DESCRIPTION JP2001313990

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DESCRIPTION JP2001313990
[0001]
[Technical Field of the Invention] The present invention covers a wide frequency band even in a
place with high humidity such as rain or fog, in a bath, in a factory where dust is generated, in a
low pressure high mountain, or in a high pressure water. A waterproof microphone (hereinafter
referred to as a waterproof microphone) capable of collecting sound well.
[0002]
2. Description of the Related Art Conventionally, for example, a condenser type microphone
divides the inside of a case into front and rear chambers by a sound pressure-electric signal
conversion unit, and the sound pressure-electric signal conversion unit has a plate-like electrode
and an electrode periphery It consists of a thin conductive diaphragm that covers the entire front
of the electrode via an O-ring as a spacer disposed, and a DC voltage of 60 to 200 V is applied
between the electrode and the diaphragm. Then, when the diaphragm is vibrated by the sound
wave entering the front chamber from the outside through the opening of the case front wall, a
change in capacitance between the electrode and the diaphragm is obtained as an audio signal
from both ends of the resistance. The impedance of the signal is converted to a normal value
(200 to 600 Ω) by an impedance conversion amplifier and output. While the front chamber in
the case communicates with the outside air through the opening, the rear chamber has a gap
surrounded by the O-ring through a through hole provided in the electrode for vibration of the
diaphragm at the front. The rear side is shut off from the outside by the back wall of the case,
and the gap and the rear chamber are sealed from the outside air.
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[0003]
SUMMARY OF THE INVENTION The above-mentioned conventional condenser type microphone
has a small gap between the diaphragm and the electrode and the rear chamber sealed from the
open air, so even when used in a high humidity environment, the gap or rear There is no
possibility that water will intrude into the chamber, but if it is used in an environment where the
pressure is higher or lower than the atmospheric pressure which is the pressure at the time of
manufacturing the rear chamber, the diaphragm immerses and remains in contact with the
electrode or protrudes There is a problem that the gap is too wide and the normal sound
collection can not be performed. Therefore, a condenser type microphone has also been
prototyped, in which a shock absorbing material such as a sponge is interposed between the
diaphragm and the electrode, but the collision noise between the diaphragm and the electrode
can not be eliminated. In addition to being possible, it can not cope with the low pressure
environment and is not a drastic solution. In addition, if the entire case of the above-mentioned
conventional condenser type microphone is covered with a waterproof cover made of an elastic
material, it can be used in a bath room filled with steam or in water, but the water depth becomes
deep and high pressure is applied to the front room. If so, the above problems can not be
avoided.
[0004]
Therefore, the object of the present invention can be applied as it is to a high pressure chamber
with low air pressure or high pressure by devising the structure of the diaphragm or case so that
the pressure in the rear chamber becomes equal to the static pressure in the front chamber.
SUMMARY OF THE INVENTION An object of the present invention is to provide a waterproof
microphone which can cover the entire case with a waterproof cover and can be applied even in
deep water and can perform good sound collection over a wide frequency band.
[0005]
In order to achieve the above object, the invention according to claim 1 comprises a case having
a front wall having an opening communicating with the outside, and a communicating hole in the
thickness direction. A capacitor-type waterproof microphone comprising: a plate-like electrode
for dividing the inside of the case into a front chamber and a rear chamber; and a diaphragm
which is disposed with a gap in front of the electrode and covers the front of the electrode. The
back wall of the case is provided with through holes, respectively, which do not substantially
transfer the dynamic pressure fluctuation of the front chamber to the rear chamber, and the
static pressure fluctuation of the front chamber is It is characterized in that it is substantially
communicated to the rear room.
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[0006]
When the pressure of the installation site of the waterproof microphone in which the diaphragm
and the case back wall of claim 1 are respectively provided with the throttling hole is gradually
increased or gradually reduced from the atmospheric pressure, that is, statically increased or
decreased, The static pressure increases and decreases, and this increase and decrease is
substantially transmitted to the rear chamber through the throttling hole, and the pressure in the
rear chamber becomes equal to the pressure in the front chamber.
On the other hand, the diaphragm hole vibrates in response to the sound because the diaphragm
hole does not substantially transmit the dynamic pressure fluctuation of the front chamber due
to the sound to be collected to the rear chamber.
Therefore, unlike the conventional condenser-type microphone in which the rear chamber is
sealed, the diaphragm does not immerse and remain in contact with the electrode, or does not
protrude excessively and the gap between the electrode and the electrode does not expand
excessively. Because it vibrates normally, good sound collection can be performed over a wide
frequency band.
