and inside the insulation base ring for providing an electrical connection to the back electret; and a PCB disposed above the metal base ring and inside the metal casing to be electrically connected to the metal casing through an upper surface of the PCB, the PCB including a FET for converting the acoustic pressure being input through the vibrating plate to an electrical output and a terminal unit for providing the electrical output generated by the FET to a external circuit, wherein the PCB further comprises a first ventilation pattern disposed on a portion of a contacting surface with the metal base ring for exhausting an air inside an inner space defined by the back electret, the metal base ring and the PCB, wherein a portion of an inside diameter of the insulation base ring is larger than an average inside diameter of the insulation base ring so that an air flown in through the first ventilation pattern is exhausted, and wherein the metal casing further comprises a second ventilation pattern disposed on a portion of a contacting surface with the vibrating plate for exhausting an air so that an air flown in through a gap between the vibrating plate and the insulation base ring is exhausted.
In order to achieve the above-described objects of the present invention, there is provided a condenser microphone including an internal air ventilation system, the condenser microphone comprising: a metal casing for enclosing an internal component of the condenser microphone, the metal casing having a first through-hole at a bottom portion thereof; an insulation base ring disposed at a bottom portion of the metal casing for electrically insulating an inner sidewall of the metal casing; a vibrating plate including a diaphragm disposed at the bottom portion of the metal casing and inside the insulation base ring and a polar ring attached below the diaphragm for maintaining a tension of the diaphragm, the diaphragm vibrating according to an acoustic pressure and the polar ring providing an electrical contact between the metal casing and the diaphragm; a spacer ring disposed above the vibrating plate and inside the insulation base ring for electrically insulating an upper portion of the vibrating plate; a back electret having a second through-hole, the back electret being disposed above the spacer ring and inside the insulation base ring to face the vibrating plate, the back electret being spaced apart from the vibrating plate by the spacer ring by a predetermined distance; a metal base ring disposed above the back electret and inside the insulation base ring for providing an electrical connection to the back electret; and a PCB disposed above the metal base ring and inside the metal casing to be electrically connected to the metal casing through an upper surface of the PCB, the PCB including a FET for converting the acoustic pressure being input through the vibrating plate to an electrical output and a terminal unit for providing the electrical output generated by the FET to a external circuit, wherein the PCB further comprises a first ventilation pattern disposed on a portion of a contacting surface with the metal base ring for exhausting an air inside an inner space defined by the back electret, the metal base ring and the PCB, wherein portions of outside diameters of the metal base ring, the back electret, the spacer ring, and the vibrating plate are smaller than average outside diameters of the metal base ring, the back electret, the spacer ring, and the vibrating plate, and wherein the metal casing further comprises a second ventilation pattern disposed on a portion of a contacting surface with the vibrating plate for exhausting an air so that an air flown in through a gap between the insulation base ring and the vibrating plate is exhausted.
In order to achieve the above-described objects of the present invention, there is provided a condenser microphone including an internal air ventilation system, the condenser microphone comprising: a metal casing for enclosing an internal component of the condenser microphone, the metal casing having a first through-hole at a bottom portion thereof; an insulation base ring disposed at a bottom portion of the metal casing for electrically insulating an inner sidewall of the metal casing; a back electret having a second through-hole, the back electret being disposed at a bottom surface of the metal casing and inside the insulation base ring and being in electrical contact with the metal casing; a spacer ring disposed above the vibrating plate and inside the insulation base ring for electrically insulating an upper portion of the vibrating plate; a vibrating plate including a diaphragm disposed above the spacer ring and inside the insulation base ring and a polar ring attached above the diaphragm for maintaining a tension of the diaphragm, the diaphragm vibrating according to an acoustic pressure and the vibrating plate being spaced apart from the back electret by the spacer ring by a predetermined distance; a metal base ring disposed above the vibrating plate and inside the insulation base ring for providing an electrical connection to the back electret; and a PCB disposed above the metal base ring and inside the metal casing to be electrically connected to the metal casing through an upper surface of the PCB, the PCB including a FET for converting the acoustic pressure being input through the vibrating plate to an electrical output and a terminal unit for providing the electrical output generated by the FET to a external circuit, wherein the PCB further comprises a first ventilation pattern disposed on a portion of a contacting surface with the metal base ring for exhausting an air inside an inner space defined by the vibrating plate, the metal base ring and the PCB, wherein a portion of outside diameters of the metal base ring, the vibrating plate, the spacer ring and the back electret are smaller than an inside diameter of the insulation base ring, and wherein the metal casing further comprises a second ventilation pattern disposed on a portion of a contacting surface with the back electret for exhausting an air so that an air flown in through a gap between the back electret and the metal casing is exhausted.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a cross-sectional view illustrating a conventional condenser microphone.
Fig. 2 is a cross-sectional view illustrating a typical back-type condenser microphone including an internal air ventilation system in accordance with an embodiment of the present invention.
Fig. 3 is a configuration diagram illustrating a PCB including a first ventilation pattern in accordance with an embodiment of the present invention.
Fig. 4 is a diagram illustrating cross-sections of an insulation base ring, a metal base ring and a back electret in accordance with an embodiment of the present invention.
Fig. 5 is a perspective view illustrating a metal casing including a second ventilation pattern in accordance with an embodiment of the present invention.
Fig. 6 is a perspective view illustrating an insulation base ring including a groove in accordance with an embodiment of the present invention.
Fig. 7 is a perspective view illustrating a metal base ring and a back electret including a groove in accordance with an embodiment of the present invention.
Fig. 8 is a cross-sectional view illustrating a typical front-type condenser microphone including an internal air ventilation system in accordance with an embodiment of the present invention.
Fig. 9 is a diagram illustrating perspective views of a metal base ring and a vibrating plate including a groove in accordance with an embodiment of the present invention.
Fig. 10 is a cross-sectional view illustrating a typical back-type condenser microphone including an internal air ventilation system with built-in insulation base ring in accordance with an embodiment of the present invention.
Fig. 11 is a diagram illustrating perspective views of a metal base ring, a back electret, a spacer ring and a vibrating plate including a groove in accordance with an embodiment of the present invention.
Fig. 12 is a cross-sectional view illustrating a typical front-type condenser microphone including an internal air ventilation system with built-in insulation base ring in accordance with an embodiment of the present invention.
Fig. 13 is a diagram illustrating perspective views of a metal base ring, a vibrating plate, a spacer ring and a back electret including a groove in accordance with an embodiment of the present invention.
Fig. 14 is a perspective view illustrating an insulation base ring including a groove in accordance with an embodiment of the present invention.
Fig. 15 is a perspective view illustrating a metal casing including a second ventilation pattern in accordance with an embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will now be described in detail with reference to the accompanied drawings.
Fig. 2 illustrates a condenser microphone 100 including an internal air ventilation system in accordance with an embodiment of the present invention. A ventilation path of the condenser microphone 100 may be classified, based on an insulation base ring 40, into a ventilation path 80 inside the insulation base ring 40 and a ventilation path 82 outside the insulation base ring 40.
In case of a typical back-type condenser microphone, the ventilation path 80 inside the insulation base ring 40 in accordance with the present invention is as follows. An air inside a back chamber (an inside space of the condenser microphone defined by an upper surface of a back electret 50, an inner sidewall of a metal base ring 60, and a lower surface of a PCB 70) is exhausted to outside through a gap between a contacting surface of the PCB 70 and the metal base ring 60 - a gap between a sidewall of the insulation base ring 40 and the metal base ring 60 - a gap between a contacting surface of the insulation base ring 40 and a spacer ring 30 - a gap between a metal casing 10 and a sidewall of a polar ring 24 of a vibrating plate 20 - a gap between a bottom surface of the metal casing 10 and a contacting surface of the polar ring 24 of the vibrating plate 20 - an acoustic input hole 12 of the metal casing 10 (hereinafter referred to as "the first through hole").
In case of a typical back-type condenser microphone, the ventilation path 82 outside the insulation base ring 40 in accordance with the present invention is as follows. The air inside the back chamber is exhausted to outside through the gap between the contacting surface of the PCB 70 and the metal base ring 60 - a gap between the lower surface of the PCB 70 and an upper surface of the insulation base ring 40 - the gap between the sidewall of the metal casing 10 and the polar ring 24 of the vibrating plate 20 - the gap between the bottom surface of the metal casing 10 and the contacting surface of the polar ring 24 of the vibrating plate 20 - the first through hole 12 of the metal casing 10.
A specific internal air ventilation system wherein a shape and dimension of components 10, 20, 30, 40, 50, 60 and 70 of the condenser microphone is adjusted to improve a sensitivity of the condenser microphone through a ventilation of the air in the back chamber by forming the ventilation paths 80 and 82 inside and outside the insulation base ring 40 is described in detail herebelow. The air ventilation system in accordance with the present invention may be applied to a back type condenser microphone with built-in insulation base ring (see Fig. 10) wherein the insulation base ring 40 is in contact with the loser surface of the metal casing 10 and a front type the condenser microphone with built-in insulation base ring (see Fig. 12) as well as a typical back type condenser microphone (see Fig. 2) and a front type condenser microphone (see Fig.8) wherein the back electret 50 is disposed at the bottom surface of the metal casing 10.
Embodiments wherein the internal air ventilation system of the present invention according to types of the condenser microphone will be described herebelow.

