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DESCRIPTION JP2013153363

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DESCRIPTION JP2013153363
Abstract: In a condenser microphone including two condenser microphone units for positive
phase output and negative phase output in which respective diaphragms are arranged on the
same plane, the positive phase is obtained in a state where the respective condenser microphone
units are combined. It is possible to adjust each output level of and the opposite phase. A
microphone unit 10 for positive phase output having a fixed pole 13 connected to the gate of the
FET 15 and a microphone unit 20 for negative phase output having a diaphragm 21 connected to
the gate of the FET 25 The variable resistor 30 is connected between the terminals 15a and 25a,
and the diaphragm 11 of the positive phase output microphone unit 10 and the fixed pole 23 of
the negative phase output microphone unit 20 are connected to the slider 30a of the variable
resistor 30. Connect to [Selected figure] Figure 1
コンデンサマイクロホン
[0001]
The present invention relates to a condenser microphone having two condenser microphone
units for positive phase output and negative phase output, and outputting an audio signal as
balanced output, more specifically, adjusting each output level of positive phase and negative
phase It relates to the technology that makes it possible.
[0002]
Patent Document 1 describes a condenser microphone including two condenser microphone
units for positive phase output and negative phase output, and according to this, by adding audio
signals of positive phase and negative phase , High sensitivity can be obtained, and the
equivalent level of noise can be lowered.
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[0003]
FIG. 2 shows a condenser microphone 1B as an example thereof, which will be described. The
condenser microphone 1B includes two condenser microphone units (sometimes simply referred
to as "microphone units") 10 and 20.
[0004]
The microphone units 10 and 20 include diaphragms 11 and 21, fixed poles 13 and 23, and
impedance converters 15 and 25 as basic components.
[0005]
Although not shown in detail, the diaphragms 11 and 21 are made of a synthetic resin thin film
provided with a metal deposition film on one side, and are supported on the support rings
(diaphragm rings) 12 and 22 in a state where a predetermined tension is applied. It is stuck.
[0006]
In this condenser microphone 1B, the diaphragms 11 and 21 are arranged in parallel on the
same plane so that the distances from the sound source (not shown) are substantially equal.
[0007]
The fixed electrodes 13 and 23 are made of a metal material such as aluminum, but in this
conventional example, electret dielectric films 14 and 24 are integrally provided on the side
facing the diaphragms 11 and 21, respectively.
[0008]
That is, the microphone units 10 and 20 shown in FIG. 2 are both back electret type, and the
diaphragms 11 and 21 and the fixed electrodes 13 and 23 are opposed to each other with a
predetermined interval via an electrically insulating spacer ring (not shown). Is located in
[0009]
For the impedance converters 15, 25 field-effect transistors (FETs, preferably source-follower
FETs) with a very high input impedance and a low output impedance are generally used.
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[0010]
The drains of the impedance converters (FETs) 15 and 25 are connected to a DC drive power
supply VDD, the source is connected to the ground GND, and the output terminals 15a and 25a
are drawn from the source side.
[0011]
On the microphone unit 10 side, the fixed pole 13 is connected to the gate which is the input
terminal of the FET 15 via the capacitor C, while on the microphone unit 20 side, the diaphragm
21 is connected to the gate of the FET 25 via the capacitor C. It is connected to the gate which is
an input terminal.
[0012]
As a result, positive and negative phase audio signals different in phase by 180 ° are output
from the output terminals 15a and 25a of the microphone units 10 and 20, respectively.
The positive phase and the negative phase are relative ones. Here, one microphone unit 10 is for
positive phase output, and the other microphone unit 20 is for negative phase output.
[0013]
JP, 2006-101302, A
[0014]
As described above, in the condenser microphone 1B, sound signals of positive phase and
negative phase are balancedly output, but the two microphone units 10 and 20 used have a
sensitivity difference as an individual difference. As a result, the directional axes of the
microphone units 10 and 20 may be offset from the sound collection axis of the condenser
microphone 1B.
[0015]
Further, even if the output of the condenser microphone 1B is balanced and transmitted, it is
preferable that the respective levels of the positive phase output and the negative phase output
be identical.
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[0016]
Therefore, an object of the present invention is to combine condenser microphone units in a
condenser microphone provided with two condenser microphone units for positive phase output
and negative phase output in which respective diaphragms are arranged on the same plane. To
adjust the output levels of the positive and negative phases.
[0017]
In order to solve the above problems, according to the present invention, first and second two
condenser microphone units both having a diaphragm and a fixed pole disposed opposite to each
other with a predetermined distance and having an impedance converter. And the diaphragms of
the condenser microphone units are juxtaposed on the same plane such that the distances from
the sound source are equal, and on the first condenser microphone unit side, the fixed pole is the
impedance converter An audio signal appearing on an output terminal of the first condenser
microphone unit, and the diaphragm connected to an input terminal of the impedance converter
on the second condenser microphone unit side; The phases of the audio signals appearing at the
output terminals of the two condenser microphone units In the condenser microphone having an
opposite phase and an output form of the audio signal as a balanced output, a variable resistor is
connected between the output terminals of the impedance converters of the first and the second
condenser microphone units, and The diaphragm of the condenser microphone unit and the fixed
pole of the second condenser microphone unit are connected to each other, and the connection
point is connected to the slider of the variable resistor.
