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DESCRIPTION JP2009182758

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DESCRIPTION JP2009182758
The present invention provides a condenser microphone unit having an acoustic mass effective
to pass low-range sound waves from the front side to the back side of a diaphragm in order to
prevent wind noise. A groove 221 having a predetermined acoustic mass in the form of a pipe is
formed between an end plate 10a of a unit case 10 and an end plate 10a of a unit case 10 on the
other end surface 22b side of the diaphragm support ring 22 where the diaphragm 21 is not
attached. The first opening 22 for introducing a part of the sound wave from the front acoustic
terminal hole 11 into the groove 221 is formed on the inner peripheral surface side of the
diaphragm support ring 22 as well, the outer peripheral surface side of the diaphragm support
ring 22 The second opening 223 is opened toward the inner wall surface of the unit case 10, and
the second opening 223 is acoustically connected to the back surface side of the diaphragm 21
via the spacer The sound wave in the low band from the terminal hole 11 is guided to the back
surface side of the diaphragm 21 through the groove 221 having a predetermined acoustic mass
so that the pressure in the low band becomes equal to that of the diaphragm 21. [Selected figure]
Figure 2
Unidirectional Condenser Microphone Unit and Line Microphone
[0001]
The present invention relates to a unidirectional condenser microphone unit and a line
microphone, and more particularly to a technique for preventing wind noise.
[0002]
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In the field of microphones, wind noise mainly occurs when disturbances in the air flow occur
around the microphones.
The frequency component of wind noise is at a low frequency of about 500 Hz or less, and can
not be heard directly as a sound with a large amplitude of 20 Hz or less, but it generates sound
such as buzzing, clipping, and intermodulation distortion.
[0003]
In general, noise cones and wind screens are used to deal with wind noise, but their air
permeability changes the shielding effect of the wind, and if the eyes are clogged, the
characteristics of the microphone are degraded. I will. On the other hand, in order to enhance the
effect of shielding the wind without deteriorating the characteristics of the microphone, a
windscreen with a large outer size is required.
[0004]
As another measure, as described in Patent Documents 1 to 3, there is a method of passing sound
waves in the low region from the front acoustic terminal to the back side of the diaphragm (the
side facing the fixed electrode). . According to this, since a pressure difference does not occur
before and behind the diaphragm in the low band, wind noise and vibration noise can be
reduced.
[0005]
In the invention described in Patent Document 1, cutouts are provided in each of the diaphragm
support ring, the diaphragm and the spacer ring to form a sound wave communication path from
the front side to the back side of the diaphragm.
[0006]
In the invention described in Patent Document 2, a wire mesh having air permeability also in the
surface direction is interposed between the diaphragm support ring supporting the diaphragm
and the sound collecting surface of the unit case, and a part of the periphery of the fixed pole
The notch portion is provided in the above to form a sound wave communication passage from
the front side to the back side of the diaphragm.
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[0007]
In the invention described in Patent Document 3, a very small opening for pressure equalization
is formed in the diaphragm itself, for example, by heat from spark discharge.
[0008]
Japanese Patent Application Laid-Open No. 61-187189 Japanese Patent Application Laid-Open
No. 5-11696 Japanese Patent Application Laid-Open No. 9-84195
[0009]
However, in the case of the invention described in Patent Document 1, although it is necessary to
overlap the notch portion of the diaphragm support ring and the notch portion of the spacer
ring, when the internals of the unit case rotate, the positions of the two notch portions shift. As a
result, the communication path of the sound wave from the front side to the back side of the
diaphragm may be blocked.
[0010]
In the case of the invention described in Patent Document 2, since the wire mesh disposed
between the diaphragm support ring and the sound collecting surface of the unit case mainly
acts as an acoustic resistance, the acoustic mass component can be controlled. Have difficulty.
[0011]
The invention described in Patent Document 3 is effective when there is no acoustic tube or the
like on the front side of the diaphragm as in a studio condenser microphone, but a line
microphone (narrow directional microphone) using an acoustic tube When applied, there is a
problem that the acoustic mass can not be controlled.
[0012]
Therefore, an object of the present invention is to provide a unidirectional directivity condenser
microphone unit having an acoustic mass effective to pass low-range sound waves from the front
side to the back side of the diaphragm in order to prevent wind noise. It is.
[0013]
In order to solve the above problems, the present invention is directed to a bottomed cylindrical
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unit case integrally provided with an end plate having a front acoustic terminal hole on one end
side and an open on the other end side, a diaphragm support ring A diaphragm assembly in
which a diaphragm is stretched on an end face side, and a fixed pole assembly in which a fixed
pole is supported on an insulating seat, wherein the diaphragm and the fixed pole are electrically
insulating spacers An acoustoelectric transducer disposed opposite to each other is
accommodated in the unit case with the diaphragm assembly as the end plate side, and the
acoustoelectric transducer is pressed and fixed on the other end face side of the unit case In the
unidirectional condenser microphone unit provided with the fixing means, a groove having a
pipe-shaped predetermined acoustic mass is formed between the end plate and the other end
face side of the diaphragm support ring, Of diaphragm support ring A first opening for
introducing a portion of the sound wave from the front acoustic terminal hole into the groove is
formed at a predetermined portion on the circumferential surface side, and the first surface is
formed on the outer circumferential surface side of the diaphragm support ring. A second
opening formed toward the inner wall surface of the unit case is formed in a predetermined
portion, and the second opening is acoustically connected to the back side of the diaphragm via
the spacer. It is characterized by
[0014]
According to a preferred aspect of the present invention, the groove is formed over the entire
circumference of the diaphragm support ring, and the first opening and the second opening are
disposed at a position 180 ° opposite to each other.
