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JPS5940798

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DESCRIPTION JPS5940798
[0001]
[Technical field 1 of the invention] The present invention relates to a noise reduction device for
micro bon, and relates to a noise reduction device for microphone provided with a sensor for
detecting an external vibration received by a cabinet containing a microphone unit. [Technical
Background of the Invention] In general, as a method of reducing vibration noise due to external
imaging in an acoustic transducer such as a microphone, one as shown in FIG. 1 is known. The
microphone unit 1 is housed in the cabinet 3 via the damper 2 and the back cavity 4 is formed
by the support 5 on the back side of the sound pickup portion of the microphone 1 and the pair,
and the support 5 On the back, a sensor 6 having the same configuration as the microphone unit
1 and having a function of detecting external vibration of the cabinet 3 is attached in the
opposite direction to the microphone unit 1, and the vibration portion detecting the external
vibration of the sensor 6 A space body 9 having a plurality of air chambers 8 is disposed, and the
space body 9 is supported by the cabinet 3 via a damper 10. The microphone unit 1, the support
5, the sensor 6 and the space body 9 are arranged linearly. In the noise reduction device of the
microphone 1-1 phone configured as described above, as shown in FIG. 2, the outputs of the
microphone unit 1 and the microphone are coupled in reverse phase relation to each other, so
external to the cabinet 3 When vibration is applied, the output of the sensor 6 cancels the output
of the microphone unit 1 so that the output becomes almost zero. Therefore, it becomes possible
to suppress the external vibration added to the cabinet 3. In the extrusion for providing the space
body 9 having the air chamber 8 in which the sensor 6 is sealed, the microphone concate 1 and
the sensor 6 have a reverse phase relationship and have the same configuration even when an
external input sound is input. Therefore, the microphone unit 1 and the sensor 6 prevent the
cancellation of the output signal in the absence of external vibration. [Problems of the
Background Art] However, the conventional microphone noise reduction device configured as
described above affects the sensor 6 because the sealed air chamber 8 formed in the sensor 6
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acts as a compliance with the diaphragm. In order to operate it under the same condition as the
microphone unit 1 by less, it is necessary to make the size of the air chamber 8 sufficiently large,
and there is a drawback that the cabinet 3 becomes large. Further, the phase relationship
between the microphone unit 1 and the sensor 6 largely changes depending on the frequency,
and it is difficult not only to expect a uniform cancellation effect in a wide band, There is a
drawback that the effect can not be expected almost at all for the external vibration that is sharp.
Furthermore, since the sensor 6 is floated by the damper 10, the characteristic vibration of the
sensor 6 is easily changed due to the change of temperature, and the vibration noise preventing
effect is also reduced. is there. SUMMARY OF THE INVENTION The present invention has been
made to eliminate such conventional drawbacks, and it is a noise reduction of a microphone
capable of reducing noise due to external vibration added to a microphone unit with a simple
configuration and with certainty. The purpose is to provide a device. SUMMARY OF THE
INVENTION In order to achieve this object, the present invention provides a microphone unit for
converting an external input sound into an electrical signal, a cabinet containing the microphone
unit, and the microphone unit attached to the outside of the cabinet It is characterized by
comprising a sensor which detects vibration and converts it into an electric signal, and means
which suppresses the output signal of the microphone unit in response to the output signal of the
sensor. [First Embodiment of the Invention The present invention will be described in detail. FIGS.
3 to 5 are diagrams for explaining an embodiment of the noise reduction apparatus for
microphones according to the present invention. A conventionally known microphone unit 11 for
converting an external input sound into an electric signal in FIG. 3 is attached to a C cabinet 13
via a damper 12. A sensor 14 for detecting an external vibration applied to the cabinet 13 is
attached to the side surface of the microphone unit 11, and the microphone unit 11 and the
sensor 14 are integrated. As shown in FIG. 4, the sensor 14 comprises a shield case 15 and a
piezoelectric element 17 supported in the shield case 15 via a damper 16. One electrode 17a of
the piezoelectric element 17 is an impedance conversion element. The use electrode 17b is
connected to the ground pattern (not shown) of the printed circuit board 19 and the output
electrode of the microphone unit is connected to a predetermined position of the printed circuit
board 19 There is. The microphone unit 11 and the sensor 14 shown in FIGS. 3 and 4 can change
the output level of the microphone unit 11 according to the detection level of the sensor 14 for
detecting external vibration by the circuit shown in FIG. It is possible. That is, the microphone
unit 11 is connected to the power supply 10B through the resistor R1 and to the base of the
transistor Q1 through the resistor R2 and the capacitor C1, and the emitter of the transistor Q1
is grounded through the resistor R3. ing. The collector of the transistor Q1 is connected to the
emitters of the differential pair transistors Q2 and Q3, and the collector of the transistor Q2 is
connected to the power supply 10B and to the collector of the transistor Q4 of one of the
differential pair transistors Q4 and Qs. ing.
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The base of the transistor Q2 is connected to the connection point of the resistors Rs and R6
inserted between the power supply 10B and the ground, and a differential pair transistor. The
base of the other transistor Q5 of Q4 and Qs is also connected to this connection point. Further,
the base of the transistor Q3 is connected to the base of the] -transistor Q4, and the collector is
connected to the connection point of the resistor R4 and the transistor Q5, and serves as an
output terminal. The collector of the transistor Q5 is connected to the collector of the transistor
Q3. The emitters of the differential pair transistors Q4 and Qs are respectively connected to the
collector of the transistor Q6, the emitters of the transistors Q and 6 are grounded via a resistor
R7, and the base is a resistor R8 inserted between the resistor R5 and the ground It is grounded
through the parallel circuit of the capacitor c2. On the other hand, the sensor 14 is connected to
the power supply 10B via the resistor R9, and is connected to the base of the transistors Q3 and
Q4 '(1) via the capacitor C3 and the AC-DC converter 20. The output voltage of the AC-DC
converter 20 is configured to be inversely proportional to the output level of the sensor 14. The
output terminal 21 is connected between the resistor R4 and the collector of the transistor Q5.
Next, the operation of the noise reduction apparatus for a microphone of the present invention
configured as described above will be described. Under the condition that external vibration is
not applied to the cabinet 13, there is no output from the sensor 14, and when the external input
sound comes to the microphone t-11, the output from the microphone: one unit 11 passes
through the resistor R2 and the capacitor C1. Is added to the base of the transistor Q1, and a
collector current flows to the transistor Q + accordingly. At this time, the relationship between
the base voltage v1 of the differential pair transistors Q2 and Qs set by the resistors R5 and R6
and the resistor R8 and the base voltage V2 of the differential pair transistors Q3 and Q4 is
shown in FIG. Since the flow is set, an output corresponding to the microphone unit 11 can be
obtained at the output terminal 21. Conversely, when the output of the microphone unit 11 is
applied to the base of the transistor QI and the output signal is output from the output terminal
21, if external vibration is applied to the microphone unit 11 and the sensor 14 generates an
output signal, the transistor Q3 , And the base current VfV2 of Q4 is lowered, the current of the
transistor Q3 becomes smaller, and the level of the output signal of the output terminal 21
becomes smaller. ?????????????????????
The transistors Q5 and Q6 hold constant the DC voltage of the output terminal 21 when the
differential pair transistors Q3 and Q4 perform switching operation, and prevent noise
generation at the time of switching. Therefore, the output signal of the microphone unit 11 is
suppressed and reduced according to the level of the sensor 14. In the above embodiment, as the
circuit 22 for suppressing the signal from the microphone unit 11 by the output signal from the
sensor 14, one shown in FIG. 5 is an example, and various suppressing means can be used.
[Effect J of the Invention As described above, the noise reduction device for a microphone
according to the present invention is attached to a microphone concatenate for converting an
external input sound into an electrical signal, and detects external vibration of the cabinet and
converts it into an electrical signal. Since the sensor and means for suppressing the output signal
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of the microphone unit corresponding to the output signal of the sensor are provided, the sensor
for outputting a signal for suppressing the output signal of the microphone unit has a
configuration different from that of the microphone unit It consists of a vibration pickup element
and can be integrally molded with the microphone unit, eliminating the need for an air slit. As a
result, not only is it possible to suppress external vibrations transmitted to the cabinet, but the
overall configuration of the device is simplified and miniaturized. Further, since the sensor can
output the signal without depending on the frequency or the phase of the vibration noise and can
also output a signal with a sharp impact on the rising edge, a good noise reduction is possible. In
addition, since the sensor is directly attached to the microphone unit, the pickup for external
shooting becomes faithful, and it is less susceptible to temperature changes, and the assembly is
simple.
[0002]
Brief description of the drawings
[0003]
FIG. 1 is a cross-sectional view showing a conventional microbon noise reduction device, FIG. 2 is
an equivalent circuit diagram of FIG. M1, FIG. M3 is a plan view of BIIllli showing one
embodiment of a microphone noise reduction device of the present invention, FIG. 4 is an
enlarged sectional view showing the sensor shown in FIG. 3 in an enlarged manner, and FIG. 5 is
a circuit diagram without showing an example of the suppressing means of the present invention.
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