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JPH11331987

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This translation is machine-generated. It cannot be guaranteed that it is intelligible, accurate,
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DESCRIPTION JPH11331987
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
microphone, and more particularly to a microphone having means for reducing vibration noise.
[0002]
2. Description of the Related Art In microphones, especially in hand-held microphones, vibration
noise generated by vibration of the microphone case is often a problem. The microphone unit is
roughly divided into a vibrating portion that includes a diaphragm and is supported so as to be
able to vibrate on the microphone case side, and a fixing portion such as a magnetic circuit fixed
to the microphone case.
[0003]
The electrical signal output by the sound wave of the microphone depends on the relative
displacement or relative velocity between the vibrating part and the fixed part. The relative
displacement or relative velocity is also caused by the vibration of the microphone case, which is
taken out as vibration noise. That is, this vibration noise is generated when the mass of the
vibrating portion tries to stay at the original position when the microphone case is displaced in a
certain direction.
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[0004]
A representative example of the one that obtains the electrical signal output by the sound wave
by the relative displacement between the vibrating part and the fixed part is the condenser
microphone, and a representative example of the one that is obtained by the relative velocity is
the dynamic microphone In terms of resistance control and elasticity control, in general, the
magnitude of vibration noise is in the order of directional dynamic microphone> nondirectional
dynamic microphone> nondirectional condenser microphone.
[0005]
Vibration noise of low frequency components has directivity of cos θ with respect to the
vibration axis of the diaphragm, but vibration noise of relatively high frequency components is
generated by solid propagation in the path of microphone case → elastic support member →
diaphragm In order to have no particular directionality.
In order to reduce such vibration noise, conventionally, the following methods are known.
[0006]
When mounting a microphone unit to a microphone case, a so-called shock mounting method in
which vibration isolation is performed using a viscoelastic body such as rubber. In addition to the
microphone unit, a method of mounting a vibration detection unit that detects only vibration
noise, and canceling the output signals of both units.
[0007]
The vibration damping effect by the above-mentioned shock mounting method depends on the
resonant frequency and the resonant sharpness of the vibration system. Therefore, the reduction
effect of the vibration noise can be expected only in the frequency band higher than the
frequency correlated with the resonance frequency. That is, if the resonant frequency of the
vibration system is set low, it is possible to widen the frequency band having the vibration
damping effect.
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[0008]
However, if the resonance frequency is set low, the microphone unit will be displaced from the
normal position by gravity even in the steady state, so if an external impact is applied to the
microphone case, the displacement of the microphone unit becomes large, and the microphone
unit Collides with the microphone case. As a result, larger vibration noise is generated.
[0009]
In the above output signal cancellation method, the level and the phase of the output signals of
both units are adjusted and subtracted using the microphone unit that picks up the sound wave
and the vibration detection unit having the same conversion method as this. Vibration noise can
be reduced to some extent.
[0010]
However, making the output signals of both the microphone unit and the vibration detection unit
identical over a wide frequency band not only requires extremely precise adjustment, but is also
quite difficult in practice.
Therefore, it is necessary to limit the frequency band to be subjected to vibration reduction to an
appropriate range and additionally use the shock mounting method or the like for other
frequency bands.
[0011]
Also, an enclosure is provided in the vibration detection unit so that sound waves do not enter.
That is, since the vibration detection unit detects the vibration in the sealed space, the resonance
frequency of the diaphragm increases, and the output signal level decreases.
[0012]
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Also, since the microphone unit is placed in a free space, and the vibration detection unit is
placed in an enclosed space, such as in an enclosed space, the balance of the output signals of
both units may be lost due to temperature etc. is there. These things make the level adjustment of
the output signal of both units, and the adjustment operation of phasing more difficult.
[0013]
Furthermore, when the phase or level adjusted in advance changes due to a temperature rise or
the like and the cancellation of the vibration noise does not operate normally, the vibration noise
may increase in reverse.
