JP2013187788A - Non-directional microphone - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a non-directional microphone that can cancel vibration noise with relatively simple structure and with high accuracy.SOLUTION: A non-directional microphone according to the invention is constructed by using common space contacting with opposing faces of both diaphragms in the central part as dumping space and forming separate acoustic space and an acoustic terminal contacting with the opposite side faces of the opposing faces of both diaphragms. When each of the diaphragms is mutually displaced toward the same direction by vibration noise, the vibration noise can be cancelled with high accuracy because the dumping space itself is only deformed without compression or expansion. On top of that, because it only needs to form the common dumping space on the respective diaphragms in the central part of the microphone, it can achieve the above operation effect with relatively simple structure.

Description

  The present invention relates to an omnidirectional microphone that cancels noise caused by mechanical vibration, and relates to a technique that is effective when applied to, for example, a mobile phone, an IC recorder, or a video camera.

  If a recording device such as an IC recorder is used in a pocket, mechanical vibrations may be recorded with it when it moves. Also, in a recording device such as a video camera, mechanical vibration noise generated when the lens moves for focusing may be recorded. This vibration noise is generated by the displacement of the diaphragm of the microphone due to the inertial force due to the mechanical vibration of the apparatus. For example, Patent Document 1 discloses a technique for canceling such vibration noise. In this document, a pair of diaphragms are arranged in a capsule of a microphone, and a pair of back electrode plates facing the outside of the capsule are provided on the diaphragms, and a circuit board is provided between the pair of diaphragms. Is placed. In the example of FIG. 2 of the same document, a through hole is formed in a circuit board, and a sound wave is input by communicating the hole with a sound hole formed on the side surface of the capsule. Both end faces of the capsule are closed. In the example of FIG. 8, sound holes are formed on both end faces of the capsule to input sound waves, and the gap between both diaphragms is shielded by the circuit board. In any configuration, in-phase output can be obtained for sound waves input to a pair of diaphragms, and anti-phase output can be obtained for vibration noise caused by mechanical vibration. Thus, vibration noise can be canceled.

JP 2011-223133 A

  The present inventor has studied to improve the effect of canceling mechanical vibration noise. According to this, in Patent Document 1, the damping space on the opposite side to the pressure receiving surface of the diaphragm that receives the input sound wave is separated for each diaphragm. In the example of FIG. 2 of the same document, an acoustic space that receives an input sound wave from the center is only shared by both diaphragms, and the damping space is formed separately for each diaphragm. In the example of FIG. 8 of the same document, each diaphragm receives input sound waves from both end faces of the capsule, but the damping space in the center is separated for each diaphragm by the circuit board. In this way, when the damping space on the opposite side of the pressure receiving surface of the diaphragm that receives the input sound wave is separated for each diaphragm, the diaphragm is subjected to mechanical vibration and tends to be displaced in the same direction. When this happens, one damping space expands and the other damping space tends to shrink. However, if special considerations are not taken so that the displacement speed of expansion and the displacement speed of reduction are the same in both damping spaces, the output is likely to generate displacement errors and attenuation errors, so that sufficient vibration noise can be produced. It has been found by the present inventors that it cannot be canceled.

  An object of the present invention is to provide an omnidirectional microphone capable of canceling vibration noise with high accuracy by a relatively simple configuration.

  The above and other objects and novel features of the present invention will be apparent from the description of this specification and the accompanying drawings.

  The following is a brief description of an outline of typical inventions disclosed in the present application.

  That is, in the omnidirectional microphone according to the present invention, a common space that is in contact with the opposing surfaces of both diaphragms is a damping space at the center, and an individual surface that is in contact with the opposite surface of both diaphragms is in contact with each other. An acoustic space and an acoustic terminal are formed.

  According to this, when the diaphragms are displaced in the same direction with respect to the vibration noise, the damping space itself only needs to be deformed without compressive expansion, so that the vibration noise can be canceled with high accuracy. Is possible. Moreover, a configuration in which a damping space common to the respective diaphragms is formed at the center of the microphone is relatively simple.

  The effects obtained by the representative ones of the inventions disclosed in the present application will be briefly described as follows.

  That is, it is possible to provide an omnidirectional microphone that can cancel vibration noise with high accuracy by a relatively simple configuration.

FIG. 1 is an axial sectional view showing an omnidirectional microphone according to an embodiment of the present invention. FIG. 2 is an axial sectional view showing an omnidirectional microphone according to another embodiment of the present invention.

1. First, an outline of a typical embodiment of the invention disclosed in the present application will be described. Reference numerals in the drawings referred to in parentheses in the outline description of the representative embodiments merely exemplify what are included in the concept of the components to which the reference numerals are attached.

