JP5484936B2 - Narrow directional microphone - Google Patents

Description

  The present invention relates to a narrow directivity microphone in which a microphone unit is mounted in an acoustic tube. More specifically, the present invention relates to a narrow directional microphone having an acoustic tube with an acoustic resistance material attached thereto.

  As a narrow directivity microphone, one using an elongated acoustic tube is known. In this method, a microphone unit is mounted on the inner peripheral side of one end of an acoustic tube, and a sound wave that enters from a front end opening, which is the other end of the acoustic tube, is detected by the microphone unit and converted into an audio signal. As a conventional narrow directivity microphone using an acoustic tube, for example, there is an invention disclosed in Patent Document 1. In general, a narrow directivity microphone uses an acoustic tube made of metal, synthetic resin, or the like, and a slit-like opening is provided in the central axis direction on the peripheral wall of the acoustic tube, and an acoustic tube made of a synthetic resin thin film, nonwoven fabric, or the like. A resistance material is attached to the peripheral wall of the acoustic tube, and the opening is covered with the acoustic resistance material. The narrow directivity microphone having such a configuration allows the sound wave that enters from the front end opening of the acoustic tube to circulate from the circumferential direction to interfere with the sound wave that is guided from the peripheral wall opening of the acoustic tube through the acoustic resistance material, from the front of the acoustic tube. Narrow directivity that realizes electroacoustic conversion by focusing only incoming sound waves is realized.

  Here, an outline of an example of a conventional narrow directivity microphone using an acoustic tube will be described. 2 and 3, the narrow directivity microphone 1 includes an acoustic tube 2, an acoustic resistance material 4, a microphone unit 8, a circuit board 10, a microphone case 5, a wire mesh as a shield material 9, and a connector 6. . The acoustic tube 2 is an elongated cylindrical member made of metal or the like, and a plurality of slit-shaped openings 3 are formed on the peripheral wall thereof in parallel with the central axis of the acoustic tube 2. When the connector 6 side of the acoustic tube 2 is the rear end and the other end is the front end, the microphone unit 8 is disposed on the inner peripheral side of the rear end portion. In FIG. 2, an acoustic resistance material 4 is attached to the outer peripheral wall surface of the acoustic tube 2 so as to cover the opening 3. The acoustic tube 2 is open at both ends in the length direction. Sound waves are introduced from the opening at the front end of the acoustic tube 2.

  As shown in FIG. 2, an acoustic resistance material 4 is attached to the narrow directional microphone 1 on the outer peripheral side of the acoustic tube 2, and a wire mesh as a shielding material 9 is used to block electromagnetic waves entering from the outside. Is attached around the acoustic resistance material 4. The acoustic tube 2 is further covered with a cylindrical microphone case 5 from the outer peripheral side of the wire mesh as the shield material 9. The microphone case 5 has a length that is approximately twice the length of the acoustic tube 2. The acoustic tube 2 is fitted to the front half of the microphone case 5, and the microphone case 5 covers the entire acoustic tube 2. A connector 6 is attached to the rear end of the microphone case 5. A circuit board 10 is disposed in the internal space of the rear half of the microphone case 5 formed between the connector 6 and the microphone unit 8. A position corresponding to the slit-shaped opening 3 of the acoustic tube 2 is cut off on the peripheral wall of the microphone case 5, so that introduction of sound waves from the opening 3 is not hindered.

JP-A-62-118697

  In the conventional narrow directivity microphone configured as shown in FIGS. 2 and 3, the acoustic resistance material 4 may be damaged when a strong stress is applied from the outside. The acoustic tube 2 has a cylindrical shape, and an opening 3 is formed in the cylindrical surface. The acoustic resistance material 4 is attached to cover the opening 3, and the wire mesh 9 covers the outside. Therefore, an external force is applied to the microphone. This is because the shield material 9 provided with a wire mesh or the like presses the acoustic resistance material 4. The acoustic resistance material 4 is particularly weak because there is no support at the portion corresponding to the opening 3, and when the acoustic resistance material 4 is pushed, the portion corresponding to the opening 3 is damaged. When the acoustic resistance material 4 is damaged, the acoustic resistance changes and the frequency response is deteriorated. In addition, since the acoustic resistance material 4 is affixed to the outside of the cylindrical acoustic tube 2, if an elastic material such as a nonwoven fabric is used as the acoustic resistance material 4, the acoustic resistance material 4 becomes elastic and easily peels off. Therefore, it is necessary to make a large bonding surface between the acoustic resistance material 4 and the acoustic tube 2. Therefore, the acoustic resistance material 4 must be enlarged, which increases the cost. Moreover, since the opening 3 of the acoustic tube 2 has a volume corresponding to the thickness of the acoustic tube 2, the volume of the acoustic tube 2 affects the transmission of sound waves from the opening 3 through the acoustic tube 2. May end up. Therefore, there is a possibility of affecting the narrow directivity of the microphone.

