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JP2007053522

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DESCRIPTION JP2007053522
A condenser microphone capable of effectively shielding a strong electromagnetic wave of high
frequency and effectively causing noise even when a device emitting a high frequency
electromagnetic wave such as a cellular phone is used in the vicinity. Get A microphone unit
storage unit 40 for storing a condenser microphone unit 41, a circuit board for converting an
audio signal converted by the capacitor microphone unit 41 into an external output signal, and a
circuit board storage unit for storing the circuit board And an output connector unit 10 for
outputting the signal converted at the circuit board to the outside. The microphone unit storage
unit 40, the circuit board storage unit, and the output connector unit 10 are independently
shielded. The audio circuit board 31 and the DC / DC converter circuit board 21 are
accommodated in the circuit board accommodating portion, and the DC / DC converter circuit
board accommodating portion 20 is surrounded by the independent shield members 74.
[Selected figure] Figure 1
コンデンサーマイクロホン
[0001]
The present invention relates to a condenser microphone, and more particularly to a shield
structure capable of effectively avoiding the influence of electromagnetic wave noise even when
a portable telephone or the like is used in the vicinity of the microphone.
[0002]
The condenser microphone includes a condenser microphone unit, an electric circuit including an
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1
impedance converter, and the like in a microphone case, and a connector for outputting a signal
to the outside.
The microphone unit is housed in a unit housing portion, and the unit housing portion is
composed of a plurality of parts such as a metal mesh, a metal part supporting the metal mesh, a
metal coupled to the microphone body, and a connector part.
[0003]
FIG. 3 shows an example of a conventional condenser microphone. This condenser microphone is
a microphone called side entry type mainly used in a studio. In FIG. 3, the microphones are
roughly divided into a connector unit 10, a converter storage unit 20, an audio circuit board
storage unit 30, and a unit storage unit 40 in order from the bottom. The connector portion 10
has a stepped cylindrical member 11 which is a base of a microphone and which is composed of
a small diameter portion 12 and a large diameter portion 13. Three terminal pins 14 are held in
parallel with each other in the central axis direction of the cylindrical member 11 in the small
diameter portion 12 of the cylindrical member 11. The connector portion 10 can be held in a
vertical posture by being coupled to a connector portion of a microphone stand not shown, or
can be coupled to a cable side connector provided at the end of the microphone cable.
[0004]
A support plate 15 is fixed to the upper end of the large diameter portion 13 of the cylindrical
member 11 in a posture in the horizontal direction, and a DC / DC converter circuit board 21
integrally coupled back to back at the center of the upper surface of the support plate 15. The
audio circuit board 31 is supported by a pair of columns 24 and 24 and fixed in a vertically
standing posture. The columns 24, 24 are located on the radially outer peripheral edge of the
support plate 15, and are superimposed on the upper ends of the columns 24, 24, and the
cylindrical microphone frame 60 is screwed with the flange 61 at its lower end. It is fixed by
doing. A shock mount 62 is supported on an upper end portion of the microphone frame 60 via
an appropriate intervening member, and a condenser microphone unit 41 is fixed on the shock
mount 62 in a vertically standing posture. The configuration of the condenser microphone unit
41 itself is the same as that of the condenser microphone unit known in the prior art, and is
arranged opposite to a fixed pole fixed on the inner peripheral side of the support frame with an
appropriate gap to this fixed pole. And a vibrating plate. A polarization voltage is applied to the
fixed pole. In response to the sound wave, the diaphragm vibrates, and the gap between the
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diaphragm and the fixed electrode changes, whereby the capacitance between the diaphragm and
the fixed electrode changes. By extracting the change in capacitance as a change in voltage, the
sound wave can be converted into an electrical signal. Since the output impedance of the
condenser microphone unit 41 is high, an impedance converter for converting to a low
impedance is incorporated. In the example shown in FIG. 3, the FET 63 which is the main body of
the impedance converter is incorporated on the lower surface side of the shock mount 62, and
the signal subjected to impedance conversion is input to the audio circuit board 31.
[0005]
The inner peripheral portion of the lower end of the cylindrical microphone case 50 is fitted on
the outer periphery of the large diameter portion 13 of the cylindrical member 11, and both are
connected by an appropriate connecting means. An inward flange 51 is formed on the inner
peripheral side near the upper end of the microphone case 50, and the inward flange 51 abuts
on the lower flange portion 61 of the lower end of the microphone frame 60 from the upper side.
