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JP2011239048

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DESCRIPTION JP2011239048
PROBLEM TO BE SOLVED: To provide a narrow directional microphone in which an acoustic tube
and a microphone unit are reliably and stably conducted to enhance the electromagnetic
shielding effect without eccentricity of the microphone unit even if the structure prevents wind
noise and the like. SOLUTION: The narrow directional microphone 1 includes an acoustic tube 20
having a sound wave introduction port 20a covered with an acoustic resistance material on an
outer peripheral surface, and a microphone unit 30 disposed on the rear end side of the acoustic
tube 20. A conductive cloth 40 having a ring-shaped planar shape and having a leg portion 40b
extending from the outer peripheral edge of the ring-shaped portion 40a is attached to the sound
collecting surface of the microphone unit 30, The leg portion 40 b is interposed between the
inner peripheral surface of the acoustic tube 20 and the outer peripheral surface of the
microphone unit 30. [Selected figure] Figure 1
Narrow directional microphone, conductive cloth, and method of manufacturing narrow
directional microphone.
[0001]
The present invention relates to noise prevention and shielding techniques for narrow directional
microphones, and more particularly, to a conductive cloth attached to the narrow directional
microphone, a narrow directional microphone comprising the conductive cloth, and a narrow
directivity comprising the conductive cloth The present invention relates to a method of
manufacturing a 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 the
opening. Is covered with an acoustic resistor.
[0003]
The narrow directional microphone using the acoustic tube having such a configuration has
narrow directivity by making the sound wave entering from the front end opening of the acoustic
tube interfere with the sound wave entering from the opening of the acoustic tube through the
acoustic resistor. Is realized. That is, by directing the acoustic tube to the sound source, the
narrow directional microphone picks up only the sound coming from a specific direction (the
front) while excluding the surrounding noise without picking up the sound of the back surface or
the outer peripheral surface. It can be converted into an electrical signal.
[0004]
In the narrow directional microphone as described above, for example, the invention described in
Patent Document 1 discloses a configuration in which a microphone unit is attached by a holding
member in an acoustic pipe, and FIG. 5 shows an example thereof. As shown in FIG. 5, the
holding member 60 is fitted with the microphone unit 30 so that the gap 110 is provided
between the outer peripheral surface of the holding member 60 and the inner peripheral surface
of the acoustic tube 20. Has a convex portion. The narrow directional microphone has an
elongated cylindrical acoustic tube 20, and the acoustic tube 20 has an elongated slit-like
opening 20a in the peripheral wall. When the acoustic tube 20 is subjected to wind pressure, a
pressure difference occurs between the front end side and the rear end side, and such a narrow
directional microphone is likely to generate wind noise. As a countermeasure, as described above,
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2
by providing the gap 110 between the outer peripheral surface of the holding member 60 and
the inner peripheral surface of the acoustic tube 20, the air chambers before and after the
microphone unit 30 are communicated, Wind noise can be canceled by eliminating the pressure
difference in the chamber. However, in such a structure, since the gap 110 is generated in the
microphone unit 30 with respect to the inner circumferential surface of the acoustic tube 20, the
microphone unit 30 tends to be decentered, which causes a problem of largely impairing the
acoustic performance. In addition, since the holding material 60 is made of elastic rubber,
electrical conduction between the acoustic tube 20 and the microphone unit 30 can not be
ensured. Therefore, in this structure, the shielding effect against the electromagnetic wave
entering from the outside is insufficient. In particular, when a portable telephone or the like,
which has been widely spread in recent years, is used around, high frequency current flows into
the inside of the microphone unit 30 by the strong electromagnetic waves to generate noise.