[0007]
The waterproof microphone according to claim 2 is provided with a communication hole
provided in the wall of the case so as to connect the front chamber and the outside of the back
wall, and a waterproof cover made of an elastic material that covers the case in a watertight
manner. It is characterized by
[0008]
When the waterproof microphone of claim 2 is gradually immersed in water, the entire case is
covered with a waterproof cover made of an elastic material, and the wall of the case is provided
with a communication hole for communicating the outside of the front chamber and the back
wall, The waterproof cover is compressed under the hydrostatic pressure according to the water
depth.
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Then, the air pressure in the case uniformly increases in the front chamber, the gap, and the rear
chamber so as to balance the static increase of the hydrostatic pressure by the throttling hole
and the communicating hole. On the other hand, the diaphragm hole vibrates according to the
sound because the diaphragm hole does not substantially transmit the dynamic pressure
fluctuation of the front chamber through the waterproof cover by the sound of water to be
collected to the rear chamber. Therefore, unlike the conventional condenser-type microphone in
which the rear chamber is sealed, the diaphragm does not immerse and remain in contact with
the electrode, or does not protrude excessively and the gap between the electrode and the
electrode does not expand excessively. Because it vibrates normally, good sound collection can be
performed over a wide frequency band. Since the case is covered with a waterproof cover, the
members in the case are not wet with water, and the entry of corrosive substances and dust in
the air is prevented. Therefore, this waterproof microphone can be used not only in water but
also in wet or humid environments on land.
[0009]
The waterproof microphone according to claim 3 is characterized in that the diaphragm is
formed by depositing metal on a synthetic resin plate and by permanently charging the surface.
[0010]
In the waterproof microphone of the third aspect, since the diaphragm is made of a so-called
electret material whose surface is permanently charged, the DC power source applied between
the electrode and the diaphragm becomes unnecessary, so that the size and weight can be
reduced.
In addition, since the diaphragm in contact with the external atmosphere is made of a synthetic
resin plate on which metal is vapor-deposited, it can be used even in a slight humidity or
corrosive environment without covering the entire case with a waterproof cover.
[0011]
In the waterproof microphone according to claim 4, an electronic circuit for impedance
conversion to equalize the impedance of the sound pressure-electric signal converter including
the diaphragm and the electrode to the impedance of the external output circuit is provided in
the rear chamber. It is characterized by
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[0012]
The electrical signal representing the sound is energetically the most energy-wise, since the
generally high impedance of the sound pressure-electric signal converter including the
diaphragm and electrodes of the waterproof microphone of claim 4 is equal to the generally low
impedance of the external output circuit. It is efficiently transmitted to the output circuit.
Therefore, with the waterproof microphone having a compact configuration, a good audio signal
can be obtained even in high mountains or water where the transmission distance of the output
signal is as long as several hundred meters.
[0013]
In the waterproof microphone according to claim 5, the electronic circuit includes a plurality of
equalizers according to a frequency band to be received, and the pressure sensor and the
equalizer are selected in the case based on a detection signal of the pressure sensor. And a
control unit to be operated.
[0014]
In the waterproof microphone according to claim 5, the pressure sensor detects an air pressure
in the case which increases according to the water depth, for example, through the waterproof
cover, and the control unit detects, for example, a sound collection signal of underwater
conversation based on the detection signal. The equalizer is selected to operate so as to convert
the frequency band to the normal frequency band of the sound to be heard on land.
That is, in the above-mentioned waterproof microphone, correction of the characteristic of the
sound collection signal and correction of the sensitivity caused by the sound wave transmission
characteristic different depending on the medium can be performed by the selected appropriate
equalizer.
[0015]
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BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in
detail below by the embodiments shown in the drawings. FIG. 1 is a longitudinal sectional view
showing a capacitor type waterproof microphone according to an embodiment of the present
invention. This waterproof microphone has a case 1 having an opening 2 communicating with
the outside on the front wall 1a, a back wall 3 for closing the back of the case 1, and a sound
pressure-electricity device for dividing the inside of the case 1 into a front chamber 5 and a rear
chamber 6 A signal conversion unit 4 is provided. The sound pressure-electric signal conversion
unit 4 is disposed on the periphery of a plate-like electrode 7 having a plurality of through holes
8 for circulating air to vibrate the diaphragm 11, and the electrode 7 in contact with the inner
surface of the case. It consists of an O-ring 9 as a spacer, and a diaphragm 11 which covers the
entire front surface of the electrode 7 with a narrow gap 10 formed by the O-ring 9.