[Typical back type condenser microphone]

Fig. 2 illustrates an embodiment wherein the internal air ventilation systems 80 and 82 in accordance with the present invention are applied to the back type condenser microphone 200.
A metal casing 10 of the typical back type condenser microphone 200 encloses internal components 20, 30, 40, 50, 60 and 70 of the condenser microphone 200 and has a first through-hole 12 at a bottom surface. The metal casing is manufactured by coating gold on aluminum or copper having gold. A cross-section along a horizontal axis of the metal casing is circular or rectangular and the metal casing is in cylinder shape with a closed bottom portion so that the components may be enclosed inside. An upper edge of the metal casing is bent inward after enclosing the internal components 20, 30, 40, 50, 60 and 70 to seal the internal components 20, 30, 40, 50, 60 and 70.
A vibrating plate 20 is enclosed at a bottom surface of the metal casing 10, and includes a diaphragm 22 vibrating according to an acoustic pressure and a polar ring 24 attached below the diaphragm 22 for maintaining a tension of the diaphragm and for providing an electrical connection between the metal casing 10 and the diaphragm 22. The diaphragm 22 consists of a PET film having gold or nickel coated thereon, and the polar ring 24 consists of a metal (or a conductive material) having a hollow inside so that the acoustic pressure may be applied to the diaphragm 22.
A spacer ring 30 is disposed above the vibrating plate 20 for electrically insulating an upper portion of the vibrating plate 20. The spacer ring 30 may consist of a PET film having a hollow inside.
An insulation base ring 40 is disposed above the spacer ring 30 and inside the metal casing 10 for electrically insulating an inner sidewall of the metal casing 10. The insulation base ring 40 may consist of a non-conductive resin in a circular shape having a hollow inside. The vibrating plate 20 and a back electret 50 is electrically connected to a PCB 70 through the metal casing 10 and a metal base ring 60 by an insulation function of the insulation base ring 40, respectively.
The back electret 50 is disposed above the spacer ring 30 and inside the insulation base ring 40 to face the vibrating plate 20. The back electret 50 is spaced apart from the vibrating plate 20 by a predetermined distance, and includes a second through-hole 52. The back electret 50 is formed by laminating a dielectric film on a metallic back plate and injecting a charge into the dielectric film. The back electret 50 forms a capacitor with the vibrating plate 20.
The metal base ring 60 is disposed above the back electret 50 and inside the insulation base ring 40 to provide an electrical connection to the back electret 50. The metal base ring 60 consists of a conductive material such as a metal having a hollow inside.
The PCB 70 is disposed above the metal base ring 60 and inside the metal casing 10 to be electrically connected to the metal base ring 60 and the metal casing 10 through a bottom surface and an upper surface thereof, respectively. The PCB 70 includes a FET for converting the acoustic pressure being input through the vibrating plate 20 to an electrical output and a terminal unit for providing the electrical output generated by the FET to an external circuit.
The internal air ventilation system for forming the ventilation path 80 inside the insulation base ring 40 may be embodies by following three embodiments. In accordance with a first embodiment, outside diameters of the metal base ring 60 and the back electret 50 which are the components that are enclosed inside the insulation base ring 40 are designed to be smaller than an inside diameter of the insulation base ring 40 to form the ventilation path 80. In accordance with a second embodiment, a slit such as a groove for an air ventilation is added on the inner sidewall of the insulation base ring 40 along a vertical axis. In accordance with a third embodiment, a slit such as a groove for an air ventilation is added on outer sidewalls of the metal base ring 60 and the back electret 50 enclosed by the insulation base ring 40 along the vertical axis. The internal air ventilation system inside the insulation base ring 40 of the back type condenser microphone 200 through the three methods will now be described herebelow.

[The first embodiment: an air ventilation system inside the insulation base ring by adjusting component dimensions of the typical back type condenser microphone]

The air ventilation system inside the insulation base ring 40 by the adjustment of the component dimensions of the typical back type condenser microphone is configured as follows.
The PCB 70 further comprises a first ventilation pattern 72 disposed on a portion of a contacting surface with the metal base ring 60 for exhausting an air inside an inner space (the back chamber) defined by the back electret 50, the metal base ring 60 and the PCB 70. Fig. 3 illustrates the first ventilation pattern 72 formed on the PCB 70. A portion indicated by dotted lines denotes the contacting surface with the metal base ring 60, and the first ventilation pattern 72 may be, but not limited to, a slit in a shape of a groove formed along the contacting surface of the metal base ring 60 as shown. It is sufficient that of the slit has a shape suitable for exhausting an air inside the contacting surface of the metal base ring 60 through the first ventilation pattern 72 of the PCB 70. The air in the back chamber is exhausted to outside through the first ventilation pattern 72 by passing through the contacting surface with the metal base ring 60.
Next, the outside diameter of the metal base ring 60 is formed to be smaller than an inside diameter of the insulation base ring 40 so that the air flown in through the first ventilation pattern 72 may be exhausted. Since the outside diameter of the metal base ring 60 is smaller than the inside diameter of the metal base ring 60, a space d1 is formed between vertical cross-sections of the metal base ring 60 and the insulation base ring 40 as shown in Fig. 4, and therefore, the air flown in through the first ventilation pattern 72 is exhausted downward through the gap between the insulation base ring 40 and the metal base ring 60.
Next, an outside diameter of the back electret 50 is formed to be smaller than the inside diameter of the insulation base ring 40 so that an air flown in through a gap between metal base ring 60 and the insulation base ring 40 is exhausted similar to the metal base ring 60. Since the outside diameter of the back electret 50 is smaller than the inside diameter of the insulation base ring 40, the space d1 is formed between vertical cross-sections of the back electret 50 and the insulation base ring 40 as shown in Fig. 4, and therefore, the air flown in through the first ventilation pattern 72 is exhausted downward through the gap between the back electret 50 and the metal base ring 60.
Next, the insulation base ring 40 is partially in contact with , i.e. not in complete contact with the spacer ring 30 so that an air flown in through a gap between the back electret 50 and the insulation base ring 40 may be exhausted. The spacer ring 30 consisting of a film material is in complete contact with and fixed by the back electret 50 while the insulation base ring 40 is not in complete contact with the spacer ring 30. Therefore, the air flown in through the gap between the back electret 50 and the insulation base ring 40 is exhausted through a contacting surface of the spacer ring 30 and the insulation base ring 40.
Next, an outside diameter of the vibrating plate 20 is formed to be smaller than an inside diameter of the metal casing 10 so that an air flown in through a gap between the spacer ring 30 and the insulation base ring 40 is exhausted. Through such structure, a gap is formed on vertical cross-sections of the metal casing 10 and the vibrating plate 20 as shown in Fig. 1, and the air is exhausted downward through the gap.
Next, the metal casing 10 further comprises a second ventilation pattern 14 disposed on a portion of a contacting surface with the vibrating plate 20 for exhausting an air so that an air flown in through a gap between the vibrating plate 20 and the metal casing 10 is exhausted. Fig. 5 illustrates the metal casing 10 including the second ventilation pattern 14. That is, the air may be exhausted through the second ventilation pattern 14 extending over the contacting surface with the polar ring 24 of the vibrating plate 20 on a portion of a bottom surface of the metal casing 10 and then through the first through-hole 12. A shape of the second ventilation pattern 14 is not limited to that shown Fig. 5. It is sufficient that of the groove has a shape suitable for exhausting the air through the contacting surface with the polar ring 24.
Above-described first ventilation pattern 72, the gap between the insulation base ring 40 and the metal base ring 60, the gap between the insulation base ring 40 and the back electret 50, the non-adhesion structure of the insulation base ring 40 and the spacer ring 30, the gap between the metal casing 10 and the vibrating plate 20, and the first ventilation pattern 72 of the metal casing 10 forms the air ventilation system inside the insulation base ring 40 in the typical back type condenser microphone 200 so that the air in the back chamber is easily exhausted to the outside, thereby improving acoustic characteristics.
A depth of the first ventilation pattern 72, a difference between the inside diameter of the insulation base ring 40 and the outside diameter of the metal base ring 60, a difference between the inside diameter of the insulation base ring 40 and the outside diameter of the back electret 50, a difference between the inside diameter of the metal casing 10 and the outside diameter of the vibrating plate 20 and a depth of the second ventilation pattern 14, which form the internal air ventilation system, are equal to or larger than 0.03mm, respectively to achieve air ventilation effect.

[The second embodiment: an air ventilation system inside an insulation base ring using a groove of the insulation base ring of a typical back type condenser microphone]

In order to form the internal air ventilation system even in case that the insulation base ring 40, the metal base ring 60 and the back electret 50 are adhered due to a design (it is more difficult to maintain a certain gap between components as the condenser microphone is miniaturized) or a defect during an assembly process of the typical back type condenser microphone 200, a portion of an outside diameter of the insulation base ring 40 may be formed to be smaller than an average outside diameter of the insulation base ring 40 so that an air flown in through the first ventilation pattern 72 may be exhausted as shown in Fig. 6.
For example, as shown in Fig. 6, when a groove 42 is disposed on the sidewall of the insulation base ring 40 along its vertical axis, the air is exhausted through the groove 42 even when the metal base ring 60 and the back electret 50 enclosed in the insulation base ring 40 are adhered to each other, thereby minimizing a defect due to a degradation of the sensitivity characteristic.
In accordance with this embodiment, a configuration of the condenser microphone 100 is the same as that of the first embodiment, the first ventilation pattern 72 formed on the PCB 70, the non-adhesion structure of the insulation base ring 40 and the spacer ring 30, the distance between the metal casing 10 and the vibrating plate 20 and the second ventilation pattern 14 of the metal casing 10 are also the same as those of the first embodiment.
However, contrary to the first embodiment, a portion of the inside diameter of the insulation base ring 40 is larger than the average inside diameter of the insulation base ring 40 so that an air flown in through the first ventilation pattern 72 may be exhausted. That is, when the insulation base ring 40 is formed to include a groove on a portion of the inner sidewall of the insulation base ring 40 along its vertical axis, or to have a cross-section of the inner sidewall thereof in a shape of a polygon, a diameter at the groove or an apex of the polygon is larger than a diameter at other portions of the insulation base ring 40 so that the air ventilation path is secured through this part.
In accordance with the second embodiment, it is preferable that a depth of the first ventilation pattern 72, a difference between a maximum and a minimum inside diameter of the insulation base ring 40, a difference between the inside diameter of the metal casing 10 and the outside diameter of the vibrating plate 20, a depth of the second ventilation pattern 14 and a maximum value of a gap between the metal casing 10 and the insulation base ring 40 are equal to or larger than 0.03mm, respectively.