[0014]
The present invention has been made to solve such conventional problems, and its object is to
reduce vibration noise with a simple structure and without the need for complicated adjustment
operations and the like. It is to provide a microphone that
[0015]
SUMMARY OF THE INVENTION In order to achieve the above object, the present invention
provides a microphone unit for converting sound into an electric signal, and a microphone
support for elastically supporting the microphone unit via an elastic body. A microphone
including the vibration detection unit provided on the microphone support unit for detecting the
vibration applied to the microphone support unit, and activated based on a detection signal from
the vibration detection unit; And an output signal processing unit for attenuating the converted
signal and outputting it to the output unit.
[0016]
In this case, the output signal processing unit has an attenuator formed of a resistive element,
and the embodiment of the present invention also includes an aspect of attenuating the
conversion signal output from the microphone unit by the attenuator in the operating state.
[0017]
Further, the output signal processing unit may include a high pass filter, and in the operating
state, the low pass component in the converted signal output from the microphone unit may be
attenuated by the high pass filter. The present invention is also included.
[0018]
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In the present invention, the vibration detection unit is a shock sensor using a piezoelectric
element that generates a voltage when an impact is applied, and the output signal processing
unit operates based on a detection signal based on a voltage generated by the shock sensor. It is
preferable that
[0019]
According to the present invention, when an impact is applied to the microphone support, the
vibration detection unit detects the impact and outputs a detection signal.
The output signal processing unit is activated based on the detection signal from the vibration
detection unit.
[0020]
On the other hand, in mechanical analysis, an impact applied to the microphone support
propagates through the microphone support and reaches the microphone unit, but since the
microphone unit is supported by the microphone support via the elastic body, The impact is
delayed by this elastic body and applied to the microphone unit.
At this time, since the output signal processing unit is already in operation, noise due to impact is
removed by the output signal processing unit.
[0021]
DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, in order to better understand the
technical concept of the present invention, preferred embodiments thereof will be described with
reference to the drawings.
[0022]
FIG. 1 is a schematic partial cross-sectional view showing this microphone.
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According to this, this microphone includes the microphone case (microphone grip) 1, the shock
mount 2, the microphone unit 3, the shock sensor 4 as a vibration detection unit, the output
signal processing unit 5, and the output connector 6 as an output unit.
[0023]
The shape of the microphone case 1 is cylindrical, and the shock mount 2, the microphone unit
3, the shock sensor 4, the output signal processing unit 5 and the output connector 6 are
provided on the inner side.
An upper portion of the microphone case 1 is a wind screen 11 that covers the microphone unit
3.
Further, an output connector 6 connected to a cable is attached to the lower part of the
microphone case 1.
[0024]
The shock mount 2 is for reducing the impact applied to the microphone case 1, and preferably
an elastic body exhibiting viscoelasticity is used.
The shock mount 2 has a ring shape, and is fitted and held inside the microphone case 1 with the
microphone unit 3 inserted therein.
As a result, as shown in FIG. 2, the microphone case 1 supports the microphone unit 3 by the
equivalent spring 21 by the shock mount 2.
[0025]
The microphone unit 3 converts external sound into an electrical signal. For the conversion of
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sound, a dynamic microphone or a condenser microphone is used. The microphone unit 3
outputs the conversion signal, which is the conversion result, to the output signal processing unit
5.
[0026]
The shock sensor 4 detects vibration or impact applied to the microphone case 1. The shock
sensor 4 includes a pair of piezoelectric elements 41 and 42 as shown in FIG. When acceleration
due to impact is applied to the piezoelectric elements 41 and 42 in the direction of arrow A, for
example, one of the piezoelectric elements 41 expands while the other piezoelectric element 42
contracts.
[0027]
As a result, charges are generated in the piezoelectric elements 41 and 42, and the shock sensor
4 outputs a detection signal based on the charges. At this time, as shown in FIG. 3B, the detection
signal output from the shock sensor 4 has an oscillating waveform of voltage due to impact.
[0028]
The output signal processing unit 5 attenuates the conversion signal from the microphone unit 3
based on the shock detected by the shock sensor 4. The output signal processing unit 5 includes
an amplifier 51, a detector 52, a smoothing circuit 53, a comparator 54, an analog switch circuit
55, and an attenuator 56, as shown in FIG.
