JPS6238700A - Condenser microphone - Google Patents

Abstract

PURPOSE:To improve the sensitivity over a wide band and S/N by providing a high-frequency microphone unit and a middle/low-frequency microphone unit and synthesizing outputs via a HPF and a LPF. CONSTITUTION:Two back electrodes are provided to a diaphragm, outputs of the back electrodes 1, 2 and back electrodes 12, 13 are extracted while being synthesized respectively. Then the sensitivity is improved by 6dB in comparison with the privision of one back electrode to one diaphragm. The outputs of the back electrodes 1, 2 and back electrodes 12, 13 are synthesized while being subtracted respectively, then even-order harmonic noises are canceled. The output of the high-frequency microphone unit obtained by synthesizing the outputs of the back electrodes 1, 2 and the output of the middle/low-frequency microphone unit obtained by synthesizing the output of the back electrodes 12, 13 are synthesized via the HPF and LPF respectively.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention relates to a condenser microphone,
In particular, it is concerned with widening the bandwidth of condenser microphones.

[Summary of the invention]

The present invention relates to a condenser microphone that includes a push-pull type microbond in charge of a first band, which is composed of a first diaphragm in the center and two electrodes disposed oppositely above and below the first diaphragm. A second microphone unit is placed around the microphone unit that handles this first band.
A push-pull type microphone unit in charge of the second band is provided, which is composed of a diaphragm and two electrodes arranged opposite to each other above and below the second diaphragm. By making the diaphragms substantially flush, sufficient output can be obtained over a wide band, and noise characteristics can be improved.

[Conventional technology]

In order to widen the microphone band, it is necessary to increase the damping of the diaphragm. However, when the damping of the diaphragm is increased, the sensitivity decreases.

For this reason, with conventional microphones that use a single diaphragm to cover both high and low frequencies, it has not been possible to obtain sufficient sensitivity over a wide range.

Therefore, for example, as shown in the specification of Utility Model Application No. 59-60512, two microphone units, a high-frequency microphone unit and a mid-low frequency microphone unit, are provided, and the outputs of these microphone units are combined. However, it depicts a microphone that is able to obtain sufficient sensitivity over a wide band.

[Problem that the invention seeks to solve]

However, when the high-frequency microphone unit and the mid-low-frequency microphone unit are arranged in this way, if the high-frequency microphone unit and the low-mid-frequency microphone unit are located far apart, the microphone unit for the high frequency range may be reached. There is a problem in that there is a difference in arrival time between the sound reaching the mid-low range microphone unit and the sound reaching the mid-low range microphone unit, resulting in disturbances in the characteristics.

In other words, as shown in FIG. 5, when sounds A1 and A2 from the same sound source are obliquely incident on the high frequency microphone unit 51 and the mid-low frequency microphone unit node 52, the high frequency microphone unit 51 The time for sound AI to arrive at the mid-low range microphone unit 52
2, there is a difference in arrival time corresponding to the distance d. This distance d is the distance between the high frequency microphone unit 51 and the mid-low frequency microphone unit 52! , where θ is the incident angle of the sound source, d=β·sin θ. When the wavelength λ of the sounds A1 and A2 from the sound source is λ=2d, the phase of the sound AI reaching the high-frequency microphone unit 51 and the phase of the sound A2 reaching the mid-low frequency microphone unit 52 are shifted by 180 degrees. It turns out. The phases of the sounds A1 and A2 reaching the high-frequency microphone unit 51 and the mid-low frequency microphone unit 52 are 1 with respect to each other.
An 80 degree shift will result in a large attenuation of the output.

As an example, if the distance β is 34 mm, the angle θ is 90 mm.
The frequency r at which attenuation occurs is f=c/λ=c/21=340/2X34X0.001=5000Hz, where C is the speed of sound. Therefore, the 90 degree characteristic has a crossover frequency of 5K.
When close to Hz, a large attenuation occurs at 5KHz.

Therefore, an object of the present invention is to provide a condenser microphone that can obtain sufficient sensitivity over a wide band.

Another object of the present invention is to provide a condenser microphone whose characteristics are not disturbed by sounds from any angle.

Still another object of the present invention is to provide a condenser microphone with improved S/N ratio and good sensitivity.

[Means for solving problems]

This invention arranges a first vibration 4Fi, 3 in charge of the first band in the center, and arranges first and second electrodes 1.2 facing each other above and below the first diaphragm 3, First and second electrodes1. A second diaphragm 14 in charge of the second band is attached to the first diaphragm 3 on the same surface as the first diaphragm 3 and a surface in the vicinity thereof.
The third and fourth electrodes 12 and 13 are arranged to face each other above and below the second diaphragm 14,
This is a condenser microphone in which the outputs of the second band and the fourth electrode 12, 13 are combined to extract the output of the second band.