[0016]
The diaphragm 11 and the back wall 3 are respectively provided with throttle holes 12 and 13
penetrating in the thickness direction. While these throttling holes 12 and 13 do not
substantially (significantly) transmit dynamic pressure fluctuation due to voice and the like of the
anteroom 5 connected to the outside and the outside of the case 1 through the opening 2, the
elevation or The diameter is set to substantially (significantly) transfer static pressure
fluctuations in the outer and front chambers 5 to the rear chamber 6 due to a gradual increase in
water depth and the like.
[0017]
The diaphragm 11 is formed by vapor-depositing metal on the surface of a so-called electret
material in which the surface of a synthetic resin plate is permanently charged by electrical
treatment, and a DC power (polarization voltage) is applied between the diaphragm 11 and the
electrode 7 It has the advantage of being resistant to moisture and corrosive environments as
compared to diaphragms made entirely of metal. In the rear chamber 6, for impedance
conversion to equalize the impedance of the sound pressure-electric signal conversion unit 4
including the diaphragm 11 and the electrodes 7 with the sound of the external output circuit by
the sound entering the front chamber The electronic circuit 14 is provided to connect the
electrode 7 and the back wall 3, and on the outer surface of the back wall 3, + and − output
terminals 15 and 16 for audio signals are provided.
[0018]
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The electronic circuit 14 has resistors R1 to R7, capacitors C1 to C4 and two stages of transistors
Q1 and Q2 forming an emitter follower as shown in the circuit diagram of FIG. To amplify the
high impedance of the sound pressure-electric signal conversion unit 4 to the low impedance of
the signal line or the speaker connected to the output terminals 15 and 16, thereby making the
waterproofing possible. It has been confirmed that the output impedance of the microphone is
suppressed to 100 Ω or less, and an audio signal can be transmitted well even if the output
signal line becomes as long as 200 m. Further, since the electronic circuit 14 uses a two-wire
transmission method in which the + side output terminal 15 is also used as a power supply line
to the voice-electric signal conversion unit 4, the configuration is simplified compared to the
three-wire system. Has the advantage of being
[0019]
The waterproof microphone of the above configuration operates as follows. For example, if the
pressure outside the case 1 is gradually decreased or gradually increased from the atmospheric
pressure, that is, increased or decreased statically from the atmospheric pressure, for example,
by raising the waterproof microphone to high mountains or placing it in a high pressure chamber
where the pressure gradually increases, The pressure of the front chamber 5 in communication
with the pressure of the front chamber 5 correspondingly increases or decreases statically, but
the increase or decrease of the pressure is, as shown by the arrows in FIG. The pressure in the
rear chamber 6 becomes equal to the pressure in the front chamber 5 substantially through the
through hole 8 of the electrode 7 and to the rear chamber 6. On the other hand, the diaphragm
holes 12 and 13 do not substantially transmit the dynamic pressure fluctuation of the outside
and the front chamber 5 due to the sound to be collected to the rear chamber 6, so that the
diaphragm 11 makes the pressure in the case large and small. It vibrates according to the voice
regardless of it. That is, the diaphragm 11 is immersed at an external high voltage and remains in
contact with the electrode 7 like a conventional condenser type microphone in which the rear
chamber is sealed, or is protruded at an external low voltage to form a gap 10 with the electrode
7. Vibrates properly according to the voice without excessive spreading. Therefore, according to
this condenser type microphone, sound can be collected well over a wide audio frequency band
which can not be collected by the conventional microphone under high pressure and low
pressure environments.
[0020]
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The resonance frequency of the rear chamber 6 is increased as the diameter of the aperture
holes 12 and 13 is reduced, so that the resonance point may be set optimally according to the
frequency of the sound to be collected. Also, even when the outside air temperature rises or falls
and the pressure difference statically fluctuates between the outside and the rear chamber 6,
sound is collected well over a wide audio frequency band by the same operation as described
above. be able to. In the capacitor type microphone of the above embodiment, since the
diaphragm 11 deposits a metal film on the surface of the synthetic resin, for example, an electret
material permanently charged by electric treatment, a direct current between the diaphragm 11
and the electrode 7 is generated. In addition to eliminating the need for a power supply, it is
possible to miniaturize and simplify the system, and has the advantage of being more resistant to
moisture and corrosive environments than a diaphragm made entirely of metal. In addition, since
this capacitor type microphone matches the impedance to the low impedance of the external
output circuit by the electronic circuit, it is possible to cover the entire mountain or case with a
waterproof cover where the transmission distance of the output signal becomes several hundred
meters long. There is an advantage that a good audio signal can be obtained.