[0015]
In the present invention, it is preferable that a mesh material made of synthetic resin having air
permeability in the surface direction is used as the spacer, but the spacer includes the second
opening and the back surface side of the diaphragm. Acoustically connecting notches may be
formed.
[0016]
The present invention also includes a narrow directional line microphone formed by combining
the above unidirectional condenser microphone unit and an acoustic tube.
[0017]
According to the present invention, a groove having a pipe-like predetermined acoustic mass is
formed between the end plate of the diaphragm support ring and the end plate of the unit case
on the other end face (surface on the anti-diaphragm side) side. A first opening for introducing a
part of the sound wave from the front acoustic terminal hole into the groove is formed at a
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predetermined site on the inner peripheral surface side of the diaphragm, and at a predetermined
site on the outer peripheral surface side of the diaphragm support ring From the front acoustic
terminal hole, a second opening opened toward the inner wall surface of the unit case is formed,
and the second opening is acoustically connected to the back side of the diaphragm via the
spacer. The sound wave in the low frequency range is guided to the back side of the diaphragm
through the groove having a predetermined acoustic mass, and the pressure noise is equalized in
the low frequency range, so that the wind noise is effectively reduced.
[0018]
The acoustic mass is determined by the width, depth, and length of the groove formed in the
diaphragm support ring, but the groove is formed over the entire circumference of the
diaphragm support ring, and the first opening and the second opening are made 180 By
arranging them in opposite positions, the acoustic mass in the left and right groove portions can
be balanced.
[0019]
By using a synthetic resin mesh material having air permeability in the surface direction as the
spacer, sound waves in the low region can be made to act on the back surface side of the
diaphragm without particularly performing alignment with the second opening. it can.
[0020]
In the case of a line microphone (narrow directional condenser microphone) using an acoustic
tube, the large acoustic impedance of the acoustic tube is added to the front acoustic terminal of
the microphone unit, so the acoustic mass corresponding to the large acoustic impedance
However, according to the present invention, the acoustic mass can be optimally set by the width,
depth and length of the groove formed in the diaphragm support ring.
[0021]
Next, an embodiment of the present invention will be described with reference to FIGS. 1 to 3,
but the present invention is not limited to this.
FIG. 1 may be referred to as a unidirectional directivity condenser microphone unit (hereinafter
simply referred to as a "microphone unit") according to an embodiment of the present invention.
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2 is an exploded sectional view of FIG. 1, and FIG. 3 is a plan view showing a diaphragm support
ring which is an essential part of the present invention.
[0022]
Referring to FIGS. 1 and 2, this microphone unit basically comprises a unit case 10, a diaphragm
assembly 20, a fixed electrode assembly 30, an electrically insulating spacer 40 and a circuit
board 50.
[0023]
The unit case 10 is a bottomed cylindrical body made of, for example, an aluminum material, and
integrally includes an end plate 10a having a front acoustic terminal hole 11 on one end surface
side.
The other end 10 b side of the unit case 10 is open.
[0024]
The diaphragm assembly 20 includes the diaphragm 21 and the diaphragm support ring 22, and
the diaphragm 21 is stretched on a side of one end surface 22 a of the diaphragm support ring
22 with a predetermined tension.
The diaphragm 21 may be a thin film of synthetic resin on which a metal vapor deposition film is
formed.
The diaphragm support ring 22 is, for example, a metal ring such as an aluminum material.
[0025]
The fixed pole assembly 30 includes a fixed pole 31 and an insulating seat 32.
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Although the metal plate which has many ventilation holes 311 is used for the fixed pole 31, an
electret film may be provided in the surface.
The insulating seat 32 is a disc made of a synthetic resin, and one surface of the insulating seat
32 supports the fixed electrode 31.
[0026]
A sound wave introducing hole 321 for making a sound wave from a rear acoustic terminal hole
51 described later act on the back surface side of the diaphragm 21 through the air hole 311 of
the fixed electrode 31 is bored in the insulating seat 32.
A back air chamber 322 communicating with the sound wave introduction hole 321 is formed on
the support surface side of the insulating seat 32, and a predetermined acoustic resistance
material 323 is accommodated in the back air chamber 322.
[0027]
The circuit board 50 is disposed on the back surface side (fixed pole opposite support surface
side) of the insulating seat 32 in order to close the open surface on the other end 10 b side of the
unit case 10.
