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JPS59200599

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DESCRIPTION JPS59200599
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an
electroacoustic transducer used in, for example, stereo recording, and in particular, each acoustic
transducer unit (hereinafter referred to as "microphone unit") constituting this device is provided
on the back side of a diaphragm. And a second acoustic circuit for determining the directivity
characteristics of each unit is formed in common. [Background Art and Problems Thereof] In
general, a sound wave from a sound source causes all the diaphragm (vibration body) to vibrate
and this vibration causes, for example, a voice coil in a magnetic field to move or electrostatic
capacitance between the diaphragm and the fixed electrode An electro-acoustic transducer
(hereinafter referred to as "micro-bon") is known which converts mechanical vibration caused by
sound waves into electrical signals. As a microphone having the above-described function, there
is a unidirectional microphone having a particularly high sensitivity in the front direction of the
microphone. FIG. 1 is a cross-sectional view showing an example of a microphone unit 1 of a socalled dynamic type unidirectional microphone, and a diaphragm 3 capable of vibrating with
respect to a plate 2 on the front side of the microphone unit 1 is shown. It is attached. Further, a
voice coil 4 is integrally mounted in the unit inward direction of the diaphragm 3 so that it can
be vibrated along with the vibration of the diaphragm 3 by the sound wave from the voice
source. On the other hand, a magnet 6 is attached to the bottom surface of the yoke 5 having a
U-shaped cross section which constitutes the magnetic path of the microphone unit 1 as shown.
The magnet 6 generates a predetermined magnetic field in the gap 15 between the inner
peripheral surface of the plate 2 and the pole piece 7 attached to the tip of the magnet 6. The
pole piece 7 is positioned inside the voice coil 4. In the unit 1 configured as described above,
when the sound wave from the sound source is transmitted, the die 77 ram 3 vibrates according
to the sound level of the sound wave. Along with this, the voice coil 4 vibrates in the gap 15
where the magnetic field is generated by the magnet 6. Therefore, an induced electromotive
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force is generated in the voice coil 4 according to the strength of the vibration, and the sound
wave is converted into an electrical signal. Further, on the back side of the microphone unit 1,
there is provided a so-called second acoustic circuit composed of a bank cavity 8, braking
resistors 9 and 10, acoustic holes 11, 12 and 13 and the like. That is, an acoustic hole 11 is
formed through the side wall of the yoke 5, and the acoustic hole 11 is covered with a braking
resistor 9.
The damping resistance 9 is a so-called directional resistance, and the resistance value of the
resistance 9 mainly becomes a factor determining the directivity of the microphone 1 and the
housing 14 on the back side of the yoke 5. Are in communication with the inside of 5. And these
acoustic holes 12.13 are covered with the braking resistance 10. The braking resistance 10 is a
so-called damper resistance, and has a function of restricting excessive vibration of the diaclam 3
as a raw matter. In addition, a back cavity S is formed on the inner side of the yoke 5 on the back
side of the diaphragm 3 and the inner side of the housing 14. The second acoustic circuit
constituted by the braking resistors 9, 10, the acoustic holes 11, 12, 13 and the pack cavity 8
vibrates the diaphragm 3 according to the positional relationship between the microphone and
the sound source as the whole circuit. Regulate the amount. That is, when the sound source shifts
vertically and 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 Reduce the signal level (output power). Thereby, this kind of unidirectional
microphone can obtain high sensitivity in the front direction. The directivity characteristic of the
unidirectional microphone unit 1 as described above is determined by the volume of the bank
cavity 8 constituting the second acoustic circuit, the size and number of the acoustic holes 11, 12
and 13, and the damping resistances 9 and 10. Determined by resistance value etc. That is, when
the volume of the bank cavity 8 changes, the resonance frequency of the acoustic circuit
changes, and when the size of the acoustic hole 11.12.13 changes, the acoustic circuit is supplied
into the acoustic circuit through the hole 11.12.13. The band of the sound wave changes, and in
these changes, the regulation amount of the vibration amount of the diaphragm 3 changes. By
the way, in general, when performing stereo recording, it is known to use a plurality of
unidirectional microphone units 1 as described above. For example, when 2-channel stereo
recording is to be performed, two unidirectional microphone units IR and IL't are arranged in 4-,
and sound information of R channel (light channel) is obtained by one microphone unit 1R. The
other microphone unit IL obtains sound information of Lh LO channel (left channel). And as this
kind of thing, what is shown in FIG. 2 and FIG. 4 is known. That is, although the ones shown in
FIG. 2 are disposed such that the back surfaces of the microphone units IR and IL face each
other, those shown in FIG. 3 have the respective units IR and IL form a predetermined angle with
each other. It is arranged as follows.
