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JP2006287687

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DESCRIPTION JP2006287687
To obtain an acoustic tube which can be easily manufactured and which is easy to miniaturize. By
using this acoustic tube, a directional microphone having a simple structure and easy to
miniaturize is obtained. An acoustic tube (10) integrally formed, wherein an acoustic resistance
material (12) disposed on an inner circumferential surface of the acoustic tube (10) is integrated
with the acoustic tube by the formation of the acoustic tube (10). Preferably, the material of the
acoustic tube 10 is resin, and the acoustic resistance material 12 is a mesh of resin. The acoustic
tube 10 preferably has a slit-like acoustic resistance portion 11, and the acoustic resistance
member 12 may be present in the acoustic resistance portion 11. It is preferable to configure a
directional microphone by using the above-mentioned acoustic tube 10. [Selected figure] Figure
1
Acoustic tube and directional microphone
[0001]
The present invention relates to, for example, an acoustic pipe usable for a microphone and a
directional microphone using the same, and more particularly to an acoustic pipe and a
directional microphone capable of simplifying a manufacturing process and downsizing. is there.
[0002]
For example, in a directional microphone, an acoustic tube having a leak is disposed at the front
acoustic terminal of the microphone unit, and sound waves from angles other than the main
sound collecting axis are from the front of the acoustic tube to the side acoustic resistance. And
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is configured to enter the acoustic tube.
The sound wave entering from the front of the acoustic tube and the sound wave entering from
the above-mentioned acoustic resistance are attenuated by the phase difference between the two,
and sharp directivity is obtained by emphasizing the sound wave of the main sound collection
axis.
[0003]
As an example of a specific configuration of the above-mentioned acoustic tube, it has a plurality
of through holes for acoustic resistance on the peripheral surface, and an acoustic resistance
material made of felt, resin mesh, non-woven fabric, etc. is provided on the outer peripheral
surface of the acoustic tube. There is Then, an outer casing having an inner diameter larger than
the outer diameter of the acoustic resistance and having a plurality of through holes formed on
the circumferential surface is fitted to the outer circumferential surface of the acoustic tube, and
the microphone unit is disposed in the acoustic tube Those are known (see, for example, Patent
Document 1).
[0004]
However, in the configuration of the acoustic tube described in Patent Document 1, since the
acoustic resistance material made of non-woven fabric etc. is provided on the outer periphery of
the acoustic tube, it is necessary to fit the outer casing further on the outer periphery side of the
acoustic resistance material Yes, the structure is complicated and the manufacturing process
becomes complicated. Then, the narrow directivity microphone which made the outer case
unnecessary by providing an acoustic resistive material in the inner peripheral side of an
acoustic tube is known (for example, refer to patent documents 2).
[0005]
FIG. 2 shows a conventional example of an acoustic tube based on the same idea as the acoustic
tube described in Patent Document 2. As shown in FIG. In FIG. 2, a plurality of slits 2 constituting
an acoustic resistance portion in a direction parallel to the central axis of the acoustic tube are
arranged in the circumferential direction of the metal cylindrical elongated cylindrical acoustic
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2
tube 1 in parallel in the central axis direction. It is formed penetrating the peripheral wall of the
acoustic tube 1. The slits 2 may be formed in only one row, or in two or more rows, for example,
in two rows in total at mutually opposing positions of the peripheral walls. An acoustic resistance
material 3 is attached to the inner peripheral surface of the acoustic tube 1. The acoustic
resistance material 3 is made of, for example, a resin mesh, and is adhered to the inner
peripheral surface of the acoustic tube 1 by adhesion using, for example, a double-sided adhesive
tape. The right side in FIG. 2 of the acoustic tube 1 is the proximal end, and the left side is the
distal end, and a microphone unit (not shown) is attached to the proximal end. The front damper
4 is fitted on the tip end side, the grille mesh 5 is fitted on the outside thereof, and the grille 6 is
fitted on the outside thereof.