[0005]
In the invention described in Patent Document 2, a conductive cloth is used when the
microphone unit is fixed in an acoustic tube as a method of high frequency countermeasure. In
the method of attaching the microphone unit while using the conductive cloth, as in the invention
described in Patent Document 1 and FIG. 5, the method using the fastener 70 which is held in the
acoustic tube 20 by elasticity and presses the microphone unit 30 There is a method of using an
adhesive. When the fastener 70 is used, as shown in FIG. 5, the microphone unit 30 can only be
pressed in one direction. Therefore, it becomes necessary to further press the holding member
60 from the front and back, which complicates the structure and makes assembly difficult. In the
method using an adhesive, when the adhesive penetrates into the conductive cloth, the elasticity
of the conductive cloth is lost, causing a contact failure between the outside of the microphone
unit and the inside of the acoustic tube, and the shielding effect against electromagnetic waves is
reduced. Furthermore, when the adhesive penetrates into the conductive cloth, the acoustic mass
between the inner circumferential surface of the acoustic tube and the outer circumferential
surface of the microphone unit may vary, resulting in a variation in acoustic characteristics.
[0006]
Japanese Patent Application Publication No. 2006-128850 Japanese Utility Model Application
Publication No. 07-25692
[0007]
Therefore, according to the present invention, even in the structure for preventing wind noise
and the like, eccentricity of the microphone unit does not occur, and the microphone unit and the
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3
acoustic tube can be reliably and stably conducted to obtain a sufficient shielding effect. It is an
object of the present invention to provide a narrow directional microphone capable of
[0008]
A narrow directional microphone according to the present invention includes an acoustic tube
having a sound wave introduction port covered with an acoustic resistance material on an outer
peripheral surface, and a microphone unit disposed on the rear end side of the acoustic tube in
the microphone case. A directional microphone having a ring shape in plan view and a
conductive cloth having a leg portion extending from the outer peripheral edge of the ring-like
main body portion is attached to the sound collection surface of the microphone unit The legs of
the conductive cloth are mainly characterized in that they are interposed between the acoustic
tube and the outer peripheral surface of the microphone.
[0009]
According to the narrow directional microphone of the present invention, the sound collecting
surface of the microphone unit has a ring shape in a plan view, and a leg portion extending from
the outer peripheral edge of the ring-shaped main body portion A conductive cloth is attached,
and the legs of the conductive cloth are interposed between the inner circumferential surface of
the acoustic tube and the outer circumferential surface of the microphone unit, so that a gap can
be created between the acoustic tube and the microphone unit. The air chambers before and
after the unit are communicated with each other at the boundary of the unit, and wind noise and
the like can be prevented from the structure.
In addition, since the amount of adhesive used can be reduced at the time of assembly, the
elasticity of the conductive cloth will not be lost due to the penetration of the adhesive, and the
electricity between the outside of the microphone unit and the inside of the acoustic tube It is
possible to reliably and stably secure the target conduction, to form a good electromagnetic wave
shield, and to prevent a failure due to an external impact such as occurrence of eccentricity in the
microphone unit.
[0010]
It is a fragmentary sectional view showing the example of the narrow directivity microphone
concerning the present invention.
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4
It is an outer peripheral view which shows the said Example.
It is a top view (a) and (b) a side view showing an embodiment of the conductive cloth of the
narrow directional microphone according to the present invention. It is a schematic diagram
which shows the manufacturing method of the narrow directivity microphone concerning this
invention to process order. It is a fragmentary sectional view which shows the example of the
conventional narrow directivity microphone.
[0011]
Hereinafter, embodiments of the narrow directional microphone according to the present
invention will be described with reference to the drawings. The present invention is not limited to
the configurations of the embodiments described below. Components or parts substantially the
same as the components or parts of the prior art shown in FIG. 5 are denoted by the same
reference numerals.
