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DESCRIPTION JP2006033216

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DESCRIPTION JP2006033216
PROBLEM TO BE SOLVED: To strengthen a shield in a flexible pipe portion in a gooseneck type
condenser microphone in which a condenser microphone unit is supported via a support pipe
including a flexible pipe. SOLUTION: A capacitor microphone unit and an output module unit
provided with a circuit board for audio signal output are provided, and the capacitor microphone
unit is supported by the output module unit via a support pipe including a flexible pipe, and the
capacitor microphone is In the condenser microphone in which the unit and the circuit board are
electrically connected via the microphone cable 40 having the shield-covered wire 43 inserted
into the support pipe, at least the flexible pipes 31 and 32 of the microphone cable 40 The
portion to be wired inside is exposed at multiple points to the flexible pipes 31 and 32, with the
shield-covered wire 43 exposed. [Selected figure] Figure 2
コンデンサマイクロホン
[0001]
The present invention relates to a gooseneck type condenser microphone in which a condenser
microphone unit is supported via a support pipe including a flexible pipe, and more specifically,
noise generation caused by high frequency electromagnetic wave noise generated from, for
example, a portable telephone Relates to the technology for preventing
[0002]
For example, as described in Patent Document 1, a gooseneck-type condenser microphone is
preferably adopted from the viewpoints of simple appearance and easy adjustment of angle and
height as in conference facilities such as an international conference hall. It is done.
18-04-2019
1
[0003]
In the goose neck type condenser microphone, the condenser microphone unit and the output
module part are separately configured, and the condenser microphone unit is supported by the
output module part via a support pipe including a flexible pipe in part or all, The bendability of
the flexible pipe allows the condenser microphone unit to be easily brought close to the speaker's
mouth.
[0004]
Usually, the condenser microphone unit incorporates an FET (field effect transistor) as an
impedance converter, and the output module section includes a circuit board for audio signal
output in a cylindrical shield case, and the condenser microphone unit is a support pipe It is
connected to the circuit board through a dedicated microphone cable inserted inside.
[0005]
The microphone cable includes a power supply line that supplies power to the condenser
microphone unit, a signal line that transmits an audio signal output from the impedance
converter to the output module unit, and a shield coating that electrostatically shields and
grounds these. A two-core shield-covered wire including a wire and the outer peripheral surface
of the shield-covered wire covered with an outer sheath (skin) is used.
The output module unit is sometimes called a power module unit because power is supplied to
the condenser microphone unit.
[0006]
The audio signal is unbalancedly transmitted at the microphone cable, so it is vulnerable to
external noise (electromagnetic waves).
Therefore, when a strong electromagnetic wave is applied to the microphone cable, it may enter
the inside of the condenser microphone unit or the output module as a high frequency current
and be detected by a semiconductor element or the like to generate noise.
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[0007]
In particular, considerably strong electromagnetic waves (for example, electric field strength
reaching tens of thousands times the electric field strength generated in the market by
commercial radio waves in the range of several cm to several 10 cm) from mobile phones that
are rapidly spreading in recent years In the field of microphones, it is urgently required to take
measures against electromagnetic waves by mobile phones.
[0008]
The flexible pipe acts as a shield for the microphone cable but is not perfect.
That is, a flexible pipe is produced by forming a coil spring carrying a restoring force with a
round wire such as steel, and sandwiching a triangular wire made of a copper alloy or the like
that plastically deforms in a triangular shape in cross section into gaps between each coil spring.
Although they have low resistance (for example, about 1 Ω) at the contact portion of the wires,
they have impedance.
[0009]
The condenser microphone unit and the output module unit are each provided with a rigid shield
case, but when viewed as a whole of the microphone, the shield is incomplete at the flexible pipe.
Therefore, a high frequency current due to strong electromagnetic waves may enter the
microphone through the flexible pipe, resulting in the generation of noise as described above.
[0010]
Unexamined-Japanese-Patent No. 11-341576 (FIG. 1)
[0011]
Therefore, an object of the present invention is to strengthen a shield in a flexible pipe portion in
a gooseneck type condenser microphone in which a condenser microphone unit is supported via
a support pipe including a flexible pipe.
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[0012]
In order to solve the above problems, the present invention includes a condenser microphone
unit and an output module section provided with a circuit board for audio signal output in a
shield case, and the condenser microphone unit is connected via a support pipe including a
flexible pipe. A condenser microphone supported by the output module portion and electrically
connected through a microphone cable having a shield coating wire through which the
condenser microphone unit and the circuit board are inserted into the support pipe, The portion
of the microphone cable wired in at least the flexible pipe is characterized in that the shieldcovered wire is exposed.
[0013]
In the case where the support pipe includes a metal pipe in addition to the flexible pipe, the
microphone cable also includes an aspect in which the shield-covered wire is exposed over the
entire length thereof.
[0014]
According to the present invention, the resistance value of the flexible pipe is extremely reduced
because the shielded cable of the microphone cable contacts the inner surface of the flexible pipe
at many points.
Therefore, the shield function against electromagnetic waves is greatly improved, and the
generation of noise can be effectively suppressed.
[0015]
Next, embodiments of the present invention will be described with reference to FIGS. 1 to 3, but
the present invention is not limited thereto.
