JP2007053522A - Condenser microphone - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a condenser microphone for shielding strong electromagnetic waves at a high frequency effectively even if using equipment for emitting electromagnetic waves at a high frequency, such as a portable telephone, thereby to prevent the cause of noise effectively. <P>SOLUTION: The condenser microphone comprises a microphone unit storage 40 for storing a condenser microphone unit 41, a circuit board for converting a sound signal converted by the condenser microphone unit 41 to an external output signal, a circuit board storage for storing the circuit board, and an output connector 10 for outputting the signal converted by the circuit board. The microphone unit storage 40, the circuit board storage, and the output connector 10 are shielded independently each. The circuit board storage stores a sound circuit board 31, and a DC/DC converter circuit board 21. A DC/DC converter circuit board storage 20 is surrounded by an independent shielded member 74. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a condenser microphone, and more particularly, to a shield structure that can effectively avoid the influence of electromagnetic noise even when a mobile phone or the like is used near the microphone.

  The condenser microphone includes a condenser microphone unit, an electric circuit including an impedance converter, and the like in a microphone case, and includes 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 that supports the metal mesh, a metal that is coupled to the microphone body, and a connector part.

  FIG. 3 shows an example of a conventional condenser microphone. This condenser microphone is a microphone called a 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 that forms the basis of a microphone and includes a small diameter portion 12 and a large diameter portion 13. In the small diameter portion 12 of the cylindrical member 11, three terminal pins 14 are held parallel to each other in the central axis direction of the cylindrical member 11. The connector portion 10 can be held in a vertical posture by being connected to a connector portion of a microphone stand (not shown), or can be connected to a cable-side connector provided at the end of the microphone cable.

  A support plate 15 is fixed to the upper end of the large-diameter portion 13 of the cylindrical member 11 in a horizontal orientation, 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. And the audio circuit board 31 are fixed in a posture in which they stand upright in the vertical direction while being supported by a pair of support columns 24 and 24. The support columns 24 and 24 are positioned on the outer peripheral edge of the support plate 15 in the radial direction, and a cylindrical microphone frame 60 is screwed to the flange portion 61 at the lower end of the support plate 24 and 24 so as to overlap with the upper ends thereof. By being fixed. A shock mount 62 is supported on an upper end portion of the microphone frame 60 via an appropriate interposition member, and the condenser microphone unit 41 is fixed on the shock mount 62 in a vertically rising posture. The configuration of the condenser microphone unit 41 itself is the same as the configuration of a conventionally known condenser microphone unit, and is arranged with a fixed pole fixed on the inner peripheral side of the support frame and facing this fixed pole with an appropriate gap. Having a vibrating plate. A polarization voltage is applied to the fixed pole. The diaphragm vibrates in response to the sound wave, and the gap between the diaphragm and the fixed pole changes to change the capacitance between the diaphragm and the fixed pole. By taking out this change in capacitance as a change in voltage, sound waves can be converted into electrical signals. 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, an FET 63 that forms the main body of an impedance converter is incorporated on the lower surface side of the shock mount 62, and an impedance-converted signal is input to the audio circuit board 31.

  The lower end inner periphery of a 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 this inward flange 51 hits the flange portion 61 at the lower end of the microphone frame 60 from above, so that the microphone case 50 is moved in the vertical direction. The position is regulated. The microphone case 50 surrounds 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 equally divided into two parts by the DC / DC converter circuit board 21 and the audio circuit board 31 coupled back to back. Of the internal space of the microphone case 50, the space on the DC / DC converter circuit board 21 side is the converter storage section 20, and the space on the audio circuit board 30 side is the audio circuit board storage section 30.

  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 is coupled to each other by appropriate means such as welding. The mesh 55 has a bottomed cylindrical shape formed by joining two meshes in a bellows shape, and is coupled to the microphone case 50 as described above with the open end of the tube facing down. A space surrounded by the two meshes 55 and 55 joined together constitutes the unit storage unit 40, the microphone unit 41 is located in the unit storage unit 40, and the microphone unit 41 is covered by the two meshes 55 and 55. It has been broken. The band 56 is disposed along the connecting line between the two meshes 55 and 55, and the band 56 is connected to the two meshes 55 and 55 by means such as welding, thereby increasing the bonding strength between the two meshes 55 and 55. Also, the beauty is enhanced.

