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JP2008258998

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DESCRIPTION JP2008258998
An acoustic tube for a narrow directional microphone, a narrow directional microphone, and a
narrow directional microphone in which directivity does not deteriorate even when water
droplets adhere to an acoustic tube and generation of wind noise and vibration noise in the
acoustic tube is suppressed. Provide a manufacturing method of A narrow directional
microphone acoustic tube 20 is an acoustic tube mounted on one end side of a microphone unit
included in a narrow directional microphone, and a flexible resin having a plurality of small
openings 22 in its peripheral wall. It is characterized in that it comprises a tube 21 and a resin
tube support member 23 disposed in close contact with the inner circumferential side of the
flexible resin tube. Further, the narrow directional microphone acoustic tube 20 is mounted on
one end side of the microphone unit 30 to form the narrow directional microphone 1. [Selected
figure] Figure 1
Acoustic tube for narrow directional microphone, narrow directional microphone, and method of
manufacturing acoustic tube for narrow directional microphone
[0001]
The present invention relates to a narrow directional microphone acoustic tube for narrowing the
directivity of a microphone, a narrow directional microphone including the narrow directional
microphone acoustic tube, and a method of manufacturing the narrow directional microphone
acoustic tube. More particularly, the present invention relates to a technique for improving the
generation of noise in an acoustic tube for a narrow directional microphone.
[0002]
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1
A narrow directional microphone is a microphone that has an extremely limited angular range
for picking up sound and can capture sound with sensitivity to an extremely narrow range of the
front (front side).
As such a narrow directional microphone, one using an elongated acoustic tube (interference
pipe) is known. In this method, the microphone unit is mounted on the inner peripheral side of
one end of the acoustic tube, and the sound wave entering from the opening at the front end
which is the other end of the acoustic tube is detected by the microphone unit and converted into
an audio signal. As an example of an acoustic tube used for a narrow directional microphone, for
example, a metal tube is used, an opening is provided in the peripheral wall of the metal tube,
and an acoustic resistor made of a synthetic resin thin film or non-woven fabric is attached to
this opening. There is one in which the opening is covered by an acoustic resistor.
[0003]
The narrow directional microphone using the acoustic tube having such a configuration makes
the sound wave entering from the front end opening of the acoustic tube interfere with the sound
wave entering from the peripheral wall (tube side) opening of the acoustic tube through the
acoustic resistor. Thus, narrow directivity is realized. That is, a narrow directional microphone
directs the sound tube to a sound source, thereby picking up only the voice coming from a
specific direction (front) while eliminating the surrounding noise without picking up the back and
side sounds. It can be converted to a signal.
[0004]
An example of a conventional narrow directional microphone using an acoustic tube made of the
above-described metal tube is shown in FIGS. In FIGS. 4 and 5, the narrow directional
microphone 100 includes a microphone case 110, an acoustic tube 120, an opening 122, an
acoustic resistor 124, a microphone unit 130, and a grip 140. The acoustic tube 120 is an
elongated cylindrical member made of metal or the like, and a plurality of slit-like openings 122
are formed in the peripheral wall thereof in parallel with the central axis of the acoustic tube
120. The slit-like openings 122 are formed along a plurality of straight lines in the direction of
the central axis of the acoustic tube 120, and are formed at equal intervals in the circumferential
direction of the acoustic tube 120. The acoustic tube 120 is open at both ends in the longitudinal
direction, and the acoustic resistor 124 is attached to the peripheral wall of the acoustic tube
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2
120 so as to cover the opening 122. In the figure, assuming that the left end of the acoustic tube
120 is the front end and the right end is the rear end, the microphone unit 130 is disposed on
the inner peripheral side of the rear end of the acoustic tube 120. A cylindrical grip 140 is
integrally coupled to the rear end of the microphone case 110 following the microphone case
110.
[0005]
Therefore, according to the narrow directivity microphone 100 shown in FIG. 4 and FIG. 5, the
sound wave entering from the front end opening of the acoustic tube 120 and the sound wave
entering from the opening 122 of the peripheral wall of the acoustic tube 120 via the acoustic
resistor 124 The narrow directivity is realized by interference between
[0006]
However, in the conventional narrow directional microphone, when the acoustic resistance value
of the acoustic resistor 124 covering the opening 122 of the peripheral wall of the acoustic tube
120 changes, the directivity is degraded.
For example, when using a narrow directional microphone outdoors, when water droplets enter
the narrow directional microphone due to rainfall or the like and the water droplets wet the
acoustic resistor, the value of the acoustic resistance increases or the sound wave passes It loses
its directivity and degrades.
