JP2016213817A - Capacitor microphone unit and capacitor microphone and manufacturing method of capacitor microphone unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a capacitor microphone unit which flattens frequency response in a high frequency band.SOLUTION: A capacitor microphone unit includes a unit case 2c including a sound wave introduction hole, a diaphragm 22 which is housed in the unit case and vibrated by a sound wave from the sound wave introduction hole, and an acoustic resistor 50 disposed between the sound wave introduction hole and the diaphragm. The acoustic resistor includes two elastic members 51, 52 which are in pressure contact with each other. At least one of the two elastic members is curved into a protruding shape before making the pressure contact. A protruding side surface of the one of the elastic members which is curved into the protruding shape serves as a pressure contact surface which makes pressure contact with the other elastic member.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a condenser microphone unit, a condenser microphone, and a method of manufacturing a condenser microphone unit.

  The control method of the omnidirectional condenser microphone is elastic control. Therefore, the resonance frequency of the mechanical vibration system of the omnidirectional condenser microphone is designed to be a high frequency near the upper limit of the sound collection band. As a result, the frequency response in the frequency band below the resonance frequency of the omnidirectional condenser microphone is flat.

  When the resonance frequency of the condenser microphone is set outside the audible band, the frequency response of the entire sound collection band becomes flat, but the sensitivity of the condenser microphone decreases. On the other hand, when the resonance frequency of the condenser microphone is set near the center of the sound collection band, the sensitivity of the condenser microphone increases, but in the frequency band higher than the resonance frequency, the frequency response decreases with an inclination of −12 dB / Oct. Therefore, the resonance frequency is set near the upper limit (about 10 kHz) of the sound collection band and the resonance sharpness is adjusted, so that the frequency response of the sound collection band of the condenser microphone is flattened.

FIG. 5 is a side sectional view of a conventional omnidirectional condenser microphone unit.
The condenser microphone unit (hereinafter referred to as “unit”) 2 a includes a unit case 2 c and an electroacoustic transducer 20. The electroacoustic transducer 20 converts a sound wave from a sound source into an electric signal and outputs the electric signal. The electroacoustic transducer 20 is accommodated in the unit case 2c. The unit 2a is attached to a circuit case (not shown).

  The unit case 2c is made of metal. The unit case 2c has a bottomed cylindrical shape. The bottom surface of the unit case 2c is located on the front side of the unit case 2c (the direction of the microphone directed toward the sound source during sound collection; the same applies hereinafter). The unit case 2c includes a sound wave introduction hole 2h, an opening end 2e, a flange portion 2f, and a female screw portion 2s. The sound wave introduction hole 2h introduces sound waves from the sound source into the unit case 2c. The sound wave introduction hole 2h is disposed on the bottom surface of the unit case 2c. The open end 2e is a rear end of the unit case 2c. The flange portion 2f is configured by the bottom surface of the unit case 2c in which the sound wave introduction hole 2h is disposed. The female screw portion 2s corresponds to a male screw portion of a circuit case (not shown). The female screw portion 2s is disposed on the rear end side of the inner peripheral surface of the unit case 2c.

  The electroacoustic transducer 20 includes a diaphragm holder (diaphragm ring) 21, a diaphragm 22, a spacer 23, a fixed pole 24, an insulator 25, a support body 26, an insulating seat 27, and an electrode lead terminal. 28 and a contact pin 29.

  The diaphragm holder 21 holds the diaphragm 22. The diaphragm holder 21 has a ring shape. The diaphragm holder 21 has a hole in the center. The diaphragm 22 has a disk shape. The diaphragm 22 has a metal (preferably gold) deposited film on one side. The diaphragm 22 is a synthetic resin thin film. The diaphragm 22 is held by the diaphragm holder 21 in a state where a predetermined tension is applied. The spacer 23 is made of synthetic resin or the like. The spacer 23 has a thin ring shape. The fixed pole 24 is made of metal. The fixed pole 24 has a disk shape. An electret plate is affixed to at least one surface side of the fixed pole 24, for example, the surface facing the diaphragm 22. The fixed pole 24 and the electret plate constitute an electret board. The diaphragm 22 is disposed to face the fixed pole 24 with the spacer 23 interposed therebetween. An air layer (gap) having a width corresponding to the thickness of the spacer 23 is formed between the diaphragm 22 and the fixed pole 24. The diaphragm 22 and the fixed pole 24 constitute a capacitor. The capacitance of this capacitor changes when the diaphragm 22 is vibrated by the sound wave from the sound source passing through the sound wave introduction hole 2h.