Position is regulated. The microphone case 50 encloses the DC / DC converter circuit board 21
and the audio circuit board 31. In other words, the cylindrical internal space of the microphone
case 50 is divided approximately equally by the back-to-back coupled DC / DC converter circuit
board 21 and the audio circuit board 31. Of the internal space of the microphone case 50, the
space on the DC / DC converter circuit board 21 side is the converter housing portion 20, and
the space on the audio circuit board 30 side is the audio circuit board housing portion 30.
[0006]
The outer periphery of the lower end portion of the mesh 55 is fitted on the inner peripheral side
of the upper end portion of the microphone case 50, and they are mutually coupled by an
appropriate means such as welding. The mesh 55 is in the form of a bottomed tube by joining
two meshes in a staggered manner, and is coupled to the microphone case 50 as described above
with the open end of the tube down. A space surrounded by the two coupled meshes 55 forms a
unit storage portion 40. The microphone unit 41 is located in the unit storage portion 40, and
the microphone unit 41 is covered by two meshes 55, 55. It is The band 56 is disposed along the
connection line of the two meshes 55, 55, and the band 56 is bonded to the two meshes 55, 55
by means such as welding to enhance the bonding strength of the two meshes 55, 55. Also, I am
enhancing the aesthetics.
[0007]
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Not only the side-entry type condenser microphone as described above, but also condenser
microphones of other types block the entry of high frequency electromagnetic waves from the
outside and prevent the generation of noise caused by the entrance of electromagnetic waves. It
is supposed to be. For example, the microphone case, the mesh, the metal component supporting
the mesh, the metal component coupled to the microphone body, etc. are connected to one
another by soldering, brazing, bonding, etc., and each junction shows electrical conduction at
multiple points. And a shield is planned. However, even if each junction is electrically conducted
at a plurality of points, the shield tends to be imperfect. In particular, in the case where
components are adhered to each other by an adhesive and electrical conduction is attempted at a
plurality of points, the shield is likely to be imperfect because it is electrically in point contact.
[0008]
The applicant has a base made of an electrical insulator connected to the rear end of the
microphone grip in order to reliably prevent electromagnetic waves from entering the inside of
the microphone from the connector portion, and at least the upper surface of the base A
configuration has been proposed in which the lower surface and the lower surface are covered
with an electrostatic shield member which is nonconductive to each signal pin and conductive to
the ground pin (see, for example, Patent Document 1).
[0009]
A condenser microphone unit comprising a condenser microphone and a shield case integrally
holding a support and a circuit board block by caulking, the circuit board block comprising a
ground pattern portion held in electrical continuity with the shield case. A mounting structure
has been proposed (see, for example, Patent Document 2).
Furthermore, a support that supports the circuit board block on one end and supports the
condenser microphone that detects the sound pressure as a change in capacitance on the other
side is integrally caulked with the condenser microphone, the support, and the circuit board
block. There is proposed a mounting structure of a condenser microphone unit having a shield
case for holding by and attaching a conductive tape to the outer surface of the shield case and
fixing a part of the conductive tape to a ground pattern (for example, see Patent Document 3) ).
[0010]
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JP, 2005-94575, A JP, 11-155198, A JP, 11-155, 197 A
[0011]
The invention described in Patent Document 1 relates to a shield structure that prevents
electromagnetic waves from entering the inside of the microphone from the connector portion.
The inventions described in Patent Documents 2 and 3 are intended to provide a shield by
covering the entire microphone with a shield case. According to the invention described in each
of the above patent documents, it effectively functions as a shielding structure of electromagnetic
waves from the outside assumed conventionally. For example, the interference by
electromagnetic waves such as VHF and UHF used in broadcasting can be sufficiently coped with
by the shield structure proposed in each of the above patent documents.