[0007]
On the other hand, the applicant has proposed a narrow directional microphone improved to be
able to exhibit high directivity. In this narrow directional microphone, a plurality of openings are
provided on a peripheral wall of an acoustic tube, and an acoustic resistor made of non-woven
fabric or the like is attached to a part of the openings. Further, the opening is a first opening, and
an opening provided circumferentially spaced from the first opening is a second opening, and the
second opening is made of a synthetic resin thin film. A diaphragm is attached and each of a
plurality of openings is covered (see, for example, Patent Document 1). As a result, sound waves
other than sound waves from a limited angle range of sound source can be greatly attenuated,
and a microphone with extremely narrow directivity can be obtained. However, even in the
narrow directional microphone described in Patent Document 1 above, when the acoustic
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3
resistor gets wet due to water droplets such as rainfall and absorbs moisture, the value of the
acoustic resistance increases or the sound wave is not transmitted, and the directivity is to
degrade.
[0008]
In a narrow directional microphone using an acoustic tube, the microphone unit has a front
acoustic terminal and a rear acoustic terminal, and the rear end of the acoustic tube is connected
to the front acoustic terminal of the microphone unit. Therefore, in the state where the acoustic
tube is attached to the microphone unit, the distance between the front acoustic terminal and the
rear acoustic terminal becomes extremely long, so that the wind noise becomes large.
[0009]
Therefore, the applicant arranges the microphone unit inside the acoustic tube so as to provide a
gap between the outer circumferential surface of the microphone unit and the inner
circumferential surface of the acoustic tube, and the front acoustic terminal and the rear acoustic
terminal of the microphone unit The narrow directional microphone acoustically shorted by the
acoustic impedance which consists of said clearance gap was proposed (for example, refer patent
document 2). As a result, a very low frequency sound wave such as wind noise can be shorted by
this acoustic impedance to reduce wind noise.
[0010]
Also, the vibration noise of the narrow directional microphone depends on the mass of air in the
acoustic tube. For this reason, as the acoustic tube is longer, the mass of air in the acoustic tube
increases and the vibration noise becomes larger. According to the narrow directional
microphone described in Patent Document 2, vibration noise can also be reduced by acoustically
shorting the front acoustic terminal and the rear acoustic terminal of the microphone unit by
acoustic impedance. Thus, according to the invention described in Patent Document 2, there is an
advantage that wind noise and vibration noise can be reduced.
[0011]
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Also in the narrow directional microphone described in Patent Document 2, an opening is
provided in the peripheral wall of the acoustic tube, this opening is covered with an acoustic
resistor attached to the peripheral wall of the acoustic tube, and the sound wave entering from
the front end opening of the acoustic tube The narrow directivity is realized by causing the sound
waves coming from the peripheral wall opening of the acoustic tube through the acoustic resistor
to interfere with each other. Therefore, when the acoustic resistor gets wet due to rainfall or the
like, there is a problem that the directivity deteriorates as described above. In other words,
although various noise measures are taken, the problem of directivity deterioration due to water
wetting is not taken into consideration.
[0012]
Therefore, the present applicant uses a film provided with a plurality of minute holes as a narrow
directional microphone that does not deteriorate directivity even if water droplets adhere to the
acoustic tube, rounds this film into a cylindrical shape, and Proposed a narrow directional
microphone (see, for example, Patent Document 3). 6 and 7 show an example of a narrow
directional microphone of the same technical concept as the narrow directional microphone
described in Patent Document 3. FIG. 6 and 7, the narrow directional microphone 150 includes a
microphone case 160, an acoustic tube 170, a minute hole 172, a microphone unit 180, and a
grip 190. The acoustic tube 170 is formed by using an elongated rectangular sheet-like resin film
as a material and rolling it in the short side direction into an elongated cylindrical shape. For
example, a fluorocarbon resin is used as the sheet-like resin film, and two or three minute holes
172 with a diameter of 0.2 to 0.4 mm are provided per square centimeter. The outer periphery of
the acoustic tube 170 is held by a microphone case 160. An elongated window hole 162 is
formed in the peripheral wall of the microphone case 160 in parallel with the axis of the
microphone case 160. In the figure, assuming that the left end of the acoustic tube 170 is the
front end and the right end is the rear end, the microphone unit 180 is disposed on the inner
peripheral side of the rear end of the acoustic tube 170. Further, a cylindrical grip 190 is
integrally coupled to the rear end of the microphone case 160 following the microphone case
160.
