JPS59200599A - Electroacoustic transducer - Google Patents

Abstract

PURPOSE:To obtain a signal for accurate stereophonic sound recording with a small number of components by forming a back cavity and a control resistance constituting an acoustic circuit in common with regard to plural unidirectional microphone units. CONSTITUTION:A microphone 20 is equipped with the unidirectional microphone units 20L and 20R on the left and right. The 2nd acoustic circuits is provided between the back surfaces of those units 20R and 20L. Namely, the back cavity 45 is formed in the housing which connects the units 20R and 20L together, and acoustic holes 46 of the cavity 45 are covered with the 1st damping body 47. The cavity 45 is further packed and disposed with the 2nd damping body 48. The units 20R and 20L, therefore, has the common acoustic circuit and the units 20R and 20L for both channels of the pair microphone 20 have nearly the same directional characteristics.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an electroacoustic transducer used, for example, in stereo recording, and particularly to each acoustic transducer unit (hereinafter referred to as a "microphone unit") constituting this device.
(2) A second acoustic circuit, which is provided on the back side of the diaphragm and determines the directional characteristics of each unit, is commonly formed.

[Background technology and its problems]

In general, sound waves from a sound source cause the entire diaphragm (vibrating body) to vibrate, and this vibration can be used to move, for example, a voice coil in a magnetic field, or to change the capacitance between the diaphragm and a fixed pole. An electroacoustic transducer (hereinafter referred to as a "microbon") that converts the mechanical vibration caused by the sound wave into an electrical signal is known.

As a microphone having the above-mentioned functions, there is a unidirectional microphone that has particularly high sensitivity in the front direction of the microphone.

FIG. 1 is a cross-sectional view of a main part showing an example of a microphone unit 1 of a so-called dynamic type unidirectional microphone. On the front side of this microphone unit 1, there is a diaphragm 3 that can freely vibrate with respect to a plate 2. installed. A voice coil 4 is integrally attached to the inside of the diaphragm 3 so that it can vibrate as the diaphragm 3 vibrates due to the sound waves from the sound source.

On the other hand, as shown in the figure, a magnet 6 is attached to the bottom surface of a yoke 5 having an opening-shaped cross section and forming a magnetic path of the microphone unit 1. This magnet 6 generates a predetermined magnetic field in a gap 15 between the inner peripheral surface of the plate 2 and a pole piece 7 attached to the tip of the magnet 6. The pole piece 7 is located inside the voice coil 4.

In the unit 1 configured as described above, when a sound wave from a sound source is transmitted, the @recording die 77 ram 3 vibrates according to the sound level of the sound wave. Accordingly, the voice coil 4 vibrates within the gap 15 where a magnetic field is generated by the magnet 6. Therefore, an induced electromotive force is generated in the voice coil 4 according to the strength of vibration, and the sound wave is converted into an electrical signal.

Further, on the back side of the microphone unit 1, there are a bank cavity 8, braking resistors 9, 10, and acoustic holes 11, 12.
．． A so-called second acoustic circuit composed of 13 and the like is provided. That is, the acoustic hole 1 is formed in the side wall of the yoke 5.
1 is formed through the braking resistor 9.
covered with. This braking resistor 9 is what is called a directional resistor, and the resistance value of this resistor 9 is a factor that mainly determines the directivity of the microphone 1. is communicated with the inside of the recess 5. And these acoustic holes 12.13
is covered with a braking resistor 10.

This braking resistor 10 is what is called a damper resistor, and has the function of regulating excessive vibration of the diaphragm 3.

Further, a back cavity S is formed inside the yoke 5 on the back side of the diaphragm 3 and inside the housing 14.

A second acoustic circuit constituted by the braking resistors 9, 10, acoustic holes 11, 12, 13, and pack cavity 8,
This circuit as a whole regulates the amount of vibration of the diaphragm 3 according to the positional relationship between the microphone and the sound source.

That is, when the sound source shifts vertically or horizontally from the front side of the microphone unit 1, the amount of vibration of the diaphragm 3 is regulated according to the amount of shift, and the electrical signal output from the voice coil 4 is controlled. Lower the signal level (output power).

Thereby, this type of unidirectional microphone can obtain high sensitivity in the front direction.

The directional characteristics of the unidirectional microphone unit 1 as described above are determined by the volume of the bank cavity 8 constituting the second acoustic circuit, the size and number of the acoustic holes 11, 12, 13, and the braking resistors 9, 10. Determined by resistance value etc.

That is, when the volume of the bank cavity 8 changes, the resonance frequency of this acoustic circuit changes, and the acoustic holes 11, 12, 13
When the size of the diaphragm 3 is changed, the band of sound waves supplied into the acoustic circuit through the holes 11, 12, and 13 changes, and these changes change the amount of regulation of the amount of vibration of the diaphragm 3.