[0012]
However, not limited to the inventions described in the above-mentioned patent documents, the
shield structure in the conventional condenser microphone is insufficient as a countermeasure
for the mobile phone which has been widely spread in recent years. As in recent years, under
circumstances where a mobile phone is used freely anywhere, it often happens that the mobile
phone is used near a condenser microphone. The frequency of electromagnetic waves used in
mobile phones is higher than that of VHF, UHF, etc. When the mobile phone emitting this high
frequency electromagnetic wave is placed near the condenser microphone, the condenser
microphone having the conventional shield structure can not block the penetration of the
electromagnetic wave emitted from the mobile phone.
[0013]
In FIG. 3, the penetration path of the high frequency electromagnetic wave is indicated by an
arrow. Arrow A indicates an electromagnetic wave that is about to intrude from the connector
unit 10. The electromagnetic wave intruding from the connector portion 10 intrudes into the
audio circuit board 31 as shown by the arrow B, and is mixed into the audio signal as noise. The
DC / DC converter circuit board 21 converts a direct current power supply into an alternating
current of about 1 MHz, boosts it, rectifies it, converts it into a direct current, and applies this
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direct current voltage to the fixed electrode as a polarization voltage. . Therefore, an alternating
current signal of about 1 MHz is generated also from the DC / DC converter circuit board 21, and
this alternating current signal wraps around to the audio circuit board 31 as shown by the arrow
C and penetrates by electromagnetic coupling. The AC signal also penetrates the FET 63 and the
microphone unit 41 as indicated by the arrow D, and penetrates the voice signal of the
microphone by electromagnetic coupling. When the AC signal is large, the AC signal is output
from the microphone together with the audio signal. This alternating current signal causes a
problem such as causing noise in an apparatus to which the microphone is connected, for
example, a mixer. The output connector of the microphone is provided with a filter for blocking
high frequency current entering from the microphone cable side. When the elements constituting
this filter are in the same shield as the audio signal circuit, the AC signal is electromagnetically
coupled with the audio signal circuit depending on the arrangement of parts of the signal circuit,
and the high frequency current intruding from the cable causes noise. Become. In addition, a high
frequency electromagnetic wave emitted from a cellular phone or the like intrudes into the unit
storage unit 40 through the mesh 55 as shown by an arrow E in FIG. Although the microphone
unit 41 itself is unlikely to be affected by the electromagnetic wave, the electromagnetic wave
penetrates the audio circuit board 31 through the unit storage unit 40 and causes noise of the
audio signal.
[0014]
The present invention has been made in view of new problems that can not be solved by the
conventional shield structure of such a condenser microphone, and even if a device such as a
mobile phone that emits high frequency electromagnetic waves is used in the vicinity It is an
object of the present invention to provide a condenser microphone capable of effectively
shielding high frequency and strong electromagnetic waves and effectively causing noise.
[0015]
The present invention comprises a condenser microphone unit, a microphone unit storage unit
for housing the condenser microphone unit, a circuit board for converting an audio signal
converted by the condenser microphone unit into a signal that can be output to the outside, and
the circuit A condenser microphone comprising: a circuit board storage section for storing a
board; and an output connector section for outputting a signal converted by the circuit board to
the outside, the microphone unit storage section, the circuit board storage section, The output
connector sections are most characterized in that they are independently shielded.
[0016]
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The circuit board includes an audio circuit board, and a DC / DC converter circuit incorporated
with a DC / DC converter for boosting DC voltage and supplying polarized voltage to the
microphone unit and integrally coupled to the audio circuit board. The circuit board, which is
composed of a board and includes an audio circuit board and a DC / DC converter circuit board,
is accommodated in a circuit board accommodating portion surrounded by a microphone case,
and the circuit board accommodating portion faces the side facing the audio circuit board. It is
preferable that the side facing the audio circuit board storage unit and the DC / DC converter
circuit board be a DC / DC converter circuit board storage unit.
It is further preferable that the DC / DC converter circuit board storage portion be surrounded by
an independent shield member.
Each shield member may be made of a conductive cloth.
[0017]
Because the microphone unit storage unit, the circuit board storage unit, and the output
connector unit are independently shielded, an electromagnetic wave source of high frequency is
present in the vicinity of the microphone and an electromagnetic wave of high frequency tries to
enter the microphone. The electromagnetic wave is prevented from invading the circuit board
accommodating portion through the microphone unit accommodating portion, and the shielding
member is prevented from invading the circuit board accommodating portion through the
connector portion, and noise caused by the electromagnetic wave is generated. It is possible to
effectively avoid mixing in the audio signal.