[Effect]

Back electrodes 1 and 2 are arranged oppositely above and below the first diaphragm 3, and the diaphragm 3 and the back electrodes 1 and 2 constitute a high frequency microphone unit.

Outputs having mutually opposite phases are taken out from the back electrodes 1 and 2. By subtracting the outputs of back electrodes 1 and 2 from each other, the output of the high frequency microphone unit is extracted.

Back electrodes 12 and 13 are arranged oppositely above and below the second diaphragm I4, and the diaphragm 14 and the back electrodes 12 and 13 constitute a mid-low frequency microphone unit. Back electrode 1
Outputs having mutually opposite phases are taken out from 2 and 13. By subtracting the outputs of the back electrodes 12 and 13 from each other, the output of the high frequency microphone unit is extracted.

The second diaphragm 14 is arranged around the first diaphragm 3.
l. The first diaphragm 3 and the second diaphragm 14 are on the same plane. Therefore, no phase difference occurs between the sound reaching the first diaphragm 3 and the sound reaching the second diaphragm 14.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of the present invention, and in FIG.
and 2 is a disk-shaped back electrode formed, for example, by metal vapor deposition on the surface of a synthetic resin, and 3 is a disk-shaped diaphragm formed, for example, from a thin metal plate. These back electrodes 1 and 2 and the diaphragm 3 constitute a high frequency microphone UNISO.

The metal mounting surfaces of the back electrodes 1 and 2 are opposed to each other, and the diaphragm 3 is disposed between the back electrodes 1 and 2, which are opposed to each other.

The back electrodes 1 and 2 and the diaphragm 3 are insulated, and capacitances are formed between the back electrode 1 and the diaphragm 3 and between the back electrode 2 and the diaphragm 3, respectively.

A plurality of holes 4 are bored in the back electrode 1 . A terminal 5 is attached to the center of the back electrode 1. This terminal 5 is electrically connected to the metal-deposited surface of the back electrode 1, and the output of the back electrode 1 is derived from this terminal 5. A plurality of holes 6 are bored in the back electrode 2 . Back pole 2
A terminal 7 is attached to the center of the. This end 7 is connected to the metal vapor deposited surface of the back electrode 2 by 5JLA, and from this terminal 7 to the back electrode 2
The output of is derived.

A metal case 8 is attached around the back electrode 1.2 and the diaphragm 3. This case 8 and the diaphragm 3 are electrically connected. Furthermore, a cavity case 9 is provided at the bottom of the back electrode 2.
is fixed.

A plurality of holes IO are bored in the cavity case 9. These holes 10 are formed by the resistor plate 11 with a distance of several tens of μm.
It is closed so that a gap of m is formed.

The gap formed between the perforation 10 and the resistor plate 11 forms an acoustic resistance, thereby adjusting the directivity and sensitivity.

Reference numerals 12 and 13 are ring-shaped back electrodes formed by, for example, depositing metal on the surface of a synthetic resin, and 14 is a ring-shaped diaphragm formed of, for example, a thin metal plate. These back electrodes 12 and 13 and the diaphragm 14 constitute a mid-low range microphone unit.

The metal-deposited surfaces of back electrodes 12 and 13 are opposed to each other, and this back electrode 1
A diaphragm 14 is arranged between the diaphragms 2 and 13 facing each other so as to be on the same plane as the diaphragm 3 of the high frequency microphone unit. The back electrodes 12 and 13 and the diaphragm 14 are insulated, and capacitances are formed between the back electrode 12 and the diaphragm 14 and between the back electrode 13 and the diaphragm 14, respectively.

What about back electrode 12? ! Several holes 15 are drilled. Further, a plurality of holes 16 are bored in the back electrode 13 . Although not shown, lead wires are soldered to one ends of the metal-deposited surfaces of the back electrodes 13 and 14, respectively, and the outputs of the back electrodes 13 and 14 are derived from these lead wires.

A metal case 17 is attached around these back electrodes 12, 13 and diaphragm 14. This nozzle 17 and the diaphragm 14 are electrically connected. Further, a cavity case 18 is fixed to the lower part of the back electrode 13.

A plurality of holes 19 are bored in the cavity case 18 .

These holes 19 are formed by the resistor plate 20 by several tens of μm.
is closed so that a void is created.

The gap formed between the hole 19 and the resistor plate 20 forms acoustic resistance, thereby adjusting the directivity and sensitivity.

The outputs of the high frequency microphone unit are taken out from terminals 5 and 7 led out from the back electrodes 1 and 2 of the high frequency microphone unit in opposite phases.

By subtracting these outputs, the combined output of back electrodes 1 and 2 is obtained. Outputs of the mid-low range microphone unit are taken out in opposite phases from respective lead wires (not shown) derived from the back electrodes 12 and 13 of the mid-low range microphone unit.

