JP2012244511

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DESCRIPTION JP2012244511
An object of the present invention is to provide a narrow directional microphone and an adapter
for a narrow directional microphone capable of obtaining high directivity even at low frequencies
without lengthening an acoustic tube. A microphone unit (4), a first acoustic tube (2) in which a
plurality of first openings (22) are formed in a peripheral wall along an axial direction and the
microphone unit (4) is mounted inside, a first acoustic tube (2) And a first acoustic resistance
material 3 for closing the opening 22 of the narrow directional microphone 1. The narrow
directional microphone 1 further includes a second acoustic tube 6 which is placed on the outer
side of the first acoustic tube 2 with a predetermined gap, and the second acoustic tube 6 has a
plurality of second acoustic tubes 6 along the axial direction on the peripheral wall. The opening
62 is formed, and a second acoustic resistance material is provided to close the second opening
62 of the second acoustic tube 6. [Selected figure] Figure 1
Narrow directional microphone and adapter for narrow directional microphone
[0001]
The present invention relates to a narrow directional microphone and an adapter for a narrow
directional microphone in which a microphone unit is mounted in an acoustic tube. More
specifically, the present invention relates to a narrow directional microphone and an adapter for
a narrow directional microphone that can obtain high directivity even at low frequencies without
lengthening an acoustic tube.
[0002]
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1
As an example of a conventional narrow directional microphone using an acoustic tube, an
acoustic tube made of a metal tube or the like is used, and an opening such as a slit is provided
on a peripheral wall of the acoustic tube in the central axis direction There is one in which an
acoustic resistor is attached to a peripheral wall of an acoustic tube and the opening is covered
with the acoustic resistor. The narrow directional microphone having such a configuration
achieves narrow directivity by causing the sound wave coming around from the front end
opening of the acoustic tube to interfere with the sound wave guided from the peripheral wall
opening of the acoustic tube through the acoustic resistor. .
[0003]
As a narrow directional microphone, as shown in Patent Document 1, one using an elongated
acoustic tube 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.
[0004]
Specifically, the above-mentioned acoustic tube is an interference pipe which is made of metal
such as aluminum and whose axial direction both ends are open. An opening for resistance is
provided. An acoustic resistance material made of non-woven fabric or the like is attached to the
circumferential surface of the interference pipe so as to cover these openings.
[0005]
The plurality of openings are also formed in portions spaced 180 degrees in the circumferential
direction, and the acoustic resistance material is similarly attached. A plurality of axially
elongated holes are provided at intervals in the circumferential direction at intervals of 90
degrees in the circumferential direction with respect to the row of the openings and on the
circumferential surface from the front end to the rear end .
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[0006]
A diaphragm made of a thin film of synthetic resin such as vinylidene fluoride is attached to the
interference pipe so as to cover these long holes.
[0007]
The outline of another example of the conventional narrow directional microphone using the
acoustic tube as described above will be described with reference to the drawings.
As shown in FIG. 3, the narrow directional microphone 1 includes an acoustic tube 2, an acoustic
resistance material 3, a microphone unit 4, and a grip 5. The acoustic tube 2 is an elongated
cylindrical member made of metal or the like, and a plurality of openings 22 are formed in the
peripheral wall thereof in parallel with the central axis of the acoustic tube.
[0008]
In FIG. 3, assuming that the left end of the acoustic tube 2 is the front end and the right end is
the rear end, the microphone unit 4 is disposed on the inner peripheral side of the rear end. An
acoustic resistance material 3 is attached to the peripheral wall of the acoustic tube 2 so as to
cover the opening 22. The acoustic tube 2 is open at both ends in the longitudinal direction. An
opening 24 at the front end of the acoustic tube introduces sound waves from the front. A
cylindrical grip 5 is integrally connected to the rear end of the acoustic tube 2 following the
acoustic tube 2.