Therefore, the present invention prevents the acoustic resistance material affixed to the outside of the acoustic tube from being damaged by external stress, thereby preventing the acoustic resistance material from changing and degrading the frequency response. In addition, it is an object of the present invention to provide a narrow directional microphone capable of preventing the volume of the opening of the acoustic tube from affecting the transmission of sound waves from the opening through the acoustic tube.
It is another object of the present invention to provide a narrow directivity microphone in which the acoustic resistance material is difficult to peel off, the adhesion area of the acoustic resistance material can be reduced, the acoustic resistance material is saved.

A narrow directivity microphone according to the present invention includes a microphone unit, an acoustic tube in which an opening is formed in the peripheral wall along the axial direction, and the microphone unit is mounted inward, and is attached to an outer surface of the acoustic tube. an acoustic resistance member which has an associated by closing the opening formed in a cylindrical shape together with the acoustic resistance member has a shield member surrounding the acoustic tube, said acoustic tube is formed by integral molding of resin, the acoustic the attaching surface of the acoustic resistance member of the tube, it becomes flat surfaces, and most important feature Rukoto which have a space between the shielding member and the acoustic resistance member.

  According to the narrow directivity microphone of the present invention, since the surface of the acoustic resistance material of the acoustic tube is flat, even if stress is applied to the shield material surrounding the acoustic resistance material, the acoustic resistance material is stressed. Therefore, the acoustic resistance material can be prevented from being damaged, and the volume of the acoustic tube opening is reduced so that the volume of the acoustic tube opening affects the transmission of sound waves from the opening through the acoustic tube. Since it can be made small, good narrow directivity can be obtained. In addition, because the acoustic resistance material is flat, the acoustic resistance material is difficult to peel off, the adhesive area of the acoustic resistance material is reduced, and the cost of the acoustic resistance material itself is reduced. Can do.

It is a cross-sectional view showing an embodiment of a narrow directional microphone according to the present invention. It is a cross-sectional view showing an example of a conventional narrow directivity microphone. It is a longitudinal cross-sectional view of the said conventional narrow directivity microphone.

  Embodiments of a narrow directivity microphone according to the present invention will be described below with reference to the drawings. The narrow directivity microphone according to the present invention is characterized by the shape of the acoustic tube and the configuration of the attachment surface of the acoustic resistance material, and other configurations may be the same as the configuration of the conventional example shown in FIG. There is no problem. Therefore, an outline of the configuration of the narrow directivity microphone will be described with reference to FIG.

  In FIG. 3, a narrow directional microphone 1 includes an acoustic tube 2 in which an opening 3 is formed in the peripheral wall along the axial direction and a microphone unit 8 is mounted inward, and an outer surface of the acoustic tube 2. An acoustic resistance material 4 that is attached and closes the opening 3, a shield material 9 that surrounds the acoustic resistance material 4 and a wire net that surrounds the acoustic tube 2, a circuit board 10, a microphone case 5, and a connector 6 are provided. . The acoustic tube 2 is an elongated cylindrical member made of metal or the like, and a plurality of slit-shaped openings 3 are formed on the peripheral wall thereof in parallel with the central axis of the acoustic tube 2. When the connector 6 side of the acoustic tube 2 is the rear end and the other end is the front end, the microphone unit 8 is disposed on the inner peripheral side of the rear end portion. An acoustic resistance material 4 is attached to the outer peripheral wall surface of the acoustic tube 2 so as to cover the opening 3. The acoustic tube 2 is open at both ends in the length direction. Sound waves are introduced from the opening at the front end of the acoustic tube 2. A front cap 7 is provided at the tip of the microphone case 5 for protection.

