KR20040105368A - An unidirectional condenser microphone - Google Patents

Abstract

PURPOSE: An omnidirectional condenser microphone is provided to reduce a degradation of sound by using a phase delay filter having guaranteed characteristics on an air ventilation and a sound resistance. CONSTITUTION: An omnidirectional condenser microphone includes a case(101) and a printed circuit board(109). A vibration membrane(103), a spacer(104), and an insulation ring(105) are sequentially laminated on a bottom of the case. A back electret(106) is inserted to face the spacer in the insulation ring. The printed circuit board is laminated on an upper portion of a metal ring(107) inserted to an upper portion of the insulation ring. The microphone is inserted and fixed into the insulation ring via the metal ring. More than one sound inflow holes(113) is formed in the back electret. A phase delay filter(111) for attenuating a rear sound is implemented on an upper portion of the sound inflow holes. The phase delay filter covers a rear sound hole(110).

Description

Unidirectional Condenser Microphone {AN UNIDIRECTIONAL CONDENSER MICROPHONE}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to condenser microphones, and more particularly, to a unidirectional condenser microphone for reproducing only a sound incident in a certain direction with a large output and attenuating a sound other than a certain direction.

In general, the condenser microphone is used to convert the voice into an electrical signal by using the capacitance change due to the vibration of the film caused by the sound wave, and largely omnidirectional and positive depending on the directivity indicating the sensitivity change due to the incident angle of the incident sound wave. It is divided into directivity and single directivity.

Here, the unidirectional condenser microphone 10 reacts only in a constant direction from the front, and conventionally, as shown in FIGS. 1A and 1B, the vibrating membrane 12 and the spacer 13 are disposed on the inner bottom of the case 11. And an insulating ring 14 are sequentially stacked, and a back electret 15, also called a back electrode, is inserted into the insulating ring 14 so as to face the spacer 13, and the insulating ring 14 14) The printed circuit board 17 is stacked on the upper portion of the metal ring 16 fitted to the inner upper portion.

Phase delay filters 18a and 18b are inserted on the back electret 15, and the phase delay filters 18a and 18b are mechanically fixed by the metal ring 16. Polyethylene resin sintered product 18a or copper sintered product 18b was used.

However, since the phase delay filters 18a and 18b are located inside the microphone 10, the thickness of the microphone 10 is as thick as the thickness of the phase delay filters 18a and 18b, or the existing microphone 10 There was a problem that the acoustic chamber 19 is reduced inside the acoustic performance is reduced.

In addition, the internal structure of the conventional microphone 100 is limited or greatly designed to fix the phase delay filters 18a and 18b and to secure conductivity between the back electret 15 and the printed circuit board 17. There was a problem that needs to be changed.

In addition, when the polyethylene-based resin sintered product is used as the phase delay filter 18a as shown in FIG. 1A, the thickness (about 2 mm) is thickened to secure air permeability, and the copper sintered product is phased as shown in FIG. 1B. In the case of using the delay filter 18b, there is a problem that it is difficult to secure air permeability and inferior mass productivity.

Accordingly, the present invention has been made to solve the above-described problems, by providing a phase delay filter having a super thin plate on the back electret and excellent ventilation and mass productivity, giving a directivity, it is possible to minimize the structure change of the existing microphone It is an object of the present invention to provide a single directional condenser microphone capable of sufficiently securing an acoustic chamber to prevent degradation of acoustic characteristics.

1A and 1B are longitudinal cross-sectional views of a conventional unidirectional condenser microphone;

2 is an exploded perspective view of a unidirectional condenser microphone according to the present invention;

Figure 3 is a longitudinal cross-sectional view of the assembled state of the unidirectional condenser microphone according to the present invention

Figure 4a is a plan view showing an embodiment of a back electret in the present invention,

Figure 4b is a plan view showing a second embodiment of the back electret in the present invention,

Figure 4c is a plan view showing a third embodiment of the back-ilxlet in the present invention.

5 is a direct response characteristic diagram of a condenser microphone according to the present invention;

6 is a frequency response characteristic diagram of a condenser microphone according to the present invention.