[0018]
In the present invention, a source follower field effect transistor is preferably used for each of the
above-mentioned impedance converters.
[0019]
Preferably, the first and second condenser microphone units are both back electret types having
an electret dielectric film at the fixed pole.
[0020]
According to the present invention, since the difference level between the positive phase level
and the negative phase level according to the sliding position is obtained from the slider of the
variable resistor, each output of the first and second condenser microphone units By measuring
the level and adding a difference level according to the level difference to the diaphragm of the
first condenser microphone unit and the fixed pole of the second condenser microphone unit via
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the slider, positive phase, reverse The output levels of the phases can be easily adjusted to the
same level.
[0021]
FIG. 1 is a circuit diagram showing an embodiment of a condenser microphone according to the
present invention.
The circuit block diagram which shows the condenser microphone concerning a prior art
example.
[0022]
Next, an embodiment of the present invention will be described with reference to FIG. 1, but the
present invention is not limited to this.
In the description of this embodiment, the same reference numerals as in the conventional
example described above with reference to FIG.
[0023]
As shown in FIG. 1, the condenser microphone 1A also includes two microphone units of a
condenser microphone unit 10 for positive phase output and a condenser microphone unit 20
for negative phase output.
[0024]
The outputs of the microphone units 10 and 20 are 180 ° out of phase with each other, but the
microphone units 10 and 20 basically have the diaphragms 11 and 21, fixed poles 13 and 23,
and impedance converters 15 and 25. And are included.
[0025]
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Although not shown in detail, the diaphragms 11 and 21 are made of a thin film of synthetic
resin provided with a metal deposition film on one side, and the support rings (diaphragm rings)
12 and 22 are in a state where a predetermined tension is applied. It is stuck.
The support rings 11, 21 are preferably attached to the metal deposition film side.
[0026]
Also in this condenser microphone 1A, the diaphragms 11 and 21 are juxtaposed on the same
plane so that the distances from the sound source (not shown) are substantially equal.
[0027]
The fixed electrodes 13 and 23 are made of a metal material such as aluminum, and electret
dielectric films 14 and 24 are integrally provided on the side facing the diaphragms 11 and 21,
respectively.
The electret dielectric films 14 and 24 are negatively charged by corona discharge or the like.
[0028]
That is, the microphone units 10 and 20 are both back electret type, and the diaphragms 11 and
21 and the fixed poles 13 and 23 are disposed opposite to each other at a predetermined
distance via an electrically insulating spacer ring (not shown). There is.
[0029]
In this embodiment, source-follower type field effect transistors (FETs) are used for the
impedance converters 15 and 25, the drain is connected to a DC driving power supply VDD, and
the source is connected to the ground GND. Output terminals 15a and 25a are drawn from the
source side.
[0030]
Further, in this embodiment, since the microphone unit 10 is for positive phase output, the fixed
pole 13 is connected to the gate which is the input terminal of the FET 15 through the capacitor
C, while the microphone unit 10 Since the reference numeral 20 is for reverse phase output, the
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diaphragm 21 is connected to the gate which is the input terminal of the FET 25 through the
capacitor C.
[0031]
According to the present invention, the output level of the positive phase signal output from the
output terminal 15a of the microphone unit 10 and the output level of the negative phase signal
output from the output terminal 25a of the microphone unit 20 are adjusted to the same level. In
order to do this, the variable resistor 30 is connected between the output terminal 15a and the
output terminal 25a.
[0032]
Also, the diaphragm 11 of the microphone unit 10 and the fixed pole 23 of the microphone unit
20 are electrically connected, and the connection point is electrically connected to the slider 30 a
of the variable resistor 30.
[0033]
A level difference between the output level of the positive phase signal and the output level of
the negative phase signal appears on the slider 30a according to the voltage dividing ratio of the
variable resistor 30 by the slider 30a.
[0034]
That is, when the slider 30a is caused to slide toward the output terminal 15a side of the
microphone unit 10, a positive phase difference signal appears on the slider 30a, while the slider
30a corresponds to that of the microphone unit 20. When sliding toward the side of the output
terminal 25a, a difference signal of reverse phase appears on the slider 30a.
[0035]
Therefore, while observing the signal waveforms of the output terminals 15a and 25a with, eg,
an oscilloscope, the slider 30a is operated to set the above difference level to the diaphragm 11
of the microphone unit 10 and the fixed pole 23 of the microphone unit 20. Thus, the output
levels of the output terminals 15a and 25a can be made the same level.
[0036]
As described above, according to the present invention, with the two microphone units 10 and
20 combined, each output level of positive phase and negative phase can be adjusted, so that the
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pointing axis is normal and the balance is strong against noise. An accurate condenser
microphone can be realized.
[0037]
In the above embodiment, both of the microphone units 10 and 20 are of the back electret type,
but the fixed poles 13 and 23 of the microphone units 10 and 20 may be set to a negative
potential by a polarization power supply (not shown) .
[0038]
1A, 1B condenser microphone 10 microphone unit for positive phase output 20 microphone unit
for negative phase output 11, 21 diaphragm 12, 22 support ring 13, 23 fixed pole 14, 24
electret dielectric film 15, 25 impedance converter ( FET) 15a, 25a Output terminal 30 Variable
resistor 30a Slider
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