  The insulator 25 supports the fixed pole 24 in a state where it is electrically insulated from the unit case 2 c and the diaphragm 22. The insulator 25 includes a plurality of communication holes. The penetrating direction of the communication hole is the thickness direction of the insulator 25 (the left-right direction in FIG. 5).

  The support 26 is attached to the rear surface of the insulator 25 in an airtight state. An air chamber is formed between the fixed pole 24 and the insulator 25 and between the insulator 25 and the support body 26 through a communication hole of the insulator 25.

  The insulating seat 27 is disposed behind the support body 26. The insulating seat 27 includes a connecting hole. The penetration direction of the connecting hole is the thickness direction of the insulating seat 27 (the left-right direction in FIG. 5).

  The electrode lead terminal 28 takes out a signal from the fixed electrode 24. The electrode lead terminal 28 is attached to the center portion of the insulator 25. The rear end portion of the electrode lead terminal 28 is inserted into the front half portion of the connection hole of the insulating seat 27. The contact pin 29 is electrically connected to the electrode lead terminal 28 via an elastic material (not shown) such as a conductive sponge. The contact pin 29 is inserted into the rear half of the connecting hole of the insulating seat 27.

  The electroacoustic transducer 20 is fixed in the unit case 2c by a lock ring 20r fitted into the female screw portion 2s.

  For example, a field effect transistor (FET) or a circuit is incorporated in the circuit case. The FET constitutes an impedance converter of the electroacoustic transducer 20. The circuit is, for example, a circuit that converts a change in capacitance generated between the diaphragm 22 and the fixed pole 24 into an electric signal and outputs the electric signal.

FIG. 6 is a mechanical equivalent circuit of a conventional omnidirectional condenser microphone.
In the figure, p is the sound pressure of the sound wave from the sound source, m0 is the mass of the diaphragm 22, s0 is the stiffness of the diaphragm 22, and r0 is the braking of the diaphragm 22 by the air layer between the diaphragm 22 and the fixed pole 24. Resistance, rf is the front side of the diaphragm 22 (the front opening end facing the rear opening end where the diaphragm 22 is held among the two opening ends facing the holes of the ring-shaped diaphragm holder 21). The acoustic resistance, sf is the stiffness of the air chamber in front of the diaphragm 22 (the internal space of the hole of the ring-shaped diaphragm holder 21), and s1 is the stiffness of the air chamber behind the diaphragm 22.

  The braking resistance r0 of the diaphragm 22 reduces the resonance sharpness to some extent. However, due to the shape effect, the frequency response in the frequency band above the resonance frequency is increased. Therefore, it is necessary to adjust the frequency response by adding an acoustic resistance material in front of the diaphragm 22. In the past, it has been proposed to adjust the frequency response by making the acoustic resistance of the acoustic resistance material in front of the diaphragm variable (see, for example, “Patent Document 1”).

JP 2000-50386 A

  However, when an acoustic resistance material having the same area as the vibration part of the diaphragm 22 is added in front of the diaphragm 22, the frequency response is affected by internal loss due to vibration of the acoustic resistance material.

FIG. 7 is a graph showing the frequency response of a condenser microphone in which no acoustic resistance material is added in front of the diaphragm.
The figure shows that the frequency response in the frequency band above the resonance frequency is increasing.

FIG. 8 is a graph showing the frequency response of a condenser microphone in which an acoustic resistance material made of a nonwoven fabric is added in front of the diaphragm.
The figure shows that the frequency response near 2-3 kHz increases due to the vibration of the acoustic resistance material, and the frequency response near 15 kHz decreases due to the internal loss of the material.

  The present invention has been made to solve the above-described problems of the prior art, and an object thereof is to provide a condenser microphone unit that can flatten the frequency response in a high frequency band.

