JP5118987B2 - Unidirectional condenser microphone unit and line microphone - Google Patents

Description

  The present invention relates to a unidirectional condenser microphone unit and a line microphone, and more particularly to a technique for preventing wind noise.

  In the field of microphones, wind noise is mainly generated when air flow disturbances occur around the microphone. The frequency component of the wind noise is at a low frequency of approximately 500 Hz or less, and those having a large amplitude of 20 Hz or less are not directly heard as sound, but generate a sound such as an unevenness, sound interruption, and intermodulation distortion.

  Wind noise is generally dealt with by noise cones and wind screens, etc., but the wind shielding effect differs depending on the air permeability, and if it is clogged too much, the characteristics of the microphone will deteriorate. End up. On the other hand, in order to enhance the wind shielding effect without deteriorating the characteristics of the microphone, a windscreen having a large outer shape is required.

  As another countermeasure, as described in Patent Documents 1 to 3, there is a method of passing low-frequency sound waves from the front acoustic terminal to the back surface side of the diaphragm (the surface facing the fixed pole). . According to this, since a pressure difference does not occur before and after the diaphragm in a low range, wind noise and vibration noise can be reduced.

  In the invention described in Patent Document 1, notches are provided in each of the diaphragm support ring, the diaphragm and the spacer ring to form a sound wave communication path from the front side to the back side of the diaphragm.

  In the invention described in Patent Document 2, a metal mesh having air permeability is also interposed between the diaphragm support ring that supports the diaphragm and the sound collecting surface of the unit case, and a part of the periphery of the fixed pole. A notch portion is provided in the upper surface of the diaphragm to form a sound wave communication path from the front surface side to the rear surface side of the diaphragm.

  In the invention described in Patent Document 3, a very small opening for pressure equalization is formed in the diaphragm itself by heat from, for example, spark discharge.

Japanese Utility Model Publication No. 61-187189 Japanese Utility Model Publication No. 5-11696 JP-A-9-84195

  However, in the case of the invention described in Patent Document 1, it is necessary to overlap the notch portion of the diaphragm support ring and the notch portion of the spacer ring. However, when the built-in unit case rotates, the positions of both notch portions are shifted. In other words, the sound wave communication path from the front side to the back side of the diaphragm may be blocked.

  In the case of the invention described in Patent Document 2, since the wire mesh disposed between the diaphragm support ring and the sound collecting surface of the unit case mainly acts as an acoustic resistance, the acoustic mass component can be controlled. Have difficulty.

  The invention described in Patent Document 3 is effective when there is no acoustic tube or the like on the front side of the diaphragm as in a studio condenser microphone. However, the invention is not limited to a line microphone (narrow directional microphone) using an acoustic tube. When applied, there is a problem that the acoustic mass cannot be controlled.

  Accordingly, an object of the present invention is to provide a unidirectional condenser microphone unit having an acoustic mass effective to pass low-frequency sound waves from the front side to the back side of the diaphragm in order to prevent wind noise. There is.

In order to solve the above problems, the present invention provides a bottomed cylindrical unit case that is integrally provided with an end plate having a front acoustic terminal hole on one end surface side and that is open on the other end surface side, and a diaphragm support ring. Including a diaphragm assembly in which a diaphragm is stretched on an end surface side, and a fixed pole assembly in which a fixed pole is supported on an insulating seat, and the diaphragm and the fixed pole are connected with an electrically insulating spacer. An acoustoelectric transducer arranged oppositely is housed in the unit case with the diaphragm assembly as the end plate side, and the acoustoelectric transducer is pressed and fixed to the other end surface side of the unit case. In the unidirectional condenser microphone unit provided with the fixing means,
On the other end surface side of the diaphragm support ring, a pipe-like groove having a predetermined acoustic mass is formed between the diaphragm and the end plate. A first opening for introducing a part of the sound wave from the front acoustic terminal hole into the groove is formed, and a predetermined portion on the outer peripheral surface side of the diaphragm support ring is provided on the inner side of the unit case. A second opening that is open toward the wall surface is formed, and the second opening is acoustically connected to the back side of the diaphragm via the spacer, and the spacer also has a surface direction. A mesh material made of synthetic resin having air permeability is used .

  According to a preferred aspect of the present invention, the groove is formed over the entire circumference of the diaphragm support ring, and the first opening and the second opening are disposed at positions facing each other by 180 °.

  The present invention also includes a narrow directivity line microphone formed by combining the unidirectional condenser microphone unit and an acoustic tube.