  The material of the acoustic tube 2 is arbitrary. For example, an elongated rectangular plate mainly made of metal such as aluminum or iron may be used as a material, and this may be rounded in the short side direction to form an elongated cylindrical shape. However, as described below, the present invention has a feature in the configuration of the acoustic tube 2, and in order to realize the characteristic configuration of the acoustic tube 2, the acoustic tube 2 is formed by integral molding of synthetic resin. Make it. Both ends of the acoustic tube 2 are open. In FIG. 3, when the connector 6 side is the rear end and the opposite side is the front end, the microphone unit 8 is disposed on the inner peripheral side of the rear end of the acoustic tube 2. The outer circumferences of the acoustic tube 2 and the shield material 9 are covered with a substantially first half portion of a substantially cylindrical microphone case 5.

  A connector 6 is provided at the rear end of the microphone case 5 for drawing out an audio signal converted into an electric signal by the microphone unit 8. A circuit board 10 incorporating an electrical circuit that relays between the connector 6 and the microphone unit 8 and applies electrical processing to the electrical signal is disposed inside the rear half of the microphone case 5. The configuration of the rear end portion of the narrow directivity microphone 1 is not limited to the above-described configuration, and an appropriate configuration can be adopted. For example, a grip may be provided, or a wireless microphone provided with appropriate wireless communication means may be used.

  In FIG. 1, the acoustic tube 2 has a cylindrical shape, and the surface to which the acoustic resistance material 4 is to be attached is formed as a flat surface to be a pasting surface 2A. The sticking surface 2A is a surface parallel to the central axis of the acoustic tube 2. The sticking surface 2A is formed so that the acoustic tube 2 is cut out from the outer peripheral surface within the thickness range of the acoustic tube 2, and thus the thickness remains between the sticking surface 2A and the inner peripheral surface of the acoustic tube 2. Yes. A plurality of slit-shaped openings 3 that communicate the inside and outside of the acoustic tube 2 are formed on the attachment surface 2A in parallel to the central axis of the acoustic tube 2 and at appropriate intervals in the central axis direction. The length of the attachment surface 2A It is also parallel to the direction. The acoustic resistance material 4 is affixed to the flat affixing surface 2A by an appropriate bonding method. As an adhesion method, a liquid adhesive may be used, and a double-sided tape may be used. The sticking surface 2A of the acoustic resistance material 4 is formed at two intervals in the circumferential direction of the acoustic tube 2 at intervals of 180 degrees. Accordingly, the two pasting surfaces 2A face each other in parallel. The cross-sectional shape of the acoustic tube 2 is symmetric with respect to the circumferential diameter axis A. A shield material 9, which is a wire mesh surrounding the acoustic tube 2 together with the acoustic resistance material 4, is formed in a cylindrical shape. In designing the affixing surface 2A, a plane can be provided by reducing the thickness within the range of the thickness of the cylindrical acoustic tube 2 as described above.

  In this way, a space is created between the shield material 9 and the acoustic resistance material 4. Therefore, even if an external force is applied to the microphone and the shielding material 9 surrounding the surroundings of the acoustic resistance material 4 is stressed and the shielding material 9 is deformed, the shielding material 9 can be prevented from hitting the acoustic resistance material 4, Thus, the acoustic resistance material 4 can be prevented from being damaged. Further, the acoustic resistance material 4 can be attached to the flat application surface 2A of the acoustic tube 2 without being bent. Therefore, even if a material having elasticity is used as the acoustic resistance material 4, the elasticity does not work and it is difficult to peel off, and the adhesion area between the acoustic resistance material 4 and the acoustic tube 2 and the area of the acoustic resistance material 4 itself can be reduced. Therefore, the cost can be reduced. Further, the volume of the opening 3 of the acoustic tube 2 can be reduced, and the volume of the opening 3 of the acoustic tube 2 can be reduced by affecting the transmission of sound waves from the opening 3 through the acoustic tube 2. Good narrow directivity can be obtained.