[0018]
In the one having a DC / DC converter circuit board incorporating a DC / DC converter for
boosting DC voltage and supplying polarized voltage to the microphone unit, the DC / DC
converter circuit board is integrated with the audio circuit board By being housed in the circuit
board housing portion, it is possible to prevent the AC oscillation signal emitted by the DC / DC
converter from leaking to the external circuit, and to prevent the noise from being mixed in the
audio signal.
Furthermore, if the DC / DC converter circuit board housing portion is surrounded by an
independent shield member, the AC oscillation signal of the DC / DC converter can be prevented
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from coming around to the audio circuit board, and noise is mixed in the audio signal. Can be
prevented more effectively.
[0019]
Hereinafter, an embodiment of a condenser microphone according to the present invention will
be described with reference to the drawings. Although the illustrated embodiment is an example
of a side entry type condenser microphone, the technical concept of the present invention can be
applied not only to the side entry type but also to other types of condenser microphones. The
same components as those of the prior art of the condenser microphone shown in FIG. 3 are
denoted by the same reference numerals.
[0020]
The condenser microphone according to this embodiment is roughly divided into a connector
section 10, a DC / DC converter storage section 20, an audio circuit board storage section 30,
and a unit storage section 40 in this order from the bottom in FIG. 1 and FIG. The connector
portion 10 has a cylindrical member 11 forming a base of a microphone, and the cylindrical
member 11 is a stepped member including a lower small diameter portion 12 and an upper large
diameter portion 13. Three terminal pins 14 are held in parallel with each other in the central
axis direction of the cylindrical member 11 in the small diameter portion 12 of the cylindrical
member 11. The connector portion 10 can be held in a vertical posture by being coupled to a
connector portion of a microphone stand not shown, or can be coupled to a cable side connector
provided at the end of the microphone cable.
[0021]
A support plate 15 is mounted on the upper end of the large diameter portion 13 of the
cylindrical member 11 in a posture in the horizontal direction, and is fixed to the cylindrical
member 11 by an appropriate fixing means. At the center of the upper surface of the support
plate 15, the DC / DC converter circuit board 21 and the audio circuit board 31 integrally
coupled back to back are supported by the pair of columns 24 and 24 in a vertically standing
posture It is fixed. The columns 24, 24 are located on the radially outer peripheral edge of the
support plate 15. The cylindrical microphone frame 60 is superimposed on the upper ends of the
columns 24, 24, and the flange portion 61 of the lower end of the microphone frame 60 is The
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microphone frame 60 is fixed by screwing on the columns 24. A shock mount 62 is supported on
an upper end portion of the microphone frame 60 via an appropriate intervening member, and a
condenser microphone unit 41 is fixed on the shock mount 62 in a vertically standing posture.
[0022]
The configuration of the condenser microphone unit 41 itself is the same as that of the
condenser microphone unit known in the prior art, and is arranged opposite to a fixed pole fixed
on the inner peripheral side of the support frame with an appropriate gap to this fixed pole. And
a vibrating plate. A polarization voltage is applied to the fixed pole. In response to the sound
wave, the diaphragm vibrates, and the gap between the diaphragm and the fixed electrode
changes, thereby changing the electrostatic capacitance between the diaphragm and the fixed
electrode. Sound waves can be converted into electrical signals by taking out as a change of Since
the output impedance of the condenser microphone unit 41 is high, an impedance converter for
converting to a low impedance is incorporated. In the illustrated embodiment, the FET 63 which
is the main body of the impedance converter is incorporated on the lower surface side of the
shock mount 62 so that the impedance-converted signal is input to the audio circuit board 31.
The microphone according to this embodiment is a side entry type in which a microphone unit
41 in which two units are coupled in a back-to-back manner rises vertically and can convert
sound waves from both horizontal directions into electric signals. It is a condenser microphone.
[0023]
The inner peripheral portion of the lower end of the cylindrical microphone case 50 is fitted on
the outer periphery of the large diameter portion 13 of the cylindrical member 11, and both are
connected by an appropriate connecting means. An inward flange 51 is formed on the inner
peripheral side near the upper end of the microphone case 50, and the inward flange 51 abuts
on the lower flange portion 61 of the lower end of the microphone frame 60 from the upper side.
