JP2008118260

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DESCRIPTION JP2008118260
PROBLEM TO BE SOLVED: To provide a variable directional electret condenser microphone unit
capable of continuously changing directivity from omnidirectional to bidirectional, and a
microphone using the same. SOLUTION: A single plate comprising a diaphragm, a diaphragm
holder to which the diaphragm is fixed, and a fixed electrode which is disposed opposite to the
diaphragm with a gap therebetween and constitutes the capacitor. A bi-directional condenser
microphone unit in which fixed electrodes of the directional electret condenser microphone unit
are opposed to each other, and an acoustic resistance material fixed by an insulating seat is
disposed between the fixed poles and integrally coupled; The variable directional electret
condenser microphone unit has a variable capacitance capacitor that connects the fixed pole of
the unidirectional electret condenser microphone unit to the diaphragm of the other
unidirectional electret condenser microphone unit. [Selected figure] Figure 1
Variable directivity electret condenser microphone unit and condenser microphone
[0001]
The present invention relates to a variable directional electret condenser microphone unit
capable of continuously changing directivity from nondirectionality to bidirectionality and a
microphone using the same.
[0002]
Several inventions are known for variable directional condenser microphones that can vary the
directivity of the condenser microphone.
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For example, the invention of a microphone of variable directivity is known that includes phase
shift means for phase shifting the output from each condenser microphone, and addition means
for adding the output and the output of the phase shift means. Reference 1).
[0003]
There is also known an invention of changing the characteristics of the microphone units
disposed on the front and the left and right to change the directivity of the entire microphone
(see, for example, Patent Document 2).
[0004]
There is also known an invention of changing directivity by changing a ratio of mixing a plurality
of microphone outputs (see, for example, Patent Document 3).
[0005]
Patent Document 1: Japanese Unexamined Patent Publication No. 11-069481 Japanese Utility
Model Application Publication No. 02-075895 Patent Document 1: Japanese Patent Publication
No. 61-055838
[0006]
In addition, a bidirectional directivity condenser microphone unit (hereinafter referred to as
bidirectional directivity microphone unit can be obtained by arranging fixed poles of two
pairs of unidirectional directivity condenser microphone units (hereinafter referred to as
unidirectional unit ) facing each other. In the bi-directional unit , the directivity from the
bi-directional unit as a whole can be changed by changing the polarity of the diaphragm and the
fixed pole of the single-directional unit on the back side.
[0007]
FIG. 3 is a cross-sectional view showing an example of a bi-directional unit in which two single
directional units are disposed to face each other.
In FIG. 3, the bi-directional unit 1 is formed by the diaphragm holder 11a, the diaphragm 12a
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and the fixed pole 13a, and is disposed on the front side of the bi-directional unit 1; A single
directional unit B formed by the diaphragm 11 b and the fixed pole 13 b and disposed on the
back side of the bidirectional unit 1 is disposed opposite to each other with the insulating seat 14
interposed.
A damper 15, which is an acoustic resistance, is provided near the center of the insulating seat
14, and thereby, a back air chamber 16 is formed between the fixed pole 13a and the fixed pole
13b.
These members are fixed to the insulating seat 14 by pressing rings 19 fitted to the front and
rear end outer peripheral portions of the insulating seat 14 to constitute the bi-directional unit 1.
[0008]
Diaphragm electrodes 17a and 17b, which are outputs from the diaphragm 12 and the fixed pole
13 of the single pointing unit A and the single pointing unit B, and fixed pole electrodes 18a and
18b are provided.
The diaphragm electrodes 17a and 17b are electrically connected to the diaphragms 12a and
12b via the diaphragm holders 11a and 11b for fixing the diaphragms 12a and 12b. The fixed
electrode 18a and 18b are connected to the fixed electrode 13a and 13b and electrically
connected via a wire extending from the slit provided in the insulating seat 14 to the outside of
the unit 1.
[0009]
When the capacitor portion formed by the diaphragm 12 and the fixed electrode 13 of the unit A
and the unit B requires application of a polarization voltage, the polarity and the magnitude of
the polarization voltage are changed. The directivity of the pointing unit 1 can be changed. FIG.
4A is an explanatory view showing necessary configurations and respective connections in order
to explain an example of changing the polarity of the polarization voltage. FIG. 4B is an
explanatory view showing necessary configurations and respective connections in order to
explain an example in which the magnitude of the polarization voltage is changed.