Explanation of symbols on the main parts of the drawings

100: microphone 101: case

102: front acoustic hole 103: vibration membrane

104: spacer 105: insulation ring

106: back electret 107: metal ring

108: field effect transistor 109: printed circuit board

110: rear acoustic hole 111: phase delay filter

112: polling 113: sound wave inlet hole

114: acoustic chamber

In the unidirectional condenser microphone of the present invention for achieving the above object, a vibration membrane, a spacer, and an insulating ring are sequentially stacked on the bottom surface of the case, and a back electret is inserted into the insulating ring facing the spacer. A printed circuit board having a rear acoustic hole is stacked on the upper portion of the metal ring, which is inserted into the upper portion of the insulating ring, and a phase delay filter is mounted to cover the sound wave inlet hole formed in the back electret. By delaying the phase of the back sound delivered to the diaphragm passing through the hole, it can react only to the front sound.

The phase delay filter covering the sound wave inlet hole of the back electret is mounted on the top face of the back electret to impart directivity to the microphone.

The phase delay filter may be selected from any one of well-known and proven fluorine resin, acrylic, cellulose, polyimide, polyester, glass fiber, and silica based products, thereby ensuring thinness and breathability. Mass production is also possible.

Hereinafter, with reference to the accompanying drawings, preferred embodiments of the present invention will be described in detail.

Figure 2 is an exploded perspective view of a unidirectional condenser microphone according to the present invention, Figure 3 is an assembled longitudinal cross-sectional view of the unidirectional condenser microphone according to the present invention.

As shown, the microphone 100 of the present invention, the vibration membrane 103, the spacer 104 and the insulating ring 105 are sequentially stacked on the inner bottom surface of the case 101, the inside of the insulating ring 105 The back electret 106 is inserted facing the spacer 104, and a metal ring 107 is inserted into the upper portion of the insulating ring 105.

In addition, a printed circuit board 109 having a field effect transistor (FET) 108 is stacked on the bottom surface of the metal ring 107, and a back sound through which a back sound passes is formed on the printed circuit board 109. The hole 110 is formed.

In addition, a plurality of sound wave inlet holes 113 are formed at predetermined positions of the back electret 106, and the phase delay filter 111 is disposed on the upper surface of the back electret 106, that is, the acoustic chamber 114 side. It is mounted to cover the sound wave inlet hole (113).

Hereinafter, the components will be described in detail as follows.

The case 101 serves to prevent the inflow of foreign substances or electrical noise from the outside by sealing / compressing and integrating each component of the microphone 100. The material is generally made of aluminum, and the shape is cylindrical. The front surface (bottom surface in the drawing) is formed in a predetermined number of front sound holes 102 are formed so that the front sound flowing from the front of the microphone 100 can pass.

The vibrating membrane 103 is usually formed by vacuum deposition of gold (Au), nickel (Ni), etc. on a PET or PPS film, and by sound waves in a state where a minute gap is maintained with the back electret 106 faced. When the oscillation causes a distance change, the distance change acts as a change in the electrical capacitance, and is supported on the inner bottom of the case 101 by the polling 112.

The back electrets 106 are stacked at positions spaced apart from the vibrating membrane 103 by the spacer 104, and the edges thereof are pressed while being interviewed with the lower end of the metal ring 107. The peripheral edge is interviewed with the inner circumference of the insulating ring 105.

The back electret 106 is manufactured by punching a panel in which a FEP film is adhered to a copper plate or an SUS plate, etc., usually formed with one or more sound wave inlet holes 113 at a predetermined position, and having a high voltage of several KV. It is charged to act as a bipolar plate, the charging potential is to determine the sensitivity of the corresponding directional microphone (100).

Here, the sound wave inlet hole 113 is formed in the center as shown in Figure 4a, or as shown in Figure 4b three acoustic holes are formed at a predetermined interval to be arranged in a triangular, or shown in Figure 4c As described above, a plurality may be arranged in an annular shape.

The phase delay filter 111 is a resistor for sound, and delays the phase of the sound passing through the sound wave inlet hole 113 of the back electret 109 to have a directivity characteristic in the microphone 100.

The phase delay filter 111 is attached to the upper portion of the phase electret filter 109 so as to cover the sound wave inlet hole 113 through a double-sided tape or an adhesive, and an outer circumferential surface thereof is inside the metal ring 107. It is inserted into and fixed.

Accordingly, the rear sound flowing into the sound wave inlet hole 113 through the rear acoustic hole 110 and the acoustic chamber 114 is attenuated by the phase delay filter 111.

In addition, the material of the phase delay filter 111 is a known fluorine resin, acryl, cellulose, polyimide, polyester, glass fiber, silica filter, which has been verified for excellent quality in terms of negative damping ability and breathability. Any one of them can be selected and used.