By subtracting these outputs, back electrodes 12 and 13
The composite output is obtained.

In this way, two back electrodes are provided for one diaphragm,
By combining and extracting the outputs of the back electrodes 1 and 2 and the outputs of the back electrodes 12 and 13, the sensitivity increases by 6 dB compared to the case where one back electrode is provided for one diaphragm. At the same time, since the outputs of the back electrodes 1 and 2 and the outputs of the back electrodes 12 and 13 are subtracted and combined, even-order noise is canceled.

In this way, the output of the high-frequency microphone unit obtained by combining the outputs of back electrodes 1 and 2, the mid-low frequency microphone unit obtained by combining the outputs of back electrodes 12 and 13, and the The outputs of the two are combined via a high-pass filter and a low-pass filter, respectively. As a result, as shown in FIG. 2, sufficient sensitivity can be obtained over a wide range from low to high frequencies. However, since the diaphragm 14 of the mid-low range microphone unit is arranged on the same surface around the diaphragm 3 of the high range microphone unit, the sound reaching the high range microphone unit and the mid-low range microphone unit are different from each other. There is no phase difference between the sound reaching the microphone unit.

In the above-mentioned embodiment, the microphone unit consisting of the diaphragm 3 provided at the center was used for high frequencies, and the microphone unit consisting of the diaphragm 14 provided at the periphery was used for mid-low frequencies. The microphone unit in the middle part may be used for medium and low frequencies, and the microphone unit in the peripheral part may be used for high frequencies.

Furthermore, microphone units in charge of other bands may be arranged around the microphone unit made up of the diaphragm 12.

〔Effect of the invention〕

According to this invention, since a high-frequency microphone unit and a middle-low frequency microphone unit are provided, sufficient sensitivity can be obtained over a wide band. Of course,
The diaphragm 14 of the mid-low range microphone unit is arranged around the diaphragm 3 of the high range microphone unit, and the diaphragm 3 of the high range microphone unit and the diaphragm 14 of the mid-low range microphone unit are on the same surface. Since the two diaphragms 3.14 are placed above each other, there is no phase difference between the sounds reaching the two diaphragms 3.14, and the characteristics of the sounds from any angle are not disturbed. Furthermore, back electrodes 1 are placed above and below the diaphragm 3.
and 2 are arranged, and back electrodes 12 and 1 are arranged above and below the diaphragm 14.
3 is arranged, the output of the high-frequency microphone unit is obtained by combining the outputs of the back electrodes I and 2, and the output of the mid-low frequency microphone unit is obtained by combining the outputs of the back electrodes 12 and 13. I have to. Therefore, sensitivity is increased, even-order noise is removed, and the S/N ratio is improved.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of an embodiment of the present invention, FIG. 2 is a frequency characteristic diagram used to explain the embodiment of the invention, and FIG. 3 is a route diagram used to explain a conventional microphone. Explanation of main symbols in the drawings 1.2.12.13: Back electrode, 3, 14: Vibration plate. Agent Patent Attorney Tadashi Sugiura Tomo-1 Jida 1 Fig. 1 44 GoEL Tokuko Takeji Neyyo Raiida + 14 da + Hino 3F Fig. 2 3
Figure (1) 明釧傳巾, 箪, 3 Wataru Chiku 14〒, ``Fukihiro 1'' ``Blowing out tya procedural amendment document January 1985 IO Director General of the Patent Office Uga Michibe 1, Indication of the incident η. Patent Application No. 178428 of 1985 2. Title of the invention: Condenser microphone 3, relationship with the case of the person making the amendment Patent applicant address: 6-7-35, Kitashinyo, Tokyo Parts Co., Ltd. Name (2)
18) Sony Corporation Representative Director Norio Oga 4, Agent address: 420 Sankyo Building, 25-48-10 Higashiikebukuro, Toshima-ku, Tokyo (03) 980-03396.7 Details of the invention in the subject specification of the city official Correct the explanation to ``Darkness 7, 7iIi Positive Content''. (2) Ibid., page 1, line 10 and page 13, line 13, “
Correct "noise" to "high frequency distortion". that's all

Claims (1)

[Claims] A first diaphragm in charge of the first band is placed in the center,
First and second electrodes are arranged above and below the first diaphragm to face each other, and the outputs of the first and second electrodes are combined to extract the output of the first band, and A second diaphragm in charge of a second band is arranged on the same surface as the diaphragm and a surface in the vicinity thereof so as to surround the periphery of the first diaphragm, and a third diaphragm and a third diaphragm are arranged above and below the second diaphragm. A fourth electrode is placed facing each other, and the outputs of the third and fourth electrodes are combined to form a second electrode.
A condenser microphone that extracts output in the band.