[0013]
As described above, according to the narrow directivity microphone 150 shown in FIGS. 6 and 7,
the introduction of the sound wave from the front end opening of the acoustic tube 170 causes
the sheet-like resin film to operate as an acoustic capacity and acoustic mass. The minute holes
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172 opened at the bottom act as acoustic resistance. Therefore, since the acoustic tube 170 is
made up of only the film in which the minute holes 172 are opened innumerably, even if the
water droplet adheres to the acoustic tube, the water droplet does not penetrate inside the
acoustic tube, and the directivity deteriorates. There is nothing to do.
[0014]
However, in the narrow directional microphone described in Patent Document 3, the weight is
light because the acoustic tube is made of only the sheet-like resin film. Therefore, it is easy to be
blown by the wind, and there is a problem that the film is broken when it is blown by the wind. In
addition, when the sound tube was shaken to a large extent and vibration was applied, noise was
similarly generated. As described above, in the conventional narrow directional microphone, it is
very difficult to achieve improvement in directivity deterioration due to water wetting and
reduction in wind noise and vibration noise.
[0015]
JP-A-62-118697 JP-A-62-18698 JP-A-2006-109285
[0016]
The present invention has been made in view of the above circumstances, and is for narrow
directional microphones in which directivity does not deteriorate even when water droplets
adhere to the acoustic tube, and the generation of wind noise and vibration noise in the acoustic
tube is suppressed. An object of the present invention is to provide a method of manufacturing
an acoustic tube, a narrow directional microphone, and a narrow directional microphone.
[0017]
An acoustic tube for a narrow directional microphone according to the present invention is an
acoustic tube mounted on one end side of a microphone unit included in the narrow directional
microphone, and a flexible resin tube having a plurality of small openings in a peripheral wall
thereof And a resin tube support member disposed in intimate contact with the inner peripheral
side of the flexible resin tube.
[0018]
A method of manufacturing an acoustic tube for a narrow directional microphone according to
the present invention is an acoustic tube mounted on one end side of a microphone unit provided
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in a narrow directional microphone, wherein flexibility is provided with a plurality of small
openings in a peripheral wall. A method of manufacturing an acoustic tube for a narrow
directional microphone, comprising: a resin pipe; and a resin pipe support member disposed in
intimate contact with the inner peripheral side of the flexible resin pipe, the flexible pipe
comprising: Step A: providing a plurality of small openings in the peripheral wall of the resin
tube, step B: inserting the resin tube support member into the flexible resin tube, shrinking the
flexible resin tube by heat treatment, and the outer periphery of the resin tube support member
At least a step C of closely attaching the flexible resin tube and covering the resin tube
supporting member.
[0019]
According to the acoustic tube for a narrow directional microphone of the present invention, the
resin tube support member supports the flexible resin tube from the inner peripheral side while
in close contact with the flexible resin tube.
Therefore, the overall weight of the flexible resin tube is increased by closely contacting and
integrating the resin tube supporting members, and the flexible resin tube can be prevented from
fluttering and fluttering by wind.
In addition, the flexible resin tube has its strength increased by the core material of the resin
tube supporting member, and it is supported without rattling, and is not bent even if it is blown
by a wind or greatly shaken.
Thereby, wind noise and vibration noise can be reduced.
In addition, since the acoustic tube is provided with a small opening, the acoustic tube is
prevented from resonating by the sound wave, and even if the water droplet adheres to the
acoustic tube, the water droplet does not penetrate inside the acoustic tube . Therefore, it is
possible to provide an acoustic tube for a narrow directional microphone in which the directivity
does not deteriorate even when water droplets adhere to the acoustic tube, and the generation of
wind noise and vibration noise in the acoustic tube is suppressed.
[0020]
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7
According to the method of manufacturing an acoustic tube for a narrow directional microphone
of the present invention, the flexible resin tube is shrunk by being subjected to the heat
treatment in a state in which the resin tube support member is inserted therein, and it is
efficiently and simply Can cover the outer periphery of the resin tube support member.
Therefore, the flexible resin tube is closely covered and fixed to the outer periphery of the resin
tube support member, and the resin tube support member supports the flexible resin tube. When
the material of the flexible resin tube is made of a water-repellent fluorine resin, the directivity
does not deteriorate even if water droplets adhere to the acoustic tube. When the resin tube
support member is a coil spring or a tubular net having a shape retaining property, the flexible
resin tube is firmly held by the coil spring or a tubular net having a shape retaining ability, and
wind noise It is possible to easily and easily manufacture an acoustic tube for a narrow
directional microphone in which the generation of vibration noise is suppressed.