[0029]
The amplifier 51 amplifies the detection signal from the shock sensor 4 and outputs the
amplified detection signal to the detector 52. When the detector 52 receives the detection signal
of the amplifier 51, the detector 52 detects the detection signal and generates a detection signal
shown in FIG. 5 (a).
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[0030]
The detector 52 outputs the generated detection signal to the smoothing circuit 53. When the
smoothing circuit 53 receives the detection signal of the detector 52, the smoothing circuit 53
smoothes the detection signal to generate a smooth signal shown by a solid line in FIG. 5 (b). The
smoothing circuit 53 outputs the generated smoothed signal to the comparator 54.
[0031]
The comparator 54 controls the analog switch circuit 55 based on the smoothed signal of the
smoothing circuit 53. That is, in the comparator 54, the reference level 54A is set in advance.
The reference level 54A represents a level for reducing vibration noise generated by impact.
[0032]
The comparator 54 compares the smoothed signal from the smoothing circuit 53 with the
reference level 54A. When the smoothed signal is equal to or higher than the reference level
54A, the comparator 54 outputs a drive signal to the analog switch circuit 55. Conversely, if the
smoothed signal is smaller than the reference level 54A, the comparator 54 stops the output of
the drive signal.
[0033]
The analog switch circuit 55 controls the attenuator 56 based on the drive signal of the
comparator 54. That is, the analog switch circuit 55 includes the switch 55A. When receiving the
drive signal from the comparator 54, the analog switch circuit 55 closes the switch 55A to
connect the contact 55B of the switch 55A to the contact 55C. Also, when the drive signal is not
received, the analog switch circuit 55 opens the switch 55A. By opening and closing the switch
55A, the analog switch circuit 55 controls the attenuation of the attenuator 56 as described
below.
[0034]
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The attenuator 56 attenuates the converted signal output from the microphone unit 3. To this
end, the attenuator 56 is provided with resistors 56A, 56B, 56C. The resistor 56A is inserted in a
signal line 7A that connects between the output terminal 3A of the microphone unit 3 and the
output terminal 6A of the output connector 6. The resistor 56 B is inserted in a signal line 7 B
that connects between the output terminal 3 B of the microphone unit 3 and the output terminal
6 B of the output connector 6.
[0035]
One end of the resistor 56C is connected to the terminal on the output terminal 6A side of the
resistor 56A, and the other end of the resistor 56C is connected to the contact 55B of the analog
switch circuit 55. The terminal on the output terminal 6B side of the resistor 56B is connected to
the contact 55C of the analog switch circuit 55.
[0036]
When the switch 55A of the analog switch circuit 55 is closed, the resistor 56C is connected
between the terminal on the output terminal 6A side of the resistor 56A and the terminal on the
output terminal 6B side of the resistor 56B. As a result, between the output terminals 3A, 3B of
the microphone unit 3 and the output terminals 6A, 6B of the output connector 6, an attenuator
by the resistors 56A, 56B, 56C is inserted. The attenuator attenuates the conversion signal from
the microphone unit 3 and outputs it to the output terminals 6A and 6B of the output connector
6.
[0037]
Next, the operation of the first embodiment will be described. A human voice or the like is
converted into an electrical signal by the microphone unit 3. The converted signal from the
microphone unit 3 is output from the output terminals 3A and 3B to the output terminals 6A and
6B of the output connector 6 through the resistors 56A and 56B.
[0038]
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In this state, when an impact is applied to the microphone case 1, the shock sensor 4
immediately detects the impact. As a result, the comparator 54 of the output signal processing
unit 5 outputs the drive signal to the analog switch circuit 55. Thereby, the switch 55A of the
analog switch circuit 55 is closed, the resistor 56C of the attenuator 56 is connected between the
resistor 56A and the resistor 56B, and the attenuator by the resistors 56A, 56B, 56C is inserted
into the signal lines 7A, 7B. Ru.