[0016]
FIG. 1 shows an example of a gooseneck condenser microphone according to the present
invention as a cross-sectional view.
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The condenser microphone has a condenser microphone unit 10, an output module unit (power
module unit) 20, and a support pipe 30 for supporting the condenser microphone unit 10 as a
basic configuration.
[0017]
The condenser microphone unit 10 has a cylindrical shield case 11 made of, for example, a brass
material, and the microphone capsule 12 is attached to the tip of the shield case 11.
Although not shown, the diaphragm and the fixed pole are included in the microphone capsule
12 in a state of facing each other.
An electret may be used as a polarization material.
Similarly, although not shown, the shield case 11 accommodates an FET (field effect transistor)
as an impedance converter electrically connected to the fixed pole.
[0018]
The output module unit 20 includes a cylindrical shield case 21 which is also used as a support
base.
The shield case 21 is also formed of, for example, a conductive material such as brass. In the
shield case 21 is housed a circuit board 22 having an audio output circuit (not shown) including
a filter circuit, an amplifier circuit and the like. In addition, the shield case 21 is installed on a
table via a suitable receiving bracket or the like.
[0019]
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At one end side (upper end side in this example) of the shield case 21, a mouthpiece 23 for fitting
and fixing the support pipe 30 is provided. An output connector 24 is attached to the other end
side (lower end side in this example) of the shield case 21.
[0020]
In the condenser microphone, generally, a 3-pin type output connector defined in EIAJ RC-5236
"Latch-lock type round connector for audio equipment" is used as the output connector 24, and
the output connector 24 is via a balanced shield cable. Are connected to a phantom power supply
(both not shown).
[0021]
Although the support pipe 30 may use a flexible pipe over the entire length, in this example, the
support pipe 30 is a metal pipe 33 between two flexible pipes, ie, the base flexible pipe 31 and
the distal flexible pipe 32. It connects by.
[0022]
In this example, the base side flexible pipe 31 has a diameter larger than that of the tip side
flexible pipe 32, but this is due to design requirements, and both of the flexible pipes 31 and 32
are made of steel or other round wire. It is manufactured by sandwiching a triangular wire rod
made of copper alloy etc. which plastically deforms in a triangular shape in cross section into the
gap of each coil spring from above, and the round wire rod and the triangular wire have strong
friction. Can be deformed to the position of, and the deformed state is self-held.
[0023]
In the support pipe 30, a microphone cable 40 for electrically connecting the condenser
microphone unit 10 and the output module unit 20 is inserted.
A portion of the microphone cable 40 is shown in FIG.
The microphone cable 40 is a two-core shield-covered wire, and includes a power supply wire
42a and a signal wire 42b inserted into the inner sheath 41, and a mesh-like shield-covered wire
43 wound around the entire outer peripheral surface of the inner sheath 41. ing.
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[0024]
In a cable having a shield-covered wire, not only the microphone cable but generally the shieldcovered wire is covered by an outer sheath (skin) over the entire length, but in the present
invention, at least the flexible pipes 31, 32 of the microphone cable 40. In the portion to be
wired, the outer sheath is removed and the shielded wire 43 is exposed.
[0025]
According to this, the shield-covered wire 43 of the microphone cable 40 is electrically
connected to the inner surfaces of the flexible pipes 31 and 32 at many points, and the resistance
value of the flexible pipes 31 and 32 is reduced. Shields can be strengthened.
[0026]
As an example, a 39 cm long flexible pipe is prepared, and the direct current resistance value
between both ends when it passes through a usual microphone cable having an outer sheath over
the entire length is 0.4 Ω, but the outer sheath is The microphone cable according to the present
invention, which was removed to expose the shield-coated wire, was inserted into a flexible pipe,
and the DC resistance value between both ends was measured, which was 0.01 Ω or less.
[0027]
FIG. 3 shows an equivalent circuit of the connection portion between the shield-covered wire 43
and the flexible pipes 31 and 32. As shown in FIG.
In FIG. 3, Ra is a contact resistance mainly between wires of the flexible pipe, and Rb is a contact
resistance with the shield-covered wire 43.
[0028]
As described above, according to the present invention, a large number of short circuit-like
closed circuits are formed between the shield coating wire 43 and the flexible pipes 31 and 32
by the resistor Rb. The high frequency current is converted to heat energy and dissipated in the
short circuit closed circuit.
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Thus, noise generation due to electromagnetic waves is suppressed.
[0029]
In the case where the flexible pipes 31 and 32 and the metal pipe 33 are mixed in the support
pipe 30 as in the above-described example, the outer sheath is removed over the entire length,
and the metal as well as the portion of the flexible pipe is The shield covering wire 43 may be
exposed also in the portion wired in the pipe 33.
[0030]
FIG. 1 is a cross-sectional view showing an example of a condenser microphone according to the
present invention.
BRIEF DESCRIPTION OF THE DRAWINGS The perspective view which shows the principal part of
this invention.
The equivalent circuit in the connection part of a shield covering wire and a flexible pipe in this
invention.
Explanation of sign
[0031]
DESCRIPTION OF SYMBOLS 10 capacitor microphone unit 20 output module part 21 shield case
22 circuit board 30 support pipe 31, 32 flexible pipe 33 metal pipe 40 microphone cable 42a
power wire 42b signal wire 43 shield coating wire
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