JP4087784B2 - Microphone - Google Patents

Description

  The present invention relates to a microphone that can be used by being mounted on, for example, a recording device, a video camera, a mobile phone, or the like. It is something to be offered.

Various proposals have been made for removing wind noise generated in a microphone. FIG. 13 shows the structure of a conventional microphone with a windshield. In FIG. 13, reference numeral 1 denotes a microphone unit such as an electret condenser microphone, 2 denotes a housing that supports the microphone unit 1, and 3 denotes a wind screen that covers the sound receiving surface of the microphone unit 1.
The wind screen 3 is formed of a porous resin material such as urethane resin, for example, and allows passage of sound while preventing passage of wind pressure, so that the sound pressure directly hits the pressure receiving surface (vibration plate) of the microphone unit 1. It prevents the generation of wind noise. Such a structure is also described in Patent Document 1.

On the other hand, one of wind noises is noise called puff noise or pop noise. This puff noise or pop noise refers to noise generated when a speaker uses a plosive sound such as “pa” or “te” when a microphone is used close to the speaker's lips. This noise is thought to be caused by turbulence generated when a high air velocity generated from the lips hits a protective grid provided to cover the microphone capsule. A microphone for removing this type of noise is proposed in Patent Documents 2 to 4.
Japanese Utility Model Publication No. 63-165959 Japanese Patent No. 3089024 JP 2002-262380 A JP-A-8-322096

The conventional technique shown in FIG. 13 and Patent Document 1 has a drawback that the shape of the entire microphone becomes large because the wind screen 13 is disposed so as to be exposed to the outside.
In addition, even if the microphones described in Patent Documents 2 to 4 can remove puff noise or pop noise, they do not have a function of removing low sound noise coming from the surroundings. In other words, there is a lot of low-frequency noise in the vicinity of large machines such as construction sites, and when this low-frequency noise is transmitted to the other party on a mobile phone, the speaker's voice is drowned out by the low-frequency noise. There is a problem that the voice of the speaker cannot be transmitted to the other party.

In addition, even when recording with a recorder or a video recorder with a recording function, if low frequency noise is mixed from the surroundings, there is a problem that the voice of the speaker is drowned out by the low frequency noise during reproduction.
An object of the present invention is to provide a microphone having a windshield effect while having a small size and a function of removing low-frequency noise.

According to a first aspect of the present invention, there is provided a microphone unit comprising a sound hole forming surface having a plurality of sound holes formed on one surface, and a diaphragm disposed on the back side of the sound hole forming surface, and the microphone unit. A porous filter element that covers all of the plurality of sound holes formed on the sound hole forming surface, and a cylindrical filter body that is attached to the sound hole forming surface and whose end is closed by a closing plate A cylindrical case configured to support the microphone unit in the cylindrical body in a posture that forms a cavity by the closing plate, the body adjacent to the closing plate, and the mounting surface of the porous filter element of the microphone unit If, comprising a sound hole group to communicate with the outside of the internal and hollow cavity of the cylindrical casing, the vibration plate constituting the microphone unit proposes a microphone that has small holes in a part are formed .

According to a second aspect of the present invention, there is proposed the microphone according to the first aspect, wherein the sound hole group is formed on both the closing plate and the trunk portion.
According to a third aspect of the present invention, in the microphone according to the first aspect, the sound hole group is formed only on the closing plate, and the formation position of the sound hole group is arranged over a range wider than the plane area of the porous filter element. Propose a microphone.
According to a fourth aspect of the present invention, there is proposed the microphone according to the first aspect, wherein the sound hole group is formed over the entire circumference in the circumferential direction of the trunk portion.

A fifth aspect of the present invention proposes the microphone according to any one of the first to fourth aspects, wherein the cylindrical case is formed of a metal case having one end closed by a closing plate.
According to a sixth aspect of the present invention, there is proposed a microphone according to any one of the first to fourth aspects, wherein the cylindrical case is formed integrally with a cabinet for storing the apparatus main body .

According to a seventh aspect of the present invention, there is proposed a microphone according to any one of the first to sixth aspects, wherein the microphone unit has a structure in which a circuit of a low-pass filter is incorporated.