[0012]
1 and 2, the narrow directional microphone 1 comprises an acoustic tube 20 and a microphone
unit 30 disposed on the rear end side of the acoustic tube 20, where the left end is the front end
and the right end is the rear end in FIG. have. The acoustic tube 20 is an elongated cylindrical
part whose both ends are open, and has an opening 20a which is a slit-like sound wave
introduction port covered by the acoustic resistance material 50 attached to the outer peripheral
surface. The microphone unit 30 is surrounded by a cylindrical unit case with a bottom on the
outside, and has a sound collecting surface corresponding to the bottom of the unit case on the
left side of FIG. The microphone unit 30 is disposed on the inner peripheral side of the rear end
portion of the acoustic tube 20. Although not shown, a printed circuit board is disposed on the
rear end side (right side in FIG. 1) of the microphone unit 30, and a cord 80 for sending an audio
signal to the outside is drawn from here. The cord 80 is in electrical communication with the
internal components of the microphone unit 30. The electroacoustic conversion method of the
microphone unit 30, the internal configuration, and the like are arbitrary.
[0013]
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5
As shown in FIGS. 1, 3 (a) and 3 (b), the sound collecting surface of the microphone unit 30
radially extends from the outer peripheral edges of the main portion 40a and the main portion
40a having a ring-shaped planar shape. The ring-shaped main body portion 40a of the
conductive cloth 40 having the plurality of leg portions 40b is attached. As shown in FIG. 1, in
the conductive cloth 40, a ring-shaped main body portion 40 a is attached to the outer peripheral
edge of the sound collecting surface of the microphone unit 30, and the leg portion 40 b is bent
along the outer peripheral surface of the microphone unit 30. It is pasted. The leg portion 40 b of
the conductive cloth 40 is interposed between the acoustic tube 20 and the outer peripheral
surface of the microphone unit 30, so the case of the acoustic tube 20 and the microphone unit
30 is electrically connected via the conductive cloth 40. As shown in FIGS. 3 (a) and 3 (b), the
conductive cloth 40 is formed to have a ring-shaped main body 40a and legs 40b, as shown in
FIG. A gap 120 is formed between the inner circumferential surface of the acoustic tube 20 and
the outer circumferential surface of the microphone unit 30 in a portion other than the leg
portion 40 b of the conductive cloth 40.
[0014]
Three legs of conductive cloth 40 are formed so as to extend radially outward from the center of
its ring-shaped main body portion 40a, and three legs 40 are provided at intervals of
approximately 120 degrees, respectively. . In addition, the leg part 40b can not take a linear
form, but can take a suitable shape, for example, can also be made wavy. The number of legs 40b
can be similarly set appropriately.
[0015]
With such a configuration, in the narrow directional microphone 1, since the front and rear air
chambers are communicated by the gap 120 with the microphone unit 30 as a boundary, the
pressure difference between the front and rear air chambers disappears, and noise such as wind
noise Can be prevented. In addition, since the amount of adhesive used to attach the conductive
cloth 40 to the microphone unit 30 can be adjusted at the time of assembly of the microphone
unit 30, the conductive cloth 40 loses elasticity due to penetration of the adhesive. By the
elasticity of the conductive cloth 40, the acoustic tube 20 and the microphone unit 30 can be
reliably and stably conducted. Thereby, the narrow directional microphone 1 according to the
present embodiment can form a good electromagnetic wave shield. Further, since the conductive
cloth 40 is interposed between the acoustic tube 20 and the outer peripheral surface of the
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microphone unit 30, the elasticity of the conductive cloth 40 can prevent the microphone unit 30
from being eccentric.
[0016]
The features of the narrow directional microphone 1 according to the present invention are as
described in the claims, and any design change can be made without departing from the technical
concept described in the claims. be able to. For example, a microphone case can be provided on
the outer periphery of the acoustic tube 20 for its protection. A cylindrical grip may be integrally
coupled to the rear end of the acoustic tube 20 following the microphone case (not shown).
Furthermore, at the rear end of the grip, a connector (not shown) for drawing out the audio
signal converted into the electric signal by the microphone unit 30 can be provided. As a material
of the case of the microphone unit 30, an appropriate one can be selected as long as it is a
conductor, and it may be, for example, aluminum.
