JP4073093B2 - Condenser microphone - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a condenser microphone, and more particularly, to a variable directivity condenser microphone in which a pair of subunits are combined to form a double-sided type.
[0002]
[Prior art]
The double-sided condenser microphone is a microphone in which a fixed electrode and a diaphragm are respectively arranged on the front acoustic terminal side and the rear acoustic terminal side in a unit housing having a front acoustic terminal and a rear acoustic terminal. By changing the directivity, the directivity can be continuously varied from omnidirectional to unidirectional through unidirectional.
[0003]
In this condenser microphone, the inside of the unit housing is surrounded by the front and rear diaphragms. Therefore, when a pressure difference occurs between the inside of the unit and the outside of the unit, the diaphragm is displaced according to the pressure difference. , It will deviate from the position where it should originally be.
[0004]
That is, when the external air pressure is higher than the air pressure inside the unit, the diaphragm is displaced to the inside of the unit, and depending on the situation, it contacts the fixed pole. Conversely, if the pressure inside the unit is higher than the pressure outside the unit, the diaphragm swells like a balloon and may be broken in extreme cases.
[0005]
In order to prevent this, it is necessary to make the inside of the unit and the outside of the unit pressure equivalent. There are various methods for this, but generally a hole is made in the diaphragm.
[0006]
Since the double-sided microphone unit has variable directivity, the tension of the diaphragm is generally set low. Therefore, even if the hole is opened, the entire diaphragm is not broken. Incidentally, perforation of the diaphragm is performed by spark discharge or the like.
[0007]
[Problems to be solved by the invention]
However, when the temperature and humidity change suddenly and condensation occurs on the surface of the diaphragm, the water droplets enter the unit through the hole, causing the diaphragm and the fixed electrode to be electrically short-circuited, generating noise, Depending on the situation, the sound cannot be picked up. For example, such a situation occurs when a microphone that is in a cold state is used in such a way as to directly take a breath.
[0008]
The present invention has been made to solve such problems, and an object of the present invention is to provide a condenser microphone in which the inside of the unit and the outside of the unit can be made pressure equivalent without making a hole in the diaphragm. Is to provide.
[0009]
[Means for Solving the Problems]
To achieve the above object, the present invention provides a counter-arranged diaphragm and the fixed pole with a predetermined interval, it is arranged so as to secure a predetermined sound volume chamber on the back side of the fixed electrode, on the bottom A relay ring including a pair of subunits each including an insulating seat having an opening covered with a first acoustic resistance material, the insulating seats being back to back so that the acoustic volume chambers communicate with each other through the opening. In the condenser microphone that is integrally combined with each other, a second sound made of a sheet material having a donut-like elasticity that is disposed concentrically with respect to the opening is provided between the insulating seats of the subunits. resistance material is disposed, said acoustic volume chamber of each subunit is characterized by being vented to atmosphere through the second acoustic resistance material and the relay ring.
[0010]
According to the present invention, the second acoustic resistance member is Ri Do donut-shaped sheet material which is arranged concentrically with respect to the opening, since the air leakage path is radially thin its thickness However, a sufficient acoustic resistance value can be obtained, and there is no problem such as when a gap is generated between the insulating seats and air leaks.
[0011]
Further, by the second acoustic resistance member has a bullet power resistance, can absorb such backlash between the subunits at the set elevation. In addition, a nonwoven fabric is preferably employ | adopted for the said 2nd acoustic resistance material.
[0012]
According to the present invention, the inside of the unit and the outside of the unit are connected to each other through a path in the acoustic resistance material, and the pressure is equivalent, but the path connecting the pressure difference inside and outside the unit is the same as viewed from each subunit, It is also one of the features of the present invention that the difference in the directivity frequency response of the subunits is difficult to occur.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
The invention will now be described in more detail on the basis of the embodiments shown in the drawings.
[0014]
This double-sided condenser microphone includes a microphone unit 1 shown in the sectional view of FIG. The microphone unit 1 includes two subunits 2A and 2B.