According to the microphone proposed in claim 1 of the present invention, the sound holes formed in the microphone unit are all covered with the porous filter element, and all the sound holes are covered with the porous filter element. With this structure, even if the wind enters the cavity through the sound hole group from the outside of the cylindrical case, the wind does not directly hit the sound hole formed in the microphone unit. Occurrence is suppressed. And since the small through-hole was formed in the diaphragm which comprises a microphone unit, the vibration of a diaphragm is suppressed to the low frequency sound wave by existence of this through-hole, and the rate which converts low frequency noise into an electric signal Can be lowered. As a result, a microphone having a function of removing low frequency noise can be provided.
Further, according to the microphone proposed in claim 2 of the present invention, since the sound hole group is formed on both the closing plate and the body portion constituting the cylindrical case, the microphone is temporarily provided through the sound hole group formed on the closing plate. Even if wind pressure is applied from the front toward the sound hole forming surface of the unit, the wind pressure penetrates into the porous filter element, and most of it is absorbed and reduced inside the porous filter element. The air is also discharged from the side surface of the porous filter, and the discharged air flow is exhausted from the sound hole group formed in the body portion of the cylindrical case to the outside of the cavity. Therefore, even when wind pressure is applied from the front, the air pressure inside the cavity does not rise, and generation of wind noise or pop noise can be suppressed in this respect.

  Further, according to the third aspect of the present invention, the sound hole group is formed only on the closing plate, and the formation position of the sound hole group protrudes outside the range of the area of the plane of the porous filter element and is wide. Therefore, even if wind pressure is applied from the front of the blocking plate and wind pressure enters the porous filter element, the air flow due to the wind pressure is exhausted from the side of the porous filter element to the outside. The flow of air escapes to the outside of the cavity from the pore located outside the part facing the porous filter element in the sound hole group formed in the blocking plate, and prevents the air pressure inside the cavity from rising. Can do. Therefore, even with this structure, generation of wind noise and pop noise can be suppressed.

Furthermore, according to the microphone structure proposed in claim 4 of the present invention, the sound hole group is formed over the entire circumference in the circumferential direction of the body portion of the cylindrical body, so that the sound coming from all directions can be received inside the cylindrical case. Can be introduced. However, no matter which direction the wind pressure enters the inside of the cylindrical case, the wind pressure crosses the cylindrical portion and is exhausted from the sound hole group located on the opposite side to the outside of the cylindrical case. Therefore, even in this structure, the pressure inside the cylindrical case does not increase, and the generation of wind noise and pop noise can be suppressed.
According to the microphone structure proposed in claim 5 of the present invention, the cylindrical case is formed of a metal case, and the microphone unit and the porous filter element are accommodated in the metal case. A microphone that generates less noise can be obtained.

Furthermore, according to the sixth aspect of the present invention, the cylindrical case is formed integrally with the cabinet that houses the device, and a part of the cabinet is used as a supporting portion of the microphone. Since the generation of pop noise is reduced, it is suitable for application to a device such as a mobile phone or a video camera .

Further, according to the seventh aspect of the present invention, since the low frequency elimination filter circuit is built in the microphone unit, it is possible to provide a microphone having a further enhanced function of removing low frequency noise.

  The cylindrical case has at least two surface plates with different directions, the first sound hole group is formed on one of the two surface plates with different directions, and the second sound hole group is formed on the other surface plate. Thus, a first sound hole group and a second sound hole group having different directions are obtained. At the same time, a microphone unit is arranged on the back side of the surface plate area in which the first sound hole group and the second sound hole group are formed. The sound hole forming surface of the microphone unit is arranged in a posture facing the area where the first sound hole group and the second sound hole group are formed, and the sound hole forming surface, the first sound hole group, and the second sound hole group are formed. A cavity is formed by the processed surface plate, and a porous filter element is disposed inside the cavity.

  By providing the first sound hole group and the second sound hole group that are opened in directions different from each other, even if the wind pressure enters from one sound hole group, the wind pressure is caused by the other sound hole group. It is discharged to the outside and does not cause an increase in pressure particularly in the vicinity of the sound hole forming surface of the microphone unit inside the cylindrical case, and the generation of wind noise and pop noise can be reduced.

