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JPH0534796

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DESCRIPTION JPH0534796
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
narrow directional microphone, and more particularly to the reduction of wind noise in a narrow
directional microphone in which an acoustic tube is fitted to a microphone unit.
[0002]
2. Description of the Related Art Various types of narrow directional microphones, called line
microphones or the like in which the directivity is narrowed by fitting one end of an acoustic
tube to the tip of a microphone unit, have been provided conventionally. An example of a
conventional narrow directional microphone will be described with reference to FIG. 2. The
narrow directional microphone 1 has a microphone unit 4 having a front acoustic terminal 2 and
a rear acoustic terminal 3 and openings 5 for a plurality of acoustic resistances on its peripheral
surface. And the acoustic pipe 6 in which One end of the acoustic tube 6 is fitted to the front
acoustic terminal 2 side of the microphone unit 4, and the rear acoustic terminal 3 side of the
microphone unit 4 is positioned in a free sound field. On the outer peripheral surface of the
acoustic tube 6, an acoustic resistance material 7 made of non-woven fabric such as felt or nylon
mesh is provided. An outer casing 9 having an inner diameter larger than the outer diameter of
the acoustic resistance member 7 and having a plurality of through holes 8 formed therein is
fitted to the outer peripheral surfaces of the microphone unit 4 and the acoustic tube 6. The
microphone unit 4 is supported in the outer casing 9 by a fixing ring 10.
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[0003]
On the other hand, in the microphone, a pressure difference is generated by wind before and
after the diaphragm of the microphone unit, and this pressure difference becomes wind noise.
The wind noise increases in the order of the nondirectional microphone, the unidirectional
microphone, and the narrow directional microphone as described above. The wind noise of the
narrow directional microphone is large because one end of the acoustic tube 6 is directly and
completely connected to the front acoustic terminal 2 of the microphone unit 4. The tip 11 of the
front end becomes the sound inlet of the front acoustic terminal 2, the distance to the rear
acoustic terminal 3 becomes long, a very large pressure difference occurs, and as a result, a large
wind noise is generated in the bass region .
[0004]
In order to improve such a defect, for example, in Japanese Patent Application Laid-Open No. 62118698, the outer peripheral surface of the microphone unit is spaced from the inner peripheral
surface of the acoustic pipe in the rear end of the acoustic pipe. It has been proposed to position
and form a passage between the front and rear acoustic terminals to reduce the pressure
differential due to wind. With this structure, even if there is a pressure difference between the
front acoustic terminal and the rear acoustic terminal, the air on the high pressure side can be
made to flow to the low pressure side, thereby reducing the pressure difference and reducing
wind noise. about
[0005]
However, the microphone unit needs to be supported by the anti-vibration support mechanism
for securely protecting the rear portion from the vibration, and furthermore, the air from the
front acoustic terminal to the rear acoustic terminal is It is necessary to form a leak path, and the
complex vibration isolation support mechanism not only makes the assembly difficult but also
increases the overall size.
[0006]
Therefore, the object of the present invention is to support the microphone unit with an
antivibration support mechanism which is simple in mechanism and extremely easy to assemble,
thereby reducing the pressure difference between the front acoustic terminal and the rear
acoustic terminal and reducing wind noise. Providing a narrow directional microphone.
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[0007]
SUMMARY OF THE INVENTION The narrow directional microphone according to the present
invention has a cylindrical portion in which the outside diameter of the microphone unit is
smaller than the inside diameter of the acoustic tube and which is a rear acoustic terminal at the
rear, An elastic ring made of breathable elastic rubber or foamable synthetic resin is on the
microphone unit side of this cylindrical portion, and an elastic ring made of non-breathable
elastic rubber or foamable synthetic resin on the other end , And the microphone unit is
supported in the acoustic tube by these elastic rings.
[0008]
[Operation] According to this configuration, a gap is generated between the outer peripheral
surface of the microphone unit and the cylindrical body and the inner peripheral surface of the
acoustic pipe, and this space inserts two elastic rings into the cylindrical body with a gap. By
positioning the air-permeable elastic ring in the cylindrical part on the microphone unit side, a
leak path of air communicating from the front acoustic terminal to the rear acoustic terminal is
formed, and the front acoustic terminal and the rear are formed. Even if there is a pressure
difference with the acoustic terminal, the high pressure side air can flow into the low pressure
side, the pressure difference becomes smaller, and wind noise can be reduced.
Furthermore, the elastic support mechanism of this microphone unit has a very simple structure
in which only two elastic rings are fitted to a cylindrical body, and it is extremely easy to
assemble without enlargement.
[0009]
DESCRIPTION OF THE PREFERRED EMBODIMENT The present invention will be described with
reference to an embodiment shown in the drawings. FIG. 1 shows the main part, and this narrow
directivity microphone 21 is an acoustic tube made of metal such as aluminum. A microphone
unit 23 fitted in the rear end of the acoustic tube 22 and an outer casing 24 fitted so as to cover
the outer periphery of the acoustic tube 22 are provided.