  Not only the side-entry condenser microphones described above, but also other types of condenser microphones block the entry of high-frequency electromagnetic waves from the outside and prevent the generation of noise caused by the entry of electromagnetic waves. It is like that. For example, microphone cases, meshes, metal parts that support meshes, metal parts that are connected to the microphone body, etc. are connected to each other by soldering, brazing, bonding, etc., and each junction is electrically connected at multiple points. The shield is designed. However, even if each junction is electrically connected at a plurality of points, the shield tends to be incomplete. In particular, in the case where components are bonded to each other with an adhesive to achieve electrical continuity at a plurality of points, since they are electrically point contacts, the shield tends to be incomplete.

  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 part, and at least the upper surface of the base And a lower surface are covered with an electrostatic shield member that is non-conductive with each signal pin and conductive with the ground pin (see, for example, Patent Document 1).

  In addition, a condenser microphone, a support, and a shield case that integrally holds the circuit board block by caulking, and the circuit board block includes a ground pattern portion that is held electrically connected to the shield case. A mounting structure has been proposed (see, for example, Patent Document 2). Furthermore, a circuit board block is supported on one end side and a support body that supports a condenser microphone that detects sound pressure as a change in capacitance on the other side, and the condenser microphone, the support body, and the circuit board block are integrally crimped. And a capacitor microphone unit mounting structure in which a conductive tape is attached to the outer surface of the shield case and a portion of the conductive tape is fixed to a ground pattern (see, for example, Patent Document 3). ).

JP 2005-94575 A Japanese Unexamined Patent Publication No. 11-155198 JP-A-11-155197

The invention described in Patent Document 1 relates to a shield structure that prevents electromagnetic waves from entering a microphone from a connector portion. The inventions described in Patent Documents 2 and 3 are intended to shield the entire microphone by covering it with a shield case.
According to the invention described in each of the above patent documents, it effectively functions as a shield structure for electromagnetic waves from the outside that has been conventionally assumed. For example, interference due to electromagnetic waves such as VHF and UHF used in broadcasting can be adequately dealt with by the shield structures proposed in the above patent documents.

  However, the invention is not limited to the inventions described in the above-mentioned patent documents, and the shield structure in the conventional condenser microphone is insufficient as a countermeasure for mobile phones that have rapidly spread in recent years. In recent years, mobile phones are frequently used near condenser microphones under the circumstances where mobile phones are easily used everywhere. The frequency of electromagnetic waves used in mobile phones is higher than VHF, UHF, etc. When a mobile phone that emits high-frequency electromagnetic waves is placed near a condenser microphone, the conventional condenser microphone having a shield structure cannot block the penetration of electromagnetic waves emitted from the mobile phone.

In FIG. 3, an intrusion path of a high frequency electromagnetic wave is indicated by an arrow. An arrow A indicates an electromagnetic wave that is about to enter from the connector unit 10. The electromagnetic wave that has entered from the connector section 10 enters the audio circuit board 31 as indicated by an arrow B, and is mixed into the audio signal as noise.
The DC / DC converter circuit board 21 converts a direct current power source into alternating current of about 1 MHz, boosts it, rectifies and converts it into direct current, and applies the direct current voltage to a fixed pole as a polarization voltage. . Therefore, an AC signal of about 1 MHz is also generated from the DC / DC converter circuit board 21, and this AC signal wraps around the audio circuit board 31 as indicated by an arrow C and enters by electromagnetic coupling. The AC signal also enters the FET 63 and the microphone unit 41 as indicated by an arrow D, and enters the microphone audio signal by electromagnetic coupling. When the AC signal is large, the AC signal is output from the microphone together with the audio signal. This AC signal causes problems such as noise in a device to which the microphone is connected, for example, a mixer. A filter is provided at the output connector portion of the microphone in order to prevent high-frequency current from entering from the microphone cable side. When the elements constituting this filter are in the same shield as the audio signal circuit, depending on the component arrangement of the signal circuit, the AC signal is electromagnetically coupled to the audio signal circuit, and the high-frequency current entering from the cable may cause noise. Become.
Further, high-frequency electromagnetic waves emitted from a mobile phone or the like enter the unit housing portion 40 through the mesh 55 as indicated by an arrow E in FIG. The microphone unit 41 itself is rarely affected by electromagnetic waves, but the electromagnetic waves enter the audio circuit board 31 through the unit housing portion 40 and cause noise in the audio signal.

  The present invention has been made in view of a new problem that cannot be solved by the conventional shield structure of such a condenser microphone. Even if a device such as a mobile phone that emits high-frequency electromagnetic waves is used nearby. An object of the present invention is to provide a condenser microphone that can effectively block high-frequency and strong electromagnetic waves and effectively prevent noise.