[0009]
Japanese Patent Application Laid-Open No. 62-118697
[0010]
As described above, the directivity of the narrow directional microphone is generated by the
interference with the sound wave by the acoustic tube, and therefore, is influenced by the
wavelength of the sound wave and the length of the acoustic tube.
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Specifically, narrow directivity can be obtained to a low frequency band by using a long acoustic
pipe, but narrow directivity can be obtained only in a high frequency band when using a short
acoustic pipe.
[0011]
Therefore, narrow directivity can be obtained up to a low frequency band if a long acoustic tube
is used, but if the acoustic tube is long, the total length of the microphone becomes long, which
makes it inconvenient to handle.
[0012]
Also, high narrow directivity may be required even at the expense of frequency characteristics.
[0013]
The present invention has been made in view of the above problems, and an object of the present
invention is to obtain a narrow directional microphone capable of obtaining narrow directivity to
a low frequency band without lengthening an acoustic tube.
[0014]
Another object of the present invention is to provide an adapter for a narrow directional
microphone that can cope with the case where high narrow directivity is required even at the
expense of frequency characteristics.
[0015]
The narrow directional microphone according to the present invention includes a microphone
unit, a first acoustic tube having a plurality of first openings formed in the peripheral wall along
the axial direction and in which the microphone unit is mounted, and an acoustic tube. A narrow
directional microphone comprising: a first acoustic resistance member closing an opening, the
narrow directional microphone further comprising: a second acoustic tube which is covered on
the outside of the first acoustic tube with a predetermined gap, 2) The main feature of the
acoustic tube is that a plurality of second openings are formed along the axial direction in the
peripheral wall, and the second acoustic resistance material is used to close the second opening
of the second acoustic tube. I assume.
[0016]
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According to the present invention, narrow directivity can be obtained to a low frequency band
without lengthening the acoustic tube.
Further, according to the present invention, it is possible to cope with the case where high
narrow directivity is required even at the expense of frequency characteristics.
[0017]
FIG. 1 is a partial cross-sectional side view showing an embodiment of a narrow directional
microphone according to the present invention.
It is principal part sectional drawing of the said narrow directivity microphone.
The 2nd acoustic pipe used for said narrow directivity microphone is shown, (A) is a side view,
(B) is a longitudinal cross-sectional view, (C) is a front view.
It is a principal part expanded sectional view of the above-mentioned 2nd sound pipe.
It is principal part sectional drawing which shows the state which removed the 2nd acoustic pipe
from the said narrow directivity microphone. It is a side view showing an example of the
conventional narrow directivity microphone unit.
[0018]
Hereinafter, embodiments of the narrow directional microphone according to the present
invention will be described with reference to the drawings. The same components as those of the
conventional narrow directional microphone are denoted by the same reference numerals.
[0019]
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As shown in FIGS. 1 to 5, the narrow directional microphone includes a first acoustic pipe 2, a
first acoustic resistance material 3, a second acoustic pipe 6, a second acoustic resistance
material 66, a microphone unit 4, a grip 5, an outer It has a cover 7.
[0020]
The first acoustic tube 2 is an elongated cylindrical member made of metal or the like, and a
plurality of first openings 22 are formed in the peripheral wall thereof in parallel with the central
axis of the acoustic tube.
[0021]
The first acoustic resistance material 3 is attached to the peripheral wall of the first acoustic tube
2 so as to cover the first opening 22.
Both ends in the longitudinal direction of the first acoustic tube 2 are open.
An opening 24 at the front end of the first acoustic tube 2 introduces sound waves from the
front. A cylindrical grip 5 is integrally coupled to the rear end of the first acoustic tube 2
following the first acoustic tube 2. The outer side of the first acoustic tube 2 and the grip 5 is
covered with a cylindrical outer cover 7 having a plurality of openings 72 through which sound
waves pass on the side walls.