Here, the phase delay filter 111 has a thickness of 50 to 400 μm and a pore size of about 0.025 to 15 μm in order to obtain excellent directivity.

As the fluorine resin system, any one of polytetrafluoroethyelene (PTFE), perfluoroalkoxy (PFA), and polyviny lidene fluoride (PVDF) filter may be selected and used.

As the acrylic resin, any one of polymethyl methacrylate (PMMA), polymethyl acrylate (PMA), polyacrylonitrile (Polyacrylon trile (PNA)) filter can be selected and used.

As the cellulose type, any one of cellulose, cellulose nitrate, and cellulose acetate filter may be selected and used.

On the other hand, the spacer 104 is interposed between the vibrating membrane 103 and the back electret 106 to serve as a gap body and an electrical insulator to maintain a constant distance from each other, usually PET film as a press mold It is produced by punching.

The metal ring 107 has a function of electrically connecting the gate of the field effect transistor 108 and the back electret 106, and is usually manufactured by pre-pressing brass and plating with gold.

The insulating ring 105 has the back electret 106 and the metal ring 107 inserted therein, and acts as a mechanical support and an insulator, and is usually injection molded from ABS or polybutylene terephthalate (PBT) material. Are manufactured.

The field effect transistor 108 functions as an impedance converter which outputs a change in electrical capacitance detected by the back electret 106 as a change in impedance and transmits a change signal to an amplifier (not shown) at a later stage. The printed circuit board 109 is provided on the bottom surface.

The printed circuit board 109 serves as a rear cover and an output terminal of the microphone 100. The printed circuit board 109 is classified into a contact type, a pin type, and a soldering type according to its purpose, and is located from the rear of the plurality of microphones 100 at predetermined positions. A rear sound hole 110 is formed through which the sound of the sound (rear sound) is introduced.

Referring to Figure 3 describes the operation of the present invention, the front sound flowing from the front of the case 101 is introduced into the front acoustic hole 102 of the case 101 to vibrate the vibrating membrane 103, When a distance change occurs between the back electret 106 due to the vibration of the vibrating membrane 103, a change in capacitance with respect to the distance change is caused by the field effect transistor 108 via the metal ring 107. Is detected in the audio signal.

On the other hand, the rear sound flowing from the rear of the case 101 passes through the rear acoustic hole 110 and the acoustic chamber 114 of the printed circuit board 109 and then directly passes through the phase delay filter 111 as an acoustic wave resistor. While the phase is delayed and the phase delayed sound waves pass through the sound wave inlet hole 113 of the back electret 106 to vibrate the vibrating membrane 103.

Accordingly, the front sound is canceled from the rear sound to have omnidirectional omnidirectional characteristics, and the unidirectional microphone 100 exhibits the directivity characteristic shown in FIG. 4 and the frequency response characteristic as shown in FIG. 5.

The present invention is not limited to the above embodiments, and of course, various modifications can be made within the scope of the technical idea of the present invention.

As described above, according to the unidirectional condenser microphone according to the present invention, since the phase delay filter which is ultra-thin and has excellent air permeability and filter function is mounted on the back electret, it is not necessary to increase the thickness of the existing microphone, Since the size of the chamber is also almost the same as that of the conventional one, it is possible to obtain an effect of preventing the degradation of the acoustic performance.

In addition, since the phase delay filter is attached by using a double-sided tape or the like instead of being fixed by a separate mechanism, the directivity characteristic of the phase delay filter can be obtained without changing the existing microphone internal structure. .

In addition, by using a conventional phase delay filter that has already been verified as an acoustic resistor and hardly changing the internal structure of the existing microphone, it is possible to contribute to mass production.

Claims (2)

The vibrating membrane 103, the spacer 104, and the insulating ring 105 are sequentially stacked on the inner bottom surface of the case 101, and the back electret 106 faces the spacer 104 inside the insulating ring 105. In the unidirectional condenser microphone formed of a printed circuit board 109 is stacked on top of the metal ring 107 is inserted into the upper portion of the insulating ring 105, One or more sound wave inlet holes 113 are formed in the back electret 106 and a phase delay filter 111 is mounted on the back electret 106 to attenuate the rear sound. A unidirectional condenser microphone, characterized in that mounted to cover the hole (110). The method of claim 1, wherein the phase delay filter 111 has a thickness of 50 ~ 400㎛, pore size of 0.025 ~ 15㎛, fluorine resin, acrylic, cellulose, polyimide, polyester, glass fiber and A unidirectional condenser microphone, characterized in that one of the silica-based products.