[0015]
Since the subunits 2A and 2B have the same configuration, only one subunit 2A will be described here, and the other subunit 2B will be described by adding b to the end of the reference numeral of the same part. .
[0016]
The subunit 2A includes a cover plate 20a having a front acoustic terminal hole 21a (a rear acoustic terminal hole 21b on the subunit 2B side). In this embodiment, a diaphragm 30a is stretched over the cover plate 20a. Has been. A signal extraction electrode 22a is implanted in the cover plate 20a.
[0017]
A fixed pole 40a is disposed so as to face the diaphragm 30a. Although not shown in detail, a spacer ring is interposed between the diaphragm 30a and the fixed pole 40a, whereby a gap is provided between the diaphragm 30a and the fixed pole 40a. According to FIG. 1, only one hole 41 a is shown in the fixed pole 40 a, but a large number of holes are actually drilled.
[0018]
An insulating seat 50a is disposed on the back side of the fixed pole 40a. The insulating seat 50a is formed of a dish-shaped disk body having a shallow bottom, and a predetermined acoustic volume chamber 51a is secured on the back side of the fixed pole 40a. An opening 52a is provided at the center of the bottom of the insulating seat 50a. On both surfaces of the opening 52a, that is, on the inner surface side and the outer surface side of the insulating seat 50a, acoustic resistance materials 61a and 62a made of, for example, a felt material are stretched.
[0019]
A male screw 53a is formed on the outer peripheral wall of the insulating seat 50a. The subunit 2A includes a lock ring 70a for fixing the cover plate 20a and the fixed pole 40a to the insulating seat 50a. That is, the lock ring 70a has a female screw 71a that is screwed into the male screw 53a of the insulating seat 50a, and the cover plate 20a and the fixed electrode 40a are insulated by tightening the lock ring 70a on the cover plate 20a. It is fixed to the seat 50a.
[0020]
Each of the subunits 2A and 2B is disposed so as to face each other with their insulating seats 50a and 50b back to back, and is integrated with a relay ring 80 that is screwed over the male screws 53a and 53b of the respective insulating seats 50a and 50b. Assembled into.
[0021]
In this way, the double-sided microphone unit 1 in which the acoustic volume chambers 51a and 51b of the subunits 2A and 2B communicate with each other via the openings 52a and 52b is obtained. An acoustic resistance material 90 is disposed between 50a and 50b, and the acoustic volume chambers 51a and 51b of the subunits 2A and 2B are communicated with the outside of the unit through the acoustic resistance material 90.
[0022]
The subunits 2A and 2B are connected by the relay ring 80, but the screw portion is not airtight, so that the inside and the outside of the microphone unit 1 are connected via the acoustic resistance material 90 and the screw portion of the relay ring 80. Ventilation state and pressure equivalent.
[0023]
In this embodiment, the acoustic resistance material 90 comprises a donut-shaped sheet 91 as shown in the plan view of FIG. 2A and the cross-sectional view of FIG. 2B, and is concentric with the openings 52a and 52b. Arranged in a shape. The material is preferably a non-woven fabric.
[0024]
In this way, the inside of the microphone unit 1 and the outside of the unit are connected by acoustic resistance along the radial direction of the donut-shaped sheet 91. Therefore, even if the thickness is small, a sufficient acoustic resistance value can be obtained, and there is no problem such as when a gap is generated between the insulating seats 50a and 50b and air leaks.
[0025]
In addition, since the acoustic resistance material 90 has a slight elasticity, rattling when the subunits 2A and 2B are combined is absorbed. Furthermore, since the acoustic resistance material 90 is common to the subunits 2A and 2B, that is, the air leakage path is the same, there is an advantage that it is difficult to make a difference in the directivity frequency response of the subunits 2A and 2B.