By the way, when performing stereo recording, it is generally known to use a plurality of unidirectional microphone units 1 as described above. For example, when performing two-channel stereo recording, unidirectional microphone units IR and IL't are used.
Two microphone units are arranged, and one microphone unit 1R
- Obtain the sound information of the channel (right channel), and also obtain the sound information of the LhLO channel (left channel) to the other microphone unit IL.

As this type of device, those shown in FIGS. 2 to 4 are known.

That is, in the case shown in Fig. 2, the rear surfaces of the microphone units IR and IL are arranged so as to face each other, and in the case shown in Fig. 3, the IR and IL are arranged at a predetermined angle with each other. It is arranged like this. Furthermore, in the case shown in FIG. 4, the sides of each unit (IR and IL) are arranged in a workpiece facing each other.

In order to perform accurate stereo recording with this type of device, the directional characteristics of the microphone units (IR and IL) must be the same. However, in the conventional devices shown in Figures 2 to 4, Because independent unidirectional microphone units IR and IL were used, the directional characteristics of the microphone unit IR for the R channel and the microphone unit IL for the L channel were different, making accurate stereo recording difficult. The disadvantage was that it was not possible to obtain a signal for In addition, acoustic holes 11, 12.1 constituting each second acoustic circuit for each unit IR, IL.
3 and the braking resistances 9 and 10, and this adjustment is not easy. In particular, in the case of the one shown in Fig. 4, the distance from the sound source of each microphone IR and IL Since the sound pressure levels at the IR and IL edges of each microphone unit are different, it is also impossible to obtain an accurate signal for stereo recording.

[Purpose of the invention]

The present invention was made in view of the above-mentioned circumstances,
In particular, for multiple unidirectional microphone units used for stereo recording, by sharing the second acoustic circuit that determines the directional characteristics of these microphone units, it is possible to obtain accurate signals for stereo recording. It is an object of the present invention to provide an electroacoustic transducer that can perform the electroacoustic transducer, and to reduce the number of parts of the electroacoustic transducer to reduce costs.

[Summary of the invention]

The gist of the present invention is to form a back cavity and a braking resistor that constitute all the acoustic circuits of a plurality of acoustic conversion units in order to achieve the above object.

〔Example〕

Hereinafter, preferred embodiments of the present invention will be described in FIGS. 5 to 11.
This will be explained in detail using figures.

Note that this embodiment uses a dynamic type pair microphone 2.
0 to which the present invention is applied.

First, FIG. 5 and FIG. 6 are diagrams showing the first embodiment, respectively, and the microphone 20 has unidirectional microphone units 20 L and R channel on the left and right.
It is equipped with a unidirectional 7-channel microphone unit 20R.

That is, the microphone units 20L and 20R are arranged so that their back sides face each other, and the front direction of each unit and unit 20R and 20L is orthogonal to the square direction of the microphone 20.

Further, on the front side of each of these microphone units 20R920L, high frequency compensation plates 23.
24 is installed. And these high frequency compensation plates 2
A plurality of high frequency compensation holes 25, 25, .
27. Note that the high-frequency compensation plates 26 and 27 compensate for the high-frequency components of the microphone output and expand the usable frequency band of the microphone 20.

That is, an acoustic circuit is constructed on the front side of the diaphragms 26 and 27 inside the high-frequency compensation plates 26 and 27, and the high-frequency components of the rainbow microphone output are fully compensated for in this acoustic circuit.

The diaphragm 26 and 27 above are diaphragm rings 28
．． It is attached to the plates 21 and 22 via 29 so as to be able to vibrate freely. And this diaphragm 26
, 27, voice coils 31, 32 are integrally attached.

In addition, magnets 35, 36 are protruding from the center of the yokes 33, 34 forming the magnetic path, as shown in FIG. The magnets 35 and 36 are used to generate a magnetic field inside the microphone units 2OR and 20L.

Further, pole pieces 237 and 38 are attached to the tips of the magnets 35 and 36, respectively.

The voice coils 31 and 32 are connected to this pole piece 37.
gap 39. between 38 and said plate 21.22.
40.

On the other hand, a second acoustic circuit is provided between the back surfaces of each of the microphone units 20R and 2OL.

That is, a back cavity 45 is formed within the outer casing that connects the microphone unit 20R220L, and this cavity 45 has a plurality of acoustic holes 46, 46,
...Communicates with the outside world. Then, the acoustic hole 4
6, 46... is the first braking body (directional resistance) 4 from the outside
A second damper (damper resistor) 48 made of a synthetic resin material such as urethane is filled in the cavity 45 covered by the reference numeral 7. Note that this second braking body 48 is for each unit) 20R.