[The third embodiment: an air ventilation system inside an insulation base ring using grooves of the metal base ring and the back electret of a typical back type condenser microphone]

The third embodiment, similar to the second embodiment, in order to form the internal air ventilation system even in case that the insulation base ring 40, the metal base ring 60 and the back electret 50 are adhered, a portion of an outside diameter of the metal base ring 60 may be formed to be smaller than an average outside diameter of the metal base ring 60 so that an air flown in through the first ventilation pattern 72 may be exhausted, and a portion of an outside diameter of the back electret 50 may also be formed to be smaller than an average outside diameter of the back electret the back electret 50 as shown in Fig. 7.
For example, as shown in Fig. 7, when grooves 62 and 52 are disposed on outer sidewalls of the metal base ring 60 and the back electret 50 along their vertical axis, the air is exhausted through the grooves 62 and 52 even when the metal base ring 60 and the back electret 50 are adhered to the insulation base ring 40, thereby minimizing the defect due to the degradation of the sensitivity characteristic.
In accordance with this embodiment, a configuration of the condenser microphone 100 is the same as that of the first embodiment, and the first ventilation pattern 72 formed on the PCB 70, the non-adhesion structure of the insulation base ring 40 and the spacer ring 30, the distance between the metal casing 10 and the vibrating plate 20 and the second ventilation pattern 14 of the metal casing 10 are also the same as those of the first embodiment.
However, contrary to the first embodiment, portions of the outside diameters of the metal base ring 60 and the back electret 50 are smaller than the average outside diameters of the metal base ring 60 and the back electret 50 so that the air flown in through the first ventilation pattern 72 may be exhausted. That is, when the metal base ring 60 and the back electret 50 are formed to include grooves on portions of the outer sidewalls of the metal base ring 60 and the back electret 50 along its vertical axis, or to have a cross-section of the outer sidewalls thereof in a shape of a polygon, a diameter at the groove or at a center of each sides of the polygon is larger than a diameter at other portions of the metal base ring 60 and the back electret 50 so that the air ventilation path is secured through this part.
In accordance with the third embodiment, it is preferable that the depth of the first ventilation pattern 72, a difference between a maximum and a minimum outside diameter of the metal base ring 60, a difference between a maximum and a minimum outside diameter of the back electret 50, a difference between the inside diameter of the metal casing 10 and the outside diameter of the vibrating plate 20, a depth of the second ventilation pattern 14 and are equal to or larger than 0.03mm, respectively.

[A fourth embodiment: an air ventilation system inside an insulation base ring by adjusting component dimensions of a typical front type condenser microphone]

Fig. 8 illustrates a typical front-type condenser microphone 300. Since a typical front-type condenser microphone structure is identical to the typical back-type condenser microphone 200 except that positions of a vibrating plate 20 and a back electret 50 are interchanged, a description in detail is omitted.
In accordance with the fourth embodiment, a PCB 70 of a air ventilation system 80 further comprises a first ventilation pattern 72, an outside diameter of the metal base ring 60 is smaller than an inside diameter of the insulation base ring 40 so that an air flown in through the first ventilation pattern 72 may be exhausted, and an outside diameter of the vibrating plate 20 is smaller than the inside diameter of the insulation base ring 40 so that an air flown in through a gap between metal base ring 60 and the insulation base ring 40 may be exhausted.
Next, the insulation base ring 40 is partially in contact with the spacer ring 30 so that an air flown in through a gap between the vibrating plate 20 and the insulation base ring 40 may be exhausted. An outside diameter of the back electret 50 is smaller than an inside diameter of the metal casing 10 so that an air flown in through a gap between the spacer ring 30 and the insulation base ring 40 may be exhausted. The metal casing 10 further comprises a second ventilation pattern 14 disposed on a portion of a contacting surface with the back electret 50 for exhausting an air so that an air flown in through a gap between the back electret 50 and the metal casing 10 is exhausted.
Since the air ventilation system 80 inside the insulation base ring 40 of the typical front-type condenser microphone 300 manufactured in accordance with the embodiment is identical to that of the first embodiment, a description in detail is omitted.
In accordance with the fourth embodiment, it is preferable that a depth of the first ventilation pattern 72, a difference between the inside diameter of the insulation base ring 40 and the outside diameter of the metal base ring 60, a difference between the inside diameter of the insulation base ring 40 and the outside diameter of the vibrating plate 20, a difference between the inside diameter of the metal casing 10 and the outside diameter of the back electret 50 and a depth of the second ventilation pattern 14 are equal to or larger than 0.03mm, respectively.

[A fifth embodiment: an air ventilation system inside an insulation base ring using a groove of the insulation base ring of a typical back type condenser microphone]

In accordance with an assembly process of the typical back type condenser microphone 300, in order to form the internal air ventilation system even in case that the insulation base ring 40, the metal base ring 60 and the vibrating plate 20 are adhered to each other, a portion of an outside diameter of the insulation base ring 40 may be formed to be smaller than an average outside diameter of the insulation base ring 40 so that an air flown in through the first ventilation pattern 72 may be exhausted as shown in Fig. 6.
For example, as shown in Fig. 6, when a groove 42 is disposed on the sidewall of the insulation base ring 40 along its vertical axis, the air is exhausted through the groove 42 even when the metal base ring 60 and the vibrating plate 20 enclosed in the insulation base ring 40 are adhered to each other, thereby minimizing a defect due to a degradation of the sensitivity characteristic.
In accordance with this embodiment, a configuration of the condenser microphone 300 is the same as that of the fourth embodiment, and the first ventilation pattern 72 formed on the PCB 70, the non-adhesion structure of the insulation base ring 40 and the spacer ring 30, the distance between the metal casing 10 and the back electret 50 and the second ventilation pattern 14 of the metal casing 10 are also the same as those of the fourth embodiment.
However, contrary to the first embodiment, a portion of the inside diameter of the insulation base ring 40 is larger than the average inside diameter of the insulation base ring 40 so that an air flown in through the first ventilation pattern 72 may be exhausted. When the insulation base ring 40 is formed to include a groove on a portion of the inner sidewall of the insulation base ring 40 along its vertical axis, or to have a cross-section of the inner sidewall thereof in a shape of a polygon, a diameter at the groove or an apex of the polygon is larger than a diameter at other portions of the insulation base ring 40 so that the air ventilation path is secured through this part.
In accordance with the fifth embodiment, it is preferable that a depth of the first ventilation pattern 72, a difference between a maximum and a minimum inside diameter of the insulation base ring 40, a difference between the inside diameter of the metal casing 10 and the outside diameter of the vibrating plate 20, a depth of the second ventilation pattern 14 and a maximum value of a gap between the metal casing 10 and the insulation base ring 40 are equal to or larger than 0.03mm, respectively.

[A sixth embodiment: an air ventilation system inside an insulation base ring using grooves of a metal base ring and a vibrating plate of a typical back type condenser microphone]

The sixth embodiment, similar to the fifth embodiment, in order to form the internal air ventilation system even in case that the insulation base ring 40, the metal base ring 60 and the vibrating plate 20 are adhered, a portion of an outside diameter of the metal base ring 60 may be formed to be smaller than an average outside diameter of the metal base ring 60 so that an air flown in through the first ventilation pattern 72 may be exhausted, and a portion of an outside diameter of the vibrating plate 20 may also be formed to be smaller than an average outside diameter of the vibrating plate 20.
For example, as shown in Fig. 9, when grooves 62 and 26 are disposed on outer sidewalls of the metal base ring 60 and the vibrating plate 20 along their vertical axis, the air is exhausted through the grooves 62 and 26 even when the metal base ring 60 and the vibrating plate 20 are adhered to the insulation base ring 40, thereby minimizing the defect due to the degradation of the sensitivity characteristic.
In accordance with this embodiment, a configuration of the condenser microphone 300 is the same as that of the fourth embodiment, and the first ventilation pattern 72 formed on the PCB 70, the non-adhesion structure of the insulation base ring 40 and the spacer ring 30, the distance between the metal casing 10 and the back electret 50 and the second ventilation pattern 14 of the metal casing 10 are also the same as those of the fourth embodiment.
However, contrary to the fourth embodiment, portions of the outside diameters the metal base ring 60 and the vibrating plate 20 are smaller than the average outside diameters of the metal base ring 60 and the vibrating plate 20 so that the air flown in through the first ventilation pattern 72 may be exhausted. That is, when the metal base ring 60 and the vibrating plate 20 are formed to include grooves on portions of the outer sidewalls of the metal base ring 60 and the vibrating plate 20 along its vertical axis, or to have a cross-section of the outer sidewalls thereof in a shape of a polygon, a diameter at the groove or at a center of each sides of the polygon is larger than a diameter at other portions of the metal base ring 60 and the vibrating plate 20 so that the air ventilation path is secured through this part.
In accordance with the sixth embodiment, it is preferable that the depth of the first ventilation pattern 72, a difference between a maximum and a minimum outside diameter of the metal base ring 60, a difference between a maximum and a minimum outside diameter of the vibrating plate 20, a difference between the inside diameter of the metal casing 10 and the outside diameter of the back electret 50, a depth of the second ventilation pattern 14 and are equal to or larger than 0.03mm, respectively.