FIG. 1 shows a first embodiment of a microphone according to the present invention. In FIG. 1, 10 is a cylindrical case, 20 is a microphone unit, and 30 is a porous filter element.
In this example, the cylindrical case 10 is formed of a conductive metal plate such as aluminum and has a cylindrical shape as shown in FIG. A first sound hole group 11 </ b> A is formed on the closing plate 11 of the cylindrical case 10, and a second sound hole group 12 </ b> A is formed on the peripheral surface 12 adjacent to the closing plate 11.
A porous filter element 30 such as a urethane resin is accommodated in a cavity 14 surrounded by the closing plate 11 formed with the first sound hole group 11A and the second sound hole group 12A and the peripheral surface 12. Further, the microphone unit 20 is fitted into the opening of the cylindrical case 10 to complete the microphone.

  The configuration characterized by this invention is that the cylindrical case 10 has a closing plate 11, and the first sound hole group 11 </ b> A and the second sound hole group 12 </ b> A are provided on the closing plate 11 and the peripheral surface 12 adjacent to the closing plate 11. The porous filter element 30 is accommodated in the cavity 14 formed and surrounded by the portion where the first sound hole group 11A and the second sound hole group 12A are formed. The sound hole forming surface is closed, the diaphragm used in the microphone unit 20 has a hole in a part thereof, and the microphone unit 20 has a built-in low-pass filter.

By forming the first sound hole group 11 </ b> A and the second sound hole group 12 </ b> A in directions different from each other by approximately 90 °, and further disposing the second sound hole group 12 </ b> A so as to face the side surface of the porous filter element 30. Even if a strong wind pressure enters from the first sound hole group 11A, the wind pressure is attenuated by the porous filter element 30, but is further discharged from the side surface of the porous filter element 30, and the discharged air flow Is exhausted to the outside from the second sound hole group 12A. Thereby, generation | occurrence | production of a wind noise and pop noise is suppressed.
FIG. 3 shows an example of the internal structure of the microphone unit 20. In this example, the structure of an electret condenser microphone will be described as an example. As is well known, the electret condenser microphone integrally accommodates the diaphragm 21, the back electrode 22, the insulating ring 23 that supports the back electrode 22, the gate ring 24, the circuit board 25, and the opening. It is comprised with the metallic capsule 26 which crimps and integrates.

The capsule 26 has a closed end on the opposite side of the opening, and a plurality of sound holes 26A are formed on the closed end surface, and this surface serves as a sound hole forming surface 26B.
The diaphragm 21 includes a film 21A formed of a polymer material and a conductive ring 21B that applies tension to the film 21A to maintain the film 21A in a stretched state. A conductive layer is formed on one surface of the film 21 </ b> A by vapor deposition or the like, and this conductive layer is disposed to face the back electrode 22, and forms a capacitance between the diaphragm 21 and the back electrode 22.
The film 21 </ b> A constituting the diaphragm 21 is charged in the thickness direction, and this charging generates an electric field between the back electrode 22 and converts the vibration of the diaphragm 21 into an electrical signal.

Here, in the present invention, the holes 21 </ b> C are formed in the film 21 </ b> A constituting the diaphragm 21. In the example shown in FIG. 3, a case where a hole 21 </ b> C is formed at a substantially central position of the diaphragm 21 is shown. The hole 21C is formed by, for example, a laser beam and has a diameter of about several hundreds of micrometers. By forming the hole 21C having such a diameter, a low-frequency sound wave having a long wavelength is transmitted to both the front side and the back side of the film 21A at the same time, and exhibits an action of suppressing vibration of the film 21A. For this reason, it is possible to reduce the sensitivity to low-frequency sound waves.
On the other hand, the present invention proposes a structure in which a low-pass filter circuit is further mounted on the circuit board 25. FIG. 4 shows the structure of the low-frequency elimination filter circuit. A block diagram indicated by a broken line in FIG. 4 shows the capsule 26 described in FIG. The capsule 26 is electrically connected to a common potential, and acts as a member that covers and shields the entire microphone unit 20.

