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DESCRIPTION JP2006101311

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DESCRIPTION JP2006101311
PROBLEM TO BE SOLVED: To reliably prevent adhesion of dust to a microphone unit without
particularly preparing a voltage circuit for a dust collection electrode. SOLUTION: A microphone
unit 40 including a diaphragm and a fixed pole is housed in a head case 30 having a protective
cover 31 through which sound waves can pass, and between a diaphragm and the fixed pole
from a predetermined polarized power supply In a condenser microphone to which a polarization
voltage is applied, the entire bottom of the microphone unit 40 is covered in a non-contact state
in the head case 30 and a bottomed cylinder made of a metal mesh body to which a polarization
voltage is applied from a polarization power supply The dust collection electrode 50 is provided.
[Selected figure] Figure 1
コンデンサマイクロホン
[0001]
The present invention relates to condenser microphones, and more particularly to dustproof
technology for microphone units.
[0002]
The condenser microphone includes a microphone unit in which a diaphragm and a fixed pole
are disposed opposite to each other with a predetermined distance, and a polarization voltage is
applied between the diaphragm and the fixed pole to form a capacitor, thereby causing vibration.
The change in capacitance due to the vibration of the plate is taken out as an audio signal
through an impedance converter such as a field effect transistor or a vacuum tube.
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[0003]
The polarization voltage applied to the microphone unit is usually a DC voltage of several tens of
volts to several hundreds of volts, and the dust that is suspended in the air is a microphone unit
due to the electrostatic attraction generated by the polarization voltage. Adhere by suction.
[0004]
Dust includes various things such as particulates and fibers, but when fibrous dust adheres so as
to connect between the grounding system on the diaphragm side and the signal system on the
fixed electrode side, that part It becomes a path of leakage current.
The amount of dust adhesion increases in proportion to the time during which the polarization
voltage is applied, and when humidity is added to this, leakage current may flow and large noise
may be generated.
[0005]
As one of the methods for preventing this, it has been practiced to cover the microphone unit
with a dust collection filter made of a porous material such as urethane foam or a highly
permeable material such as nylon mesh or non-woven fabric.
However, particularly for condenser microphones used in recording studios and the like, it is not
preferable to cover the dust collection filter on the microphone unit in terms of sound quality
and appearance.
[0006]
From such a thing, patent document 1 is disclosing the dustproof technology which replaces a
dust collection filter.
That is, in Patent Document 1, a dust collection electrode set to a voltage higher than the
polarization voltage is disposed in the vicinity of the microphone unit, and dust is
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electrostatically attracted to the dust collection electrode. In this case, an electret material is
preferable as the dust collection electrode, but a plate-like electrode, a linear electrode, or a
needle-like electrode can also be used.
[0007]
Unexamined-Japanese-Patent No. 2003-92792
[0008]
According to Patent Document 1 mentioned above, since the voltage of the dust collection
electrode is higher than the polarization voltage of the microphone unit, most of the floating dust
is electrostatically attracted to the dust collection electrode side, but the microphone unit Since
the exposed state is in the head case (outer casing), dust may still be attracted to the microphone
unit by the polarization voltage.
[0009]
In addition, when the dust collection electrode is an electret material, dust is adsorbed even when
the microphone is not used, so the amount of accumulated dust continues to increase.
Even if it is cleaned, it is difficult to remove dust cleanly.
[0010]
When the collection electrode is not an electret material but is a metal electrode such as a platelike electrode, a linear electrode, or a needle-like electrode, for example, a voltage doubler
rectification circuit or the like is necessary to generate a voltage higher than the polarization
voltage The cost is increased by that amount.
[0011]
Therefore, an object of the present invention is to provide a condenser microphone in which
adhesion of dust to the microphone unit can be reliably prevented without particularly preparing
a voltage circuit for the dust collection electrode.
[0012]
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In order to solve the above problems, according to the present invention, a microphone unit
including a diaphragm and a fixed electrode disposed opposite to each other is accommodated in
a head case having a protective cover through which sound waves can pass, and a predetermined
polarized power supply In the condenser microphone to which a polarization voltage is applied
between the diaphragm and the fixed pole, the whole of the microphone unit is covered in a noncontact state in the head case, and the polarization is performed by the polarization power
source. It is characterized in that a bottomed cylindrical dust collection electrode made of a metal
mesh body to which a voltage is applied is disposed.
[0013]
In the present invention, the dust collection electrode is preferably made of a metal mesh of 40
to 60 mesh.
Particularly preferred mesh is 50 mesh.
In addition, as for the diameter of the wire which comprises a mesh, about 0.1 mm is preferable.
[0014]
According to the present invention, since the entire microphone unit is surrounded by the dust
collection electrode made of a metal mesh, adhesion of dust to the microphone unit can be
reliably prevented.
In addition, since the voltage is obtained from the polarized power supply, it is not necessary to
particularly prepare a voltage circuit for the dust collection electrode.
[0015]
Furthermore, when the switch of the polarization power supply is turned off when the
microphone is not used, etc., no polarization voltage is applied to the dust collection electrode, so
dust adheres to the dust collection electrode more than necessary. Also, if light vibration is
applied, dust adhering to the dust collection electrode can be removed.