It has a function to prevent mutual interference of 20L.

A plurality of acoustic holes 49 are conventionally formed on the back side of each of the yokes 33 and 34, and the second acoustic holes 49 as described above are
The sound waves supplied through the acoustic circuit are transmitted through these acoustic holes 49.
．． O reaches the diaphragm 26, 27 from the inside (back side) via the The sound waves from the above reach the diaphragms 26, 27 from the outside (front side) of each microphone unit 20R, 20L via the high frequency compensation holes 25, 25, . . . 46..., 49... from the inside (back side) of the microphone units 20R, 20L to reach the diaphragms 26, 27.

Then, as the sound source S is shifted from the front of each microphone unit 20R, 2OL, the second acoustic circuit changes the sound wave St- that reaches the diaphragms 26, 27 from the front side to the sound wave S2 that reaches the diaphragm 26, 27 from the back side.
This sound wave S2 is controlled so as to cancel the noise.

Therefore, the sound source S is each microphone unit 20R,
The closer it is to the front of the 20L, the more this microphone unit 2
The output level (voltage level) of 0R and 20L is not high.
The farther the sound source S is from the front of the microphone units 20R, 20L, the more the microphone units 20R, 20
The output level of L is small and has high sensitivity to the front of each microphone unit 20R920L.

In addition, as mentioned above, the microphone units 20R and 11-R channel of this pair of microphones 20 are connected to each other.
The channel microphone units 20L have a common second acoustic circuit.

Therefore, as shown in FIG. 7, there are two microphones for each channel of this pair of microphones 20:
The directional characteristics of 20L are approximately the same.

In addition, FIG. 7 shows each microphone unit 20R920 of the pair microphone 20 when the sound source S has a frequency of 1 [KH7l:l and a distance of 5o [imaginary, :l] from the microphone 20.
It is a directional characteristic diagram showing the directional characteristic of L.

Furthermore, the microphone according to the present invention is not limited to the above-mentioned microphone 20, for example, the microphones shown in FIGS.
It may be configured as shown in the figure.

That is, FIG. 9 shows a case in which the volume of the back cavity 45 in the above embodiment is increased, and FIG. 10 shows a case in which the acoustic holes 46, 46, . is also placed on the front side of the pair microphone 20.

In addition, FIG. 11 shows each microphone unit 20R, 20
L and K are arranged so as to form a predetermined angle with each other, for example, a 90 degree angle, and the effects of the present invention can naturally be achieved in each case as well.

Further, in this embodiment, the back cavity 45 has a second
By filling and arranging the brake bodies 48, it is possible to prevent the sound wave S1 supplied from the front of one speaker unit 20R or 20L from adversely affecting the output of the other speaker unit 20L or 20R. .

That is, as shown by the dotted line in FIG.
Especially when there is no brake member 48, the microphone unit 20L for the L channel is
The frequency of the sound source is between 200 (Hz) and 500 [:H
z), a high level signal is output, and the unidirectionality deteriorates. On the other hand, cavity 45
When the second control body 48 fills the peak, the above-mentioned peak can be suppressed as shown by the solid line in FIG. 8, without adversely affecting the directivity characteristics of the microphone units 20R and 20L.

Note that FIG. 8 is a diagram showing the response frequency characteristics according to the position of the sound source of the paired microphone 20 of this embodiment.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view of the main parts of a dynamic unidirectional microphone unit, Figure 2 is a schematic diagram of a microphone used for stereo recording, Figure 3 is a schematic diagram of another microphone, and Figure 4 is the same. FIG. 3 is a schematic diagram of another microphone. FIG. 5 is a schematic perspective view of a dynamic pair microphone according to the present invention, and FIG. 6 is a Vl-Vl diagram in FIG.
7 is a directional characteristic diagram of the pair of microphones in FIG. 5, and FIG. 8 is a response frequency characteristic diagram. FIG. 9 is a diagram showing another embodiment according to the present invention.
Figure 9A is a top view, and Figure 9B is a sectional view. 10 is a diagram similarly showing another embodiment, FIG. 10A is a side view, and FIG. 10B is a sectional view. FIG. 11 shows another embodiment, in which FIG. 11A is a side view and FIG. 11B is a sectional view. 20...Hair microphone 20R...Microphone unit for right channel 20L...Microphone unit for left e channel 45...Bank cavity 46.49...Acoustic hole 1F, one 4147 ...3 Impulse resistance 48...Second braking body patent applicant Sony Corporation representative Patent attorney Mr. Koike

Claims (1)

[Claims] An electroacoustic transducer device characterized in that bank cavities and braking resistors constituting acoustic circuits of a plurality of acoustic transducer units are formed in common.