[A seventh embodiment: an air ventilation system inside an insulation base ring by adjusting component dimensions of a back type condenser microphone with a built-in insulation base ring]

Fig. 10 illustrates a back type condenser microphone 400 with a built-in insulation base ring. Contrary to the typical back type condenser microphone 200 wherein the insulation base ring 40 is disposed above the spacer ring 30, an insulation base ring 40 of the back type condenser microphone 400 with the built-in insulation base ring is directly disposed on a bottom surface of metal casing 10, and a vibrating plate 20 and a spacer ring 30 are enclosed by the insulation base ring 40, not by the metal casing 10. A configuration other than the above is identical to the typical condenser microphone 200. Therefore, a description in detail is omitted.
In accordance with the seventh embodiment, a configuration of the ventilation system 80 inside the insulation base ring 40 by adjusting the component dimensions is as follows. A PCB 70 further comprises a first ventilation pattern 72 disposed on a portion of a contacting surface with the metal base ring 60 for exhausting an air inside the back chamber as shown in Fig. 3.
Next, the outside diameter of the metal base ring 60 is formed to be smaller than an inside diameter of the insulation base ring 40 so that the air flown in through the first ventilation pattern 72 may be exhausted, and an outside diameter of the back electret 50, similar to the metal base ring 60, is formed to be smaller than the inside diameter of the insulation base ring 40 so that an air flown in through a gap between metal base ring 60 and the insulation base ring 40 is exhausted.
Next, an outside diameter of the spacer ring 30 is formed to be smaller than the inside diameter of the insulation base ring 40 so that an air flown in through a gap between the back electret 50 and the spacer ring 30 may be exhausted, and an outside diameter of the vibrating plate 20 is formed to be smaller than an inside diameter of the insulation base ring 40 so that an air flown in through a gap between the spacer ring 30 and the insulation base ring 40 may be exhausted. The metal casing 10 further comprises a second ventilation pattern 14 disposed on a portion of a contacting surface with the vibrating plate 20 for exhausting an air so that an air flown in through a gap between the vibrating plate 20 and the insulation base ring 40 may be exhausted through a second ventilation pattern 14 as shown in Fig. 5.
In case of the back type condenser microphone 400 with the built-in insulation base ring, since outer sidewalls of the metal base ring 60, the back electret 50, the spacer ring 30 and the vibrating plate 20 are all facing an inner sidewall of the insulation base ring 40, the air ventilation system 80 inside an insulation base ring 40 is formed by designing outside diameters of internal components 60, 50, 30 and 20 to be smaller than the inside diameter of the insulation base ring 40.
The first ventilation pattern 72 of the PCB 70, gaps between the insulation base ring 40 and the metal base ring 60, the back electret 50, the spacer ring 30 and the vibrating plate 20 and the second ventilation pattern 14 of the metal casing 10 form the air ventilation system 80 inside an insulation base ring 40 of the back type condenser microphone 400 with the built-in insulation base ring so that the air in the back chamber may be easily exhausted to improve an acoustic characteristic of the condenser microphone 400.
On the other hand, it is preferable that a depth of the first ventilation pattern 72, a difference between the inside diameter of the insulation base ring 40 and the outside diameters of the metal base ring 60, the back electret 50, the spacer ring 30 and the vibrating plate 20, and a depth of the second ventilation pattern 14, which form the internal air ventilation system 80, are equal to or larger than 0.03mm, respectively.

[A eighth embodiment: an air ventilation system inside an insulation base ring using a groove of the insulation base ring of a back type condenser microphone with a built-in insulation base ring]

In accordance with an assembly of the back type condenser microphone 400 with a built-in insulation base ring 40, in order to form the internal air ventilation system even in case that the insulation base ring 40, the metal base ring 60 which is an internal component, the back electret 50, the spacer ring 30, and the vibrating plate 20 are adhered to each other, a portion of an outside diameter of the insulation base ring 40 may be formed to be smaller than an average outside diameter of the insulation base ring 40 so that an air flown in through the first ventilation pattern 72 may be exhausted as shown in Fig. 6.
For example, as shown in Fig. 6, when a groove 42 is disposed on the sidewall of the insulation base ring 40 along its vertical axis, the air is exhausted through the groove 42 even when the metal base ring 60, the back electret 50, the spacer ring 30, and the vibrating plate 20 enclosed in the insulation base ring 40 are adhered to each other, thereby minimizing a defect due to a degradation of the sensitivity characteristic.
In accordance with this embodiment, a configuration of the condenser microphone 400 is the same as that of the seventh embodiment, the first ventilation pattern 72 formed on the PCB 70 and the second ventilation pattern 14 of the metal casing 10 are also the same as those of the seventh embodiment.
However, contrary to the seventh embodiment, a portion of the inside diameter of the insulation base ring 40 is larger than the average inside diameter of the insulation base ring 40 so that an air flown in through the first ventilation pattern 72 may be exhausted. When the insulation base ring 40 is formed to include a groove on a portion of the inner sidewall of the insulation base ring 40 along its vertical axis, or to have a cross-section of the inner sidewall thereof in a shape of a polygon, a diameter at the groove or an apex of the polygon is larger than a diameter at other portions of the insulation base ring 40 so that the air ventilation path is secured through this part.
In accordance with the eighth embodiment, it is preferable that a depth of the first ventilation pattern 72, a difference between a maximum and a minimum inside diameter of the insulation base ring 40 and a depth of the second ventilation pattern 14 are equal to or larger than 0.03mm, respectively.

[A ninth embodiment: an air ventilation system inside an insulation base ring using grooves of a metal base ring, a back electret, a spacer ring and a vibrating plate of a 1 back type condenser microphone with a built-in insulation base ring]

The ninth embodiment, similar to the eighth embodiment, in order to form the internal air ventilation system even in case that the insulation base ring 40, the metal base ring 60, the back electret 50, the spacer ring 30 and the vibrating plate 20 are adhered to each other, a portion of outside diameters of the metal base ring 60, the back electret 50, the spacer ring 30 and the vibrating plate 20 may be formed to be smaller than average outside diameters of the metal base ring 60, the back electret 50, the spacer ring 30 and the vibrating plate the vibrating plate 20, respectively so that an air flown in through the first ventilation pattern 72 may be exhausted as shown in Fig. 11.
For example, as shown in Fig. 11, when grooves 62, 52, 32 and 26 are disposed on outer sidewalls of the metal base ring 60, the back electret 50, the spacer ring 30 and the vibrating plate 20 along their vertical axis, the air is exhausted through the grooves 62, 52, 32 and 26 even when the metal base ring 60, the back electret 50, the spacer ring 30 and the vibrating plate 20 are adhered to the insulation base ring 40, thereby minimizing the defect due to the degradation of the sensitivity characteristic.
In accordance with this embodiment, a configuration of the condenser microphone 400 is the same as that of the seventh embodiment, and the first ventilation pattern 72 formed on the PCB 70 and the second ventilation pattern 14 of the metal casing 10 are also the same as those of the seventh embodiment.
However, contrary to the seventh embodiment, portions of the outside diameters of the metal base ring 60, the back electret 50, the spacer ring 30 and the vibrating plate 20 are smaller than the average outside diameters of the metal base ring 60, the back electret 50, the spacer ring 30 and the vibrating plate 20 so that the air flown in through the first ventilation pattern 72 may be exhausted. That is, when the metal base ring 60, the back electret 50, the spacer ring 30 and the vibrating plate 20 are formed to include the grooves 62,52,32 and 26 on portions of the outer sidewalls of the metal base ring 60, the back electret 50, the spacer ring 30 and the vibrating plate 20 along its vertical axis, or to have a cross-section of the outer sidewalls thereof in a shape of a polygon, a diameter at the groove or at a center of each sides of the polygon is larger than a diameter at other portions of the metal base ring 60, the back electret 50, the spacer ring 30 and the vibrating plate 20 so that the air ventilation path is secured through this part.
In accordance with the ninth embodiment, it is preferable that the depth of the first ventilation pattern 72, a difference between a maximum and a minimum outside diameter of the metal base ring 60, the back electret 50, the spacer ring 30 and the vibrating plate 20 and a depth of the second ventilation pattern 14 and are equal to or larger than 0.03mm, respectively.

[A tenth embodiment: an air ventilation system inside an insulation base ring by adjusting component dimensions of a front type condenser microphone with a built-in insulation base ring]

Fig. 12 illustrates the front-type condenser microphone 500 with the built-in insulation base ring 40. Since the front-type condenser microphone 500 with the built-in insulation base ring 40 is identical to the back-type condenser microphone 500 with the built-in insulation base ring 40 except that positions of a vibrating plate 20 and a back electret 50 are interchanged, a description in detail is omitted.
In accordance with the tenth embodiment, a PCB 70 of a air ventilation system 80 further comprises a first ventilation pattern 72, an outside diameters of the metal base ring 60, the vibrating plate, the spacer ring 30 and the back electret 50 is smaller than an inside diameter of the insulation base ring 40 so that an air flown in through the first ventilation pattern 72 may be exhausted.
The metal casing 10 further comprises a second ventilation pattern 14 disposed on a portion of a contacting surface with the back electret 50 for exhausting an air so that an air flown in through a gap between the back electret 50 and the metal casing 10 may be exhausted through the first through-hole 12.
Since the air ventilation system 80 inside the insulation base ring 40 of the front-type condenser microphone 500 with the built-in insulation base ring 40 manufactured in accordance with the embodiment is identical to that of the seventh embodiment, a description in detail is omitted.
In accordance with the tenth embodiment, it is preferable that a depth of the first ventilation pattern 72, a difference between the inside diameter of the insulation base ring 40 and the outside diameters of the metal base ring 60, the vibrating plate, the spacer ring 30 and the back electret 50, and a depth of the second ventilation pattern 14 are equal to or larger than 0.03mm, respectively.