[0022]
The second acoustic tube 6 is an elongated cylindrical member having a diameter larger than
that of the first acoustic tube, and like the first acoustic tube 2, a plurality of slit-like second
openings parallel to the central axis of the acoustic tube on its peripheral wall 62 are formed.
[0023]
The second acoustic tube 6 is provided in the narrow directional microphone 1 so as to cover the
outer cover 7 at a predetermined interval.
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Thereby, a predetermined space is formed between the second acoustic pipe 6 and the first
acoustic pipe 2 located inside the outer cover 7, and this space becomes the air chamber 8. At
the end of the narrow directional microphone 1 opposite to the sound collecting direction, the
gasket 64 establishes close contact between the second acoustic pipe 6 and the first acoustic
pipe 2. Among the plurality of first openings 22 of the first acoustic tube 2, the first opening 222
opposite to the sound collecting direction of the narrow directional microphone 1 is covered with
the second acoustic tube 6 in order to prevent resonance. Absent. The microphone unit 4 is
mounted inside the portion of the first acoustic tube 2 not covered by the second acoustic tube 6.
[0024]
A second acoustic resistance material 66 is attached to the peripheral wall of the second acoustic
tube 6 so as to cover the second opening 62. Both ends in the longitudinal direction of the
second acoustic tube 6 are open.
[0025]
In the narrow directional microphone 1 formed in this manner, sound waves from the front (the
opening direction of the front end of the second acoustic tube 6) are guided into the opening 24
at the front end of the first acoustic tube 2 and are almost attenuated. Without reaching the
diaphragm of the microphone unit 4.
[0026]
On the other hand, sound waves from angles other than the front, that is, sound waves that enter
from the second opening 62 of the second acoustic tube 6 and pass through the second acoustic
resistance material 66 are between the second acoustic tube 6 and the first acoustic tube 2 It
enters into the air chamber 8 formed.
Then, the sound wave that has entered the air chamber 8 enters the inside of the first acoustic
tube 2 via the first acoustic resistance 3 of the inner first acoustic tube 2. Sound waves from
angles other than the front of the first acoustic tube 2 also enter the air chamber 8 from the front
of the first acoustic tube 2. Since there is a phase difference between the sound waves entering
the air chamber 8 from the front and the sound waves entering the air chamber 8 from the
second opening 62, these sound waves interfere with each other. Fit. And sound waves from
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angles other than the front are attenuated by this interference.
[0027]
As described above, according to the narrow directional microphone according to the present
invention, sound waves from angles other than the front are attenuated by interference, so that
the conventional narrow directivity can be obtained even at low frequencies without increasing
the length of the acoustic tube. Narrow directivity higher than a microphone can be obtained.
The narrow directional microphone according to the present invention is inferior in frequency
characteristics to the conventional narrow directional microphone in which the acoustic tube is
sufficiently long. However, it can be suitably used when high narrow directivity is required even
at the expense of frequency characteristics.
[0028]
When the first acoustic pipe and the second acoustic pipe are integrated by adhesion, the second
acoustic pipe can not be removed. However, by attaching the second acoustic tube as a
removable adapter to a conventional narrow directional microphone not provided with the
second acoustic tube, the same effect as the narrow directional microphone according to the
present invention can be provided. it can.
[0029]
For example, the second acoustic tube can be attached as an adapter to a narrow directional
microphone as described in Patent Document 1, and the narrow directivity can be further
enhanced. If the second acoustic tube is configured to be attachable to and detachable from a
narrow directional microphone as an adapter, the adapter is attached when higher narrow
directivity is required, and the frequency characteristic is considered more important than the
narrow directivity. In this case, the adapter can be removed and used.
[0030]
DESCRIPTION OF SYMBOLS 1 narrow directivity microphone 2 1st acoustic tube 22 1st aperture
3 1st acoustic resistance material 4 microphone unit 5 grip 6 2nd acoustic tube 62 2nd aperture
64 gasket 66 2nd acoustic resistance 7 outer cover 72 aperture 8 air chamber
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