  According to the present invention, a pipe-shaped groove having a predetermined acoustic mass between the end plate of the unit case and the end plate of the unit case is formed on the other end surface (surface on the side opposite to the vibration plate) of the vibration plate support ring. A first opening for introducing a part of the sound wave from the front acoustic terminal hole into the groove is formed in a predetermined portion on the inner peripheral surface side of the diaphragm, and the predetermined portion on the outer peripheral surface side of the diaphragm support ring A second opening that is opened toward the inner wall surface of the unit case is formed, and the second opening is acoustically connected to the rear surface side of the diaphragm via a spacer, so that from the front acoustic terminal hole The low-frequency sound wave is guided to the back side of the diaphragm through a groove having a predetermined acoustic mass, and the front and back of the diaphragm are pressure-equivalent in the low range, so that wind noise is effectively reduced.

  The acoustic mass is determined by the width, depth, and length of the groove formed in the diaphragm support ring, but the groove is formed over the entire circumference of the diaphragm support ring, and the first opening and the second opening are 180 degrees. By arranging at opposite positions, the acoustic mass in the left and right groove portions can be balanced.

  By using a mesh material made of synthetic resin that also has air permeability in the surface direction for the spacer, it is possible to cause low-frequency sound waves to act on the back side of the diaphragm without performing alignment with the second opening in particular. it can.

  In the case of a line microphone (narrow directional condenser microphone) that uses an acoustic tube, the large acoustic impedance of the acoustic tube is added to the front acoustic terminal of the microphone unit. However, according to the present invention, the acoustic mass can be optimally set according to the width, depth, and length of the groove formed in the diaphragm support ring.

  Next, an embodiment of the present invention will be described with reference to FIGS. 1 to 3, but the present invention is not limited to this. 1 is a cross-sectional view showing a unidirectional condenser microphone unit (hereinafter sometimes simply referred to as “microphone unit”) according to an embodiment of the present invention, FIG. 2 is an exploded cross-sectional view of FIG. 1, and FIG. It is a top view which shows the diaphragm support ring which is the principal part of this invention.

  1 and 2, this microphone unit includes a unit case 10, a diaphragm assembly 20, a fixed pole assembly 30, an electrically insulating spacer 40, and a circuit board 50 as a basic configuration.

  The unit case 10 is a bottomed cylindrical body made of, for example, an aluminum material, and integrally includes an end plate 10a having a front acoustic terminal hole 11 on one end face side. The other end 10b side of the unit case 10 is open.

  The diaphragm assembly 20 includes a diaphragm 21 and a diaphragm support ring 22, and the diaphragm 21 is stretched with a predetermined tension on one end surface 22 a side of the diaphragm support ring 22. The diaphragm 21 may be a synthetic resin thin film on which a metal vapor deposition film is formed. The diaphragm support ring 22 is a metal ring such as an aluminum material.

  The fixed pole assembly 30 includes a fixed pole 31 and an insulating seat 32. A metal plate having a large number of air holes 311 is used for the fixed electrode 31, but an electret film may be provided on the surface thereof. The insulating seat 32 is made of a synthetic resin disc and supports the fixed pole 31 on one surface thereof.

  The insulating seat 32 is provided with a sound wave introduction hole 321 for allowing sound waves from a rear acoustic terminal hole 51 to be described later to act on the back side of the diaphragm 21 through a vent hole 311 of the fixed pole 31. A back air chamber 322 communicating with the sound wave introduction hole 321 is formed on the support surface side of the insulating seat 32, and a predetermined acoustic resistance material 323 is accommodated in the back air chamber 322.

  The circuit board 50 is disposed on the back surface side (fixed pole opposite support surface side) of the insulating seat 32 in order to close the open surface on the other end 10 b side of the unit case 10. A rear acoustic terminal hole 51 is formed in the circuit board 50. An FET (field effect transistor) 52 as an impedance converter is mounted on the inner surface side of the circuit board 50.

  The gate of the FET 52 is connected to the fixed pole 31 through a predetermined electrical connection means. In this embodiment, the FET 52 gate is disposed at the central portion of the insulating seat 32 and connected to the fixed pole 31 through the coil spring 54. The electrode terminal 55 is in contact with the electrically connected electrode terminal 55.

  An acoustoelectric converter is configured by arranging the spacer 40 between the diaphragm 21 and the fixed pole 31 and combining the diaphragm assembly 20 and the fixed pole assembly 30.

  Actually, after the diaphragm assembly 20, the spacer 40 and the fixed pole assembly 30 are housed in the unit case 10 in this order, the circuit board 50 is disposed on the back side of the insulating seat 32, and the other end of the unit case 10 is placed. Clamp 10b.

  In this way, the acoustoelectric converter is assembled and pressed and fixed in the unit case 10, but instead of caulking, a lock ring may be fitted on the other end 10b side of the unit case 10. .

  In the present invention, in order to prevent wind noise, the diaphragm support ring 22 has an acoustic mass effective for passing low-frequency sound waves from the front side to the back side of the diaphragm 21.