[An eleventh embodiment: an air ventilation system inside an insulation base ring using a groove of the insulation base ring of a front type condenser microphone with a built-in insulation base ring]

In accordance with an assembly process of the front type condenser microphone with a built-in insulation base ring 500, in order to form the internal air ventilation system even in case that the insulation base ring 40, the metal base ring 60, the vibrating plate 20, the spacer ring 30, and the back electret 50 are adhered to each other, a portion of an outside diameter of the insulation base ring 40 may be formed to be smaller than an average outside diameter of the insulation base ring 40 so that an air flown in through the first ventilation pattern 72 may be exhausted as shown in Fig. 6.
For example, as shown in Fig. 6, when a groove 42 is disposed on the sidewall of the insulation base ring 40 along its vertical axis, the air is exhausted through the groove 42 even when the metal base ring 60, the vibrating plate 20, the spacer ring 30, and the back electret 50 enclosed in the insulation base ring 40 are adhered to each other, thereby minimizing a defect due to a degradation of the sensitivity characteristic.
In accordance with this embodiment, a configuration of the condenser microphone 500 is the same as that of the tenth embodiment, and the first ventilation pattern 72 formed on the PCB 70 and the second ventilation pattern 14 of the metal casing 10 are also the same as those of the tenth embodiment.
However, contrary to the tenth embodiment, a portion of the inside diameter of the insulation base ring 40 is larger than the average inside diameter of the insulation base ring 40 so that an air flown in through the first ventilation pattern 72 may be exhausted. When the insulation base ring 40 is formed to include a groove on a portion of the inner sidewall of the insulation base ring 40 along its vertical axis, or to have a cross-section of the inner sidewall thereof in a shape of a polygon, a diameter at the groove or an apex of the polygon is larger than a diameter at other portions of the insulation base ring 40 so that the air ventilation path is secured through this part.
In accordance with the eleventh embodiment, it is preferable that a depth of the first ventilation pattern 72, a difference between a maximum and a minimum inside diameter of the insulation base ring 40, a difference between the inside diameter of the metal casing 10 and the outside diameter of the vibrating plate 20, a depth of the second ventilation pattern 14 and a maximum value of a gap between the metal casing 10 and the insulation base ring 40 are equal to or larger than 0.03mm, respectively.

[A twelfth embodiment: an air ventilation system inside an insulation base ring using grooves of a metal base ring, a back electret, a spacer ring and a vibrating plate of a the front-type condenser microphone with the built-in insulation base ring]

The twelfth embodiment, similar to the eleventh embodiment, in order to form the internal air ventilation system even in case that the insulation base ring 40, the metal base ring 60, the vibrating plate 20, the spacer ring 30 and the back electret 50 are adhered to each other, a portion of an outside diameter of the metal base ring 60, the back electret 50, the spacer ring 30 and the vibrating plate 20 may be formed to be smaller than average outside diameters of the metal base ring 60, the back electret 50, the spacer ring 30 and the vibrating plate 20, respectively so that an air flown in through the first ventilation pattern 72 may be exhausted as shown in Fig. 11.
For example, as shown in Fig. 11, when grooves 62, 26, 32 and 52 are disposed on outer sidewalls of the metal base ring 60, the vibrating plate 20, the spacer ring 30 and the back electret 50 along their vertical axis, the air is exhausted through the grooves 62, 26, 32 and 52 even when the metal base ring 60 and the vibrating plate 20 are adhered to the insulation base ring 40, thereby minimizing the defect due to the degradation of the sensitivity characteristic.
In accordance with this embodiment, a configuration of the condenser microphone 500 is the same as that of the eleventh embodiment, and the first ventilation pattern 72 formed on the PCB 70 and the second ventilation pattern 14 of the metal casing 10 are also the same as those of the eleventh embodiment.
However, contrary to the eleventh embodiment, portions of the outside diameters of the metal base ring 60, the vibrating plate 20, the spacer ring 30 and the back electret 50 are smaller than the average outside diameters of the metal base ring 60, the vibrating plate 20, the spacer ring 30 and the back electret 50 so that the air flown in through the first ventilation pattern 72 may be exhausted. That is, when the metal base ring 60, the vibrating plate 20, the spacer ring 30 and the back electret 50 are formed to include grooves on portions of the outer sidewalls of the metal base ring 60, the vibrating plate 20, the spacer ring 30 and the back electret 50 along its vertical axis, or to have a cross-section of the outer sidewalls thereof in a shape of a polygon, a diameter at the groove or at a center of each sides of the polygon is larger than a diameter at other portions of the metal base ring 60, the vibrating plate 20, the spacer ring 30 and the back electret 50 so that the air ventilation path is secured through this part.
In accordance with the twelfth embodiment, it is preferable that the depth of the first ventilation pattern 72, a difference between a maximum and a minimum outside diameter of the metal base ring 60, the vibrating plate 20, the spacer ring 30 and the back electret 50 and a depth of the second ventilation pattern 14 and are equal to or larger than 0.03mm, respectively.

[A thirteenth embodiment: an air ventilation system inside an insulation base ring by adjusting component dimensions in accordance with the first through sixth embodiments]

Outward arrows of Figs. 2 and 8 depict a ventilation path 82 outside an insulation base ring 40 in accordance with the first through sixth embodiments. The air ventilation system 82 outside the insulation base ring 40 in addition to above-described air ventilation system 80 inside the insulation base ring 40 provides an effect of a smooth air flow inside the condenser microphones 200 and 300.
The air ventilation system 82 outside the insulation base ring 40 in accordance with the thirteenth embodiment is as follows. The PCB 70 is not in contact with the insulation base ring 40 as shown in Figs. 2 and 8 so that the air flown in through the first ventilation pattern 72 may be exhausted, and the outside diameter of the insulation base ring 40 is formed to be smaller than the inside diameter of the metal casing 10 so that the air flown in through the gap between the PCB 70 and the insulation base ring 40 may be exhausted to outside through a gap between the vibrating plate 20 (the back electret 50 in case of the front type) and the metal casing 10, the second ventilation pattern 14 and the first through hole 12.
In this case, as shown in Figs. 2 and 8, since the ventilation path 82 is secured on the outer sidewall of the insulation base ring 40, acoustic characteristics of the condenser microphones 200 and 300 is improved.
In accordance with the thirteenth embodiment, a maximum distance between the metal casing 10 and the insulation base ring 40 is equal to or larger than 0.03mm.

[A fourteenth embodiment: an air ventilation system using a groove on an outer sidewall of an insulation base ring in accordance with the first through sixth embodiments]

The fourteenth embodiment is similar to the thirteenth embodiment in that the ventilation path 82 outside the insulation base ring 40 is included. However, contrary to the thirteenth embodiment, a groove 44 is formed on the outer sidewall of the insulation base ring 40 to secure the ventilation path 82 as shown in Fig. 14.
The air ventilation system 82 outside the insulation base ring 40 in accordance with the fourteenth embodiment is as follows. The PCB 70 is not in contact with the insulation base ring 40 as shown in Figs. 2 and 8 so that the air flown in through the first ventilation pattern 72 may be exhausted, and a portion of the outside diameter of the insulation base ring 40 is formed to be smaller than an average outside diameter of the insulation base ring 40 so that the air flown in through the gap between the PCB 70 and the insulation base ring 40 may be exhausted to outside through a gap between the vibrating plate 20 (the back electret 50 in case of the front type) and the metal casing 10, the second ventilation pattern 14 and the first through hole 12.
That is, when the insulation base ring 40 is formed to include a groove on a portion of the outer sidewall of the insulation base ring 40 along its vertical axis as shown in Fig. 14, or to have a cross-section of the outer sidewall thereof in a shape of a polygon, a diameter at the groove or at a center of each sides of the polygon is smaller than a diameter at other portions of the insulation base ring 40 so that the air ventilation path is secured through this part.
In accordance with the fourteenth embodiment, it is preferable that a maximum distance between the metal casing 10 and the insulation base ring 40 is equal to or more than 0.03mm.

[A fifteenth embodiment: an air ventilation system using a groove on an inner sidewall of a metal casing in accordance with the first through sixth embodiments]

The fifteenth embodiment is similar to the thirteenth embodiment in that the ventilation path 82 outside the insulation base ring 40 is included. However, contrary to the thirteenth embodiment, a groove 16 is formed on the inner sidewall of the metal casing 10 to secure the ventilation path 82 as shown in Fig. 15.
The air ventilation system 82 outside the insulation base ring 40 in accordance with the fifteenth embodiment is as follows. The PCB 70 is not in contact with the insulation base ring 40 as shown in Figs. 2 and 8 so that the air flown in through the first ventilation pattern 72 may be exhausted, and a portion of the inside diameter of the metal casing 10 is formed to be smaller than an average inside diameter of the insulation base ring 40 so that the air flown in through the gap between the PCB 70 and the insulation base ring 40 may be exhausted to outside through a gap between the vibrating plate 20 (the back electret 50 in case of the front type) and the metal casing 10, the second ventilation pattern 14 and the first through hole 12.
That is, when the insulation base ring 40 is formed to include a groove 16 on a portion of the inner sidewall of the metal casing 10 along its vertical axis as shown in Fig. 15, or to have a cross-section of the inner sidewall of the insulation base ring 40 in a shape of a polygon, a diameter at the groove 16 or at an apex of the polygon is smaller than a diameter at other portions of the metal casing 10 so that the air ventilation path is secured through this part. It is preferable that the groove 16 is connected to the second ventilation pattern 14 in case of disposing the groove 16. In addition, it is preferable that a maximum distance between the metal casing 10 and the insulation base ring 40 is equal to or more than 0.03mm in accordance with the fifteenth embodiment.