[0017]
Next, an example of a method of manufacturing a narrow directional microphone according to
the present invention will be described. In FIG. 4, a hot melt adhesive diluted with an organic
solvent has a cylindrical shape, and a portion indicated by a symbol B, which is a part of the
inner peripheral surface of the acoustic tube 20 whose both ends are open, The outer peripheral
surface A of the microphone unit 30 is applied. The outer peripheral surface A to which the
adhesive is applied may include the outer peripheral edge portion of the sound collecting surface
of the microphone unit 30. The position B in the acoustic tube 20 can be confirmed by using the
jig 100. The area B is appropriately set so as to be an area sufficient for bonding the microphone
unit 30 (FIG. 4A). Next, the organic solvent is volatilized to form a thin hot melt adhesive layer on
the outer peripheral surface A of the microphone unit 30 and the inner peripheral surface B of
the acoustic tube 20. In addition, since a hot melt adhesive is solid at normal temperature, it
solidifies by volatilization of the organic solvent (FIG. 4 (b)).
[0018]
Then, the ring-shaped main body portion 40 a of the conductive cloth 40 is attached to the outer
peripheral edge portion of the sound collecting surface of the microphone unit 30, and the leg
portion 40 b is bent and attached to the outer peripheral surface of the microphone unit 30. The
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microphone unit 30 is inserted into the acoustic tube 20 up to the portion positioned by the jig
100 (FIG. 4C). Next, the microphone unit 30 and the acoustic tube 20 are heated at a
temperature at which the hot melt adhesive dissolves to melt the hot melt adhesive and then
cooled to solidify the hot melt, and the acoustic tube 20 and the microphone unit 30 The
conductive cloth 40 is fixed (FIG. 4 (d)).
[0019]
By manufacturing the narrow directional microphone 1 in this manner, the sound collecting
surface of the microphone unit 30 has a ring-shaped planar shape, and the leg portion extending
from the outer peripheral edge of the ring-shaped main body portion 40 a The conductive cloth
40 having 40b is attached, and the leg portion 40b of the conductive cloth 40 is interposed
between the inner circumferential surface of the acoustic tube 20 and the outer circumferential
surface of the microphone unit 30, so the acoustic tube 20 and the microphone A gap 120 can
be created between unit 30. Therefore, as described above, the generation of noise such as wind
noise can be prevented.
[0020]
In addition, since the amount of using the hot melt adhesive can be adjusted when assembling
the microphone unit 30, the conductive cloth 40 can be attached to the above position without
losing the elasticity of the conductive cloth 40. The inner peripheral surface of the acoustic tube
20 and the outer peripheral surface of the microphone unit 30 can be electrically conducted
reliably and stably, and a good electromagnetic shield and electrostatic shield can be formed. As
described above, since the amount of using the hot melt adhesive can be adjusted, the variation
in acoustic mass between the inner circumferential surface of the acoustic tube 20 and the outer
circumferential surface of the microphone unit 30 can be reduced. Sound characteristics can be
stabilized. Further, the elasticity of the conductive cloth 40 can prevent the microphone unit 30
from being eccentric.
[0021]
In addition, the manufacturing method of the narrow directional microphone concerning this
invention can be arbitrarily changed in the range which does not deviate from the technical
thought described in the claim. For example, as a hot melt adhesive, an appropriate thing can be
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selected and used. Aronmelt (registered trademark) PES310-S30 manufactured by Toa Gosei Co.,
Ltd. is an example.
[0022]
The narrow directional microphone according to the present invention can be used as a
microphone for industrial audio equipment and as a microphone for consumer audio equipment.
For example, a microphone attached to a recording device or a video recorder, or a microphone
as an accessory It can be used as The present invention is also applicable to devices other than
narrow directional microphones, but in narrow directional microphones, the wind noise
prevention effect and the electromagnetic wave shielding effect can both be achieved at a high
level, so in narrow directional microphones It is an effective invention.
[0023]
Reference Signs List 1 narrow directional microphone 20 acoustic tube 22 hole 30 microphone
unit 40 conductive cloth 40 a ring-shaped main body 40 b leg 50 acoustic resistance material
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