  The present invention includes a unit case having a sound wave introduction hole, a vibration plate housed in the unit case and vibrated by sound waves from the sound wave introduction hole, and an acoustic resistor disposed between the sound wave introduction hole and the vibration plate, The acoustic resistor includes two elastic members pressed against each other, and at least one of the two elastic members is curved in a convex shape before the pressure welding, and is curved in a convex shape. The convex side surface of one elastic member is a pressure contact surface with the other elastic member.

  According to the present invention, the frequency response in a high frequency band can be flattened.

It is sectional drawing of the side view of the capacitor | condenser microphone unit concerning this invention. FIG. 2 is a side sectional exploded view of the condenser microphone unit of FIG. 1. It is sectional drawing of the side view of the capacitor | condenser microphone concerning this invention. It is a graph which shows the frequency response of the capacitor | condenser microphone of FIG. It is sectional drawing of the side view of the conventional condenser microphone unit. It is a mechanical equivalent circuit of a conventional condenser microphone. It is a graph which shows the frequency response of the conventional condenser microphone. It is a graph which shows the frequency response of another conventional condenser microphone.

  Hereinafter, embodiments of a condenser microphone unit, a condenser microphone, and a method of manufacturing a condenser microphone unit according to the present invention will be described with reference to the drawings.

Condenser Microphone Unit FIG. 1 is a side sectional view showing an embodiment of a condenser microphone unit (hereinafter referred to as “unit”) according to the present invention.
FIG. 2 is an exploded cross-sectional view of the unit.

  The unit 2 includes a unit case 2c, an electroacoustic transducer 20, and an acoustic resistor 50. The electroacoustic transducer 20 converts a sound wave from a sound source into an electric signal and outputs the electric signal. The electroacoustic transducer 20 is accommodated in the unit case 2c. The operation of the acoustic resistor 50 will be described later.

  The unit 2 is different from the unit 2a in that an acoustic resistor 50 is added to the conventional unit 2a shown in FIG.

  The unit case 2c is made of metal. The unit case 2c has a bottomed cylindrical shape. The bottom surface of the unit case 2c is located on the front side of the unit case 2c (the direction of the microphone directed toward the sound source during sound collection; the same applies hereinafter). The unit case 2c includes a sound wave introduction hole 2h, an opening end 2e, a flange portion 2f, and a female screw portion 2s. The sound wave introduction hole 2h introduces sound waves from the sound source into the unit case 2c. The sound wave introduction hole 2h is disposed on the bottom surface of the unit case 2c. The open end 2e is a rear end of the unit case 2c. The flange portion 2f is configured by the bottom surface of the unit case 2c in which the sound wave introduction hole 2h is disposed. The female screw portion 2s is disposed on the rear end side of the inner peripheral surface of the unit case 2c.

  The electroacoustic transducer 20 includes a diaphragm holder (diaphragm ring) 21, a diaphragm 22, a spacer 23, a fixed pole 24, an insulator 25, a support body 26, an insulating seat 27, and an electrode lead terminal. 28 and a contact pin 29.

  The diaphragm holder 21 holds the diaphragm 22. The diaphragm holder 21 has a ring shape.

  The diaphragm 22 has a disk shape. The diaphragm 22 has a metal (preferably gold) deposited film on one side. The diaphragm 22 is a synthetic resin thin film. The diaphragm 22 is held (stretched) in a state where a predetermined tension is applied to the diaphragm holder 21.

  The spacer 23 is made of synthetic resin or the like. The spacer 23 has a thin ring shape.

  The fixed pole 24 is made of metal. The fixed pole 24 has a disk shape. An electret plate is affixed to at least one surface side of the fixed pole 24, for example, the surface facing the diaphragm 22. The fixed pole 24 and the electret plate constitute an electret board.

  The diaphragm 22 is disposed to face the fixed pole 24 with the spacer 23 interposed therebetween. An air layer (gap) having a width corresponding to the thickness of the spacer 23 is formed between the diaphragm 22 and the fixed pole 24. The diaphragm 22 and the fixed pole 24 constitute a capacitor. The capacitance of this capacitor changes when the diaphragm 22 is vibrated by the sound wave from the sound source passing through the sound wave introduction hole 2h.

  The insulator 25 supports the fixed pole 24 in a state where it is electrically insulated from the unit case 2 c and the diaphragm 22. The insulator 25 includes a plurality of communication holes. The penetrating direction of the communication hole is the thickness direction of the insulator 25 (the left-right direction in FIG. 1).