A rear acoustic terminal hole 51 is bored in the circuit board 50.
Further, on the inner surface side of the circuit board 50, an FET (field effect transistor) 52 as an
impedance converter is mounted.
[0028]
The gate of the FET 52 is connected to the fixed pole 31 through a predetermined electrical
connection means. In this embodiment, the gate of the FET 52 is disposed at the central portion
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of the insulating seat 32 and fixed to the fixed pole 31 via a coil spring 54. It is in contact with
the electrically connected electrode terminal 55.
[0029]
An acoustoelectric transducer is configured by arranging the spacer 40 between the diaphragm
21 and the fixed pole 31 and combining the diaphragm assembly 20 and the fixed pole assembly
30.
[0030]
In practice, after the diaphragm assembly 20, the spacer 40 and the fixed pole assembly 30 are
housed in the unit case 10 in this order, the circuit board 50 is disposed on the back side of the
insulating seat 32, and the other end of the unit case 10 Squeeze 10b.
[0031]
In this manner, the above-mentioned acoustoelectric transducer is assembled in the unit case 10
and pressed and fixed, but instead of caulking, a lock ring may be fitted on the other end 10b
side of the unit case 10 .
[0032]
In the present invention, in order to prevent wind noise, the diaphragm support ring 22 has an
acoustic mass effective to pass sound waves in the low range from the front side to the back side
of the diaphragm 21.
[0033]
Referring also to FIG. 3, in the present invention, the groove 221 is formed on the other end
surface 22 b side of the diaphragm support ring 22.
The other end surface 22 b of the diaphragm support ring 22 is in contact with the end plate 10
a of the unit case 10, so that a pipe having a groove 221 is formed between the diaphragm
support ring 22 and the end plate 10 a.
This pipe acts as an acoustic mass that can pass low frequency sound waves.
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[0034]
In this embodiment, the groove 221 is formed over the entire circumference of the diaphragm
support ring 22, and a part of the sound wave from the front acoustic terminal hole 11 is formed
in a predetermined portion on the inner peripheral surface side of the diaphragm support ring
22. A first opening 222 is formed for introduction into the interior.
Further, a second opening 2223 opened toward the inner wall surface of the unit case 10 is
formed at a predetermined position on the outer peripheral surface side of the diaphragm
support ring 22.
[0035]
In this case, in order to balance the acoustic mass in the left and right groove portions, it is
preferable to arrange the first opening 222 and the second opening 223 at a position 180 °
opposite to each other.
Further, it is preferable to use a synthetic resin mesh material (for example, a plain weave
polyester mesh) having air permeability in the surface direction as the spacer 40.
[0036]
According to this, a part of the low frequency sound wave of the sound wave entering from the
front acoustic terminal hole 11 enters the groove 221 having a predetermined acoustic mass
from the first opening 222 and exits from the second opening 223 The space between the
diaphragm support ring 22 and the unit case 10 and the spacer 40 reach the back side of the
diaphragm 21. Therefore, pressure is equalized in the low region in the front and back of the
diaphragm, and wind noise is effectively reduced.
[0037]
The acoustic mass can be appropriately set according to the width, depth, length and the like of
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the groove 221 formed in the diaphragm support ring 22.
Therefore, the microphone unit according to the present invention is particularly suitable for a
narrow directional line microphone using an acoustic tube.
[0038]
That is, in the case of a line microphone, since the large acoustic impedance of the acoustic tube
is added to the front acoustic terminal of the microphone unit, it is necessary to acoustically
connect the front and rear of the diaphragm with an acoustic mass corresponding to the large
acoustic impedance. According to the present invention, the acoustic mass required for the
microphone unit of the line microphone is optimally set by the width, depth, length, etc. of the
groove 221 formed in the diaphragm support ring 22 as described above. Can.
Therefore, the present invention also includes a narrow directional line microphone formed by
combining the microphone unit of the above-described configuration and an acoustic tube.
[0039]
In the above embodiment, the groove 221 for the acoustic mass is formed over the entire
circumference of the diaphragm support ring 22, but may be, for example, about a half
circumference according to the specification.
Further, as the spacer 40, a spacer made of a synthetic resin film and having a notch for
acoustically connecting the second opening 223 on the sound wave outlet side and the back side
of the diaphragm 21 may be used.
[0040]
FIG. 1 is a cross-sectional view showing a unidirectional condenser microphone unit according to
an embodiment of the present invention.
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The disassembled sectional view of FIG.
The top view which shows the diaphragm support ring which is the principal part of this
invention.
Explanation of sign
[0041]
DESCRIPTION OF SYMBOLS 10 unit case 10a end plate 10b other end of unit case 11 front
acoustic terminal hole 20 diaphragm assembly 21 diaphragm 22 diaphragm support ring 221
groove 222 1st opening 223 2nd opening 30 fixed pole assembly 31 fixation Pole 32 Insulating
seat 40 Spacer 50 Circuit board 51 Rear acoustic terminal hole 52 Impedance converter (FET)
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