[0026]
For reference, FIG. 3 shows a mechanical equivalent circuit of the microphone unit 1. In this mechanical equivalent circuit, PS is a sound source for the front acoustic terminal hole 21a of the microphone unit 1, and is represented by the product PS of the sound pressure P and the effective area S of the diaphragms 30a and 30b. PSe −jkdcos ^θ is a rear sound source for the rear acoustic terminal hole 21 b of the microphone unit 1. Here, k is the distance between the front sound source and the rear acoustic terminal hole 21b, and d is the distance between the acoustic terminals between the front acoustic terminal and the rear acoustic terminal.
[0027]
s0 is the air stiffness existing in front of the diaphragms 30a and 30b, m0 is the mass of the diaphragms 30a and 30b, and these are the impedances of the diaphragms 30a and 30b. r0 is a braking resistance (impedance) due to a thin air layer between the diaphragms 30a, 30b and the fixed poles 40a, 40b.
[0028]
Further, s1 is air stiffness existing in the acoustic volume chambers 51a and 51b, s2 is air stiffness existing in the openings 52a and 52b, s3 is air stiffness existing between the acoustic resistance materials 62a and 62b, and each r is an acoustic resistance material 61a. , 61b, 62a, 62b.
[0029]
According to the present invention, the acoustic resistance r1 by the acoustic resistance material 90 and the new side sound source PS- ^{jkd / 2cosθ} are connected in parallel to the air stiffness s3 existing between the acoustic resistance materials 62a and 62b. However, since the acoustic resistance r1 is extremely large, the side sound source PS- ^{jkd / 2cos θ} can be ignored.
[0030]
That is, the sound wave does not enter the microphone unit 1 from the outside through the portion of the acoustic resistance material 90. In addition, it will be understood that the acoustic resistance r1 of the acoustic resistance material 90 acts on the subunits 2A and 2B in common by this mechanical equivalent circuit.
[0031]
【The invention's effect】
As described above, according to the present invention, the diaphragm and the fixed pole that are opposed to each other at a predetermined interval, and the predetermined acoustic volume chamber are provided on the back side of the fixed pole, and the bottom portion Including a pair of subunits comprising an insulating seat having an opening covered with a first acoustic resistance material, and relaying the insulating seats back to back so that the acoustic volume chambers communicate with each other through the opening. In a double-sided condenser microphone integrally combined through a ring, a donut-shaped elastic sheet material disposed concentrically with respect to the opening between the insulating seats of the subunits. a second acoustic resistance member disposed composed by the acoustic volume chamber of each subunit was to lead to the atmosphere through the second acoustic resistance material and the relay ring, Without opening a hole in motion plate, a unit inside and outside of the unit can be pressure equivalent.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an embodiment of a microphone unit used in a condenser microphone of the present invention.
FIG. 2 is a plan view and a sectional view showing an acoustic resistance material used in the embodiment.
FIG. 3 is a machine equivalent circuit of the embodiment.
[Explanation of symbols]
1 Microphone unit 2A, 2B Sub unit 20a, 20b Cover plate 21a Front acoustic terminal hole 21b Rear acoustic terminal hole 30a, 30b Diaphragm 40a, 40b Fixed pole 50a, 50b Insulating seat 51a, 51b Acoustic volume chamber 52a, 52b Opening 61a, 61b, 62a, 62b Acoustic resistance material 70a, 70b Lock ring 80 Relay ring 90 Acoustic resistance material

Claims (2)

Facing-arranged diaphragm and the fixed pole with a predetermined interval, are arranged so as to secure a predetermined sound volume chamber on the back side of the fixed electrode, an opening which is covered by the first acoustic resistance member on the bottom Condenser microphone comprising a pair of subunits each having an insulating seat and having the insulating seats back-to-back so that the acoustic volume chambers communicate with each other through the opening, and integrally combined via a relay ring In
Between the insulation cylinder of each subunit, the second acoustic resistance material made of a sheet material having a donut-shaped elastic that is concentrically arranged with respect to said opening are arranged, the acoustic of each subunit A condenser microphone, wherein the volume chamber communicates with the atmosphere through the second acoustic resistance material and the relay ring . The condenser microphone according to claim 1, wherein the acoustic resistance material is a nonwoven fabric.

Images