  The present invention relates to a condenser microphone unit, a microphone unit housing portion that houses the condenser microphone unit, a circuit board that converts the audio signal converted by the condenser microphone unit into a signal that can be output to the outside, and the circuit. A condenser microphone having a circuit board housing part for housing a board and an output connector part for outputting a signal converted by the circuit board to the outside, the microphone unit housing part, the circuit board housing part, The most important feature is that each output connector portion is shielded independently.

The circuit board includes a voice circuit board and a DC / DC converter circuit in which a DC / DC converter for boosting a DC voltage and supplying a polarization voltage to the microphone unit is incorporated and integrally coupled with the voice circuit board. The circuit board composed of a circuit board and composed of an audio circuit board and a DC / DC converter circuit board is stored in a circuit board storage part surrounded by a microphone case, and the circuit board storage part faces the side facing the audio circuit board. The side facing the audio circuit board housing part and the DC / DC converter circuit board may be a DC / DC converter circuit board housing part. More preferably, the DC / DC converter circuit board housing portion is surrounded by an independent shield member.
Each shield member may be a conductive cloth.

  Since the microphone unit storage part, circuit board storage part, and output connector part are shielded independently, even if a high frequency electromagnetic wave source exists in the vicinity of the microphone and a high frequency electromagnetic wave tries to enter the microphone, The electromagnetic wave is prevented from entering the circuit board housing part through the microphone unit housing part, and the shield is prevented from entering the circuit board housing part through the connector part, and noise caused by the electromagnetic wave is prevented. It is possible to effectively avoid mixing in the audio signal.

  In one having a DC / DC converter circuit board in which a DC / DC converter for boosting a DC voltage and supplying a polarization voltage to a microphone unit is incorporated, the DC / DC converter circuit board is integrated with an audio circuit board. By storing in the circuit board storage portion, it is possible to prevent the AC oscillation signal generated by the DC / DC converter from leaking to the external circuit and to prevent noise from being mixed into the audio signal. Further, when 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 from entering the audio circuit board, and noise is mixed into the audio signal. This can be prevented more effectively.

  Hereinafter, embodiments 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 idea of the present invention is not limited to the side entry type but can be applied to other types of condenser microphones. The same components as those of the conventional example of the condenser microphone shown in FIG.

  The condenser microphone according to this embodiment is roughly divided into a connector portion 10, a DC / DC converter storage portion 20, an audio circuit board storage portion 30, and a unit storage portion 40 in order from the bottom in FIGS. The connector portion 10 includes a cylindrical member 11 that forms the base of a microphone, and the cylindrical member 11 is a stepped member that includes a lower small-diameter portion 12 and an upper large-diameter portion 13. In the small diameter portion 12 of the cylindrical member 11, three terminal pins 14 are held parallel to each other in the central axis direction of the cylindrical member 11. The connector portion 10 can be held in a vertical posture by being connected to a connector portion of a microphone stand (not shown), or can be connected to a cable-side connector provided at the end of the microphone cable.

  A support plate 15 is placed in a horizontal posture on the upper end of the large-diameter portion 13 of the cylindrical member 11, and is fixed to the cylindrical member 11 by 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, which are integrally coupled back to back, are supported in a pair of support posts 24, 24 in a vertically rising posture. It is fixed. The support columns 24 and 24 are located at the outer peripheral edge in the radial direction of the support plate 15, and a cylindrical microphone frame 60 is superimposed on the upper ends of the support columns 24 and 24, and a flange portion 61 at the lower end of the microphone frame 60 is formed. The microphone frame 60 is fixed by screwing the support posts 24 and 24. A shock mount 62 is supported on an upper end portion of the microphone frame 60 via a suitable interposition member, and the condenser microphone unit 41 is fixed on the shock mount 62 in a vertically rising posture.

  The configuration of the condenser microphone unit 41 itself is the same as the configuration of a conventionally known condenser microphone unit, and is arranged with a fixed pole fixed on the inner peripheral side of the support frame and facing this fixed pole with an appropriate gap. Having a vibrating plate. A polarization voltage is applied to the fixed pole. The diaphragm vibrates in response to the sound wave, and the capacitance between the diaphragm and the fixed pole changes due to the change in the gap between the diaphragm and the fixed pole. The sound wave can be converted into an electric signal by taking it out as a change in. 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, an FET 63 that is the main component of an impedance converter is incorporated on the lower surface side of the shock mount 62, and an 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 connected back to back is standing in the vertical direction, and sound waves from both horizontal directions can be converted into electric signals. Condenser microphone.