Further, the one shown in FIG. 4 is disposed in such a manner that the side faces of the units IR
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and IL face each other. And in order to perform accurate stereo recording in this kind of thing,
the directivity characteristics of the above-mentioned microphone units IR and IL must be the
same. 0 However, in the prior art shown in FIGS. 2 to 4 Since the microphone units IR and IL of
an independent single directivity were used respectively, the directivity characteristics of the
microphone unit IR for R and channel and the microphone unit IL for L and channel differ and
accurate stereo recording can be performed. It has the disadvantage that it can not get a signal to
Also, the size of the acoustic holes 11, 12 and 13 constituting the second acoustic circuit and the
braking resistances 9, 10 have to be adjusted for each unit IR, IL, and this adjustment is not easy.
Particularly, in the case shown in FIG. 4, since the distances from the sound sources of the
microphones IR and IL are different from each other, the microphone units IR and IL have
different sound pressure levels from each other. I could not get the signal gold. SUMMARY OF
THE INVENTION The present invention has been made in view of the above-mentioned
circumstances, and in particular, with respect to a plurality of unidirectional microphone units
used for stereo recording, the directivity characteristics of the microphone units are determined.
(2) To provide an electroacoustic transducer capable of obtaining a signal for accurate stereo
recording by sharing an acoustic circuit, and to reduce the number of parts of the electroacoustic
transducer and to reduce the cost. Do. [Summary of the Invention] The present invention is
summarized in that a back cavity and a braking resistor which constitute the entire acoustic
circuit of a plurality of acoustic conversion units for achieving the above object are formed in
common. Preferred embodiments of the present invention will be described in detail with
reference to FIGS. 5 to 11. In the present embodiment, the present invention is applied to a
dynamic type paired microphone 20. First, FIGS. 5 and 6 are views showing the first
embodiment, respectively. The microphone 20 is a unidirectional microphone unit 20 L for L
channel and L microphone and L channel. A unidirectional 7-microphone unit 20R is provided.
That is, the microphone units 20L and 20R are disposed such that the back sides face each other,
and the front direction of each unit 20R and 20L is orthogonal to the square direction of the
microphone 20.
Further, high-frequency compensation plates 23.24 are attached to the plates 21 and 22,
respectively, in front of the microphone units 20R920L. Then, the high-frequency compensation
plate 23.24 is provided with a plurality of high-frequency compensation holes 25, 25 ...
respectively, and the sound waves emitted from the sound source are the high-frequency
compensation holes 25, 25 · · ·. The diaphragms 26. 27 are reached via... Note that the high
frequency compensation plates 26 and 27 compensate the high frequency components of the
microphone output to extend the use frequency band of the microphone 20. That is, an acoustic
circuit is formed on the front side of the diaphragms 26 and 27 inside the high-frequency
compensation plate 26.27, and this acoustic circuit compensates all the high-frequency 8components of the output of the digital microphone. The diaphragms 26 and 27 are attached
vibratably to the plates 21 and 22 through diaphragm rings 28 and 29 respectively. A voice coil
31.32 is integrally attached to the inside of the diaphragms 26 and 27. As shown in FIG. 6,
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magnets 35. 36 are disposed so as to project from the center of the yokes 33. 34 constituting the
magnetic path, as shown in FIG. The magnets 35. 36 are for generating a magnetic field inside
the microphone units 2OR, 20L. Further, pole tips 237 and 38 are attached to the tips of the
magnets 35. 36 respectively. The voice coil 31.32 is disposed in the gap 39.40 between the pole
piece 37.38 and the plate 21.22. On the other hand, a second acoustic circuit is provided
between the back surfaces of the microphone units 20R and 2OL. That is, a back cavity 45 is
formed in the mantle connecting the microphone unit 20R 220L, and this cavity 45 is
communicated with the outside through a plurality of acoustic holes 46, 46. The acoustic holes
46 are covered by the first damping member (directed resistance) 47 from the outside, and the
cavity 45 is made of, for example, a synthetic resin material such as urethane. The second
braking body (damper resistance) 48 formed is filled and disposed. In addition, this 2nd damping
| braking body 48 is each unit) 20R. It has a function to prevent mutual interference of 20L. And,
a plurality of acoustic holes 49 are conventionally formed on the back side of the respective
yokes 33, 34, and the sound waves supplied through the second acoustic circuit as described
above are the acoustic holes 49 of these. When the sound wave from the sound source S is
converted into an electrical signal by the paired microphone 20 configured as described above,
which reaches the diaphragm 26.27 from the inside (rear side) via the .49. The sound wave from
S reaches the diaphragm 26.27 from the outside (front side) of each of the microphone units
20R, 20L through the high-frequency compensation holes 25, 25 ... and the sound of the second
acoustic circuit The diaphragms 26, 27 reach the inside (rear side) of the microphone units 20R,
20L through the holes 46,.
