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JP2012023544

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DESCRIPTION JP2012023544
An object of the present invention is to arrange a condenser microphone unit having a large
effective diaphragm area on the rear end side of an acoustic tube without increasing the diameter
of the acoustic tube so that high sensitivity can be obtained. A narrow directional condenser
microphone in which a unidirectional directivity condenser microphone unit in which a
diaphragm and a fixed pole are disposed opposite to each other via a spacer on the rear end side
of an acoustic tube is disposed. , And a unit pair assembly 20 formed by combining two
condenser microphone units 20R and 20L with their diaphragm sides facing each other in
parallel, and each condenser microphone unit 20R centered on the tube axis X of the acoustic
tube 10 , 20L are arranged symmetrically, the unit pair assembly 20 is disposed on the rear end
side of the acoustic tube 10. [Selected figure] Figure 1
Narrow directivity condenser microphone
[0001]
The present invention relates to a narrow directional condenser microphone having an acoustic
tube, and more particularly to a narrow directional condenser microphone in which the effective
diaphragm area is increased to obtain high sensitivity.
[0002]
A narrow directional condenser microphone having an acoustic tube is also referred to as a line
microphone or a gun microphone in view of its form, and conventionally, a cylindrical condenser
microphone unit is accommodated in a cylindrical acoustic pipe. There is.
03-05-2019
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[0003]
That is, the diaphragm included in the condenser microphone unit is arranged to be
perpendicular to the tube axis (the directional axis or the sound collecting axis) of the acoustic
tube (see, for example, Patent Document 1).
[0004]
In this type of narrow directional condenser microphone, particularly when used for the purpose
of collecting a distant sound source, the sound wave from the sound source is weak, and
therefore it is required that the self-noise of the microphone be small.
[0005]
In order to do so, it is known that the effective diaphragm area of the diaphragm included in the
condenser microphone unit should be increased. However, according to the structure of the
above conventional example, the aperture of the condenser microphone unit is an acoustic tube.
There is a limit to increasing the effective diaphragm area of the diaphragm due to the restriction
of the inner diameter of the.
[0006]
If an acoustic tube with a large internal diameter is used, a unit with a large aperture can be
adopted accordingly, but the acoustic tube becomes thick, which is not preferable because it not
only looks bad but also increases weight.
[0007]
As one of methods for increasing the effective diaphragm area of a diaphragm, Patent Document
2 describes that the diaphragm has a rectangular shape (rectangular shape).
In the present specification, a condenser microphone unit having a square diaphragm may be
referred to as a square unit.
[0008]
In addition, as a microphone using a square unit, Patent Document 3 describes that three square
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units are used to form a narrow directional microphone.
Further, Patent Document 4 describes a double capsule microphone having two square units.
[0009]
As described above, various microphones using a square unit have been proposed, but all of them
have a special form adapted to the square unit, and an attempt to incorporate the square unit
into a cylindrical acoustic pipe has been made. It has not been done.
[0010]
Patent No. 2562295 gazette Patent No. 3325913 gazette Patent No. 4383242 gazette JP, 200278062, A
[0011]
Therefore, an object of the present invention is to arrange a condenser microphone unit having a
large effective diaphragm area on the rear end side of an acoustic pipe without increasing the
diameter of the acoustic pipe in a narrow directional condenser microphone having an acoustic
pipe. In order to obtain high sensitivity.
[0012]
In order to solve the above-mentioned problems, according to the present invention, a
unidirectional directivity condenser microphone unit in which a diaphragm and a fixed pole are
disposed opposite to each other via a spacer is disposed on the rear end side of the acoustic tube.
A narrow directional condenser microphone, comprising: a unit pair assembly formed by
combining two of the condenser microphone units with their diaphragm sides facing each other
in parallel and facing each other; The unit pair assembly is disposed on the rear end side of the
acoustic tube so that the microphone units are arranged symmetrically.
[0013]
According to a preferred aspect of the present invention, the diaphragm and the fixed pole of
each of the condenser microphone units included in the unit pair assembly are formed in a
rectangular shape whose long side is along the tube axis of the acoustic tube. There is.
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That is, square units are used for the respective condenser microphone units.
[0014]
In the present invention, preferably, outputs of the condenser microphone units included in the
unit pair assembly are connected in parallel to an impedance converter.
[0015]
The present invention also includes an aspect including a plurality of unit pair assemblies.
Also in this case, the first output in which the outputs of the condenser microphone units on one
side of each unit pair assembly are connected in series and the second output in which the
outputs of the condenser microphone units on the other side are connected in series Are
preferably connected to the impedance converter as a parallel connection.
[0016]
According to the present invention, two unidirectional condenser microphone units are combined
with their diaphragm sides facing each other in parallel to form a unit pair assembly, and this
unit pair assembly is a tube of an acoustic tube. By arranging the condenser microphone units on
the rear end side of the acoustic pipe so as to be arranged symmetrically about the axis, a
condenser microphone unit having a large effective diaphragm area (preferably, without
increasing the diameter of the acoustic pipe) Square unit can be used, and high sensitivity can be
achieved.