[0039]
On the other hand, vibration noise due to impact propagates from the microphone case 1 to the
shock mount 2 and is added to the microphone unit 3. At this time, the vibration noise is delayed
by the shock mount 2 and transmitted to the microphone unit 3. As a result, when the vibration
noise reaches the microphone unit 3, the attenuators by the resistors 56A, 56B and 56C are
already inserted in the signal lines 7A and 7B. . The attenuator 56 outputs the converted signal
with reduced vibration noise to the output terminals 6A and 6B of the output connector 6.
[0040]
Thus, according to the present invention, vibration noise due to impact can be reduced. At this
time, since the attenuator 56 operates with respect to vibration noise of the reference level 54A
or more set in the comparator 54, there is no variation and complicated vibration adjustment
operation is unnecessary to suppress the vibration noise. Can.
[0041]
When a condenser microphone is used as the microphone unit 3, if the output signal processing
unit 5 is configured with an element with low power consumption such as a C-MOS-IC, it is
necessary to greatly increase the power supplied to the microphone unit 3. It is possible to use
the device for connecting the microphone as it is.
[0042]
When a dynamic microphone is used as the microphone unit 3, it is possible to simplify selection
of whether to use the function of the output signal processing unit 5 by turning on and off the
power supplied to the microphone.
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[0043]
Next, Example 2 of FIG. 6 will be described.
In the second embodiment, only the attenuator 56 of FIG. 4 is different from the first
embodiment, so only the different portion will be described.
In the second embodiment, as shown in FIG. 6, an attenuator 57 comprising a high pass filter is
used in place of the attenuator 56 of FIG. In FIG. 6, the same or corresponding components as
those of the output signal processing unit 5 of FIG. 4 are designated by the same reference
numerals.
[0044]
The attenuator 57 in the second embodiment reduces only the low frequency converted signal
from the converted signal of the microphone unit 3. The low frequency conversion signal is
mainly generated by vibration noise. For this purpose, the attenuator 57 comprises resistors 57A,
57B and a coil 57C. The resistor 57A is inserted into the signal line 7A, and the resistor 57B is
inserted into the signal line 7B.
[0045]
One end of the coil 57C is connected to the terminal on the output terminal 6A side of the
resistor 57A, and the other end of the coil 57C is connected to the contact 55B of the analog
switch circuit 55. The terminal on the output terminal 6B side of the resistor 57B is connected to
the contact 55C of the analog switch circuit 55.
[0046]
When the switch 55A of the analog switch circuit 55 is closed, the coil 57C is connected between
the terminal on the output terminal 6A side of the resistor 57A and the terminal on the output
terminal 6B side of the resistor 57B.
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[0047]
Thus, an attenuator is inserted between the output terminals 3A and 3B of the microphone unit 3
and the output terminals 6A and 6B of the output connector 6 by the resistors 57A and 57B and
the coil 57C.
The attenuator attenuates only the low frequency component of the converted signal from the
microphone unit 3, that is, the converted signal due to vibration noise, by the coil 57C, and
outputs the attenuated signal to the output terminals 6A and 6B of the output connector 6.
[0048]
Thus, according to the present invention, only the low frequency conversion signal generated by
vibration noise can be selectively attenuated by the coil 57C. As a result, even if normal voice
such as human voice is generated together with vibration noise, only the conversion signal by
this voice is output to the output connector 6, it is possible to prevent the voice from being
interrupted.
[0049]
As mentioned above, although Examples 1 and 2 were explained, the present invention is not
limited to this. For example, if the microphone is to be placed on a table by a stand, the shock
sensor 4 and the output signal processing unit 5 may be attached to the stand.
[0050]
As described above, according to the present invention, when the vibration detection unit detects
an impact, the output signal processing unit is put into operation, so that it is delayed by the
elastic body and added to the output signal processing unit. The conversion signal due to impact
can be reliably attenuated, and complicated adjustment work and the like for the vibration
detection unit and the output signal processing unit can be eliminated. Further, since only the
vibration detection unit and the output signal processing unit are necessary to remove the
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conversion signal due to the impact, the structure can be prevented from being complicated.
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