[0021]
FIG. 2 is a longitudinal sectional view showing a capacitor type waterproof microphone of
another embodiment of the present invention. This waterproof microphone differs from the
embodiment of FIG. 1 only in that the detailed structure of the case 1 is changed mainly for
underwater use, the entire case is covered with a waterproof cover, and members are added to
the electronic circuit. The same members as in FIG. 1 are given the same reference numerals.
That is, the outer surface 1b of the front wall of the case 1 is inclined inward toward the central
opening 2 in consideration of shape deformation prevention by the contraction and contraction
of the waterproof cover 19 due to water pressure, and the outside of the back wall 3 in FIG. On
the top wall, bottom wall and front wall of the case 1 so that the front chamber 5 and the rear
chamber 6 of the case 1 covered by the waterproof cover 19 can be communicated with each
other. A communication hole 18 is provided, one end of which is at the periphery of the opening
2 and the other end of which is open to the outside of the back wall 3. The entire case 1 is
covered with a waterproof cover 19 made of an elastic material such as polyethylene,
polypropylene or vinyl chloride in a watertight manner. In the waterproof microphone of FIG. 2,
the communication hole 18 is provided in the wall of the case, so the diaphragm hole 12 of the
diaphragm 11 can be omitted.
[0022]
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The electronic circuit 20 provided in the rear chamber 6 includes a plurality of equalizers 21
corresponding to the frequency band to be received, a pressure sensor 22 for detecting an
internal pressure, and the equalizer based on the detection signal of the pressure sensor 22. A
control unit 23 which selects and operates 21 is added to the electronic circuit 14 of FIG. The
equalizer 21 may be provided between the transistors Q1 and Q2 in the circuit diagram of FIG. 3
or may be provided instead of the transistor Q1 and may include a band pass filter for passing a
signal of a specific frequency band.
[0023]
The control unit 23 determines whether the case 1 is placed in the atmosphere or in water based
on the atmospheric pressure represented by the detection signal of the pressure sensor 22. In
the former case, a conventional capacitor type used in the atmosphere is used. In the latter case,
the equalizer for the microphone is selected, and in the latter case, the equalizer is used to
correct the change in the frequency band of the sound collection signal due to the sound
transmission medium becoming water to the frequency band when the sound transmission
medium is the atmosphere. Activate selection. That is, in the sound collection signal from the
sound pressure-electric signal conversion unit 4, the change in the characteristics and sensitivity
attributable to the sound wave transmission characteristics in water by the appropriate equalizer
selected by the control unit 23 corresponds to the normal characteristics and sensitivity in the
air. It is corrected.
[0024]
The waterproof microphone of FIG. 2 operates as follows. When the waterproof microphone is
gradually submerged, the entire case 1 is covered with the waterproof cover 19 made of an
elastic material, so the waterproof cover 19 is compressed under the hydrostatic pressure
according to the water depth. The front wall 1b of the case 1 is inclined inward, and the rear face
of the case 1 is closed by the second back wall 17. Therefore, the waterproof cover 19 can be
contracted with ease and does not collapse. The air pressure in the case 1 is, as shown by the
arrow in FIG. 2, a hydrostatic pressure by the diaphragm hole 12 of the diaphragm 11, the
through hole 8 of the electrode 7, the diaphragm hole 13 of the back wall 3 and the
communication hole 18 of the case 1. The front chamber 5, the gap 10, and the rear chamber 6
increase equally to balance the static increase of On the other hand, since the throttling holes 12
and 13 do not substantially transmit the dynamic pressure fluctuation of the front chamber 5
through the waterproof cover 19 due to the sound wave in the water to be collected to the rear
chamber 6, the diaphragm 11 Vibrate accordingly. Therefore, unlike the conventional condenser-
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type microphone in which the rear chamber is sealed, the diaphragm 11 does not immerse and
remain in contact with the electrode 7 or the gap 10 between the electrode 7 and the electrode 7
does not expand excessively. Since the vibrator vibrates normally in response to the sound wave,
good sound collection can be performed over a wide frequency band. 0.3When it experimented
using the waterproof cover 19 of mm thickness, it was confirmed to endure 70 m of water
depths, and good sound collection can be performed in a wide frequency band of 5 Hz to 40 kHz
as compared with 700 Hz to 2 kHz in a conventional microphone. Was confirmed.