[0021]
Hereinafter, embodiments of the narrow directional microphone according to the present
invention will be described with reference to the drawings. The narrow directional microphone
acoustic tube according to the present invention and the narrow directional microphone
including the narrow directional microphone acoustic tube can be configured as shown in FIG. 1,
for example. FIG. 1 shows an embodiment of the narrow directional microphone according to the
present invention, wherein (a) is a front sectional view, (b) is a plan sectional view, and (c) is a
front view showing the acoustic tube in the above embodiment. FIG. In FIG. 1, the narrow
directional microphone 1 has a microphone case 10, an acoustic tube 20, a microphone unit 30,
and a grip 40.
[0022]
As shown in FIG. 1C, the acoustic pipe 20 has a flexible resin pipe 21 provided with a plurality of
small openings 22 in the peripheral wall, and an inner peripheral side of the flexible resin pipe
21. And a resin tube support member 23 disposed to be in close contact with each other. The
small openings 22 are opened substantially equally over the entire peripheral wall of the flexible
resin tube 21. In the present embodiment, two to three small openings 22 each having a
diameter of 0.2 to 0.4 mm are provided per square centimeter. By providing a plurality of small
openings 22 in the peripheral wall of the acoustic tube 20, even if water droplets adhere to the
acoustic tube 20, the water droplets do not enter the interior of the acoustic tube 20, and the
03-05-2019
8
directivity does not deteriorate.
[0023]
Further, in the present embodiment, the inner diameter of the flexible resin tube 21 is 18 mm,
and the length is 27 cm. As a material of the flexible resin tube 21, it is preferable to use a
fluorocarbon resin, specifically, FEP Teflon (trade name). By making the flexible resin tube 21
made of fluorine resin, water droplets due to rainfall etc. are repelled from the surface of the
acoustic tube 20, so that the intrusion into the acoustic tube 20 is effectively suppressed, and the
directivity is deteriorated. There is nothing to do.
[0024]
On the other hand, the resin tube support member 23 supports the flexible resin tube 21. For
example, as shown in FIG. 1, a coil spring can be used as the resin tube support member 23. By
covering the flexible resin tube 21 so as to be in close contact with the outer periphery of the coil
spring 23, the flexible resin tube 21 does not flutter or bend due to wind, and the generation of
wind noise and vibration noise. Can be suppressed.
[0025]
Further, it is desirable that the flexible resin tube 21 be made of a heat-shrinkable tube (shrink
tube) which shrinks by heat treatment. A heat-shrinkable tube is a tube that shrinks (slims)
diametrically when heat is applied. Examples of the material of the heat-shrinkable tube 21
include an electron beam cross-linked soft polyolefin resin cross-linked by irradiation of an
electron beam, and a soft fluorine resin obtained by electron cross-linking a soft flame-retardant
fluorine resin. Thereby, the heat shrinkable tube 21 is covered on the resin tube support member
23 which is the covering object, and the heat shrinkable tube 21 is uniformly heated to shrink
the heat shrinkable tube 21, thereby the outer periphery of the resin tube support member 23
Can be efficiently and easily coated with the heat shrinkable tube 21. Further, the heat-shrinkable
tube 21 can be fixed so as to be in close contact with the outer periphery of the resin tube
support member 23. The heat shrinkable tube 21 can be easily shrunk by the heat or steam of
the dryer.
03-05-2019
9
[0026]
Both ends of the acoustic tube 20 are open, and the microphone unit 30 is disposed on the inner
peripheral side of the rear end portion of the acoustic tube 20, where the left end is the front end
and the right end is the rear end in FIG. The outer peripheral side of the microphone unit 30 is
held by the microphone case 10 via the acoustic tube 20. The material of the microphone case
10 may be metal or plastic. Further, as in the invention described in Patent Document 2, the
microphone unit 30 is disposed inside the acoustic tube 20 so that a gap is generated between
the outer circumferential surface of the microphone unit 30 and the inner circumferential
surface of the acoustic tube 20. Wind noise may be reduced by acoustically shorting the front
acoustic terminal and the rear acoustic terminal of the unit 30 by the acoustic impedance
consisting of the gap.
[0027]
A cylindrical grip 40 is integrally coupled to the rear end of the microphone case 10 following
the microphone case 10. At the rear end of the grip 40, a connector 42 is provided for extracting
an audio signal converted into an electrical signal by the microphone unit 30 to the outside.
Further, in the grip 40, there is disposed a circuit board 43 on which an electric circuit for
relaying between the connector 42 and the microphone unit 30 and performing electrical
processing when necessary is disposed.