  Referring also to FIG. 3, in the present invention, a groove 221 is formed on the other end face 22 b side of the diaphragm support ring 22. Since the other end surface 22b of the diaphragm support ring 22 is in contact with the end plate 10a of the unit case 10, a pipe having a groove 221 is formed between the diaphragm support ring 22 and the end plate 10a. This pipe operates as an acoustic mass that can pass low-frequency sound waves.

  In this embodiment, the groove 221 is formed over the entire circumference of the diaphragm support ring 22, and a part of the sound wave from the front acoustic terminal hole 11 is grooved 221 to a predetermined portion on the inner peripheral surface side of the diaphragm support ring 22. A first opening 222 is formed for introduction therein. Further, a second opening 2223 opened toward the inner wall surface of the unit case 10 is formed at a predetermined portion on the outer peripheral surface side of the diaphragm support ring 22.

  In this case, in order to balance the acoustic mass in the left and right groove portions, it is preferable to arrange the first opening 222 and the second opening 223 at a position facing each other by 180 °. In addition, it is preferable to use a synthetic resin mesh material (for example, a plain weave polyester mesh) having air permeability in the surface direction as the spacer 40.

  According to this, a part of the low frequency sound wave out of the sound wave entering from the front acoustic terminal hole 11 enters the groove 221 having a predetermined acoustic mass from the first opening 222 and exits from the second opening 223. Since it reaches the back side of the diaphragm 21 through the gap between the diaphragm support ring 22 and the unit case 10 and the spacer 40, the front and rear of the diaphragm become pressure equivalent in a low frequency range, and wind noise is effectively reduced.

  The acoustic mass can be appropriately set depending on the width, depth, length, etc. of the groove 221 formed in the diaphragm support ring 22. Therefore, the microphone unit according to the present invention is particularly suitable for a narrow directivity line microphone using an acoustic tube.

  That is, in the case of a line microphone, since the large acoustic impedance of the acoustic tube is added to the front acoustic terminal of the microphone unit, it is necessary to acoustically connect the front and back of the diaphragm with an acoustic mass that matches the large acoustic impedance. However, according to the present invention, the acoustic mass required for the microphone unit of the line microphone is optimally set according to the width, depth, length, etc. of the groove 221 formed in the diaphragm support ring 22 as described above. Can do. Therefore, the present invention also includes a narrow directivity line microphone formed by combining the microphone unit having the above-described configuration and an acoustic tube.

  In the above-described embodiment, the acoustic mass groove 221 is formed over the entire circumference of the diaphragm support ring 22, but may be, for example, about a half circumference according to specifications. Further, as the spacer 40, a spacer made of a synthetic resin film and having a notch for acoustically connecting the second opening 223 on the sound wave exit side and the back side of the diaphragm 21 may be used.

Sectional drawing which shows the unidirectional condenser microphone unit which concerns on embodiment of this invention. The exploded sectional view of FIG. The top view which shows the diaphragm support ring which is the principal part of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Unit case 10a End plate 10b The other end of a unit case 11 Front acoustic terminal hole 20 Diaphragm assembly 21 Diaphragm 22 Diaphragm support ring 221 Groove 222 First opening 223 Second opening 30 Fixed pole assembly 31 Fixed Pole 32 Insulator 40 Spacer 50 Circuit board 51 Rear acoustic terminal hole 52 Impedance converter (FET)

Claims (3)

A bottomed cylindrical unit case that is integrally provided with an end plate having a front acoustic terminal hole on one end surface side and that is open on the other end surface side, and a diaphragm is stretched on one end surface side of the diaphragm support ring An acoustoelectric apparatus comprising a diaphragm assembly and a fixed pole assembly having a fixed pole supported by an insulating seat, wherein the diaphragm and the fixed pole are arranged to face each other via an electrically insulating spacer. Unidirectionality in which the converter is housed in the unit case with the diaphragm assembly as the end plate side, and a fixing means for pressing and fixing the acoustoelectric converter is provided on the other end surface side of the unit case. In the condenser microphone unit,
On the other end surface side of the diaphragm support ring, a pipe-like groove having a predetermined acoustic mass is formed between the diaphragm and the end plate. A first opening for introducing a part of the sound wave from the front acoustic terminal hole into the groove is formed, and a predetermined portion on the outer peripheral surface side of the diaphragm support ring is provided on the inner side of the unit case. A second opening opened toward the wall surface is formed, and the second opening is acoustically connected to the back side of the diaphragm via the spacer ;
A unidirectional condenser microphone unit characterized in that a mesh material made of synthetic resin having air permeability in the surface direction is used for the spacer .   2. The single unit according to claim 1, wherein the groove is formed over the entire circumference of the diaphragm support ring, and the first opening and the second opening are disposed at a position opposed to each other by 180 °. Unidirectional condenser microphone unit. A narrow directivity line microphone formed by combining the unidirectional condenser microphone unit according to claim 1 or 2 and an acoustic tube.

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