[A sixteenth embodiment: an air ventilation system outside an insulation base ring by adjusting component dimensions in accordance with the seventh through twelfth embodiments]

Outward arrows of Figs. 10 and 12 depict a ventilation path 82 outside an insulation base ring 40 in accordance with the seventh through twelfth embodiments. The air ventilation system 82 outside the insulation base ring 40 in addition to above-described air ventilation system 80 inside the insulation base ring 40 provides an effect of a smooth air flow inside the condenser microphones 400 and 500.
The air ventilation system 82 outside the insulation base ring 40 in accordance with the sixteenth embodiment is as follows. The PCB 70 is not in contact with the insulation base ring 40 as shown in Figs. 10 and 12 so that the air flown in through the first ventilation pattern 72 may be exhausted, and the outside diameter of the insulation base ring 40 is formed to be smaller than the inside diameter of the metal casing 10 so that the air flown in through the gap between the PCB 70 and the insulation base ring 40 may be exhausted to outside through a gap between the vibrating plate 20 (the back electret 50 in case of the front type) and the metal casing 10, the second ventilation pattern 14 and the first through hole 12. The metal casing 10 further comprises a third ventilation pattern extending from the second ventilation pattern 14 on a lower contacting surface with the insulation base ring 40 so that an air flown in through a gap between the metal casing 10 and the insulation base ring 40 may be exhausted outside through the second ventilation pattern 14 and the first through-hole 12.
In case of the condenser microphones 400 and 500 with built-in insulation base ring 40, contrary to typical condenser microphones 200 and 300, the third ventilation pattern is further required contrary to the thirteenth through fifteenth embodiment as well as the vibrating plate 20 (the back electret 50 in case of the front type) at the bottom surface of the metal casing 10 since the insulation base ring 40 is in contact.
In this case, as shown in Figs. 2 and 8, since the ventilation path 82 is secured on the outer sidewall of the insulation base ring 40, acoustic characteristics of the condenser microphones 400 and 500 is improved.
In accordance with the sixteenth embodiment, a maximum distance between the metal casing 10 and the insulation base ring 40 is equal to or larger than 0.03mm.

[A seventeenth embodiment: an air ventilation system using a groove on an outer sidewall of an insulation base ring in accordance with the seventh through twelfth embodiments]

The seventeenth embodiment is similar to the sixteenth embodiment in that the ventilation path 82 outside the insulation base ring 40 is included. However, contrary to the sixteenth embodiment, a groove 44 is formed on the outer sidewall of the insulation base ring 40 to secure the ventilation path 82 as shown in Fig. 14.
The air ventilation system 82 outside the insulation base ring 40 in accordance with the seventeenth embodiment is as follows. The PCB 70 is not in contact with the insulation base ring 40 as shown in Figs. 10 and 12 so that the air flown in through the first ventilation pattern 72 may be exhausted, and a portion of the outside diameter of the insulation base ring 40 is formed to be smaller than an average outside diameter of the insulation base ring 40 so that the air flown in through the gap between the PCB 70 and the insulation base ring 40 may be exhausted to outside through a gap between the vibrating plate 20 (the back electret 50 in case of the front type) and the metal casing 10, the second ventilation pattern 14 and the first through hole 12. The metal casing 10 further comprises a third ventilation pattern extending from the second ventilation pattern 14 on a lower contacting surface with the insulation base ring 40 so that an air flown in through a gap between the metal casing 10 and the insulation base ring 40 may be exhausted outside through the second ventilation pattern 14 and the first through-hole 12.
That is, when the insulation base ring 40 is formed to include a groove on a portion of the outer sidewall of the insulation base ring 40 along its vertical axis as shown in Fig. 14, or to have a cross-section of the outer sidewall thereof in a shape of a polygon, a diameter at the groove or at a center of each sides of the polygon is smaller than a diameter at other portions of the insulation base ring 40 so that the air ventilation path is secured through this part.
In accordance with the seventeenth embodiment, it is preferable that a maximum distance between the metal casing 10 and the insulation base ring 40 is equal to or more than 0.03mm.

[An eighteenth embodiment: an air ventilation system using a groove on an inner sidewall of a metal casing in accordance with the seventh through twelfth embodiments]

The eighteenth embodiment is similar to the sixteenth embodiment in that the ventilation path 82 outside the insulation base ring 40 is included. However, contrary to the sixteenth embodiment, a groove 16 is formed on the inner sidewall of the metal casing 10 to secure the ventilation path 82 as shown in Fig. 15.
The air ventilation system 82 outside the insulation base ring 40 in accordance with the eighteenth embodiment is as follows. The PCB 70 is not in contact with the insulation base ring 40 as shown in Figs. 2 and 8 so that the air flown in through the first ventilation pattern 72 may be exhausted, and a portion of the inside diameter of the metal casing 10 is formed to be smaller than an average inside diameter of the insulation base ring 40 so that the air flown in through the gap between the PCB 70 and the insulation base ring 40 may be exhausted to outside through a gap between the vibrating plate 20 (the back electret 50 in case of the front type) and the metal casing 10, the second ventilation pattern 14 and the first through hole 12. The metal casing 10 further comprises a third ventilation pattern extending from the second ventilation pattern 14 on a lower contacting surface with the insulation base ring 40 so that an air flown in through a gap between the metal casing 10 and the insulation base ring 40 may be exhausted outside through the second ventilation pattern 14 and the first through-hole 12.
That is, when the insulation base ring 40 is formed to include a groove 16 on a portion of the inner sidewall of the metal casing 10 along its vertical axis as shown in Fig. 15, or to have a cross-section of the inner sidewall of the insulation base ring 40 in a shape of a polygon, a diameter at the groove 16 or at an apex of the polygon is smaller than a diameter at other portions of the metal casing 10 so that the air ventilation path is secured through this part. It is preferable that the groove 16 is connected to the second ventilation pattern 14 and the third ventilation pattern in case of disposing the groove 16. In addition, it is preferable that a maximum distance between the metal casing 10 and the insulation base ring 40 is equal to or more than 0.03mm in accordance with the eighteenth embodiment.
As described above, the condenser microphone including an internal air ventilation system in accordance with the present invention further comprises the internal air ventilation system on the PCB, the insulation base ring, the metal base ring, the back electret, the spacer ring, the metal casing, the vibrating plate for smooth ventilation of air from the chamber of the condenser microphone to outside, thereby preventing a sensitivity defect induced by a closure of air ventilation path due to an excessive compression of components or faulty dimension of the components to achieve a standardization of a sensitivity characteristic of the condenser microphone.
The condenser microphone including the internal air ventilation system in accordance with the embodiments of the present invention provides an effect of a facile adjustment of an acoustic characteristic of the condenser microphone by adjusting a shape, dimension of the air ventilation system formed on each component.
The condenser microphone including the internal air ventilation system in accordance with the embodiments of the present invention provides an effect of securing the air ventilation path inside the insulation base ring and maintaining a pressure of the air inside the chamber same as an outside air by designing the outside diameters of the metal base ring and the back electret (the vibrating plate in case of the front type) being in contact with the inner sidewall of the insulation base ring to be smaller than the inside diameter of the insulation base ring, thereby improving the sensitivity characteristic.
The condenser microphone including the internal air ventilation system in accordance with the embodiments of the present invention provides an effect of securing the air ventilation path inside the insulation base ring and maintaining a pressure of the air inside the chamber same as an outside air by further comprising the groove such as the air ventilation slit on a portion of the inner sidewall of the insulation base ring even when the metal base ring and the back electret (the vibrating plate in case of the front type) which are in contact with the inner sidewall of the insulation base ring are adhered to the insulation base ring due to a manufacturing margin or a assembly margin, thereby improving the sensitivity characteristic.
The condenser microphone including the internal air ventilation system in accordance with the embodiments of the present invention provides an effect of securing the air ventilation path inside the insulation base ring and maintaining a pressure of the air inside the chamber same as an outside air by further comprising the groove such as the air ventilation slit on a portion of the outer sidewall of the metal base ring and the back electret (the vibrating plate in case of the front type) which are in contact with the inner sidewall of the insulation base ring even when the metal base ring and the back electret (the vibrating plate in case of the front type) which are in contact with the inner sidewall of the insulation base ring are adhered to the insulation base ring due to a manufacturing margin or a assembly margin, thereby improving the sensitivity characteristic.
The condenser microphone including the internal air ventilation system in accordance with the embodiments of the present invention provides an effect of effectively maintaining a pressure of the air inside the chamber same as an outside air by further comprising additional internal air ventilation system between the metal casing and the insulation base ring to divide the ventilation path of the condenser microphone into inside and outside path, thereby improving the sensitivity characteristic.
The condenser microphone including the internal air ventilation system in accordance with the embodiments of the present invention provides an effect of securing the air ventilation path inside the insulation base ring and maintaining a pressure of the air inside the chamber same as an outside air by designing the outside diameters of the insulation base ring or insulation base ring and the vibrating plate (the back electret vibrating plate in case of the front type) being in contact with the inner sidewall of the metal casing to be smaller than the inside diameter of the metal casing, thereby improving the sensitivity characteristic.
The condenser microphone including the internal air ventilation system in accordance with the embodiments of the present invention provides an effect of securing the air ventilation path inside the insulation base ring and maintaining a pressure of the air inside the chamber same as an outside air by further comprising the groove such as the air ventilation slit on a portion of the inner sidewall of the metal casing even when the insulation base ring and the vibrating plate (the back electret in case of the front type) which are in contact with the inner sidewall of the metal casing are adhered to the metal casing due to a manufacturing margin or a assembly margin, thereby improving the sensitivity characteristic.
Finally, the condenser microphone including the internal air ventilation system in accordance with the embodiments of the present invention provides an effect of securing the air ventilation path inside the insulation base ring and maintaining a pressure of the air inside the chamber same as an outside air by further comprising the groove such as the air ventilation slit on a portion of the outer sidewall of the insulation base ring or the insulation base ring and the vibrating plate (the back electret in case of the front type) which are in contact with the inner sidewall of the metal casing even when the insulation base ring and the vibrating plate (the back electret in case of the front type) which are in contact with the inner sidewall of the metal casing are adhered to the metal casing due to a manufacturing margin or a assembly margin, thereby improving the sensitivity characteristic.
While the present invention has been particularly shown and described with reference to the preferred embodiment thereof, it will be understood by those skilled in the art that various changes in form and details may be effected therein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims

A condenser microphone including an internal air ventilation system, the condenser microphone comprising:
a metal casing for enclosing an internal component of the condenser microphone, the metal casing having a first through-hole at a bottom portion thereof;

a vibrating plate,

a spacer ring,

an insulation base ring,

an back electret,

a metal base ring,

a PCB disposed above the metal base ring and inside the metal casing to be electrically connected to the metal base ring and the metal casing through a bottom surface and an upper surface of the PCB, respectively, the PCB including a FET for converting the acoustic pressure being input through the vibrating plate to an electrical output and a terminal unit for providing the electrical output generated by the FET to a external circuit,
wherein the PCB further comprises a first ventilation pattern,
wherein the metal casing further comprises a second ventilation pattern disposed on a portion of a contacting surface with the vibrating plate for exhausting an air so that an air flown in through a gap between the vibrating plate and the metal casing is exhausted.
The condenser microphone according to claim 1, wherein
the vibrating plate is enclosed in the metal casing, the vibrating plate including a diaphragm vibrating according to an acoustic pressure and a polar ring attached below the diaphragm for maintaining a tension of the diaphragm and for providing a electrical connection between the metal casing and the diaphragm;
the spacer ring is disposed above the vibrating plate for electrically insulating an upper portion of the vibrating plate;
the insulation base ring is disposed above the spacer ring and inside the metal casing for electrically insulating an inner sidewall of the metal casing;
the back electret is disposed above the spacer ring and inside the insulation base ring to face the vibrating plate, the back electret being spaced apart from the vibrating plate by a predetermined distance, and including a second through-hole;
the metal base ring is disposed above the back electret and inside the insulation base ring for providing an electrical connection to the back electret; and
wherein the first ventilation pattern is disposed on a portion of a contacting surface with the metal base ring for exhausting an air inside an inner space defined by the back electret, the metal base ring and the PCB, and
wherein an outside diameter of the metal base ring is smaller than an inside diameter of the insulation base ring so that an air flown in through the first ventilation pattern is exhausted, and
wherein an outside diameter of the back electret is smaller than the inside diameter of the insulation base ring so that an air flown in through a gap between metal base ring and the insulation base ring is exhausted, and
wherein the insulation base ring is partially in contact with the spacer ring so that an air flown in through a gap between the back electret and the insulation base ring is exhausted, and
wherein an outside diameter of the vibrating plate is smaller than an inside diameter of the metal casing so that an air flown in through a gap between the spacer ring and the insulation base ring is exhausted.
The condenser microphone in accordance with claim 2, wherein a depth of the first ventilation pattern, a difference between the inside diameter of the insulation base ring and the outside diameter of the metal base ring, a difference between the inside diameter of the insulation base ring and the outside diameter of the back electret, a difference between the inside diameter of the metal casing and the outside diameter of the vibrating plate and a depth of the second ventilation pattern are equal to or larger than 0.03mm, respectively.
The condenser microphone in accordance with claim 2, wherein the PCB is not in contact with the insulation base ring, and
wherein an outside diameter of the insulation base ring is smaller than the inside diameter of the metal casing so that an air flown in through a gap between the PCB and the insulation base ring is exhausted through the gap between the vibrating plate and the metal casing, the second ventilation pattern and the first through-hole and/or
wherein a portion of an outside diameter of the insulation base ring is smaller than an average outside diameter of the insulation base ring so that an air flown in through a gap between the PCB and the insulation base ring is exhausted through the gap between the vibrating plate and the metal casing, the second ventilation pattern and the first through-hole.
The condenser microphone in accordance with claim 2, wherein the PCB is not in contact with the insulation base ring, and
wherein a portion of an inside diameter of the metal casing is larger than an average inside diameter of the metal casing so that an air flown in through a gap between the PCB and the insulation base ring is exhausted through the gap between the vibrating plate and the metal casing, the second ventilation pattern and the first through-hole.
The condenser microphone in accordance with claim 4, wherein a depth of the first ventilation pattern, a difference between the inside diameter of the insulation base ring and the outside diameter of the metal base ring, a difference between the inside diameter of the insulation base ring and the outside diameter of the back electret, a difference between the inside diameter of the metal casing and the outside diameter of the vibrating plate, a depth of the second ventilation pattern and a maximum value of a gap between the metal casing and the insulation base ring are equal to or larger than 0.03mm, respectively.
The condenser microphone according to claim 1, wherein
the vibrating plate is enclosed in the metal casing, the vibrating plate including a diaphragm vibrating according to an acoustic pressure and a polar ring attached below the diaphragm for maintaining a tension of the diaphragm and for providing a electrical connection between the metal casing and the diaphragm;
the spacer ring is disposed above the vibrating plate for electrically insulating an upper portion of the vibrating plate;
the insulation base ring is disposed above the spacer ring and inside the metal casing for electrically insulating an inner sidewall of the metal casing;
the back electret is disposed above the spacer ring and inside the insulation base ring to face the vibrating plate, the back electret being spaced apart from the vibrating plate by a predetermined distance, and including a second through-hole;
the metal base ring is disposed above the back electret and inside the insulation base ring for providing an electrical connection to the back electret; and
the first ventilation pattern is disposed on a portion of a contacting surface with the metal base ring for exhausting an air inside an inner space defined by the back electret, the metal base ring and the PCB,
wherein a portion of an inside diameter of the insulation base ring is larger than an average inside diameter of the insulation base ring so that an air flown in through the first ventilation pattern is exhausted,
wherein the insulation base ring is partially in contact with the spacer ring so that an air flown in through a gap between the back electret and the insulation base ring is exhausted,
wherein an outside diameter of the vibrating plate is smaller than an inside diameter of the metal casing so that an air flown in through a gap between the spacer ring and the insulation base ring is exhausted.
The condenser microphone in accordance with claim 7, wherein a depth of the first ventilation pattern, a difference between an maximum inside diameter and a minimum inside diameter of the insulation base ring, a difference between the inside diameter of the metal casing and the outside diameter of the vibrating plate and a depth of the second ventilation pattern are equal to or larger than 0.03mm, respectively.
The condenser microphone in accordance with claim 7, wherein the PCB is not in contact with the insulation base ring, and
wherein an outside diameter of the insulation base ring is smaller than the inside diameter of the metal casing so that an air flown in through a gap between the PCB and the insulation base ring is exhausted through the gap between the vibrating plate and the metal casing, the second ventilation pattern and the first through-hole.
The condenser microphone in accordance with claim 7, wherein the PCB is not in contact with the insulation base ring, and
wherein a portion of an outside diameter of the insulation base ring is smaller than an average outside diameter of the insulation base ring so that an air flown in through a gap between the PCB and the insulation base ring is exhausted through the gap between the vibrating plate and the metal casing, the second ventilation pattern and the first through-hole.
The condenser microphone in accordance with claim 7, wherein the PCB is not in contact with the insulation base ring, and
wherein a portion of an inside diameter of the metal casing is larger than an average inside diameter of the metal casing so that an air flown in through a gap between the PCB and the insulation base ring is exhausted through the gap between the vibrating plate and the metal casing, the second ventilation pattern and the first through-hole.
The condenser microphone in accordance with one of claims 9 through 11, wherein a depth of the first ventilation pattern, a difference between a maximum and a minimum inside diameter of the insulation base ring, a difference between the inside diameter of the metal casing and the outside diameter of the vibrating plate, a depth of the second ventilation pattern and a maximum value of a gap between the metal casing and the insulation base ring are equal to or larger than 0.03mm, respectively.
The condenser microphone according to claim 1, wherein:
the vibrating plate is enclosed in the metal casing, the vibrating plate including a diaphragm vibrating according to an acoustic pressure and a polar ring attached below the diaphragm for maintaining a tension of the diaphragm and for providing a electrical connection between the metal casing and the diaphragm;

the spacer ring is disposed above the vibrating plate for electrically insulating an upper portion of the vibrating plate;

the insulation base ring is disposed above the spacer ring and inside the metal casing for electrically insulating an inner sidewall of the metal casing;

the back electret is disposed above the spacer ring and inside the insulation base ring to face the vibrating plate, the back electret being spaced apart from the vibrating plate by a predetermined distance, and including a second through-hole;

the metal base ring is disposed above the back electret and inside the insulation base ring for providing an electrical connection to the back electret; and