  The support 26 is attached to the rear surface of the insulator 25 in an airtight state. An air chamber is formed between the fixed pole 24 and the insulator 25 and between the insulator 25 and the support body 26 through a communication hole of the insulator 25.

  The insulating seat 27 is disposed behind the support body 26. The insulating seat 27 includes a connecting hole. The penetration direction of the connecting hole is the thickness direction of the insulating seat 27 (the left-right direction in FIG. 1).

  The electrode lead terminal 28 takes out a signal from the fixed electrode 24. The electrode lead terminal 28 is attached to the center of the insulator 25. The rear end portion of the electrode lead terminal 28 is inserted into the front half portion of the connection hole of the insulating seat 27. The contact pin 29 is electrically connected to the electrode lead terminal 28 via an elastic material (not shown) such as a conductive sponge. The contact pin 29 is inserted through the rear half of the connection hole of the insulating seat 27.

  The electroacoustic transducer 20 is fixed in the unit case 2c by a lock ring 20r fitted into the female screw portion 2s.

  The acoustic resistor 50 has a disk shape. The acoustic resistor 50 includes elastic members 51 and 52. The elastic members 51 and 52 are plate materials. The elastic members 51 and 52 are disk-shaped. The elastic members 51 and 52 are produced by electroforming, for example. The elastic members 51 and 52 are made of nickel, for example. The elastic members 51 and 52 include a plurality of openings. The through direction of the opening is the thickness direction of the elastic members 51 and 52 (the left and right direction in FIG. 2). The elastic members 51 and 52 are pressed against each other.

  Each of the elastic members 51 and 52 has a central portion in a plan view (a central portion in the vertical direction on the paper surface in FIG. 2) curved in a convex shape before pressure contact. That is, the elastic member 51 is curved backward (to the right in FIG. 2). The elastic member 52 is curved forward (leftward in FIG. 2).

  In each of the elastic members 51 and 52, the convex side surface curved in a convex shape is the pressure contact surface with the other elastic member. That is, the convex side surface (the right surface in FIG. 2) of the elastic member 51 is a pressure contact surface with the elastic member 52. The convex side surface (the left surface in FIG. 2) of the elastic member 52 is a pressure contact surface with the elastic member 51. The elastic members 51 and 52 constitute a disc-shaped acoustic resistor 50 by pressing the convex side surfaces which are the respective pressure contact surfaces.

  Of the two elastic members constituting the acoustic resistor 50, at least one elastic member may be curved in a convex shape before the press contact. In this case, the other elastic member has a flat plate shape that is not curved. The convex side surface of the curved elastic member is a pressure contact surface with the other elastic member.

● Manufacturing Method of Condenser Microphone Unit Next, a manufacturing method of the unit 2 will be described.

  First, the elastic members 51 and 52 are accommodated in the unit case 2c. At this time, the elastic members 51 and 52 are disposed so that the respective convex side surfaces face each other. Of the elastic members 51 and 52 housed in the unit case 2c, the elastic member 51 contacts the flange portion 2f. As a result, the elastic member 51 is positioned in the unit case 2c.

  Next, the electroacoustic transducer 20 including the diaphragm 22 is accommodated in the unit case 2c. At this time, the electroacoustic transducer 20 presses the elastic members 51 and 52. That is, the diaphragm holding body 21 of the electroacoustic transducer 20 housed in the unit case 2c presses the elastic member 52 toward the flange portion 2f of the unit case 2c. As a result, the elastic member 51 is pressed from the elastic member 52 to the flange portion 2f side. The electroacoustic transducer 20 accommodated in the unit case 2c is fixed in the unit case 2c by a lock ring 20r.

  When the electroacoustic transducer 20 is housed in the unit case 2c, the elastic members 51 and 52 are pressed from the diaphragm holder 21 toward the flange portion 2f, and at the same time, from the flange portion 2f to the diaphragm holder 21 ( It is pressed to the diaphragm 22) side. That is, the elastic members 51 and 52 are sandwiched between the unit case 2c and the electroacoustic transducer 20 in a state where internal stress is applied so as to press each other. The elastic members 51 and 52 are held in the unit case 2c.

