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JPH0511696

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DESCRIPTION JPH0511696
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
condenser microphone, and more particularly to a condenser microphone in which the pressure
difference between the front and back of a diaphragm due to wind is reduced to reduce the
generation of wind noise.
[0002]
2. Description of the Related Art A condenser microphone in which a change in electrostatic
capacitance between a diaphragm and a back electrode plate which is a fixed electrode located
behind the diaphragm by vibration of the diaphragm is extracted as a change in voltage. In
particular, with the advent of electret materials, there is no need for a DC high-voltage power
supply, and the microphone unit can be easily made smaller and lighter, and is widely used from
business use to general use.
[0003]
One example of such a condenser microphone unit will be described with reference to FIG. 4. The
opening of the hollow hollow insulating seat 1 made of an insulating material and having one
end opened is slightly in front of the front end of the opening. A disc-shaped back electrode plate
2 is fitted via a spacer 3 so as to protrude.
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At the front end of the opening of the back electrode plate 2, a diaphragm 5 whose peripheral
edge is supported by a ring 4 is fixed by a spacer 6 with a gap to the back electrode plate 2. An
acoustic resistance material 7 covers a through hole 8 formed in the bottom of the insulating
seat 1 and the lower surface thereof is supported by a support plate 9. 10 is a connection
terminal for connecting to an impedance converter not shown. The through hole 8 is also formed
in the back electrode plate 2, and the through hole 8 side of the insulating seat 1 serves as a rear
acoustic terminal. These constituent members are fixed by caulking or the like in a unit case 11
made of a metal such as soft aluminum by curling or the like. At the front of the unit case 11,
openings 12 for sound collection are formed, and these openings 12 become front acoustic
terminals.
[0004]
In such a condenser microphone, a pressure difference due to wind is generated before and after
the diaphragm 5 of the microphone unit, and this pressure difference becomes wind noise. This
wind noise occurs more often in unidirectional microphones than in omnidirectional
microphones. As a means for reducing such wind noise, for example, an opening between the
opening 12 at the center of the entire surface of the unit case 11 which is the front acoustic
terminal and the through hole 8 of the insulating seat 1 is connected by an acoustic tube It has
been proposed to reduce the pressure difference due to wind between the terminal side and the
rear acoustic terminal side.
[0005]
However, since such an acoustic tube is attached to the outer diameter of the microphone unit,
the outermost diameter is increased accordingly, which hinders downsizing and is expensive.
There is a drawback that you have to
[0006]
Therefore, the object of the present invention is to reduce the wind noise by reducing the
pressure difference between the front acoustic terminal and the rear acoustic terminal without
making the outer diameter large by simply modifying the conventional condenser microphone.
To provide a capacitor microphone.
[0007]
SUMMARY OF THE INVENTION This invention has a front acoustic terminal on the entire surface
of a unit case housing a diaphragm, a back plate, an insulating seat, etc. and a rear acoustic
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terminal on the rear of the insulating seat. The condenser microphone is characterized in that a
leak path of air is formed between a gap between the diaphragm and the back plate and the front
acoustic terminal.
[0008]
[Operation] With the above configuration, even if there is a pressure difference between the front
acoustic terminal and the rear acoustic terminal, the high pressure air can flow into the low
pressure side through the leakage passage. Because the pressure difference is reduced, wind
noise can be reduced.
Since this leak passage can be formed in the unit case, it is possible to enlarge by forming the
leak passage.
[0009]
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present
invention will be described below with reference to FIGS.
The same reference numerals as in the above-described conventional example denote
substantially the same components, and a detailed description thereof will be omitted.
[0010]
As in the prior art, in the back electrode plate 2 in which the plurality of through holes 8 are
formed, a rectangular notch 21 extending inward is formed in a part of the peripheral edge
thereof.
As shown in FIG. 3, the notch 21 has a length extending further inward than the inner peripheral
side of the spacer 6 located at the upper part thereof. An air-permeable wire mesh 22 is
interposed between the ring 4 supporting the diaphragm 5 and the sound collecting surface of
the unit case 11. In this embodiment, a wire mesh having a mesh of about 100 mesh is used with
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a wire of about 0.1 mm in diameter. Further, the depth of the recess for supporting the spacer 3
of the insulating seat 1 and the back electrode plate 2 is formed to have a length sufficient to
form a gap between the outer peripheral lower surface of the spacer 6 and the outer peripheral
upper surface of the insulating seat 1 There is. As a result, there is a leak passage of air from the
opening 12 of the unit case 11 through the wire mesh 22, from the gap 23 between the ring 4
and the side wall of the unit case 11 through the notch 21 to the back surface of the diaphragm
5. It will be formed.
[0011]
By configuring as described above, a part of the air applied to the diaphragm 5 from the opening
12 of the unit case 11 which is the front acoustic terminal through the wire mesh 22 to the
diaphragm 5 is separated from the outer periphery of the wire mesh 22 by the gap 23. Through
the gap between the outer circumferential surface of the insulating seat 1 and the lower surface
of the spacer 6 through the notch 21 and through the back plate 2 and the through holes 8 of
the insulating seat 1 from the back surface of the diaphragm 5 Since the air on the high pressure
side can be made to flow to the low pressure side since it flows to the rear acoustic terminal of
the unit, the pressure difference is reduced and wind noise can be reduced.
[0012]
FIGS. 5 (a) and 5 (b) show the wind noise characteristics when measured with a 1/3 octave
bandwidth, (a) shows the wind noise characteristics of this embodiment, and (b) shows FIG. 4
shows the wind noise characteristics of the conventional condenser microphone shown in FIG. 4,
and it was found that the wind noise of the embodiment is about 6 dB as a whole.
It was also found from this measurement that it is particularly effective in the frequency band
below 200 Hz.
[0013]
As described above, according to the condenser microphone of the present invention, the air leak
path is formed between the space between the diaphragm and the back plate and the front
acoustic terminal. Therefore, even if there is a pressure difference between the front and rear
acoustic terminals, the air on the high pressure side can flow into the low pressure side through
the leakage passage, so the pressure difference becomes smaller and the wind Noise can be
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reduced. Since the leak passage can be formed in the unit case and can be implemented by
adding a slight improvement to the conventional configuration, the leak passage does not
increase the size.
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