JP3049566B2 - Microphone sound tube - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a super-directional microphone, and more particularly, to a microphone attached to the tip of a microphone unit,
The present invention relates to the production of an acoustic tube capable of obtaining a narrow directivity.

[Conventional technology]

Various attempts have been made to narrow the directivity by attaching an acoustic tube (interference tube) to the tip of a microphone unit. Since the length of such a sound tube is determined by the lowest frequency at which a specific directivity is desired, when the frequency is high, an appropriate size is set on the side wall of the sound tube so that the length of the sound tube is shortened acoustically. An acoustic resistance material having an appropriate acoustic resistance is attached so as to cover the opening.

That is, the configuration of a conventional acoustic tube will be described with reference to FIG. 5. An acoustic tube 1 made of metal such as aluminum or brass or made of a synthetic resin is formed by cutting or opening an opening 2 of an appropriate size for introducing sound waves into the side surface. A plurality of acoustic resistance members 3 such as cloth, net or non-woven cloth having an appropriate acoustic resistance are covered with an adhesive or a double-sided tape so as to cover the openings 2 by a predetermined distance in the axial direction by injection molding. doing. The sound collection unit of the microphone unit 3 is located in the one end opening of the acoustic tube 1. It has been proposed to mount the microphone unit 3 inside the acoustic tube 1 to obtain a high wind noise prevention effect and to obtain a directivity higher than the characteristic inherent in the microphone unit in the middle and low frequency ranges. I have.

[Problems to be solved by the invention]

As described above, the openings 2 are formed by cutting, injection molding, or the like. However, forming a plurality of openings 2 in a tubular body at a predetermined size and at predetermined intervals requires not only skill but also the periphery of the openings. You need to pay close attention to the processing of burrs. In order to simplify the process of forming the opening, it has been proposed to form an elongated hole extending in the axial direction in the side wall of the acoustic tube. However, such a long hole is problematic in that the central portion of the elongated hole is easily opened during processing. There is a point.

Furthermore, if the microphone unit uses a large-diameter unit, the low-frequency reproduction limit can be extended,
In addition, although the S / N ratio can be improved, the microphone unit having a larger diameter than the inner diameter of the acoustic tube cannot be used in the type in which the sound collecting unit of the microphone unit 3 is located in the opening of the acoustic tube 1. There are drawbacks. For this reason, when the outer diameter is limited, how to reduce the thickness of the acoustic tube becomes a design problem. In particular, when forming an acoustic tube with a metal tube, a drawn tube of aluminum or the like is usually used, but its thickness is about 1 m, and it cannot be thinner.

SUMMARY OF THE INVENTION An object of the present invention is to provide a microphone acoustic tube which has a simple structure, is lightweight, and can be manufactured at low cost without performing processing such as machining or injection molding.

[Means for solving the problem]

An acoustic tube of a microphone according to the present invention includes a sheet-shaped adhesive tape provided with an opening for setting directivity, and a net made of metal, synthetic resin, or the like attached to an adhesive surface of the adhesive tape. And this net is bent into a hollow body to form an acoustic tube.

The present invention is also characterized in that the adhesive tape is constituted by a double-sided adhesive tape having an adhesive surface on the other surface, and an acoustic resistance material is attached to the other surface of the double-sided adhesive tape so as to cover the opening. Things.

[Action]

The opening for adjusting the directivity is provided in the adhesive tape, and the opening can be perforated while the adhesive tape is flat, so that the desired size and shape can be easily set. Since the net is adhered to the adhesive tape, the opening is not deformed, and the net can be easily formed into an arbitrary shape, so that a microphone having a desired shape can be manufactured. Further, since the sound tube can be constituted by a net and an adhesive tape, an extremely thin and lightweight acoustic tube can be manufactured.

In addition, even when the acoustic tape is provided with a double-sided adhesive tape so as to cover the opening, the acoustic resistor can be provided by a simple attaching operation.

〔Example〕

Hereinafter, the present invention will be described with reference to an embodiment shown in FIGS. 1 to 4b.

FIG. 1 shows a super-directional microphone 11 using an acoustic tube according to a first embodiment of the present invention. This microphone 11 is an electret-type microphone unit 12.
And an acoustic tube 13 that accommodates the microphone unit 12 in one axial end thereof, and a microphone case 14 that covers the outer peripheral surface of the acoustic tube 13.

As shown in FIG. 2a, the acoustic tube 13 has a double-sided adhesive tape 21 in which an adhesive is applied to both sides of a base material made of paper or a synthetic resin film sheet, and one of the double-sided adhesive tapes 21. And a thin mesh body 22 having a size substantially equal to the size of the double-sided adhesive tape 21 and made of a metal such as stainless steel or a synthetic resin, for example, about # 10 mesh.
And acoustic resistance materials 23 and 24 such as cloth or non-woven fabric attached to the other surface of the double-sided adhesive tape 21. The double-sided adhesive tape 21 has two long holes 25 corresponding to the openings 2 of the conventional example described above, and two round holes 26 for communicating with the openings 15 formed in the peripheral portion of the microphone unit 12. I have. The acoustic resistance material 23 is large enough to cover each elongated hole 25 of the double-sided adhesive tape 21, and the acoustic resistance material 24 is
It is sized to cover 26.