[0017]
Also, by connecting the outputs of the condenser microphone units included in the unit pair
assembly in parallel to the impedance converter, vibration noise such as touch noise and
handling noise can be reduced.
[0018]
The front view sectional drawing which shows the internal structure of the narrow directivity
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capacitor | condenser microphone based on embodiment of this invention.
AA arrow arrow sectional drawing of FIG.
FIG. 2 is an enlarged cross-sectional view of the unit pair assembly of FIG. 1;
BB line arrow directional view of FIG.
FIG. 4 is an exploded cross-sectional view of FIG.
The schematic diagram which shows an example of the connection wiring of a unit pair
assembly.
The schematic diagram which shows the other example of the connection wiring of a unit pair
assembly.
[0019]
Next, embodiments of the present invention will be described with reference to FIGS. 1 to 7, but
the present invention is not limited thereto.
[0020]
First, referring to FIG. 1 and FIG. 2, this narrow directivity condenser microphone comprises an
acoustic tube 10 formed in a cylindrical shape, a unit pair assembly 20 and a microphone case
30 as a basic configuration. ing.
[0021]
The acoustic tube 10 may be formed of metal or a synthetic resin material, and an acoustic wave
introducing hole 11 for interference is provided in a part of the circumferential surface thereof.
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The sound wave introduction hole 11 may be formed along the direction of the tube axis X at a
position 180 ° opposite to the circumferential surface of the acoustic tube 10, as in the normal
mode.
The tube axis X is a central axis of the sound tube 10 and is also a sound collecting axis or a
pointing axis.
[0022]
The unit pair assembly 20 may be referred to as a unidirectional condenser microphone unit
(hereinafter simply referred to as a "microphone unit") as described later.
2) and is disposed on the rear end side (the lower end side in FIGS. 1 and 2) of the acoustic tube
10.
[0023]
The microphone case 30 is a long cylindrical tube that covers the acoustic tube 10 and the unit
pair assembly 20, and is dustproof on the tip end side (upper end side in FIGS. 1 and 2) 30a that
is directed to the sound source side during sound collection. A guard net 31 is provided.
[0024]
The microphone case 30 extends further rearward than the unit pair assembly 20, and a 3-pin
output connector 34 is mounted inside the rear end 30b.
A circuit board 35 is disposed between the unit pair assembly 20 and the output connector 34 in
the microphone case 30.
[0025]
Although not shown, an impedance converter, an audio signal output circuit, and the like are
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mounted on the circuit board 35.
An FET (field effect transistor) is used for the impedance converter as in the normal mode.
[0026]
The peripheral surface of the microphone case 30 is provided with an opening 32 as an acoustic
wave through-hole from the tip end 30 a side to the storage portion of the unit pair assembly 20.
In this embodiment, the openings 32 are rectangular holes orthogonal to the axis of the
microphone case 30, and a plurality of the openings 32 are arranged in the shape of a strip at
predetermined intervals in the axial direction of the microphone case 30.
[0027]
Referring to FIGS. 3 to 5, unit pair assembly 20 includes a pair of microphone units 21R and 21L.
The microphone units 21R and 21L are unidirectional, and substantially the same unit is used
including the directional frequency characteristics.
[0028]
That is, both of the microphone units 21R and 21L are a diaphragm 211 stretched with a
predetermined tension on a metal support ring (diaphragm ring) 212, and a fixed electrode 213
supported on a synthetic resin insulating seat 214. Are disposed opposite to each other via the
spacer ring 218.
[0029]
The diaphragm 211 may be a thin film of synthetic resin having a metal deposition film on the
opposite side facing the fixed electrode 213.
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Further, although a metal plate such as aluminum is used for the fixed electrode 213, an electret
film may be provided on the surface facing the diaphragm 211.
[0030]
The insulating seat 214 is formed in the shape of a shallow dish with a bottom so that an air
chamber of a predetermined volume exists on the back side of the fixed electrode 213, and the
fixed electrode 213 is fitted and fixed to the periphery thereof. At the bottom of the insulating
seat 214, an electrode lead terminal pin 217 electrically connected to the fixed pole 213 via a
lead wire (not shown) is provided.
[0031]
In this embodiment, the microphone units 21R and 21L are both rectangular units, the
diaphragm 211 is stretched on a support ring 212 formed of a rectangular frame, and the fixed
electrode 213 and the insulating seat 214 are formed in a rectangular shape. .
[0032]
Because of the unidirectionality, the diaphragm 211 side is a front acoustic terminal, and a sound
hole 215 as a rear acoustic terminal is formed at the bottom of the insulating seat 214.
The sound holes 215 are covered by an acoustic resistance material 216 made of non-woven
fabric or mesh.