  The diaphragm 21 is electrically connected to the capsule 26, and the back electrode 22 is connected to an input terminal of an IC that operates as a preamplifier. The IC is configured in an output format having an open collector structure, and a power supply voltage is applied through a load resistor RL connected to the outside of the microphone unit 20 so that the IC maintains an operating state. The output terminal 25A corresponds to the electrode 25A formed on the circuit board 25. By connecting a coupling capacitor C to the output terminal 25A, a voltage signal generated by the vibration of the diaphragm 21 can be taken out through the coupling capacitor C. Can do.

Here, the capacitor C1 connected to the output side of the IC is a capacitor for removing high frequency noise. For example, when a high frequency signal such as 800 MHz transmitted / received by a mobile phone is emitted in the vicinity, the electromagnetic wave acts on the microphone unit 20 to generate noise. This noise is referred to herein as high frequency noise, and this high frequency noise can be removed by the presence of the capacitor C1.
A low-frequency elimination filter circuit 27 mounted in the present invention is inserted between the IC and the output terminal 25A. The low-pass filter circuit 27 includes a transistor TR connected between the output terminal 25A and a common potential, resistors R1 and R2 that apply a forward bias signal to the transistor TR, and an output signal from the IC at the base of the transistor TR. It can be constituted by a capacitor C2 for inputting a low frequency component.

The low frequency signal applied to the transistor TR through the capacitor C2 is output with its phase inverted to the collector side of the transistor TR. The low frequency component output with the phase inverted is canceled with the low frequency component arriving at the output terminal 25A through the resistor R1. Accordingly, the level of the low frequency component in the signal component output through the coupling capacitor C can be reduced.
FIG. 5 shows the frequency characteristics of the microphone unit according to the present invention. This frequency characteristic shows the frequency characteristic (solid line A) of a microphone in which a hole 21C is formed in the diaphragm 21 and a low-pass filter circuit 27 is further added. A curve B indicated by a dotted line in the figure shows a frequency characteristic of a conventional electret condenser microphone that does not take these measures.

According to this measurement example, a decrease starts from about 400 to 500 Hz, and the attenuation amount is about 6 dB larger than the conventional microphone in the vicinity of 200 Hz, and the attenuation amount suddenly increases at a frequency lower than 200 Hz.
Therefore, the sensitivity can be reduced with respect to low frequency noise, and the rate at which low frequency noise is collected as an electrical signal can be greatly reduced.
On the other hand, since the frequency of 400 Hz or more is converted into an electric signal without any change from the conventional microphone, the audio signal (400 to 2 KHz) is converted into an electric signal as before, and a voice with high clarity is obtained. Sound can be collected. In the measurement example shown in FIG. 5, the frequency at which the sensitivity starts to decrease is 400 to 500 Hz. The frequency at which the sensitivity starts to decrease is the capacitor C2 and the resistor used in the low-pass filter 27. It can be arbitrarily set by appropriately selecting the values of R1 and R2.

FIG. 6 shows a second embodiment of the present invention. The embodiment shown in FIG. 6 shows a case where the cylindrical case 10 is a cylindrical cabinet. The cabinet is formed of a resin material.
The cylindrical case 10 is also cylindrical in this example, and includes a closing plate 11 that closes one open end of the cylindrical case 10 and a peripheral surface 12 that has a different direction from the closing plate 11. A first sound hole group 11 </ b> A and a second sound hole group 12 </ b> A are formed in the closing plate 11 and the peripheral surface 12. As a result, the directions of the sound holes of the first sound hole group 11A and the second sound hole group 12A are opened in different directions of about 90 °.
The microphone unit 20 is arranged on the back side of each region of the closing plate 11 and the peripheral surface 12 in which the first sound hole group 11A and the second sound hole group 12A are formed, and the cavity 14 is formed. In this embodiment, on the inner periphery of the cylindrical case 10, a flange portion 13 projecting inwardly in a ring shape at a position separating the region where the first sound hole group 11A and the second sound hole group 12A are formed from the other region. Is formed, and the periphery of the front end surface of the microphone unit 20 is pressed against the flange portion 13 so that the microphone unit 20 is sandwiched between the flange portion 13 and the printed wiring board 40.

Further, wrapped in rubber holder 50 forming the microphone unit 20 of an elastic material in this embodiment, the rubber holder 50 is fixed to the inner wall of the cylindrical case 10 via a vibration applied to the tubular case 10 is transmitted to the microphone unit 20 The case where there is no structure is shown. In this example, a pair of spring contacts 51 are embedded in the rubber holder 50, one end of each spring contact 51 is in contact with each terminal (not shown) of the microphone unit, and the other end is formed on the printed wiring board 40. The case where the microphone unit 20 is electrically connected to the printed wiring board 40 through the spring contact 51 is shown.

The front surface side of the microphone unit 20, that is, the surface on which the sound hole forming surface 26B is formed is disposed toward the region where the first sound hole group 11A and the second sound hole group 12A are formed, and the front surface thereof is porous. The filter element 30 is attached.
The porous filter element 30 can be a porous filter element such as urethane foam as described in the embodiment of FIG. In this example, the porous filter element 30 has a cylindrical shape, one end face of which is attached to the front surface of the microphone unit 20, and the other end face is a closing plate of the cylindrical case 10 in which the first sound hole group 11A is formed. 11 is in contact with the back surface. All the sound holes of the first sound hole group 11 </ b> A are included in the range of the porous filter element 30 and are closed by the porous filter element 30. On the other hand, the second sound hole group 12 </ b> A is opened without being blocked by the porous filter element 30.

  With this structure, when the wind pressure enters from the first sound hole group 11A, or when a strong sound pressure is applied from the speaker's mouth from the first sound hole group 11A, the wind pressure or the sound pressure is the first sound. The porous filter element 30 penetrates through the hole group 11 </ b> A, but most of it is attenuated by the porous filter element 30. When there is a strong wind pressure or sound pressure that cannot be attenuated by the porous filter element 30, the wind pressure or sound pressure leaks from the side of the porous filter element 30 and passes through the second sound hole group 12A to form a cylindrical case. Escape to the outside of 10. As a result, even if a large wind pressure or a large sound pressure (sounding sound pressure that causes pop noise) intrudes, it escapes from the second sound hole group 12A, thereby avoiding wind noise and pop noise. Can do.

A third embodiment of the present invention will be described with reference to FIGS. Portions corresponding to those in FIGS. 1 and 6 are denoted by the same reference numerals, and description of the overlapping portions is omitted.
In this embodiment, the case where the cylindrical case 10 is integrally formed inside the corner portion of the flat rectangular cabinet 60 is shown. That is, the partition wall 61 is formed inside the corner portion of the cabinet 60, and the cylindrical case 10 is configured by the partition wall 61 and the side plate 63 of the cabinet. Here, although the cross-sectional shape of the cylindrical case 10 is rectangular, a circular through hole is formed in the flange portion 13 protruding inward from the partition wall 61 and the side plate 63 of the cabinet, and the front end surface of the circular microphone unit 20 is formed. The microphone unit 20 may be fixed by pressing the periphery of the through hole against the edge of the through hole.

  Also in this case, the first sound hole group 11A is formed on the surface plate 62 constituting the cabinet 60, the second sound hole group 12A is formed on the side plate 63, and the second sound hole group 12A is formed as a porous filter element. By arranging the 30 side surfaces so as to face each other, it is possible to obtain the same effects as the embodiment described in FIGS.

A fourth embodiment will be described with reference to FIGS. In this embodiment, a case where a spherical bulge is formed on the surface of the cabinet 60 and the cylindrical case 10 is formed so as to surround the inside of the bulge portion is shown. The first sound hole group 11A is formed on the entire surface of the bulge portion.
Here, the first sound hole group 11 </ b> A forms the first sound hole group 11 </ b> A over an area larger than the planar area of the porous filter element 30, and the side surface of the porous filter element 30 is formed inside the cylindrical case 10. Exposed to the cavity.
In the case of this structure, the sound pressure entering from the first sound hole group 11A is attenuated by the porous filter element 30 and proceeds toward the microphone unit 20, but the resistance of the side surface of the porous filter element 30 is reduced. Since it is low, the air leaks from the side surface of the porous filter element 30, and the leaked wind pressure is discharged from the sound hole group that is not blocked by the porous filter element 30 in the first sound hole group 11 </ b> A. It does not increase the internal pressure. Therefore, it is possible to obtain the same operational effects as the embodiment described with reference to FIGS.

A fifth embodiment of the present invention will be described with reference to FIGS. In this embodiment, an embodiment is shown in which one end side of an overall cylindrical cabinet 60 is used as a cylindrical case 10 for a microphone.
That is, the flange portion 13 is projected from the inner wall on one end side of the cylindrical cabinet 60 whose end is closed, and the microphone unit 20 wrapped in the rubber holder 50 is sandwiched between the flange portion 13 and the printed wiring board 40. Attach and fix. The sound hole forming surface 26B of the microphone unit 20 is disposed toward one closed end of the cabinet 60, and the porous filter element 30 is attached to the sound hole forming surface 26B. The cavity 14 is formed by the closed end of the cabinet 60 and the sound hole forming surface 26B. A second sound hole group 12 </ b> A that connects the inside and the outside of the cavity 14 is formed on the peripheral surface of the cylindrical case 10 on the closed end side. That is, this embodiment shows a case where the second sound hole group 12A is formed on the circumferential surface of the cylindrical case 10 over the entire circumference in the circumferential direction.

  According to this embodiment, the second sound hole group 12A is formed over the entire circumference of the body portion of the cylindrical case 10, so that even if wind pressure is applied from any direction, it simply passes through the inside of the cavity 14 and passes through. Therefore, the pressure in the cavity does not increase, the generation of wind noise and pop noise can be suppressed, and the low-frequency elimination characteristic attached to the microphone unit 20 can prevent mixing of low-frequency noise.

  The microphone according to the present invention is used by being mounted on a mobile phone or a video camera.

Sectional drawing for demonstrating Example 1 of this invention. The front view of FIG. The disassembled perspective view for demonstrating an example of the internal structure of the microphone unit used for the Example shown in FIG.1 and FIG.2. The connection diagram for demonstrating an example of the low-pass elimination filter circuit used for this invention. The characteristic curve figure which shows an example which measured the frequency characteristic of the microphone by this invention. The expanded sectional view for demonstrating Example 2 of this invention. The expanded sectional view for demonstrating Example 3 of this invention. The expansion perspective view for demonstrating the principal part of the Example shown in FIG. The expanded sectional view for demonstrating Example 4 of this invention. The front view of FIG. The expanded sectional view for demonstrating Example 5 of this invention. The side view of FIG. Sectional drawing for demonstrating the prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Cylindrical case 26B Sound hole formation surface 11 Blocking board 30 Porous filter element 11A 1st sound hole group 40 Printed wiring board 12A 2nd sound hole group 50 Rubber holder 13 Flange part 60 Cabinet 14 Cavity 20 Microphone unit

Claims (7)

A. A microphone unit comprising a sound hole forming surface having a plurality of sound holes formed on one surface, and a diaphragm disposed on the back side of the sound hole forming surface;
B. A porous filter element having a surface shape covering all of the plurality of sound holes formed on the sound hole forming surface of the microphone unit, and attached to the sound hole forming surface;
C. The microphone unit is formed of a cylindrical body whose end surface is closed by a closing plate, and the microphone unit is formed in a posture in which a cavity is formed by the closing plate, a body portion adjacent to the closing plate, and the sound hole forming surface of the microphone unit. A cylindrical case to be supported in a cylindrical body,
D. A group of sound holes communicating the inside of the cavity of the cylindrical case with the outside of the cavity;
Equipped with
E. Microphone the diaphragm you characterized in that the through-holes of small diameter for passing sound waves following low frequency 400~500Hz part is formed to constitute the microphone unit.   The microphone according to claim 1, wherein the sound hole group is formed on both the closing plate and the body.   2. The microphone according to claim 1, wherein the sound hole group is formed only on the closing plate, and the formation position of the sound hole group is arranged over a range larger than the area of the plane area of the porous filter element. A microphone to play.   2. The microphone according to claim 1, wherein the sound hole group is formed over the entire circumference of the body portion in the circumferential direction.   The microphone according to any one of claims 1 to 4, wherein the cylindrical case is formed of a metal case having one end closed by a closing plate.   5. The microphone according to claim 1, wherein the cylindrical case is formed integrally with a cabinet for storing the apparatus main body. The microphone according to any one of claims 1 to 6, wherein the microphone unit includes a low-pass filter circuit.

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