  [1] An omnidirectional microphone (1) according to an embodiment of the present invention has a back electrode (20) serving as one capacitive electrode and a back electrode (through-hole (41) serving as the other capacitive electrode). 40) are arranged opposite to each other, and a first acoustic space (90) that is in contact with one surface of the diaphragm through the through hole and communicates with the first acoustic terminal (73) is formed, and the other of the diaphragms is formed. A pair of bidirectional microphones (2A, 2B) having a second acoustic space (80) in contact with the surface and communicating with the second acoustic terminal (11) are connected to each other. The second acoustic spaces connected to each other are connected to each other as one damping space (100) common to both diaphragms.

  According to this, the respective diaphragms are displaced in opposite directions with respect to the sound waves input from the pair of acoustic terminals to the pair of diaphragms, and an in-phase output is obtained. With respect to vibration noise caused by mechanical vibration, the respective diaphragms are displaced in the same direction to obtain outputs of opposite phases. As a result, vibration noise can be canceled. At this time, the damping space is a common space in contact with the opposing surfaces of both diaphragms. Therefore, when the diaphragms are displaced in the same direction with respect to vibration noise, the damping space is not compressed and expanded. It is difficult to cause displacement errors or attenuation errors in both diaphragms, and vibration noise can be canceled with high accuracy. Further, by attaching and fixing the second acoustic terminal of the bidirectional microphone so as to communicate with each other, each second acoustic space can be easily made into one damping space common to both diaphragms. Therefore, the above-described effects can be achieved with a relatively simple configuration.

  [2] In each item 1, each of the bidirectional microphones includes a circuit board (72) on which a circuit element (72) for detecting a capacitive voltage formed on the capacitive electrode is mounted on the first acoustic space side. 70). The first acoustic terminal is formed on the circuit board.

  [3] In Item 1 or 2, each of the bidirectional microphones has a unique casing (10), and both the second acoustic terminals are in communication with each other by contacting both casing end faces. Is bound to.

  The simplest way is to add them together.

  [4] In the omnidirectional microphone (1A) according to another embodiment of the present invention, a pair of diaphragms (20, 20) serving as one capacitive electrode is common to the central portion of the casing (10A). Each of the individual acoustic spaces (130, 130) which are disposed opposite to each other with the damping space (120) sandwiched therebetween and in contact with the diaphragm on the opposite side of the damping space (back electrode) 40) is arranged opposite to the diaphragm. A circuit board (70) is disposed opposite to each of the back electrodes with the individual acoustic space interposed therebetween, and a communication hole (41) communicating with the front and back is formed in each of the back electrodes. An acoustic terminal (73) communicating with the front and back is formed.

  According to this, similarly to the first aspect, the diaphragms are displaced in opposite directions with respect to the sound waves input from the pair of acoustic terminals to the pair of diaphragms, thereby obtaining an in-phase output. With respect to vibration noise caused by mechanical vibration, the respective diaphragms are displaced in the same direction to obtain outputs of opposite phases. As a result, vibration noise can be canceled. At this time, since the damping space is a common space in contact with the opposing surfaces of both diaphragms in the central portion of the casing, the damping space is compressed and expanded when the diaphragms are displaced in the same direction with respect to vibration noise. Therefore, it is difficult to cause displacement errors and attenuation errors in both diaphragms, and vibration noise can be canceled with high accuracy. Furthermore, since the damping space has only to be formed so as to be in contact with the opposing surfaces of both diaphragms in the central portion of the casing, the above-described effects can be achieved with a relatively simple configuration.

2. Details of Embodiments Embodiments will be further described in detail.

  FIG. 1 is an axial sectional view of an omnidirectional microphone according to an embodiment of the present invention. The omnidirectional microphone 1 shown in the figure is configured by combining two identical bidirectional microphones 2A and 2B.

  Each of the bidirectional microphones 2A and 2B is formed in, for example, a casing 10 having a bottomed cylindrical shape. The casing 10 is made of, for example, aluminum, and a plurality of sound wave passage openings (hereinafter also referred to as second acoustic terminals) 11 as one acoustic terminal are formed in the bottomed portion, and an end opposite to the bottomed portion. The edge portion 12 is bent inward at the end of the assembling process, and a member (described later) configured in the cylinder of the casing 10 is locked, and an opening 13 is formed at the center thereof.

  In the cylinder of the casing, the diaphragm 20, the insulating spacer 30, the back electrode 40, the insulating chamber 50, the contact ring 60, and the circuit board 70 are arranged in this order from the back.

  The diaphragm 20 becomes one capacity electrode of the capacitor together with the back electrode 40, and the back electrode 40 that forms a counter electrode of the diaphragm 20 with a gap becomes the other capacity electrode of the capacitor.