  The narrow directivity microphone according to the present invention is not limited to the configuration of the above-described embodiments, and can be appropriately changed without departing from the technical idea described in the claims. For example, the number of pasting surfaces 2A which is a flat surface in the circumferential direction of the acoustic tube 2 is arbitrary. The location of the bonding surface 2A in the circumferential direction of the acoustic tube 2 may be one, and the cross-sectional shape thereof may be formed in a D shape, or may be formed in three or four locations. However, it is preferable to maintain the strength of the acoustic tube 2 while realizing narrow directivity when the two attachment surfaces 2A of the acoustic resistance material 4 are provided as described above. A plurality of openings 3 of the acoustic tube 2 can be formed at a plurality of locations in the circumferential direction of the acoustic tube 2 according to the number of the pasting surfaces 2A and at intervals in the central axis direction of the acoustic tube 2. The shield material 9 may be formed of a conductive plastic, for example, as long as it has a hole through which sound can pass, even if it is not a wire mesh. As the acoustic resistance material 4, an appropriate material can be selected. For example, a nonwoven fabric or the like can be used.

  The outer periphery of the shield material 9 is covered with a substantially cylindrical microphone case 5, and the microphone case 5 functions as a protective material for the acoustic tube 2. An appropriate material can be used for the microphone case 5, which may be a metal, an organic substance, or carbon. The cylindrical acoustic tube 2 is inserted into the microphone case 5. The microphone case 5 has a position corresponding to the opening 3 of the acoustic tube 2 and the attachment surface 2A of the acoustic resistance material 4, and therefore in the circumferential direction of the microphone case 5, in the direction of the central axis of the microphone case 5. An elongated window hole is formed. Since the window hole of the microphone case 5 located on the outer peripheral side of the acoustic tube 2 does not need to function as an acoustic resistance, the microphone case 5 sufficiently functions as a reinforcing material or a protective member, and the opening 3 and the acoustic It is good to enlarge to such an extent that the function of the resistance material 4 is not inhibited.

The shape of the opening 3 of the acoustic tube 2 can be appropriately changed. For example, the shape may be a square shape or a circular shape, or a combination of various shapes.
In the illustrated embodiment, the microphone unit 8 holds the outer peripheral side of the microphone unit 8 with the microphone case 5 via the acoustic tube 2 and the shield material 9. A gap is provided between the outer peripheral surface of the microphone unit 8 and the inner peripheral surface of the acoustic tube 2, and the front acoustic terminal and the rear acoustic terminal of the microphone unit 8 are acoustically short-circuited by the acoustic impedance formed by the gap, Wind noise may be reduced.

  The narrow directivity microphone according to the present invention can be used as a microphone for professional audio equipment, for example, as a microphone as an accessory for audio equipment or a video recorder.

DESCRIPTION OF SYMBOLS 1 Narrow directional microphone 2 Acoustic tube 3 Acoustic tube opening 4 Acoustic resistance material 5 Microphone case 6 Connector 7 Front cap 8 Microphone unit 9 Shield material

Claims (7)

A microphone unit, an acoustic tube in which an opening is formed in the peripheral wall along the axial direction and the microphone unit is mounted on the inside, and an acoustic sound that is attached to the outer surface of the acoustic tube and closes the opening A resistance material, and a shielding material that is formed in a cylindrical shape and surrounds the acoustic tube together with the acoustic resistance material,
The acoustic tube is formed by integral molding of resin,
The attachment surface of the acoustic resistance material of the acoustic tube is a flat surface ,
Narrow directional microphone, characterized in Rukoto which have a space between the shielding member and the acoustic resistance member.   The narrow directivity microphone according to claim 1, wherein the acoustic resistance material is made of an elastic material.   The narrow directivity microphone according to claim 1 or 2, wherein the acoustic tube is cylindrical, and an attachment surface of the acoustic resistance material is a surface parallel to the central axis of the acoustic tube.   The narrow directional microphone according to any one of claims 1 to 3, wherein a cross-sectional shape of the acoustic tube is symmetric with respect to a circumferential diameter axis.   The narrow directional microphone according to any one of claims 1 to 4, wherein there are two attachment surfaces of the acoustic resistance material.   The narrow directional microphone according to any one of claims 1 to 3, wherein a cross-sectional shape of the acoustic tube is a D-shape.   The narrow directivity microphone according to claim 1, wherein the shield material is a wire mesh.

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