Next, a condenser microphone according to the present invention (hereinafter referred to as “microphone”) will be described.

FIG. 3 is a side sectional view showing the embodiment of the microphone.
The microphone 1 includes a unit 2, a circuit case 3 c, a connector support 31, a holder 32, a contact probe 33, a board fixing part 34, an audio signal output circuit board 35, and an output transformer 36 described above. The connecting member 37, the connector case 40, and the output connector are provided.

  The circuit case 3c is made of metal. The circuit case 3c is cylindrical. The circuit case 3c includes a female screw portion 3s. The female screw portion 3s is disposed on the inner peripheral surface on the front end side of the circuit case 3c.

  The circuit case 3c accommodates a connector support 31, a holder 32, a contact probe 33, a board fixing part 34, an audio signal output circuit board 35, an output transformer 36, and a connector case 40.

  The connector support 31 is made of an insulating material. The connector support 31 is held by the holder 32. The connector support 31 is attached to the front end in the circuit case 3 c via the holder 32. The connector support 31 includes a hole. The through direction of the hole is the thickness direction of the connector support 31 (the left and right direction in FIG. 3). The contact probe 33 is electrically connected to the contact pin 29 of the unit 2. The contact probe 33 is inserted through the hole of the connector support 31.

  The board fixing unit 34 holds the audio signal output circuit board 35. The substrate fixing part 34 is provided integrally with the holder 32. The audio signal output circuit board 35 has a substantially rectangular plate shape. The audio signal output circuit board 35 is held by the board fixing part 34. The audio signal output circuit board 35 is fixed in the circuit case 3 c via the board fixing part 34. For example, a field effect transistor (FET) or a circuit is incorporated in the audio signal output circuit board 35. The FET constitutes an impedance converter of the electroacoustic transducer 20. The circuit is, for example, a circuit that converts a change in capacitance generated between the diaphragm 22 and the fixed pole 24 into an electric signal and outputs the electric signal. The gate of the FET is electrically connected to the fixed electrode 24 through the electrode lead terminal 28, the contact pin 29, and the contact probe 33.

  The output transformer 36 has a secondary coil with a center tap. The output transformer 36 makes the output impedance of the signal from the audio signal output circuit board 35 the same on the hot side and the cold side.

  The connecting member 37 connects the unit case 2c and the circuit case 3c. The connecting member 37 is cylindrical. The connecting member 37 includes a male screw portion 37s. The male screw portion 37 s is disposed on the outer peripheral surface of the connecting member 37.

  The unit case 2 c is attached to the circuit case 3 c via the connecting member 37. The male screw portion 37s of the connecting member 37 is fitted into the female screw portion 2s of the unit case 2c and the female screw portion 3s of the circuit case 3c. As described above, the electroacoustic transducer 20 and the acoustic resistor 50 are accommodated in the unit case 2c.

  The connector case 40 is made of a metal such as a brass alloy. The connector case 40 is cylindrical. The output connector is housed in the connector case 40. The output connector includes, for example, the first pin for grounding (not shown) defined in JEITA RC-5236 “Latch lock type circular connector for audio equipment”, the second pin 42 on the hot side of the signal, and the cold side And a third pin 43. The first pin is electrically connected to the connector case 40 as a ground. The output connector includes a connector base 41. The connector base 41 is made of an insulating material such as polybutadiene terephthalate resin. The connector base 41 has a disk shape. The first pin, the second pin 42 and the third pin 43 are press-fitted into the connector base 41. The first pin, the second pin 42 and the third pin 43 penetrate the connector base 41. The output connector is attached to the rear end side in the circuit case 3 c via the connector case 40. The connector case 40 also acts as a shield case for the output connector.

  The electroacoustic transducer 20 outputs an electrical signal when the diaphragm 22 is vibrated by sound waves from a sound source entering the unit case 2c through the sound wave introduction hole 2h. The microphone 1 outputs the electrical signal from the electroacoustic transducer 20 to an external device via the audio signal output circuit board 35, the output transformer 36, and the output connector in the connector case 40.

  The acoustic resistor 50 disposed between the sound wave introduction hole 2 h and the diaphragm 22 is sandwiched between the unit case 2 c and the electroacoustic transducer 20. Therefore, the acoustic resistor 50 does not vibrate even when receiving a sound wave from the sound source. As a result, the frequency response of the microphone 1 in the high frequency band is flat.