the first ventilation pattern is disposed on a portion of a contacting surface with the metal base ring for exhausting an air inside an inner space defined by the back electret, the metal base ring and the PCB,
wherein a portion of an outside diameter of the metal base ring and a portion of an outside diameter of the back electret are smaller than an average outside diameter of the metal base ring and an average outside diameter of the back electret, respectively, so that an air flown in through the first ventilation pattern is exhausted,
wherein the insulation base ring is partially in contact with the spacer ring so that an air flown in through a gap between the back electret and the insulation base ring is exhausted,
wherein an outside diameter of the vibrating plate is smaller than an inside diameter of the metal casing so that an air flown in through a gap between the spacer ring and the insulation base ring is exhausted.
The condenser microphone according to claim 1, wherein:
the back electret comprises a second through-hole, the back electret being disposed at a bottom surface of the metal casing and being in electrical contact with the metal casing;

the spacer ring is disposed above the back electret for electrically insulating an upper portion of the back electret;

the insulation base ring is disposed above the spacer ring for electrically insulating an inner sidewall of the metal casing;

the vibrating plate including a diaphragm is disposed above the spacer ring and inside the insulation base ring and a polar ring attached to an upper portion of the diaphragm for maintaining a tension of the diaphragm, the diaphragm vibrating according to an acoustic pressure and the vibrating plate being spaced apart from the back electret by the spacer ring by a predetermined distance to face the back electret;

the metal base ring is disposed above the vibrating plate and inside the insulation base ring for providing an electrical connection to the vibrating plate; and

the first ventilation pattern is disposed on a portion of a contacting surface with the metal base ring for exhausting an air inside an inner space defined by the vibrating plate, the metal base ring and the PCB,
wherein an outside diameter of the metal base ring is smaller than an inside diameter of the insulation base ring so that an air flown in through the first ventilation pattern is exhausted,
wherein an outside diameter of the vibrating plate is smaller than the inside diameter of the insulation base ring so that an air flown in through a gap between metal base ring and the insulation base ring is exhausted,
wherein the insulation base ring is partially in contact with the spacer ring so that an air flown in through a gap between the vibrating plate and the insulation base ring is exhausted,
wherein an outside diameter of the back electret is smaller than an inside diameter of the metal casing so that an air flown in through a gap between the spacer ring and the insulation base ring is exhausted.
The condenser microphone according to claim 1, wherein:
the back electret comprises a second through-hole, the back electret being disposed at a bottom surface of the metal casing and being in electrical contact with the metal casing;

the spacer ring is disposed above the back electret for electrically insulating an upper portion of the back electret;

the insulation base ring is disposed above the spacer ring for electrically insulating an inner sidewall of the metal casing;

the vibrating plate including a diaphragm is disposed above the spacer ring and inside the insulation base ring and a polar ring attached to an upper portion of the diaphragm for maintaining a tension of the diaphragm, the diaphragm vibrating according to an acoustic pressure and the vibrating plate being spaced apart from the back electret by the spacer ring by a predetermined distance to face the back electret;

the metal base ring is disposed above the vibrating plate and inside the insulation base ring for providing an electrical connection to the vibrating plate; and

the first ventilation pattern is disposed on a portion of a contacting surface with the metal base ring for exhausting an air inside an inner space defined by the vibrating plate, the metal base ring and the PCB,
wherein a portion of an inside diameter of the insulation base ring is larger than an average inside diameter of the insulation base ring so that an air flown in through the first ventilation pattern is exhausted,
wherein the insulation base ring is partially in contact with the spacer ring so that an air flown in through a gap between the vibrating plate and the insulation base ring is exhausted,
wherein an outside diameter of the back electret is smaller than an inside diameter of the metal casing so that an air flown in through a gap between the spacer ring and the insulation base ring is exhausted.
The condenser microphone according to claim 1, wherein:
the back electret comprises a second through-hole, the back electret being disposed at a bottom surface of the metal casing and being in electrical contact with the metal casing;

the spacer ring is disposed above the back electret for electrically insulating an upper portion of the back electret;

the insulation base ring is disposed above the spacer ring for electrically insulating an inner sidewall of the metal casing;

the vibrating plate including a diaphragm is disposed above the spacer ring and inside the insulation base ring and a polar ring attached to an upper portion of the diaphragm for maintaining a tension of the diaphragm, the diaphragm vibrating according to an acoustic pressure and the vibrating plate being spaced apart from the back electret by the spacer ring by a predetermined distance to face the back electret;

the metal base ring is disposed above the vibrating plate and inside the insulation base ring for providing an electrical connection to the vibrating plate; and

the first ventilation pattern is disposed on a portion of a contacting surface with the metal base ring for exhausting an air inside an inner space defined by the vibrating plate, the metal base ring and the PCB,
wherein a portion of an outside diameter of the metal base ring and a portion of an outside diameter of the back electret are larger than an average outside diameter of the metal base ring and an average outside diameter of the back electret, respectively, so that an air flown in through the first ventilation pattern is exhausted,
wherein the insulation base ring is partially in contact with the spacer ring so that an air flown in through a gap between the vibrating plate and the insulation base ring is exhausted,
wherein an outside diameter of the back electret is smaller than an inside diameter of the metal casing so that an air flown in through a gap between the spacer ring and the insulation base ring is exhausted.
The condenser microphone according to claim 1, wherein:
the insulation base ring is disposed at a bottom portion of the metal casing for electrically insulating an inner sidewall of the metal casing;

the vibrating plate including a diaphragm is disposed at the bottom portion of the metal casing and inside the insulation base ring and a polar ring attached below the diaphragm for maintaining a tension of the diaphragm, the diaphragm vibrating according to an acoustic pressure and the polar ring providing an electrical contact between the metal casing and the diaphragm;

the spacer ring is disposed above the vibrating plate and inside the insulation base ring for electrically insulating an upper portion of the vibrating plate;

the back electret comprises a second through-hole, the back electret being disposed above the spacer ring and inside the insulation base ring to face the vibrating plate, the back electret being spaced apart from the vibrating plate by the spacer ring by a predetermined distance;

the metal base ring is disposed above the back electret and inside the insulation base ring for providing an electrical connection to the back electret; and

the first ventilation pattern is disposed on a portion of a contacting surface with the metal base ring for exhausting an air inside an inner space defined by the back electret, the metal base ring and the PCB,
wherein a portion of outside diameters of the metal base ring, the back electret, the spacer ring and the vibrating plate are smaller than an inside diameter of the insulation base ring.
The condenser microphone according to claim 1, wherein:
the insulation base ring is disposed at a bottom portion of the metal casing for electrically insulating an inner sidewall of the metal casing;

the vibrating plate including a diaphragm is disposed at the bottom portion of the metal casing and inside the insulation base ring and a polar ring attached below the diaphragm for maintaining a tension of the diaphragm, the diaphragm vibrating according to an acoustic pressure and the polar ring providing an electrical contact between the metal casing and the diaphragm;

the spacer ring is disposed above the vibrating plate and inside the insulation base ring for electrically insulating an upper portion of the vibrating plate;

the back electret comprises a second through-hole, the back electret being disposed above the spacer ring and inside the insulation base ring to face the vibrating plate, the back electret being spaced apart from the vibrating plate by the spacer ring by a predetermined distance;

the metal base ring is disposed above the back electret and inside the insulation base ring for providing an electrical connection to the back electret; and

the first ventilation pattern is disposed on a portion of a contacting surface with the metal base ring for exhausting an air inside an inner space defined by the back electret, the metal base ring and the PCB,
wherein a portion of an inside diameter of the insulation base ring is larger than an average inside diameter of the insulation base ring so that an air flown in through the first ventilation pattern is exhausted.
The condenser microphone according to claim 1, wherein:
the insulation base ring is disposed at a bottom portion of the metal casing for electrically insulating an inner sidewall of the metal casing;

the vibrating plate including a diaphragm is disposed at the bottom portion of the metal casing and inside the insulation base ring and a polar ring attached below the diaphragm for maintaining a tension of the diaphragm, the diaphragm vibrating according to an acoustic pressure and the polar ring providing an electrical contact between the metal casing and the diaphragm;

the spacer ring is disposed above the vibrating plate and inside the insulation base ring for electrically insulating an upper portion of the vibrating plate;

the back electret comprises a second through-hole, the back electret being disposed above the spacer ring and inside the insulation base ring to face the vibrating plate, the back electret being spaced apart from the vibrating plate by the spacer ring by a predetermined distance;

the metal base ring is disposed above the back electret and inside the insulation base ring for providing an electrical connection to the back electret; and

the first ventilation pattern is disposed on a portion of a contacting surface with the metal base ring for exhausting an air inside an inner space defined by the back electret, the metal base ring and the PCB,
wherein portions of outside diameters of the metal base ring, the back electret, the spacer ring, and the vibrating plate are smaller than average outside diameters of the metal base ring, the back electret, the spacer ring, and the vibrating plate.
The condenser microphone according to claim 1, wherein:
the insulation base ring is disposed at a bottom portion of the metal casing for electrically insulating an inner sidewall of the metal casing;

the back electret comprises a second through-hole, the back electret being disposed at a bottom surface of the metal casing and and inside the insulation base ring and being in electrical contact with the metal casing;

the vibrating plate including a diaphragm is disposed above the spacer ring and inside the insulation base ring and a polar ring attached above the diaphragm for maintaining a tension of the diaphragm, the diaphragm vibrating according to an acoustic pressure and the vibrating plate being spaced apart from the back electret by the spacer ring by a predetermined distance;

the spacer ring is disposed above the vibrating plate and inside the insulation base ring for electrically insulating an upper portion of the vibrating plate;

the metal base ring is disposed above the vibrating plate and inside the insulation base ring for providing an electrical connection to the back electret; and

the first ventilation pattern is disposed on a portion of a contacting surface with the metal base ring for exhausting an air inside an inner space defined by the vibrating plate, the metal base ring and the PCB,
wherein a portion of outside diameters of the metal base ring, the vibrating plate, the spacer ring and the back electret are smaller than an inside diameter of the insulation base ring.