Position is regulated. The microphone case 50 encloses the DC / DC converter circuit board 21
and the audio circuit board 31. In other words, the cylindrical internal space of the microphone
case 50 is a circuit board storage part, and the circuit board storage part is substantially equal
between the DC / DC converter circuit board 21 and the audio circuit board 31 coupled back-toback. It is divided into two. In the circuit board storage section which is the internal space of the
microphone case 50, the space on the DC / DC converter circuit board 21 side is the DC / DC
converter circuit board storage section 20, and the space on the audio circuit board 30 side is the
audio circuit board storage section. It is thirty.
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[0024]
The outer periphery of the lower end portion of the mesh 55 is fitted on the inner peripheral side
of the upper end portion of the microphone case 50, and they are mutually coupled by an
appropriate means such as welding. The mesh 55 is in the form of a bottomed tube by joining
two meshes in a staggered manner, and is coupled to the microphone case 50 as described above
with the open end of the tube down. A space surrounded by the two coupled meshes 55 forms a
unit storage portion 40. The microphone unit 41 is located in the unit storage portion 40, and
the microphone unit 41 is covered by two meshes 55, 55. It is The band 56 is disposed along the
connection line of the two meshes 55, 55, and the band 56 is bonded to the two meshes 55, 55
by means such as welding to enhance the bonding strength of the two meshes 55, 55. Also, I am
enhancing the aesthetics.
[0025]
This embodiment has the following structural features in comparison with the example of the
conventional condenser microphone shown in FIG. The most significant feature is that the
microphone unit storage unit 40, the circuit board storage unit, and the output connector unit 10
are shielded independently. More specifically, the shield member 71 made of conductive cloth is
disposed on the inner periphery of the boundary between the small diameter portion 12 and the
large diameter portion 11 of the cylindrical member 11 constituting the output connector
portion 10, and the microphone frame A shield member 72 made of a conductive cloth is
disposed on the inner circumference of 60. The one shield member 71 electromagnetically shuts
off the housing portion of the circuit board including the DC / DC converter circuit board 21 and
the audio circuit board 30, and the connector portion 10, and the other shield member 72 is the
circuit described above The substrate storage unit and the microphone unit storage unit 40 are
electromagnetically isolated. Therefore, the upper and lower ends of the circuit board storage
portion are shielded by the shield members 71 and 72. The circuit board storage portion is
further shielded by covering the outer peripheral side thereof with a metal microphone case 50.
The outer peripheral side of the connector portion 10 is covered and shielded by the small
diameter portion 12 of the metal cylindrical member 11. The unit storage portion 40 is shielded
by being covered with a cylindrical metal mesh 55 with a bottom. A wire connecting the
connector portion 10 and the circuit board in the circuit board storage portion is made of an
insulation coated wire, and the insulation coated wire penetrates the shield member 71. The wire
connecting the circuit board and the microphone unit 41 is also made of an insulation coated
wire, and the insulation coated wire penetrates the shield member 72.
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[0026]
The mesh 55, the microphone frame 60, the microphone case 50, and the cylindrical member 11
are electrically connected to each other, and are electrically connected to the ground terminal,
which is one of the three terminal pins 14. A conductor 73 in which a conductive cloth is
punched out in a ring shape intervenes at a coupling portion between the cylindrical microphone
frame 60 and the microphone case 50, and the microphone frame 60 and the microphone case
50 are coupled with the conductor 73 interposed. It is done. Since the conductive pair made of
the conductive cloth has elasticity, by combining the microphone frame 60 and the microphone
case 50, the conductor 73 is crushed by the elasticity and almost all of the microphone frame 60
and the microphone case 50 are Conduction is ensured for the whole circumference, and the
electromagnetic shielding effect from the outer peripheral side of the microphone is enhanced.
[0027]
As described above, the DC / DC converter circuit board 21 itself is also a generation source of
an electromagnetic wave of about 1 MHz, and this electromagnetic wave leaks into the audio
circuit board 31 and tends to cause noise of the audio signal. Therefore, in this embodiment, one
independent DC / DC converter module is incorporated in the DC / DC converter circuit board
21, and the converter module is surrounded by independent shield members 74. The shield
member 74 may be manufactured by molding a conductive cloth by a press or the like, but since
it is difficult to mold the conductive cloth in a box shape, a conductive plate, for example, a metal
plate is formed in a box shape. It is also good.
[0028]
Although various types of conductive cloths are supplied from various manufacturers and
suitable ones can be selected and adopted, in this embodiment, for example, conductive cloth
SUI-78- manufactured by Solar Wire Mesh Co., Ltd. 5010 T was used. Also, in this embodiment, it
is desirable to use a conductive cloth stacked in several layers and having a certain thickness.
[0029]
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11
In addition to the shields by the shield members 71, 72, 73, 74, a filter 75 is provided in an
electric path connecting the connector portion 10 and the audio circuit board 31. The filter 75 is
formed on a circuit board, and the circuit board extends from the connector portion toward the
shield member 71 in the small diameter portion 12 of the cylindrical member 11 and extends to
the front of the shield member 71. The filter 75 removes noise from the audio signal circuit by
bypassing the signal of the frequency band that becomes noise when the electromagnetic wave
penetrates the audio circuit board 31.
[0030]
According to the above-described embodiment of the condenser microphone according to the
present invention, the microphone unit storage unit 40, the circuit board storage unit, and the
output connector unit 11 are shielded independently of one another. As shown by E, even if a
high frequency electromagnetic wave penetrates the inside of the microphone unit housing 40
through the mesh 55 from the outside, the electromagnetic wave from the microphone unit
housing 40 to the circuit board housing is the shield member 72. It is possible to prevent the
generation of the noise caused by the electromagnetic wave entering the circuit board storage
unit being shut off. Further, even if electromagnetic waves enter the connector portion 10, the
shielding member 71 blocks the entry of electromagnetic waves from the connector portion 10
into the circuit board storage portion, and noise caused by the electromagnetic waves entering
the circuit board storage portion It can prevent the occurrence. As described above, the
generation of noise due to the penetration of electromagnetic waves from the outside can be
effectively prevented. In particular, even if, for example, a mobile phone is used in the vicinity of
the microphone, a strong radio wave with a high frequency from the mobile phone Can be
prevented from invading the circuit board.
[0031]
In the illustrated embodiment, the members for independently shielding the microphone unit
storage unit 40, the circuit board storage unit, and the output connector unit 11 are made of
conductive cloth. The conductive cloth is easy to attach, and it is also easy to enhance the
shielding effect by stacking in layers.
[0032]
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In the illustrated embodiment, in the circuit board storage unit, together with the audio circuit
board 31, the DC / DC converter circuit board 21 for obtaining the polarization voltage from the
DC power supply includes one DC / DC converter circuit board 21. Two independent DC / DC
converter modules are incorporated, and the converter modules are surrounded by independent
shield members 74. Since the DC / DC converter module itself has an AC oscillator and is an
electromagnetic wave source, it is likely to be a noise source of the audio circuit board 31, but in
the illustrated embodiment, the DC / DC converter module is Therefore, the electromagnetic
wave does not leak from the DC / DC converter module to the outside, and the noise source of
the audio circuit board 31 is avoided.
[0033]
In the output connector section 10, the filter 75 is provided in the electric path connecting the
output connector section 10 and the audio circuit board 31, so even if noise is mixed in the audio
circuit, the filter 75 removes noise. The audio signal can be output from the output connector
unit 10.
[0034]
The present invention is applicable not only to the side-entry condenser microphone as in the
illustrated embodiment but also to other types of condenser microphones.
[0035]
The Example of the condenser microphone concerning this invention is shown, (a) is front
sectional drawing, (b) is side surface sectional drawing.
Is an exploded view of the above embodiment, (a) is a front sectional view, (b) is an side sectional
view showing an embodiment of a conventional condenser microphone, (a) is a front sectional
view, b) is a side sectional view.
Explanation of sign
[0036]
DESCRIPTION OF SYMBOLS 10 connector part 20 converter accommodating part 21 DC / DC
converter circuit board 30 audio circuit board accommodating part 31 audio circuit board 40
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microphone unit accommodating part 41 microphone unit 50 microphone case 71 shielding
member 72 shielding member 74 shielding member 75 filter
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