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[0010]
In FIG. 4A, a DC voltage of a constant voltage is used as the polarization voltage of the unit A. As
the polarization voltage source of the unit B, a DC-DC converter 3 capable of changing the
polarity of the output voltage is used. The output terminal of the converter 3 is provided with a
variable resistor, and the output voltage can be continuously changed from −100 V to +100 V
by changing the variable resistance value. The polarity can be changed. An impedance converter
P is connected to the fixed pole electrode 18 for extracting the output of the bi-directional unit 1.
[0011]
If the polarity of the output voltage of the DC-DC converter 3 is made positive, the polarities of
the polarization voltages of the unit A and the unit B become the same, so the directivity of the
unit A and the unit B becomes the same. Therefore, the bi-directional unit 1 as a whole becomes
omnidirectional. If the polarity of the output voltage of the DC-DC converter 3 is negative, the
directivity of the bi-directional unit 1 is bi-directional. Also, when the polarization voltage is not
polarized, ie, when the polarization voltage is zero, only unit A will function as a microphone unit,
and unit 1 will be unidirectional.
[0012]
Further, in FIG. 4B, the DC-DC converter 3a can change the output voltage from 0 V to 120 V by
providing a switch at the output terminal on one side. The diaphragm electrode 17a of the unit A
is directly connected to the impedance converter P, and the fixed electrode 18a and 18b are
connected to the fixed output terminal of the DC-DC converter 3a. The diaphragm electrode 17b
is connected to an output terminal which is a changeover switch of the DC-DC converter 3a. By
changing the magnitude of the polarization voltage applied to the diaphragm electrode 17b in
the bi-directional unit 1 connected in this manner, it is possible to relatively change the polarities
of the diaphragm 12b and the fixed electrode 13b, By changing the magnitude of the polarization
voltage, it is possible to switch between bi-directionality, non-directionality and unidirectionality.
[0013]
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Figure 5 shows an example of the configuration of a variable directional microphone unit using a
bi-directional electret condenser microphone in which polarization voltage is eliminated by using
electrets for the diaphragm 12a and the diaphragm 12b of the bi-directional unit 1 shown in FIG.
It demonstrates using. The diaphragm 12 of the bi-directional unit 1 in FIG. 5 is configured of an
electret, but the other configuration is the same as that of the bi-directional unit 1 described
above.
[0014]
In FIG. 5A, the output taken from the fixed pole 13a and the fixed pole 13b is connected to the
impedance converter P via the fixed pole electrode 18. Here, the impedance converter P needs to
be connected to each fixed electrode 18 one by one.
[0015]
Further, as shown in FIG. 5B, instead of connecting the impedance converter P to each of the
fixed electrode 18a and the fixed electrode 18b, the impedance converter P is connected only to
the fixed electrode 18a, The directivity can be varied by connecting the fixed electrode 18b to the
changeover switch. According to the bi-directional unit 1 in the above configuration, the bidirectional unit 1 becomes nondirectional when the impedance converter P is connected to the
diaphragm electrode 17 b by switching the above-mentioned changeover switch. When the
impedance converter P is connected to the diaphragm electrode 18b, the bi-directional unit 1 is
bi-directional. When the switch is placed at the neutral point and neither the diaphragm
electrode 17b nor the fixed electrode 18b of the unit B is connected to the impedance converter
P and the output of the unit B is not taken out, the bi-directional unit 1 is uni-directional It
becomes sex.
[0016]
In the prior art shown above, when a power supply (DC-DC converter in FIG. 4) is used to apply a
polarization voltage, the noise generated from the power supply will adversely affect the
characteristics of the microphone unit itself. . Also, in the case of a condenser microphone using
an electret for the diaphragm, when an impedance converter is connected to the output of each
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single-directional unit, the S / N ratio is degraded when the outputs are mixed. Also, if an
attenuator (PAD) is used to prevent deterioration of the S / N ratio, miniaturization of the
microphone unit becomes difficult. In addition, in the configuration in which the connection to
the impedance converter by the switch is switched back, the directivity can not be continuously
changed.
[0017]
The present invention has been made in view of the above problems, and outputs of bidirectional electret condenser microphones configured by combining unidirective electret
condenser microphone units are combined by a variable capacitance condenser, and directivity is
continuously varied. It is an object of the present invention to provide a variable directivity
electret condenser microphone unit and a microphone using the same.
[0018]
According to the present invention, there is provided a single diaphragm comprising: a
diaphragm; a diaphragm holder to which the diaphragm is fixed; and a fixed electrode disposed
opposite to the diaphragm with a gap therebetween and constituting a capacitor. Two directional
electret condenser microphone units are provided, the fixed poles of the two microphone units
are made to face each other, and an acoustic resistance material fixed by an insulating seat is
disposed between the fixed poles and integrally coupled. A variable capacitance capacitor for
connecting the bi-directional condenser microphone unit, the fixed pole of the uni-directional
electret condenser microphone unit of the above 1, and the diaphragm of the other unidirectional electret condenser microphone unit Main feature
[0019]
Further, according to the present invention, the fixed pole of the unidirectional electret capacitor
microphone unit of the above 1 is connected to the impedance converter, and the diaphragm of
the unidirectional electret capacitor microphone unit of the above 1 is grounded. The unipolar
electret capacitor microphone unit fixed pole is connected to the movable pole of the variable
capacitor, and the other unipolar electret capacitor microphone unit diaphragm is connected to
the fixed pole of the variable capacitor. It is characterized by
[0020]
According to the present invention, by combining the outputs of two unidirectional electret
condenser microphone units by a variable capacitance condenser, a microphone unit capable of
continuously changing directivity from omnidirectionality to bidirectionality. You can get
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[0021]
Hereinafter, an embodiment of a variable directivity electret condenser microphone unit
according to the present invention will be described using the drawings.
FIG. 1 is an explanatory view of a variable directional electret condenser microphone unit
configured by using a bidirectional electret condenser microphone.
The bi-directional unit 1 is shown in cross section in FIG.
A variable capacitance capacitor (varicon) 2 is connected to the bi-directional unit 1 to variably
invert the polarity of the unit B. The variable capacitance capacitor 2 schematically shows the
electrical structure.
[0022]
The physical configuration of the bi-directional unit that can be used in the embodiment of the
present invention is the same as the example of the conventional bi-directional unit described
above.
Therefore, the same components as in the conventional bi-directional unit example are denoted
by the same reference numerals and detailed description of the configuration will be omitted. In
FIG. 1, reference numeral 1 is a bi-directional unit, 11a and 11b are diaphragm supports, 12a
and 12b are diaphragms, 13a and 13b are fixed poles, 14 is an insulating seat, 15 is a damper
which is an acoustic resistance material, 16 Denotes an air chamber, 17a and 17b denote
diaphragm electrodes, 18a and 18b denote fixed electrodes, and 19 denotes a pressing ring.
[0023]
The variable capacitor 2 is a two-piece variable capacitor having two variable capacity parts, and
includes two movable poles 21a and 21b interlocking with each other, and fixed poles 22a, 23a,
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22b and 23b cooperating with the movable poles 21a and 21b. Is equipped. The movable poles
21a and 21b have a common rotation axis, and integrally rotate by rotation of the rotation axis.
The movable pole 21a cooperates with the fixed poles 22a and 23a, and when the movable pole
21a rotates, the overlapping areas with the fixed poles 22a and 23a are opposite to each other,
that is, the area with one fixed pole is As it becomes larger, the area with the other fixed pole is
configured to be smaller. Therefore, when the capacitance of the capacitor formed by the
movable pole 21a and the fixed pole 22a increases, the capacitance of the capacitor formed by
the movable pole 21a and the other fixed pole 23a decreases. The movable pole 21b cooperates
with the fixed poles 22b and 23b, and when the movable pole 21b rotates, the overlapping areas
with the fixed poles 22b and 23b are opposite to each other, that is, the area with one fixed pole
is As it becomes larger, the area with the other fixed pole is configured to be smaller. Therefore,
when the capacitance of the capacitor formed by the movable pole 21b and the fixed pole 22b
increases, the capacitance of the capacitor formed by the movable pole 21b and the other fixed
pole 23b decreases. The movable poles 21a and 21b constituting one variable capacitance
portion and the other variable capacitance portion are set to have the same phase relationship,
and one fixed pole 22a and the other fixed pole 23a, and one fixed pole 22b and the other fixed
pole 23b. Are also set to the same phase relationship.
[0024]
In FIG. 1, the diaphragm electrode 17a is grounded, and the other diaphragm electrode 17b is
connected to the fixed pole 23a constituting one variable capacitance portion of the variable
capacitor 2 and the fixed pole 22b constituting the other variable capacitance portion . Further,
the fixed electrode 18a and the movable electrode 21a constituting one variable capacitance
portion of the variable capacitor 2 are connected to the impedance converter P, and the other
fixed electrode 18b is a fixed electrode constituting one variable capacitance portion of the
variable capacitor 2. It is connected to the fixed electrode 23b which comprises 22a and the
other variable capacity part. The movable pole 21b constituting the other variable capacitance
portion of the variable capacitor 2 is grounded.
[0025]
The change in directivity of the bi-directional unit 1 due to the facing pattern of the movable pole
21 of the variable capacitor 2 and the fixed poles 22 and 23 will be described with reference to
FIG. FIG. 2A shows a state in which the movable pole 21a is opposed to the fixed pole 22a, and
the movable pole 21b is opposed to the fixed pole 22b. Thus, when the variable capacitor 2 is
adjusted, the diaphragm 12b connected to the electrode 17b of the unit A is grounded via the
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variable capacitor 2, and the fixed electrode 13b connected to the electrode 18b is connected via
the variable capacitor 2 It will be connected to the impedance converter P. That is, since each
polarity of the unit A and the unit B is the same, the bi-directional unit 1 as a whole becomes
omnidirectional.
[0026]
Moving the movable poles 21a and 21b gradually narrows the area facing the fixed poles 22a
and 22b, and gradually increases the area facing the fixed poles 23a and 23b, the directivity of
the bi-directional unit 1 gradually In the changing state, i.e. in the state of FIG. 2 (b), the bidirectional unit 1 is somewhat uni-directional. Further, in the state of FIG. 2C, since the polarities
of the diaphragm 12b and the fixed pole 13b of the unit B are the same and opposite in polarity,
the electrical output from the unit B is offset and the impedance converter P is canceled. Since it
is not input, only the output of the unit A is input to the impedance converter P, which is
unidirectional.
[0027]
Furthermore, when the movable pole 21a and the movable pole 21b are moved to make the
facing area of the fixed pole 22b and the fixed pole 23b larger than the facing area of the fixed
pole 22a and the fixed pole 23a, the bi-directional unit 1 Through directivity (the state of FIG. 2
(d)), bi-directional (FIG. 2 (e)) is obtained.
[0028]
As described above, the output level of the rear side unit is changed by connecting a variable
capacity capacitor to the output terminal of the rear side unit of the bi-directional electret
condenser microphone constituted by the unidirectional electret condenser microphone and
changing the capacitance. Since the polarity can be changed, a variable directional condenser
microphone unit can be obtained.
[0029]
The variable directional capacitor microphone unit according to the embodiment described above
can constitute a variable directional capacitor microphone by incorporating it into a microphone
case.
[0030]
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It is an explanatory view showing an example of a variable directivity electret condenser
microphone unit concerning the present invention.
It is explanatory drawing which showed the directivity according to the state of a variable
capacity capacitor in the variable directivity electret capacitor microphone unit which concerns
on this invention.
FIG. 6 is a longitudinal sectional view showing an embodiment of a conventional bi-directional
condenser microphone unit.
It is explanatory drawing which shows the example of the structure which can vary directivity
using the conventional bi-directional capacitor ¦ condenser microphone unit which applies a
polarization ¦ polarized-light voltage. It is explanatory drawing which shows the example of the
conventional structure which can change directivity using the bi-directional capacitor ¦
condenser microphone unit which used the electret for the diaphragm.
Explanation of sign
[0031]
DESCRIPTION OF SYMBOLS 1 Bi-directional capacitor microphone unit 2 Variable capacity
capacitor 3 DC-DC converter 10 Presser ring 11 Diaphragm support 12 Diaphragm 13 Fixed pole
14 Insulating seat 15 Damper 16 Back air chamber 17 Diaphragm electrode 18 Fixed pole
electrode 21 Variable capacity Movable pole of capacitor 22 Fixed pole of variable capacitor 23
Fixed pole of variable capacitor
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