FIG. 4 is a graph showing the frequency response of the microphone 1.
The figure shows that the frequency response in the high frequency band of the microphone 1 is flat compared to the frequency response of the conventional microphone shown in FIGS.

Summary According to the embodiment described above, the acoustic resistor 50 sandwiched between the unit case 2c and the electroacoustic transducer 20 does not vibrate even when receiving sound waves from the sound source. Therefore, the microphone 1 according to the present embodiment can flatten the frequency response in the high frequency band of the microphone 1.

DESCRIPTION OF SYMBOLS 1 Capacitor microphone 2 Capacitor microphone unit 2c Unit case 2e Open end 2f Flange part 2h Sound wave introduction hole 2s Female thread part 20 Electroacoustic transducer 20r Lock ring 21 Diaphragm holder 22 Diaphragm 23 Spacer 24 Fixed pole 25 Insulator 26 Support body 27 Insulating Seat 28 Electrode Lead Terminal 29 Contact Pin 3c Circuit Case 3s Female Screw Part 31 Connector Support 32 Holder 33 Contact Probe 34 Substrate Fixing Part 35 Audio Signal Output Circuit Board 36 Output Transformer 37 Connecting Member 37s Male Screw Part 40 Connector Case 41 Connector Base 42 Hot side pin 43 Cold side pin 50 Acoustic resistor 51 Elastic member 52 Elastic member

Claims (10)

A unit case having a sound wave introduction hole;
A diaphragm that is housed in the unit case and vibrates with sound waves from the sound wave introduction holes;
An acoustic resistor disposed between the sound wave introduction hole and the diaphragm;
Having
The acoustic resistor includes two elastic members pressed against each other,
At least one of the two elastic members is curved in a convex shape before the press contact,
The convex side surface of one elastic member curved in the convex shape is a pressure contact surface with the other elastic member.
Condenser microphone unit characterized by that. The diaphragm constitutes an electroacoustic transducer,
The acoustic resistor is sandwiched between the unit case and the electroacoustic transducer.
The condenser microphone unit according to claim 1. The electroacoustic transducer includes a diaphragm holding body that stretches the diaphragm,
The two elastic members are pressed and pressed from the diaphragm holder to the unit case side,
The condenser microphone unit according to claim 2. The unit case has a bottomed cylindrical shape,
The sound wave introduction hole is disposed on the bottom surface of the unit case,
The two elastic members are pressed and pressed against the diaphragm side from a flange portion provided on the bottom surface,
The condenser microphone unit according to claim 1. It is the central portion in plan view of the one elastic member that is convexly curved before the press contact,
The condenser microphone unit according to claim 1. Each of the two elastic members is curved in a convex shape,
The convex side surfaces of the two elastic members curved in a convex shape are in pressure contact with each other,
The condenser microphone unit according to claim 1. A condenser microphone unit;
A microphone case that houses the condenser microphone unit;
Having
The condenser microphone unit is the condenser microphone unit according to any one of claims 1 to 6.
Condenser microphone characterized by that. A unit case having a sound wave introduction hole;
A diaphragm that is housed in the unit case and vibrates with sound waves from the sound wave introduction holes;
An acoustic resistor disposed between the sound wave introduction hole and the diaphragm;
A method of manufacturing a condenser microphone unit comprising:
The acoustic resistor includes two elastic members pressed against each other,
At least one of the two elastic members is curved in a convex shape before the press contact,
Storing the two elastic members in the unit case;
Pressing the two elastic members while housing the diaphragm in the unit case;
Having
A method for manufacturing a condenser microphone unit. The step of storing the two elastic members in the unit case is performed simultaneously with the step of pressing the two elastic members while storing the diaphragm in the unit case.
The manufacturing method of the capacitor | condenser microphone unit of Claim 8. The diaphragm constitutes an electroacoustic transducer,
The electroacoustic transducer includes a diaphragm holding body that stretches the diaphragm,
The two elastic members are pressed against the unit case side from the diaphragm holder and are sandwiched and pressed between the unit case and the electroacoustic transducer.
10. A method for manufacturing a condenser microphone unit according to claim 8 or 9.

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