[0028]
Next, a method of manufacturing an acoustic tube for a narrow directional microphone according
to the present invention will be described. FIG. 2 is a manufacturing process diagram
schematically showing an example of a method of manufacturing an acoustic tube for a narrow
directional microphone according to the present invention. FIG. 2 shows the case where a coil
spring is used as a resin tube support member and is covered with a flexible resin tube made of a
heat-shrinkable tube. First, as shown in FIG. 2 (a), a heat-shrinkable tube material 21A is
prepared. Next, as shown in FIG. 2 (b), a plurality of small openings 22 are provided in the
peripheral wall of the heat-shrinkable tube material 21A to form a heat-shrinkable tube 21
having an opening. This opening 22 can, for example, be opened using a needle. Subsequently, as
shown in FIG. 2C, the coil spring 23 is inserted into the heat shrinkable tube 21. In the present
embodiment, the coil spring 23 is inserted into the heat-shrinkable tube 21 after the opening 22
is formed in the peripheral wall of the heat-shrinkable tube material 21A, but the present
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invention is not limited to this. Therefore, after the coil spring 23 is first inserted into the heat
shrinkable tube material 21A, a plurality of small openings 22 may be provided in the peripheral
wall of the heat shrink tube 21 material A. Thereafter, as shown in FIG. 2D, the heat-shrinkable
tube 21 in which the coil spring 23 is disposed is heat-treated to shrink the heat-shrinkable tube
21. As a result, as shown in FIG. 1C, the heat shrinkable tube 21 having a plurality of small
openings 22 in the peripheral wall is closely attached to the outer periphery of the coil spring 23,
and the heat shrinkable tube 21 covers the coil spring 23. The narrow directional microphone
acoustic tube 20 can be manufactured.
[0029]
As described above, by using the coil spring and the heat-shrinkable tube, the heat-shrinkable
tube is closely coated on the outer periphery of the coil spring, and the heat-shrinkable tube is
firmly held by the coil spring without rattling. It can be manufactured easily and easily. In
addition, since the coil spring and the heat-shrinkable tube are inexpensive and the process of
manufacturing the acoustic tube for a narrow directional microphone using these is simple, a
narrow directional microphone can be provided at low cost.
[0030]
Then, the narrow directional microphone acoustic tube 20 configured as described above is
mounted on one end side of the microphone unit 30 to form the narrow directional microphone
1. In such a narrow directional microphone 1, the acoustic tube is prevented from resonating by
the sound wave, and even if the water droplet adheres to the acoustic tube, the water droplet
does not penetrate into the inside of the acoustic tube. Furthermore, in the narrow directional
microphone 1, the acoustic tube does not flutter due to wind or the like, and the generation of
wind noise and vibration noise can be suppressed.
[0031]
Further, since the resin tube support member 23 is mainly intended to support the flexible resin
tube 21, the resin tube support member 23 is not limited to the coil spring described above.
Therefore, for example, as shown in FIG. 3, by covering the outer periphery of a tubular net or
mesh 53 having shape retention property so as to be in close contact with the heat shrinkable
tube 21, an acoustic tube for a narrow directional microphone It is good also as 50.
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[0032]
The narrow directional microphone according to the present invention can be used as a
microphone for professional audio equipment or as a microphone for consumer audio
equipment, for example, as a microphone attached to a recording equipment or a video recorder,
or a microphone as an accessory can do.
[0033]
The Example of the narrow directional microphone which concerns on this invention is shown,
(a) is front sectional drawing, (b) is a plane sectional view, (c) is a front view which shows the
acoustic tube for narrow directional microphones.
It is the schematic explaining the manufacturing method of the said acoustic tube for narrow
directivity microphones. FIG. 6 is a front view showing another narrow directional microphone
acoustic tube according to the present invention. The example of the conventional narrow
directivity microphone is shown, (a) is front sectional drawing, (b) is plane sectional drawing. The
example of the conventional other narrow directivity microphone is shown, (a) is front sectional
drawing, (b) is plane sectional drawing. It is front sectional drawing which shows another
example of the conventional narrow directivity microphone. It is a plane sectional view of the
above-mentioned narrow directivity microphone.
Explanation of sign
[0034]
Reference Signs List 1 narrow directivity microphone 10 microphone case 12 window hole 20
acoustic tube 21 flexible resin tube (heat-shrinkable tube) 22 hole 23 resin tube support member
(coil spring) 30 microphone unit 40 grip 42 connector 43 circuit board
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