  The diaphragm 20 is not particularly limited, but a metal film is deposited on one surface of a dielectric film such as a polyester film, the metal film 21 is fixed to the diaphragm ring 22, and the insulating spacer 30 is fixed to the dielectric surface. Has been. The metal film 21 of the vibration plate 20 may be formed on both surfaces of the dielectric film. A space surrounded by the metal film 21 and the inner peripheral surface of the diaphragm ring 22 constitutes a second acoustic space 80 communicating with the second acoustic terminal 11.

  The back electrode 40 has a plurality of through-holes 41 communicating with the front and back, and a part of the outer peripheral edge thereof is fitted and fixed to a recess formed in the inner periphery of the ring-shaped insulating chamber 50. The one end face is in contact with the insulating spacer 30. Although not particularly limited, the back electrode 40 is made of a conductor, such as nickel-plated brass, and a surface facing the diaphragm 20 is laminated with, for example, fluororesin for forming permanent polarization.

  The circuit board 70 is not particularly limited, but a circuit chip 72 such as a field effect transistor used for impedance conversion is mounted on a printed wiring board 71 having an appropriate wiring pattern formed on the front and back surfaces, and communicates with the front and back sides. Thus, a plurality of sound wave passage openings (hereinafter also referred to as first acoustic terminals) 73 serving as the other acoustic terminal are formed. Although not particularly shown, electrode pads as output terminals are formed on the externally exposed surface of the printed wiring board 71.

  The back electrode 40 is electrically connected to a required signal wiring pattern on the printed wiring board 71 through a conductive contact ring 60 inserted in an inner peripheral portion of the insulating chamber 50. The metal film 21 of the diaphragm 20 is conducted from the diaphragm ring 22 through the casing 10 to the required signal wiring pattern on the printed wiring board 71 through the edge portion 12 thereof.

  A space surrounded by the inner peripheral surface of the contact ring 60 from the opposite surface of the metal film 21 through the through hole 41 of the back electrode 40 constitutes a first acoustic space 90 communicating with the first acoustic terminal 72.

  As is clear from the above, each of the bidirectional microphones 2A and 2B has a first acoustic terminal 73 that communicates with one first acoustic space 90 with the diaphragm 20 in between, and also has the diaphragm 20 in between. The second acoustic terminal 11 communicates with the other second acoustic space 80. The omnidirectional microphone 1 shown in FIG. 1 includes both casings 10 so that the second acoustic terminal 11 of the bidirectional microphone 2A and the second acoustic terminal 90 of the bidirectional microphone 2B communicate with each other. , 10 are closely coupled to each other, and the second acoustic spaces 80, 80 communicated with each other constitute a single damping space 100 common to both diaphragms 20, 20. In order to perform the above-described tight coupling, it is possible to employ adhesion by an adhesive between the casing end faces, affixing and fixing with a double-sided tape, or pressing and fixing both casings with an elastic body from the outside. The airtightness between the casing end faces may be ensured using an O-ring.

  According to the omnidirectional microphone 1, the second acoustic space 80 that constitutes the damping space is hermetically sealed so that sound waves are not input from the outside, and the first acoustic terminal that communicates with each of the first acoustic spaces 90. 73 inputs sound waves from the outside. The diaphragms 20 are displaced in opposite directions with respect to the sound waves input to the diaphragms 20 corresponding to the pair of first acoustic terminals 73, respectively. In other words, if the distance between the diaphragm 20 forming the capacitor and the back electrode 40 is separated in one microphone, the other microphone is also separated, and if approaching in one microphone, the other microphone is also approached. As a result, the acoustic characteristics of the microphones 2A and 2B are in phase, and an in-phase output is obtained from an output pad (not shown) of each circuit board 70, thereby realizing an omnidirectional microphone having good acoustic sensitivity. Is done.

  On the other hand, with respect to vibration noise caused by mechanical vibration, the respective diaphragms 20 are displaced in the same direction, and outputs of opposite phases are obtained from output pads (not shown) of the respective circuit boards 70. By virtue of this, vibration noise can be canceled. In particular, since the damping space 100 is a common space sealed in contact with the opposing surfaces of the two diaphragms 20 and 20, the diaphragms 20 and 20 are displaced in the same direction with respect to vibration noise. In this case, the damping space does not need to be compressed and expanded, and it is difficult for both the diaphragms to generate a displacement error or a damping error, so that the vibration noise can be canceled with high accuracy. Further, since the distance between the diaphragms 20 and 20 is small and the damping space can be reduced, it is possible to further suppress the influence of the vibration attenuation difference between the diaphragms on the vibration noise. But vibration noise can be canceled effectively. In addition, each second acoustic space can be easily made into one damping space common to both diaphragms by attaching and fixing the second acoustic terminals of the bidirectional microphone so as to communicate with each other. Therefore, the above-described effects can be achieved with a relatively simple configuration.

  FIG. 2 shows an axial sectional view of an omnidirectional microphone according to another embodiment of the present invention. The omnidirectional microphone 1A shown in the figure is different from that shown in FIG. 1 in that it is configured as a single casing 10A. 2, the same components as those in FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted.

  A pair of diaphragms 20, 20 are disposed opposite to each other with a damper 110 interposed therebetween in the center of the casing 10 </ b> A via a spacer 110. In the individual acoustic spaces 130 and 130 that are in contact with the diaphragms 20 and 20 on the side opposite to the damping space 120, back electrodes 40 and 40 that are the other capacitive electrodes are disposed opposite to the diaphragms 20 and 20. The Circuit boards 70, 70 are arranged opposite to the back electrodes 40, 40 with the individual acoustic spaces 130, 130 interposed therebetween, and communication holes 41 communicating with the front and back are formed in the back electrodes 40, 40. The circuit boards 70 and 70 are formed with acoustic terminals 73 and 73 communicating with the front and back sides. The insulating chamber 50 and the contact ring 60 are disposed between the back electrode 40 and the circuit board 70, and the edge portions 12A at both ends of the casing 10A are folded inward at the end of the assembly process, so that the cylinder of the casing 10A is obtained. An opening 13 </ b> A that locks the member configured therein and exposes the acoustic terminal 73 is formed at the center thereof.

  According to this, as in FIG. 1, the diaphragms 20, 20 are displaced in opposite directions with respect to the sound waves input from the pair of acoustic terminals 73, 73 to the pair of diaphragms 20, 20. Output can be obtained. With respect to vibration noise caused by mechanical vibration, the respective diaphragms 20 and 20 are displaced in the same direction to obtain outputs of opposite phases. As a result, vibration noise can be canceled. In particular, since the damping space 120 is a common space in contact with the opposing surfaces of the two diaphragms 20 and 20 in the central portion of the casing 10A, the diaphragms 20 and 20 are in the same direction with respect to vibration noise. When it is displaced, the damping space does not need to be compressed and expanded, and it is difficult for both the diaphragms 20 and 20 to generate displacement errors and attenuation errors, and vibration noise can be canceled with high accuracy. Furthermore, since the damping space 120 has only to be formed so as to be in contact with the opposing surfaces of the two diaphragms 20 and 20 in the central portion of the casing 10A, the above-described effects can be achieved with a relatively simple configuration.

  Although the invention made by the present inventor has been specifically described based on the embodiments, it is needless to say that the present invention is not limited thereto and can be variously modified without departing from the gist thereof.

  For example, the present invention is effective as a zoom sound in a digital video camera, a digital still camera or the like, or as a vibration canceling microphone in an IC recorder or the like. It can also be applied to devices that need countermeasures against vibration such as touch noise.

DESCRIPTION OF SYMBOLS 1 Non-directional microphone 2A, 2B Bidirectional microphone 10 Casing 11 Second acoustic terminal 20 Diaphragm 21 Metal film 22 Diaphragm ring 30 Insulating spacer 40 Back electrode 41 Through-hole 50 Insulating chamber 60 Contact ring 70 Circuit board 72 Circuit chip 73 First acoustic terminal 80 Second acoustic space 90 First acoustic space 100 Damping space 10A Casing 110 Spacer 120 Damping space

Claims (4)

  A back electrode having a through-hole serving as the other capacitive electrode is opposed to the diaphragm serving as one capacitive electrode, and is in contact with one surface of the diaphragm through the through-hole and communicating with the first acoustic terminal. A pair of bidirectional microphones in which a second acoustic space is formed, in which a second acoustic space is formed, in which one acoustic space is formed and is in contact with the other surface of the diaphragm and communicates with a second acoustic terminal. An omnidirectional microphone in which terminals are coupled so as to communicate with each other, and each of the communicated second acoustic spaces is a single damping space common to both diaphragms. Each of the bidirectional microphones has a circuit board on which a circuit element for detecting a capacitive voltage formed on the capacitive electrode is mounted on the first acoustic space side,
The omnidirectional microphone according to claim 1, wherein the first acoustic terminal is formed on the circuit board.   3. Each of the bidirectional microphones has a unique casing, and both end faces of the casings are in contact with each other, and the second acoustic terminals are coupled to communicate with each other. Omnidirectional microphone. In the center of the casing, a pair of diaphragms that serve as one capacitive electrode are arranged opposite to each other across a common damping space,
In the individual acoustic space that is in contact with the diaphragm on the opposite side to the damping space, a back electrode that becomes the other capacitive electrode is disposed opposite to the diaphragm,
A circuit board is disposed opposite to each of the back electrodes across the individual acoustic space,
Each of the back electrodes is formed with a communication hole communicating with the front and back.
An omnidirectional microphone in which an acoustic terminal communicating with the front and back is formed on each circuit board.

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