[0010]
The outer diameter of the microphone unit 23 is set to be smaller than the inner diameter of the
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acoustic tube 22, and the outer diameter of the microphone unit 23 is approximately equal to the
outer diameter of the microphone unit 23 at the tip end of the microphone unit 23, that is, the
front acoustic terminal. A diameter elastic rubber resonator 25 is coaxially mounted.
A hollow cylindrical body 26 serving as a rear acoustic terminal is provided at the rear end of the
microphone unit 23, and the cylindrical body 26 is formed smaller than the outer diameter of the
microphone unit 23.
A plurality of openings 27 are provided on the circumferential surface of the cylindrical body 26,
and the openings 27 are covered with a wire mesh 28.
The cylindrical body 26 on the microphone unit 23 side has an outer diameter equal to at least
the inner diameter of the acoustic tube 22, is air-permeable, and is made of rubber or foam
synthetic resin elastically supporting one end of the cylindrical body 26 The front elastic ring 29
is fitted. Further, at the other end side of the cylindrical body 26, a rear elastic ring 30 having the
same diameter as that of the front elastic ring 29 and made of non-air-permeable rubber or
foamable synthetic resin is fitted.
[0011]
The tip of the resonator 25 of the microphone unit 23 is made of the same material as the front
elastic ring 29 and is fixed by the front fastener 32 through the front buffer ring 31 having an
outer diameter at least equal to the inner diameter of the acoustic tube 22. Movement is
regulated. The front fastener 32 has a ring portion whose diameter is smaller than the inner
diameter of the acoustic tube 22 and a plurality of leg portions projecting radially outward from
the ring portion, although the details are not shown. It is fixed in the acoustic tube 22 with a sex.
The rear end of the cylindrical body 26 of the microphone unit 23 is made of non-air-permeable
rubber or foamed synthetic resin, and is similar to the front fastener 32 through the rear buffer
ring 33 having an outer diameter at least equal to the inner diameter of the acoustic tube 22. The
movement is regulated by the rear fasteners 34. 35 is a connecting cord of the microphone unit
23, and 36 is a sound resistance material covering the front and rear openings 37, 38 formed on
the front and rear of the acoustic tube 22.
[0012]
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In mounting, the rear opening 38 of the acoustic tube 22 is adjusted and inserted onto the
opening 27 of the cylindrical body 26 of the microphone unit 23. Of course, the rear opening 38
of the acoustic tube 22 is aligned with the opening 39 formed in the housing 24.
[0013]
With this configuration, the resonator 25 side of the microphone unit 23 serves as the front
acoustic terminal in the mid-range and higher frequency bands, but the tip of the acoustic tube
22 is the front acoustic terminal as in the prior art in the low frequency band. As a result, the
distance between the rear acoustic terminal and the opening 39 of the outer casing 24 is
increased, and a very large pressure difference is generated between the two. However, a gap
occurs between the outer peripheral surface of the resonator 25, the microphone unit 23 and the
cylindrical body 26 and the inner peripheral surface of the acoustic pipe 22, and the cylindrical
body 26 passes from the front fastener 32 to the sponge ring 31 and the front elastic ring 29.
The air leakage path to the opening 27 of the air pressure is formed, and even if there is a
pressure difference between the front acoustic terminal and the rear acoustic terminal, the air on
the high pressure side can flow into the low pressure side. The difference is reduced and wind
noise can be reduced. Furthermore, the elastic support mechanism of the microphone unit 23 has
a very simple structure in which only the ring-like front elastic ring 29 and the rear elastic ring
30 are fitted in the cylindrical portion 26, and the assembly is also extremely easy.
[0014]
As described above, the narrow directional microphone according to the present invention has a
cylindrical unit in which the outer diameter of the microphone unit is smaller than the inner
diameter of the acoustic tube and the rear acoustic terminal is provided at the rear, An elastic
ring made of breathable elastic rubber or foamable synthetic resin is on the microphone unit side
of this cylindrical portion, and an elastic ring made of non-breathable elastic rubber or foamable
synthetic resin on the other end Are respectively fitted, and these elastic rings support the
microphone unit in the acoustic tube. Therefore, a gap is generated between the microphone unit
and the outer peripheral surface of the cylindrical body and the inner peripheral surface of the
acoustic pipe, and this gap is held by fitting the two elastic rings to the cylindrical body with a
gap. Since the elastic ring having air permeability is located in the cylindrical portion on the unit
side, a leak path of air communicating from the front acoustic terminal to the rear acoustic
terminal is formed, and between the front acoustic terminal and the rear acoustic terminal Even
if there is a pressure difference, the high pressure side air can flow into the low pressure side, the
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pressure difference becomes smaller, and wind noise can be reduced. In addition, the elastic
support mechanism of this microphone unit has a very simple structure in which only two elastic
rings are fitted to a cylindrical body, and it is extremely easy to assemble without enlargement.
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