[0033]
Further, as shown in FIG. 4, a large number of sound holes 213 a are also formed in the fixed
pole 213, and sound waves from the sound hole 215 (rear acoustic terminal) of the insulating
seat 214 pass through the sound holes 213 a of the fixed pole 213. It passes through and acts on
the back of the diaphragm 211.
[0034]
As shown in FIGS. 3 and 5, the microphone units 21R and 21L are assembled in the unit holder
22 and arranged around them with the diaphragms 211 and 211 facing each other in parallel
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and facing each other. It is fixed to the unit holder 22 by the pressing brackets 23, 23.
[0035]
The unit holder 22 is made of a synthetic resin material, and the support rings 212 and 212 are
in contact with the housing unit side of the microphone unit 21R and the housing unit side of the
microphone unit 21L, and the distance between opposing surfaces of the units is constant.
Stepped portions 222 and 223 are formed to keep the
[0036]
Also, at the one end side of the unit holder 22 to which the rear end of the acoustic tube 10 is
fitted, the sound wave coming through the acoustic tube 10 is guided to the front acoustic
terminal between the opposing surfaces of the microphone units 21R and 21L. The opening 221
is formed as a horn.
[0037]
Thus, the unit pair assembly 20 is attached to the rear end side of the acoustic tube 10 in a state
including the pair of microphone units (square units) 21R and 21L, in which case in FIGS. 1 and
2 As shown, the long side of the square unit is made to be along the tube axis X of the acoustic
tube 10, and the microphone units 21R and 21L are arranged symmetrically about the tube axis
X of the acoustic tube 10.
[0038]
Thereby, the sound wave paths to the front acoustic terminal side of the diaphragms 211 and
211 of the microphone units 21R and 21L are substantially the same, and the sound wave paths
to the rear surface of the diaphragms 211 and 211 from the rear acoustic terminal side are also
substantially the same. Thus, the microphone units 21R and 21L operate as unidirectional
directivity with almost the same directional frequency response.
[0039]
Further, when the microphone units 21R and 21L are square units and two square units are
provided, the effective diaphragm area is increased, and high sensitivity can be achieved.
In this respect, the diaphragm and the fixed pole are compared with the conventional general
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circular unit in which the circular shape is used.
[0040]
For example, in the case of a circular unit having an effective vibration diameter φ of 13 mm, the
effective diaphragm area is: 6.5 × 6.5 × 3.14 ≒ 132.7 mm <2>.
[0041]
On the other hand, the effective diaphragm area is (11.3 × 20.5) × 1 in the case of using two
square units having a short side of 11.3 mm smaller than φ 13 mm and a long side of 20.5 mm
463 mm <2>, and an effective diaphragm area of about 3.5 times as large as that of the abovementioned circular unit is obtained, and the sensitivity is greatly enhanced accordingly.
[0042]
As for touch noise and handling noise, for example, vibrations generated when the microphone
case 30 is rubbed by a hand are equally applied to the diaphragms 211 and 211 including their
vibration directions, as shown in FIG. The vibration noise is canceled by grounding the plates 211
and 211 (for example, connecting to the microphone case 30) and inputting the output 41a of
the microphone unit 21R and the output 42a of the microphone unit 21L in parallel to the
impedance converter 40. Can.
[0043]
The present invention also includes an aspect in which a plurality of unit pair assemblies 20 are
provided.
FIG. 7 shows an example in which two unit pair assemblies 20A and 20B are used.
[0044]
In this case, the diaphragms 211 and 211 of the microphone units 21R and 21R of one of the
unit pair assemblies 20A and 20B are connected in series, and the diaphragms 211 and 211 of
the other microphone units 21L and 21L are connected. Connect them in series and connect
them together to ground.
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Each diaphragm 211 may be grounded separately.
[0045]
Similarly, the fixed poles 213 and 213 of each one of the microphone units 21R and 21R are
connected in series, and the fixed poles 213 and 213 of each of the other microphone units 21L
and 21L are connected in series, The outputs 41 b and 42 b are input in parallel to the
impedance converter.
[0046]
In the above embodiment, the microphone units 21R and 21L included in the unit pair assembly
20 are square units, but it is also possible to use a circular unit for the microphone units 21R and
21L to form a unit pair assembly 20. In this case, as shown in FIG. 7, the effective diaphragm
area can be further increased by connecting a plurality of unit pair assemblies 20 as shown in
FIG.
[0047]
DESCRIPTION OF REFERENCE NUMERALS 10 acoustic tube 20, 20A, 20B unit pair assembly
21R, 21L unidirectional condenser microphone unit 211 diaphragm (front acoustic terminal)
212 support ring 213 fixed pole 214 insulation seat 215 sound hole (rear acoustic terminal) 216
acoustic Resistive material 217 Terminal pin 218 Spacer ring 22 Unit holder 221 Opening 30
Microphone case 34 Output connector 35 Circuit board 40 Impedance converter
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