In such an acoustic tube 13, first, a long hole 25 and a round hole 26 are pierced at predetermined positions of the double-sided adhesive tape 21, and then a net 22 is attached to one surface thereof. Next, double-sided adhesive tape
An acoustic resistance member 23 is attached to the other surface of 21 so as to cover each of the long holes 25, and an acoustic resistance member 24 is attached to cover each of the round holes 26. After the net 22 and the acoustic resistance members 23 and 24 have been attached to the double-sided adhesive tape 21 in this manner, the circumferential surface length of the net 22 is
The integrated double-sided adhesive tape 21, net 22 and acoustic resistance members 23 and 24 are wound around a cylindrical jig 31 having a length substantially equal to or slightly shorter than Then, the joint is bonded with a single-sided adhesive tape 27. After bonding the joints, the jig 29 is pulled out, and the hollow cylindrical acoustic tube 13 is completed. This acoustic tube 13 is a microphone case
It only has to be inserted into 14. In FIG. 1, reference numeral 28 denotes a cap formed of a netting similar to the netting 22, which is inserted and fixed in advance in the front end of the microphone case 14 in the sound pickup axis direction.

As described above, since the acoustic sound 13 is mainly formed in a tubular shape by the mesh body 22, it is lightweight and can be easily deformed into an arbitrary shape, and the opening is formed in the sheet-shaped double-sided adhesive tape 21. Therefore, it can be accurately formed into a desired size and shape. Further, since the acoustic resistance members 23 and 24 can be attached only by sticking to one surface of the double-sided adhesive tape 21, an acoustic tube having a small thickness can be manufactured very easily.

FIG. 3 is a graph showing the frequency response characteristics of a microphone using the acoustic tube 13 made in this manner. The characteristics when the sound collection opening of the microphone is set to 0 ° with respect to the sound source are represented by a.
, The characteristic when tilted by 90 ° is indicated by the dotted line of b, and the characteristic when tilted by 180 ° is indicated by the one-dot chain line of c. As can be seen from this graph, super directivity can be obtained from the low band to the high band.

FIGS. 4a and 4b show another embodiment of the acoustic tube of the present invention applied to a panel-mounted microphone. Such a microphone is, for example, a hands-free type transmitter for a car telephone. Used as a microphone. That is, the microphone unit 32 is attached to one end in the longitudinal direction of the rectangular flat plate-shaped substrate 31 so that the sound collection port faces the other end of the substrate 31 in the longitudinal direction. A substantially semi-cylindrical acoustic tube 33 is attached to the substrate 31. The acoustic tube 33 is composed of a rectangular double-sided adhesive tape 34, a net 35 adhered to one surface of the double-sided adhesive tape 34, and an acoustic resistance material 36, as in the above-described embodiment.
A long hole 37 is formed in a substantially central portion of the double-sided adhesive tape 34, that is, in a portion located near the top when formed into a semi-cylindrical shape so as to extend in the longitudinal direction. The acoustic resistance member 36 is provided so as to cover only the portion of the long hole 37. The acoustic tube 33 containing the microphone unit 32 is covered with a microphone case 38 made of a wire mesh or a perforated metal that transmits sound waves. With this configuration, the substrate 31
The microphone 39 supported above was provided on the mounting substrate 41 such that the end side of the acoustic tube 33 opposite to the end where the microphone unit 32 was located was positioned in the direction of the mouth of the sound source, that is, the talker. It is fixed to the mounting opening 42.
As a result, the engine sound and the surrounding noise can be cut, and only the voice of the caller can be reliably captured.

Although the acoustic resistance material is provided in each of the above-described embodiments, the net body is also a kind of acoustic resistance material, and if the acoustic resistance of the net body is sufficient, it is only necessary to form a large opening in the double-sided adhesive tape. Good. In this case, since the other surface does not need to be bonded, it is a matter of course that a single-sided adhesive tape may be used.

〔The invention's effect〕

As described above, since the acoustic tube of the microphone of the present invention is composed of a net and an adhesive tape, it can be configured to be extremely thin and lightweight, and can be deformed into an arbitrary shape without requiring machining or injection molding. A microphone according to the purpose can be provided. Further, since the adhesive tape is provided with an opening for adjusting the frequency, the adhesive tape can be pierced in a flat state, and the desired size and shape can be easily and accurately set. Since the net is adhered to this adhesive tape, the opening is not deformed.

If the net alone is not enough for acoustic resistance, use this adhesive tape as a double-sided adhesive tape to provide an acoustic resistance material such as cloth or non-woven fabric to cover the opening. Thus, an acoustic resistance material can be provided.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a microphone using an acoustic tube according to a first embodiment of the present invention, FIG. 2a is a perspective view showing an exploded configuration of the acoustic tube, and FIG. 2b is a flat acoustic tube. FIG. 2c is a perspective view showing a completed sound tube, FIG. 3 is a graph showing frequency response characteristics of a microphone using this sound tube, FIG. FIG. 4 is a longitudinal sectional view showing another embodiment of the present invention, FIG. 4b is a transverse sectional view thereof, and FIG. 5 is a longitudinal sectional view showing an example of a conventional acoustic tube. In the drawing, 11, 39 is a microphone, 12 is a microphone unit, 13, 33 is an acoustic tube, 21, 34 is double-sided adhesive tape,
22,35 are nets, 23,24,36 are acoustic resistance materials, 25,37 are long holes, 26
Is a round hole, and 27 is a single-sided adhesive tape.

──────────────────────────────────────────────────の Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H04R 1/20-1/40 330 G10K 11/02-11/04 G10K 11/18-11/35

Claims (2)

(57) [Claims] 1. A sheet-like adhesive tape provided with an opening for setting directivity, and a net made of metal, synthetic resin or the like adhered to an adhesive surface of the adhesive tape. ,
The acoustic tube of a microphone, wherein the mesh body is bent into a hollow body to form an acoustic tube. 2. The double-sided adhesive tape has a double-sided adhesive tape having an adhesive surface on the other surface, and an acoustic resistance material is attached to the other surface of the double-sided adhesive tape so as to cover the opening. The acoustic tube of the microphone according to claim 1, wherein: