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JP2017038121

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DESCRIPTION JP2017038121
Abstract: In a dynamic microphone, vibration noise such as handling noise is reduced without
deteriorating resonance frequency characteristics in a low frequency range. SOLUTION: A sound
wave detection microphone 41 and a speaker 42 are disposed in a back air chamber 12a
between a sub dome 12 of a diaphragm 10 and a support frame 30, and mechanical vibration
applied to the microphone unit 1 from the outside The acceleration pickup 43 for detecting the
sound, and the speaker drive means 45 for driving the speaker 42 by the outputs of the sound
wave detection microphone 41 and the acceleration pickup 43, and the output of the sound wave
detection microphone 41 is opposite phase from the speaker drive means. The outputs of the
acceleration pickup 43 drive the speaker 42 in phase. [Selected figure] Figure 2
ダイナミックマイクロホン
[0001]
The present invention relates to a dynamic microphone, and more particularly, to a dynamic
microphone having a configuration for reducing vibration noise such as handling noise without
impairing the low frequency resonant frequency characteristic.
[0002]
Dynamic microphones are often used for hand-held vocal microphones and the like, but because
they are hand-held, vibration noise (handling noise) generated by rubbing with a finger or the
like often becomes a problem.
[0003]
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As one of the methods to reduce the vibration noise, a method of reducing the weight of the
voice coil is known, but according to this, there arises a problem that the low frequency
resonance frequency is increased and a low sound can not be recorded. .
[0004]
Although there is also a method to soften the sub dome of the diaphragm (diaphragm) as a
method of lowering the resonance frequency in the low band, it is not preferable because an
abnormal resonance may appear in the high band.
[0005]
In this regard, as described in Patent Document 1, if applying a dumping agent (damping agent)
to the sub-dome, abnormal resonance in the high region can be suppressed. It takes time and
effort to manage the amount of application, and there is a problem in productivity.
[0006]
From another point of view, as described in Patent Document 2, there is a method of detecting
mechanical vibration as a noise source applied to the microphone unit with a piezoelectric
element and flowing its opposite phase to a voice coil. In this case, since the output line of the
piezoelectric element is connected in series to the voice coil, there is a problem that no sound is
emitted from the microphone if disconnection occurs on the vibration detection side.
[0007]
Japanese Utility Model Laid-Open Publication No. 5-43694 Japanese Patent Application LaidOpen No. 2009-147858 (see paragraphs 0008-0009)
[0008]
Therefore, an object of the present invention is to reduce vibration noise such as handling noise
in a dynamic microphone without deteriorating the resonance frequency characteristic in the low
frequency range.
[0009]
In order to solve the above-mentioned problems, the present invention comprises a diaphragm
having a sub dome around a center dome and having a voice coil attached to its boundary, and a
magnetic gap having a magnetic gap for giving a magnetic flux by a permanent magnet to the
voice coil. The magnetic circuit portion is supported by a central portion of a substantially disk-
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shaped support frame having a circuit portion, and the peripheral portion of the sub dome
supports the sub-dome so that the voice coil can vibrate in the magnetic gap. In a dynamic
microphone including a microphone unit supported on an outer peripheral portion of a frame, a
sound wave detection microphone and a speaker are disposed in a back air chamber existing
between the sub dome and the support frame, and the above from the outside Accelerometer for
detecting mechanical vibration applied to microphone unit And speaker driving means for
driving the speaker by the outputs of the sound wave detection microphone and the acceleration
pickup, wherein the speaker driving means is configured such that the output of the sound wave
detection microphone is in reverse phase. It is characterized in that the output is supplied to the
drive coil of the speaker as the same phase.
[0010]
According to a preferred aspect of the present invention, an operational amplifier is used as the
speaker driving means, the output of the sound wave detection microphone is input to the
inverting input terminal, and the output of the acceleration pickup is input to the noninverting
input terminal.
[0011]
Each of the sound wave detection microphone and the acceleration pickup includes a filter circuit
that matches the output level and the frequency response to the frequency response of the
microphone unit to the sound wave and the frequency response to the vibration noise.
[0012]
Preferably, a piezoelectric element having a weight as a load is used for the acceleration pickup,
and the directivity of the sound wave detection microphone is nondirectional.
[0013]
According to the present invention, when the diaphragm vibrates due to the sound wave, the
output of the sound wave detection microphone is supplied to the drive coil of the speaker as a
reverse phase to the sound wave, so the diaphragm is more easily vibrated, On the other hand,
when vibration is applied to the microphone, the output of the acceleration pickup is supplied to
the drive coil of the speaker in phase with the applied vibration, so that the diaphragm is difficult
to move and vibration noise can be reduced.
[0014]
Also, since the electrical wiring system including the sound wave detection microphone and the
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acceleration pickup is electrically separated from the voice signal output wiring system of the
voice coil, the electric wiring from the sound wave detection microphone and / or the
acceleration pickup to the speaker is Even if disconnected, the function as a microphone is not
impaired.
[0015]
FIG. 2 is a schematic cross-sectional view showing a microphone unit provided in the dynamic
microphone of the present invention.
The schematic diagram which shows the principal part of this invention.
[0016]
Next, an embodiment of the present invention will be described with reference to FIGS. 1 and 2.
However, the present invention is not limited to this.
[0017]
The dynamic microphone according to this embodiment includes the microphone unit 1
illustrated in FIG.
In this embodiment, the dynamic microphone is a hand-held vocal microphone, and the
microphone unit 1 is supported in a cylindrical microphone case (grip portion of the
microphone) 2 via a shock mount mechanism or the like (not shown). So, the detailed explanation
is omitted.
[0018]
The microphone unit 1 includes a diaphragm (diaphragm) 10, a magnetic circuit unit 20, and a
support frame 30.
[0019]
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The diaphragm 10 is made of a thin film sheet material of synthetic resin, and includes a center
dome 11 and a sub dome 12 integrally formed around the center dome 11.
The voice coil 13 is integrally attached to the boundary portion between the center dome 11 and
the sub dome 12 on the back surface side of the diaphragm 10 by an adhesive or the like.
[0020]
The magnetic circuit unit 20 includes a cup-shaped yoke member 21 whose upper surface is
open, a disk-shaped permanent magnet 22 disposed on the inner bottom surface 21 a of the yoke
member 21, and a columnar member disposed on the permanent magnet 22. A pole piece 23 is
provided.
[0021]
The permanent magnet 22 is magnetized in the plate thickness direction, whereby a magnetic
gap G for giving a magnetic flux from the permanent magnet 22 to the voice coil 13 is provided
between the upper end inner peripheral surface 21 b of the yoke member 21 and the pole piece
23. It is formed.
[0022]
The support frame 30 is formed in a substantially disk shape having an opening at the center,
and is supported in a state where the magnetic circuit unit 20 is fitted in the opening at the
center.
The peripheral portion of the sub dome 12 is supported by the outer peripheral portion of the
support frame 30 so that the voice coil 13 can vibrate in the magnetic gap G.
[0023]
In the present invention, the microphone 41 and the speaker 42 are disposed in the back air
chamber 12 a as the back air chamber 12 a of the sub dome 12 as the space existing between
the sub dome 12 and the support frame 30.
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In addition, an acceleration pickup 43 for detecting mechanical vibration applied to the
microphone unit 1 from the outside is provided.
[0024]
The microphone 41 is a sound wave detection microphone, and detects the pressure in the back
air chamber 12a which fluctuates as the diaphragm 10 vibrates by the sound wave.
The directivity of the microphone 41 is preferably omnidirectional.
One sound wave detection microphone 41 may be provided in the back air chamber 12a.
[0025]
The speaker 42 is used to adjust the pressure in the back air chamber 12a.
The speaker 42 may be either a capacitor type or a dynamic type, but in this embodiment, a
dynamic type speaker in which the speaker cone is vibrated by the current supplied to the drive
coil is adopted.
[0026]
As shown in FIG. 1, the speakers 42 are preferably arranged to be embedded in the support
frame 30.
The number of speakers 42 is determined by, for example, the aperture of the microphone unit 1,
the sound emission frequency of the speakers 42, and the like, but a plurality of the speakers 42
is not necessarily required.
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[0027]
As the acceleration pickup 43, preferably, a piezoelectric element 431 having a weight 432 for
sensitization is used.
According to this embodiment, the acceleration pickup 43 is disposed on the outer bottom
surface 21c of the yoke 21. However, the acceleration pickup 43 may be provided in a
microphone case (microphone grip) 2 as an outer casing.
[0028]
Referring to FIG. 2, the dynamic microphone includes a speaker driving means 45 for driving the
speaker 42 by the outputs of the sound wave detection microphone 41 and the piezoelectric
element 431 as the acceleration pickup 43.
[0029]
The speaker drive means 45 supplies the output of the sound wave detection microphone 41 to
the drive coil of the speaker 42 as the reverse phase, but supplies the output of the piezoelectric
element 431 to the drive coil of the speaker 42 as the same phase.
[0030]
In order to realize this, in this embodiment, an operational amplifier (op amp) 451 is used as the
speaker driving means 45, and the output of the sound wave detection microphone 42 is
inputted to its inverting input terminal (-). The output of the piezoelectric element 431 is input
to.
[0031]
The buffer circuit 41 a and the filter circuit 41 b are connected to the output stage of the sound
wave detection microphone 41, and the buffer circuit 43 a and the filter circuit 43 b are also
connected to the output stage of the piezoelectric element 431. There is.
[0032]
Among them, the filter circuits 41 b and 43 b have filter characteristics that match the output
level and frequency response of the sound wave detection microphone 41 and the piezoelectric
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element 431 to the frequency response to sound waves of the microphone unit 1 and the
frequency response to vibration noise. .
[0033]
As for the piezoelectric element 431, its output level is almost flat, so if the filter circuit 43b
adjusts the output level to follow the resonance frequency of the microphone unit 1 and drives
the speaker 42, the diaphragm accordingly. 10 is effectively displaced (responsive).
[0034]
Next, the operation will be described. For convenience of explanation, it is assumed that the
sound pressure applied to the vibration plate 10 at the peak of the sound wave is + Po and the
sound pressure applied to the valley of the sound wave is -Po.
Similarly, with regard to the mechanical vibration applied to the microphone unit 1, the
acceleration applied upward along the sound collection axis in FIGS. 1 and 2 is + V, and the
acceleration applied downward is -V.
[0035]
When sound pressure + Po is applied to the diaphragm 10 at the peak of the sound wave, the
pressure P in the back air chamber 12a rises.
The pressure rise is captured by the sound wave detection microphone 41, and an output
proportional to the pressure P is output from the sound wave detection microphone 41.
However, the speaker drive means 45 outputs a drive signal having a reverse phase to the
output. Is supplied to the drive coil of
[0036]
As a result, at the peak portion of the sound wave, a speaker cone (not shown) of the speaker 42
moves in the backward direction, and the pressure P in the back air chamber 12a is lowered by
that amount.
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[0037]
On the other hand, in the sound wave valley, the pressure applied to the diaphragm 10 is -Po,
and the pressure P in the back air chamber 12a also decreases accordingly.
The pressure drop is captured by the sound wave detection microphone 41, and an output
proportional to the pressure P is output from the sound wave detection microphone 41.
However, the speaker drive unit 45 outputs a drive signal having a reverse phase to the output. Is
supplied to the drive coil of
[0038]
As a result, in the sound wave valley, the speaker cone of the speaker 42 moves in the forward
direction, and the pressure P in the back air chamber 12a is increased by that amount.
In this manner, the diaphragm 10 vibrates easily with respect to the sound wave, and the low
resonance frequency can be further reduced.
[0039]
Next, vibration noise (handling noise) will be described.
The vibration noise is generated because the diaphragm 10 tries to stand still by inertia when an
external force is applied to the microphone unit 1 to displace it in the sound collecting axis
direction.
That is, when the magnetic gap G side of the magnetic circuit unit 20 moves with respect to the
voice coil 13 of the diaphragm 10, vibration noise is generated.
[0040]
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Therefore, when the mechanical vibration applied to the microphone unit 1 is an acceleration of
+ V in the direction to push up the microphone unit 1, the speaker cone of the speaker 42 moves
in the forward direction by the output from the piezoelectric element 431. Drive the speaker 42.
As a result, the pressure P in the back air chamber 12 a is increased, and the diaphragm 10 is
pushed up together with the magnetic circuit unit 20.
[0041]
On the other hand, when the acceleration is -V in the direction to push down the microphone unit
1, the speaker 42 is driven so that the speaker cone of the speaker 42 moves in the backward
direction by the output from the piezoelectric element 431.
Thereby, the pressure P in the back air chamber 12 a is lowered, and the diaphragm 10 is
pushed down together with the magnetic circuit unit 20.
[0042]
Thus, the speaker 42 is driven in phase with the output of the piezoelectric element 431 so as to
move the diaphragm 10 in the same direction as the direction of the mechanical vibration
applied to the microphone unit 1 (the direction along the sound collection axis). Thus, the relative
positional deviation between the diaphragm 10 and the magnetic circuit unit 20 can be
suppressed, so that vibration noise can be effectively reduced.
[0043]
In the above embodiment, the operational amplifier 451 is adopted as the speaker driving means
45. However, the driving coil of the speaker 42 is two coaxially arranged coils separated from
each other, and one of the driving coils is a microphone 41 for sound wave detection. The other
drive coil may be driven with a signal in phase with the output of the acceleration pickup.
[0044]
In any case, since the electrical wiring system including the sound wave detection microphone 41
and the acceleration pickup 43 is electrically separated from the audio signal output wiring
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system of the voice coil 13, the sound wave detection microphone 41 and / or the acceleration
pickup Even if the electrical wiring from 43 to the speaker 42 is broken, the function as the
microphone is not impaired.
[0045]
Reference Signs List 1 microphone unit 10 diaphragm 11 center dome 12 sub dome 12 a back
air chamber 13 voice coil 20 magnetic circuit unit 21 yoke 22 permanent magnet 23 pole piece
30 support frame 41 microphone for sound wave detection 41 b filter circuit 42 speaker 43
acceleration pickup 43 b filter circuit 431 Piezoelectric element 432 Weight 45 Speaker driving
means 451 Operational amplifier
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