[0006]
Japanese Utility Model Laid-Open Publication No. 6-48294
[0007]
According to the conventional acoustic tube as shown in FIG. 2, since the acoustic resistance
material 3 is adhered to the inner peripheral surface of the acoustic tube 1 by adhesion, the
manufacturing process is troublesome.
In particular, since the acoustic resistance material 3 must be attached to the inner peripheral
surface of the acoustic tube 1 without a gap, attention is required for the affixing work, and it is
difficult to affix accurately at a predetermined position and requires skill. It becomes work. In
connection with such a problem, it is also difficult to miniaturize the acoustic tube. When the
acoustic tube is miniaturized, the paste operation of the acoustic resistance material itself is
difficult, and it becomes more difficult to precisely paste in a predetermined position.
[0008]
The present invention was made to solve the problems of the prior art as described above, and
provides an acoustic tube which can be easily manufactured and which is easy to miniaturize,
and the acoustic tube It is an object of the present invention to provide a directional microphone
that has a simple structure and can be easily miniaturized.
[0009]
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The present invention is an integrally formed acoustic tube, and the main feature is that the
acoustic resistance material disposed on the inner peripheral surface of the acoustic tube is
integrated with the acoustic tube by the formation of the acoustic tube. .
It is preferable that the material of the above-mentioned sound tube be resin, and the abovementioned sound resistance material be a mesh of resin. It is preferable that the abovementioned acoustic tube has a slit-like acoustic resistance portion, and an acoustic resistance
material is present in this acoustic resistance portion. It is preferable to construct a directional
microphone by using the above-mentioned acoustic tube.
[0010]
Since the acoustic tube having the anti-sounding material disposed on the inner circumferential
surface can be obtained by integral molding, manufacture of the acoustic tube becomes
extremely easy, and no skill is required for manufacture. In addition, by setting the position of
the acoustic resistance material to a mold in advance and integrally molding the acoustic tube, it
is possible to improve the relative position accuracy of the acoustic resistance material to the
acoustic tube, and even if the outer diameter of the acoustic tube is reduced. An acoustic tube
with high accuracy can be obtained. According to the directional microphone using the acoustic
tube according to the present invention, it is possible to obtain a directional microphone with
high accuracy and smaller size at low cost.
[0011]
Hereinafter, embodiments of an acoustic tube and a directional microphone according to the
present invention will be described with reference to the drawings. In FIG. 1, reference numeral
10 indicates an acoustic tube. The acoustic tube 10 is an integrally molded product made of
resin, and a plurality of slits 11 constituting an acoustic resistance portion in a direction parallel
to the central axis of the acoustic tube 10 are provided on the peripheral wall of the elongated
cylindrical acoustic tube 10. It is formed in the axial direction at regular intervals. The slit 11 is
formed to penetrate the wall surface of the acoustic tube 10, and the inside and the outside of
the acoustic tube 10 communicate with each other through the slit 11. In the illustrated
embodiment, the slits 11 are formed in only one row, but a plurality of rows, for example, two
rows in total may be formed on opposing wall surfaces. An acoustic resistance material 12 is
disposed integrally with the acoustic tube 10 on the inner circumferential side of the acoustic
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tube 10. The acoustic resistance material 12 is made of resin mesh and is fused with the acoustic
tube 10 which is an integral molded product of resin. The acoustic resistance material 12 is a
strip-shaped member that is originally elongated and overlaps the slits 11 forming a row after
the acoustic tube 10 is formed. Therefore, after shaping, the acoustic resistance material 12 can
be seen from the outside of the acoustic tube 10 through the slit 11. The acoustic resistance
material 12 may be disposed so as to overlap each slit 11 by using a number corresponding to
the number of rows of the slits 11. Alternatively, one acoustic resistance material 12 may be
formed into a cylindrical shape so as to be inside the acoustic tube 10. It may be disposed on the
circumferential surface, and the inner circumferential surface of the acoustic tube 10 may be
covered with the acoustic resistance material 12.
[0012]
The acoustic resistance material 12 may not necessarily be a resin mesh. For example, a metal
mesh may be used, or a non-woven fabric or other cloth may be used. The material of the
acoustic tube 10 is also not limited to resin. It may be any one that can be molded by a mold, and
may be, for example, an aluminum die cast or a sintered body of metal powder.
[0013]
Assuming that one end of the acoustic tube 10 integrally formed with the acoustic resistance
material 12 is a proximal end and the other end is a distal end, a narrow directivity microphone
is configured by disposing, for example, a condenser microphone unit at the proximal end. can
do. That is, sound waves around the main sound collection axis are introduced from the tip of the
sound tube 10, and sound waves from angles other than the main sound collection axis are
sound waves and sound resistance portions that enter from the front of the sound tube 10 as
described above. By attenuating by the phase difference of the sound waves entering through the
slit 11 and the acoustic resistance material 12 of the second embodiment, a narrow directional
microphone can be obtained.
[0014]
Next, the method of manufacturing the acoustic tube 10 will be described by taking the case of
resin molding as an example. The acoustic tube 10 is manufactured by integral molding using a
molding die. The mold is constituted by a cylindrical slide mold for molding the inner
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circumferential surface of the acoustic tube 10 and a two-piece mold for molding the outer
circumferential surface of the acoustic tube 10. A projection for molding the slit 11 is integrally
provided on at least one of the two halves of the mold, and the projection protrudes in a direction
to demold the molded product. The acoustic resistance material 12 is positioned and arranged on
the outer peripheral surface of the slide mold, and then the slide mold is sandwiched between the
two molds. At this time, the acoustic resistance material 12 is pressed against the slide mold by
the projections formed on at least one of the two molds. In this state, since a molding space
having the same shape as the shape of the acoustic tube 10 to be molded is formed between the
slide mold and the two-piece mold, resin as a molding material is injected into this space.
[0015]
In this manner, the acoustic tube 10 is integrally formed in the acoustic tube 10 in the form of
so-called insert molding of the acoustic resistance material 12. After the injection molding, the
two molds are separated and the slide mold is slid and pulled out from the molded product,
whereby the acoustic tube 10 in which the acoustic resistance material 12 is integrated can be
obtained as described above. The plurality of slits formed in at least one split mold form a
plurality of slits 11 as an acoustic resistance portion shown in FIG. 1, and overlap each slit 11,
and the inner peripheral surface side of the acoustic tube 10 The acoustic resistance material 12
is integrated with the If projections for forming the slits 11 are integrally provided in both of the
two molds, two rows of the slits 11 are formed. In that case, the acoustic resistance material 12
may be two sheets, which may be disposed corresponding to the two rows of the slits 11 and
may be formed, or one acoustic resistance material may be formed in a cylindrical shape.
[0016]
According to the embodiment described above, since the acoustic tube 10 in which the
acoustically opposing member 12 is disposed can be obtained by integral molding on the inner
peripheral surface of the portion where the slits 11 exist, the acoustic tube 10 can be obtained
without requiring skill Production of the small diameter acoustic tube is also easy. In addition, by
setting the position of the acoustic resistance material 12 in advance as a molding die and
integrally molding the acoustic tube 10, it is possible to improve the relative position accuracy of
the acoustic resistance material 12 to the acoustic tube 10, and the outer diameter of the
acoustic tube Even if it is small, an acoustic tube with high accuracy can be obtained.
[0017]
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In addition, when manufacturing an acoustic pipe by aluminum die-casting or the sintered
compact of metal powder, it is desirable to make the acoustic opposition material 12 into metal
mesh.
[0018]
The main application of the acoustic tube according to the invention is a directional microphone,
but it is also applicable to other acoustic devices.
[0019]
The Example of the acoustic pipe concerning this invention is shown, (a) is a longitudinal crosssectional view, (b) is an enlarged view of the cross section in alignment with line AA in (a).
It is a longitudinal cross-sectional view which shows the example of the conventional acoustic
tube.
Explanation of sign
[0020]
10 sound tube 11 slit as a sound resistance portion 12 sound resistance material
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