  The lower end inner periphery of a 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 this inward flange 51 hits the flange portion 61 at the lower end of the microphone frame 60 from above, so that the microphone case 50 is moved in the vertical direction. The position is regulated. The microphone case 50 surrounds 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 serves as a circuit board housing portion, and the circuit board housing portion is substantially equal between the DC / DC converter circuit board 21 and the audio circuit board 31 coupled back to back. It is divided into two. Of the circuit board housing portion that 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 housing portion 20, and the space on the audio circuit board 30 side is the audio circuit board housing portion. 30.

  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 is coupled to each other by appropriate means such as welding. The mesh 55 has a bottomed cylindrical shape formed by joining two meshes in a bellows shape, and is coupled to the microphone case 50 as described above with the open end of the tube facing down. A space surrounded by the two meshes 55 and 55 joined together constitutes the unit storage unit 40, the microphone unit 41 is located in the unit storage unit 40, and the microphone unit 41 is covered by the two meshes 55 and 55. It has been broken. The band 56 is disposed along the connecting line between the two meshes 55 and 55, and the band 56 is connected to the two meshes 55 and 55 by means such as welding, thereby increasing the bonding strength between the two meshes 55 and 55. Also, the beauty is enhanced.

  Compared with the example of the conventional condenser microphone shown in FIG. 3, this embodiment has structural features in the following points. The most significant feature is that the microphone unit storage section 40, the circuit board storage section, and the output connector section 10 are shielded independently from each other. The shield structure will be described more specifically. A shield member 71 made of a conductive cloth is arranged 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. In other words, a shield member 72 made of a conductive cloth is disposed on the inner periphery of 60. The one shield member 71 electromagnetically cuts off the circuit board housing portion composed of the DC / DC converter circuit board 21 and the audio circuit board 30 and the connector portion 10, and the other shield member 72 comprises the circuit The substrate storage unit and the microphone unit storage unit 40 are electromagnetically cut off. Therefore, the upper and lower ends of the circuit board housing portion are shielded by the shield members 71 and 72. The circuit board housing portion is further shielded by being covered with a metal microphone case 50 on the outer peripheral side. The outer peripheral side of the connector part 10 is covered and shielded by a small diameter part 12 of a metal cylindrical member 11. The unit storage section 40 is covered and shielded by a bottomed cylindrical metal mesh 55. A wire connecting the connector unit 10 and the circuit board in the circuit board storage unit is formed of an insulating coated wire, and the insulating coated wire penetrates the shield member 71. The wire connecting the circuit board and the microphone unit 41 is also made of an insulating coated wire, and the insulating coated wire penetrates the shield member 72.

  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 a ground terminal that is one of the three terminal pins 14. A conductor 73 obtained by punching a conductive cloth into a ring shape is interposed 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 each other through the conductor 73. Has been. Since the conductive pair made of the conductive cloth has elasticity, the coupling of the microphone frame 60 and the microphone case 50 causes the conductor 73 to be crushed by the elasticity, so that the microphone frame 60 and the microphone case 50 are almost completely separated. Conduction is ensured over the circumference, enhancing the electromagnetic shielding effect from the outer circumference side of the microphone.

  As described above, the DC / DC converter circuit board 21 itself is also a source of electromagnetic waves of about 1 MHz, and the electromagnetic waves wrap around the audio circuit board 31 and easily cause noise in the audio signal. Therefore, in this embodiment, one independent DC / DC converter module is incorporated in the DC / DC converter circuit board 21 and this converter module is surrounded by an independent shield member 74. The shield member 74 may be manufactured by molding a conductive cloth with a press or the like. However, since it is difficult to form the conductive cloth into a box shape, a conductive plate such as a metal plate is formed into a box shape. Also good.

  Various types of conductive cloth are supplied from various manufacturers and can be selected and used as appropriate. In this embodiment, for example, conductive cloth SUI-78- manufactured by Taiyo Wire Mesh Co., Ltd. 5010T was used. In this embodiment, it is desirable to use a conductive cloth having a certain thickness by being stacked in layers.

  In addition to the shields by the shield members 71, 72, 73, 74, a filter 75 is provided on the electric path connecting the connector unit 10 and the audio circuit board 31. The filter 75 is configured as 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 by bypassing a signal in a frequency band that becomes noise due to electromagnetic waves entering the audio circuit board 31 from the audio signal circuit.

  According to the embodiment of the condenser microphone according to the present invention described above, since the microphone unit housing portion 40, the circuit board housing portion, and the output connector portion 11 are shielded independently from each other, the arrow in FIG. As indicated by E, even if high-frequency electromagnetic waves enter the microphone unit housing portion 40 through the mesh 55 from the outside, the shield member 72 prevents the electromagnetic waves from entering the circuit board housing portion from the microphone unit housing portion 40. It is interrupted and the generation | occurrence | production of the noise resulting from electromagnetic waves approaching into a circuit board accommodating part can be prevented. Further, even if electromagnetic waves enter the connector part 10, the intrusion of electromagnetic waves from the connector part 10 to the circuit board housing part is blocked by the shield member 71, and noise caused by the electromagnetic waves entering the circuit board housing part Occurrence can be prevented. In this way, it is possible to effectively prevent the generation of noise due to the invasion of electromagnetic waves from the outside. In particular, even if a mobile phone is used in the vicinity of the microphone, for example, a strong radio wave having a high frequency from the mobile phone Can be prevented from entering the circuit board.

  In the illustrated embodiment, the members that independently shield the microphone unit storage unit 40, the circuit board storage unit, and the output connector unit 11 are each made of a conductive cloth. The conductive cloth is easy to attach, and it is also easy to enhance the shielding effect by overlapping the conductive cloth.

  In the illustrated embodiment, the circuit board housing portion includes a voice circuit board 31 and a DC / DC converter circuit board 21 for obtaining a polarization voltage from a DC power source. 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 becomes an electromagnetic wave source, it is likely to be a noise source of the audio circuit board 31. However, in the illustrated embodiment, the DC / DC converter module is surrounded by an independent shield member 74. 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.

  In the output connector section 10, a filter 75 is provided in the electric circuit connecting the output connector section 10 and the audio circuit board 31. Even if noise is mixed in the audio circuit, the filter 75 removes the noise. An audio signal can be output from the output connector unit 10.

  The present invention is not limited to the side-entry condenser microphone as in the illustrated embodiment, but can be applied to other types of condenser microphones.

The Example of the condenser microphone concerning this invention is shown, (a) is front sectional drawing, (b) is side sectional drawing. Is an exploded view of the above embodiment, (a) is a front sectional view, (b) is a side sectional view. The example of the conventional condenser microphone is shown, (a) is front sectional drawing, (b) is side sectional drawing.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Connector part 20 Converter accommodating part 21 DC / DC converter circuit board 30 Audio | voice circuit board accommodating part 31 Audio | voice circuit board 40 Microphone unit accommodating part 41 Microphone unit 50 Microphone case 71 Shield member 72 Shield member 74 Shield member 75 Filter

Claims (8)

A condenser microphone unit, a microphone unit housing portion that houses the condenser microphone unit, a circuit board that converts the audio signal converted by the condenser microphone unit into a signal that can be output to the outside, and the circuit board are housed. A condenser microphone having a circuit board housing part and an output connector part for outputting a signal converted by the circuit board to the outside,
The condenser microphone, wherein the microphone unit storage portion, the circuit board storage portion, and the output connector portion are shielded independently from each other.   The microphone unit is supported by a microphone frame, the circuit board is surrounded by a microphone case, and the internal space of the microphone case serves as a circuit board storage part. A shield member attached to the microphone frame, a microphone unit storage part, 2. The condenser microphone according to claim 1, wherein the upper and lower ends of the circuit board housing portion are shielded by a shield member attached to the boundary with the output connector portion.   The condenser microphone according to claim 1, wherein the microphone unit housing portion is formed by being surrounded by a bottomed cylindrical mesh coupled to a microphone case.   3. The condenser microphone according to claim 2, wherein the microphone frame has a cylindrical shape, and the microphone frame and the microphone case are coupled to each other through a conductive cloth.   3. The condenser microphone according to claim 2, wherein each shield member is made of a conductive cloth. The circuit board includes an audio circuit board and a DC / DC converter circuit board in which a DC / DC converter for boosting a DC voltage and supplying a polarization voltage to the microphone unit is incorporated and integrally coupled with the audio circuit board. And consist of
The circuit board composed of the audio circuit board and the DC / DC converter circuit board is housed in a circuit board housing portion surrounded by a microphone case,
2. The condenser microphone according to claim 1, wherein the circuit board housing part is an audio circuit board housing part on the side facing the audio circuit board and a DC / DC converter circuit board housing part on the side facing the DC / DC converter circuit board.   7. The condenser microphone according to claim 6, wherein an independent DC / DC converter module is incorporated in the DC / DC converter circuit board, and the converter module is surrounded by an independent shield member.   The condenser microphone according to claim 1, wherein a filter is provided in an electric path connecting the connector portion and the audio circuit board.

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