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[0016]
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.
1 (a) is a front longitudinal sectional view showing an example of a condenser microphone
according to the present invention, FIG. 1 (b) is a side front longitudinal sectional view thereof,
and FIG. 2 is a schematic diagram showing an example of an application circuit of polarization
voltage in the present invention. FIG.
[0017]
As shown in FIGS. 1 (a) and 1 (b), the condenser microphone described here is a stand-type
condenser microphone used exclusively in recording studios, and for example, a microphone
housing 10 formed in a tubular shape from a brass alloy. In the microphone housing 10, the
electric circuit board 11 having the impedance converter 11a and the polarized power supply
circuit 11b (both shown in FIG. 2) is accommodated.
[0018]
The connector portion 20 is attached to the lower part of the microphone housing 10, and the
head case 30 is covered on the upper part of the microphone body 10.
A 3-pin type output connector 21 is accommodated in the connector unit 20, and the output
connector 21 is connected to a phantom power supply via a balanced shield cable (not shown).
[0019]
The head case 30 includes a protective cover 31 through which sound waves can pass.
The protective cover 31 is also called a guard net, and usually, a metal mesh capable of shielding
extraneous electromagnetic waves is used for this, but it may be made of synthetic resin. Further,
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a windscreen 32 made of a porous material such as urethane foam may be attached to the inner
surface (or the outer surface) of the protective cover 31 in order to reduce wind noise.
[0020]
The microphone unit 40 is disposed in the head case 30. In this example, the microphone unit 40
is supported by the microphone housing 10 so as to be positioned in the head case 30 via the
unit mount 12 including the support bracket 12a made of hard resin and the shock absorbing
member 12b made of rubber. .
[0021]
As shown in FIG. 1 (b), the microphone unit 40 in this example is a double diaphragm type in
which diaphragms are disposed on both sides of the fixed pole, but may be a normal single
diaphragm type. In addition, since it is a stand type microphone for recording studios, the sound
collection axis is directed in the horizontal direction.
[0022]
As schematically shown in FIG. 2, the diaphragm 41 and the fixed pole 42 are disposed opposite
to each other at a predetermined interval in the microphone unit 40, and the impedance
converter 11a is connected to the fixed pole 42, and A predetermined polarization voltage is
applied from the polarization power supply circuit 11b.
[0023]
As an example, the polarized power supply circuit 11b generates a predetermined polarized
voltage from a voltage supplied from a phantom power supply or a battery.
For the diaphragm 41, for example, a synthetic resin film having a metal vapor deposition film is
used. The diaphragm 41 is stretched on the support ring 41a with a predetermined tension, and
is connected to the grounding system of the microphone via the support ring 41a.
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[0024]
According to the present invention, in order to prevent electrostatic attraction of floating dust to
the microphone unit 40 due to the polarization voltage applied to the fixed pole 42, the entire
microphone unit 40 is collected in the head case 30. The dust electrode 50 is put on.
[0025]
In this example, the dust collection electrode 50 is formed of a metal net body formed in a
cylindrical shape with a bottom, and the opening thereof is placed on the lower side, that is, the
unit mount 12 so as not to contact the microphone unit 40 in reverse. Be done.
[0026]
As shown in FIG. 2, the dust collection electrode 50 is connected to the polarized power supply
circuit 11 b together with the fixed electrode 42.
Therefore, the polarization voltage is applied to the dust collection electrode 50 by turning on
the microphone power switch (polarization power switch) not shown when the microphone is
used.
Thus, the floating dust is electrostatically attracted to the dust collection electrode 50
surrounding the microphone unit 40 and does not adhere to the microphone unit 40.
[0027]
On the other hand, when the microphone power switch is turned off when the microphone is not
used, the polarization voltage is not applied to the dust collection electrode 50 and the
electrostatic attraction force disappears. Dust does not adhere. In addition, if light vibration is
applied, dust adhering to the dust collection electrode 50 can be removed.
[0028]
The dust collection electrode 50 is made of a metal mesh, and the mesh size is preferably 40 to
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60 mesh, particularly 50 mesh, as the fineness of the mesh may at least prevent passage of
fibrous dust. Moreover, it is preferable that the wire diameter of a metal wire is about 0.1 mm.
[0029]
Although the present invention has been described above by taking the stand-type condenser
microphone for recording studio as an example, the present invention is not limited thereto. For
example, a condenser microphone for handheld, a narrow directional gun microphone, and a tie
pin type microphone used by being worn And so on.
[0030]
(A) Front longitudinal cross-sectional view which shows an example of the capacitor | condenser
microphone by this invention, (b) The side front longitudinal cross-sectional view.
The schematic diagram which shows an example of the application circuit of the polarization
voltage in this invention.
Explanation of sign
[0031]
DESCRIPTION OF SYMBOLS 10 microphone housing 11 electric circuit board 11a impedance
converter 11b polarized power supply circuit 20 connector part 21 output connector 30 head
case 31 protective cover 40 microphone unit 41 diaphragm 42 fixed pole 50 collecting electrode
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