[0025]
The electric signal obtained by the voice-electric signal converter 4 including the diaphragm 11
and the electrode 7 is amplified and impedance-matched by the electronic circuit 20 in the rear
chamber 6, but the pressure sensor 22 of the electronic circuit 20 The control unit 23 selects the
appropriate equalizer 21 based on the detection signal, and the equalizer 21 allows the
characteristics and sensitivity of the electric signal to be characteristics and sensitivities in the
air. Corrected to Therefore, the sound signal output from the output terminals 15 and 16 can be
extended to several hundreds of meters by impedance matching as described for the waterproof
microphone in FIG. 1, and the reproduced sound of the sound signal is Due to the correction of
the characteristics and sensitivity, what has been shifted to the conventional high frequency side
becomes that of the normal frequency band that is heard in the atmosphere.
[0026]
The waterproof microphone of FIG. 2 can of course be used also in the air after removing the
waterproof cover 19, in which case the equalizer 23 for the atmosphere is selected and operated
by the control unit 23 based on the detection signal of the pressure sensor 22. As described in
the waterproof microphone, the sound can be collected well over a wide audio frequency band,
and the diaphragm 11 in which a metal film is deposited on a synthetic resin electret material
can be miniaturized and simplified, and moisture and It has the advantage of being resistant to
corrosive environments. The waterproof microphone of the above-described embodiment can be
manufactured at a cost of about 1/10 that of a conventional waterproof microphone that obtains
the same good sound collection characteristics as this in a complicated configuration.
[0027]
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The electronic circuit 20 may be provided with an equalizer for correcting the characteristics and
sensitivity of the sound collection signal in a negative pressure environment, and the control unit
23 may selectively operate the equalizer based on a detection signal representing the negative
pressure of the pressure sensor 22. Good. Also, the first stage transistor Q1 in FIG. 3 can be
replaced with an integrated circuit.
[0028]
As is apparent from the above description, in the waterproof microphone of claim 1, the
diaphragm and the back wall of the case cover the front of the plate-like electrode which divides
the inside of the case into the front and back chambers. Since the diaphragm is provided with the
throttling holes that do not substantially transfer the dynamic pressure fluctuation of the front
chamber to the rear chamber but substantially transmit the static pressure fluctuation of the
front chamber to the rear chamber As in the prior art, it does not immerse and remain in contact
with the electrode, and the gap between the electrode and the electrode does not extend
excessively, and vibrates normally in response to the sound wave, and a good collection over a
wide frequency band It can make sounds.
[0029]
According to the waterproof microphone of the second aspect of the present invention, the
communication hole is formed in the case wall so as to connect the front chamber and the
outside of the back wall, and the case is covered with the waterproof cover made of elastic
material. Due to the above-mentioned communication hole, the diaphragm is immersed in the
conventional manner due to the fluctuation of the external pressure and remains in contact with
the electrode while being prevented, and the gap with the electrode does not expand excessively.
Accordingly, it can be vibrated normally, good sound collection can be performed over a wide
frequency band, and in air, it can be favorably used even in a humid environment or a corrosive
atmosphere.
[0030]
In the waterproof microphone of claim 3, since the diaphragm permanently charges the surface
of the synthetic resin plate and metal is vapor-deposited on the surface, the DC power source to
be applied between the electrode and the diaphragm becomes unnecessary and the size and
weight are small. It can be used well even in the presence of some moisture or corrosive
environment without a waterproof cover.
[0031]
The waterproof microphone according to claim 4 is provided in the rear chamber with an
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electronic circuit for impedance conversion that equalizes the impedance of the sound pressureelectric signal conversion unit including the diaphragm and the electrode with the impedance of
the external output circuit. The generally high impedance of the sound pressure-electric signal
conversion unit can be equalized to the generally low impedance of the external output circuit, so
that the electrical signal representing the voice is energetically most efficiently transmitted to the
output circuit and good even over long transmission distances Sound signal can be obtained.
[0032]
In the waterproof microphone according to claim 5, the electronic circuit includes a plurality of
equalizers according to a frequency band to be received, and the pressure sensor and the
equalizer are selected in the case based on a detection signal of the pressure sensor. The control
unit selects and operates an appropriate equalizer according to the case internal pressure
represented by the detection signal of the pressure sensor, and a collection due to different
sound wave transmission characteristics depending on the sound wave transmission medium is
provided. Since the correction of the characteristics of the sound signal and the correction of the
sensitivity are performed, the sound emitted in the water can be collected like the sound emitted
in the atmosphere.
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