In the second acoustic circuit, as the sound source S deviates from the front of each of the
microphone units 20R and 2OL, the sound wave St-reaching the diaphragms 26 and 27 from the
front side reaches the sound wave S2 reaching the diaphragm 26 27 from the back side. The
sound wave S2 is controlled to cancel out. Therefore, the output level (voltage level) of the
microphone units 20R and 20L is higher as the sound source S is in front of the microphone
units 20R and 20L, and the more the sound source S deviates from the front of the microphone
units 20R and 20L, The output levels of the microphone units 20R and 20L decrease and have
high sensitivity to the front of each of the microphone units 20R920L. Further, as described
above, the microphone unit 20R for the 11-R channel of the pair microphone 20 and the
microphone unit 20L for the L channel have the common second acoustic circuit. Therefore, as
shown in FIG. 7, the directivity characteristics of the two microphones 20R and 20L for each
channel of the paired microphones 20 become substantially the same. FIG. 7 is a directional
characteristic diagram showing the directional characteristics of the microphone units 20R920L
of the paired microphones 20 when the sound source S has a frequency 1 [KH 7 l: l and a
distance 5 o to the microphone 20 [Imaginary: l]. The microphone according to the present
invention is not limited to the microphone 20 as described above, and may be configured as
shown in FIGS. 9 to 11, for example. That is, FIG. 9 is an enlarged view of the volume of the back
cavity 45 in the above embodiment, and FIG. 10 is any one of the acoustic holes 46.degree. Are
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also disposed on the front side of the paired microphones 20. Further, FIG. 11 shows that the
microphone units 20R and 20Lk are arranged so as to form a predetermined angle, for example,
12 times of 90.degree. With each other, and the effects of the present invention can be naturally
achieved in these respective cases. It is possible. Further, in the present embodiment, the second
damping member 48 is filled and disposed in the back cavity 45, and the sound wave S1 supplied
from the front of one of the speaker units 20R or 20L is the other speaker unit 20L or 20R. It is
possible not to adversely affect the output. That is, as indicated by the one-dot broken line in FIG.
8, in the absence of the second braking body 48, although the sound source is in front of the R
channel microphone unit 20R, the L channel sound source is used. The microphone unit 20L
outputs a high level signal when the frequency of the sound source is 200 (Hz) to 500 [: Hz], and
the directivity is degraded.
On the other hand, when the cavity 45 is filled with the second control body 48, the peak can be
suppressed as shown by the solid line in FIG. 8, and the directivity characteristics of the
microphone units 20R and 20L are not adversely affected. There is no. FIG. 8 is a diagram
showing response frequency characteristics according to the position of the sound source of the
pair microphone 20 of this embodiment.
[0002]
Brief description of the drawings
[0003]
1 is a cross-sectional view of a main part of a dynamic type unidirectional directivity microphone
unit, FIG. 2 is a schematic view of a microphone used for stereo recording, FIG. 3 is a schematic
view of another microphone similarly, and FIG. FIG. 7 is a schematic view of another microphone.
5 is a schematic perspective view of a dynamic type paired microphone according to the present
invention, FIG. 6 is an enlarged sectional view taken along the line Vl-Vl in FIG. 5, FIG. 7 is a
directional characteristic of the paired microphone in FIG. FIG. 8 is also a response frequency
characteristic diagram. FIG. 9 is a view showing another embodiment according to the present
invention, FIG. 9 is a view of Aldlll, and FIG. 9 B is a sectional view. FIG. 10 is a view showing
another embodiment, FIG. 10A is a side view, and FIG. 10B is a sectional view. FIG. 11 is also
another embodiment, FIG. 11A is a side view, and FIG. 11B is a cross-sectional view. 20: Hair
microphone 20R: Microphone unit for light channel 20L: Microphone unit for left e channel 45:
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Bank cavity 46. 49: Acoustic hole 1F, one forty 47 · · 3 impulse resistance 48 · · · 2nd brake
patent applicant Sony Corporation Attorney Attorney Attorney Koike
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