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DESCRIPTION JP2013162449

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DESCRIPTION JP2013162449
Abstract: While reducing the generation of abnormal noise due to discharge between an
electrode and a vibrating membrane, the time required for the electrostatic electroacoustic
transducer to be available is shortened. An adhesive member (20U) has a conductive layer
(210U) and an insulating layer (220U). The insulating layer 220U is formed of a highly insulating
material. The conductive layer 210U is a layer formed by vapor-depositing a metal that conducts
electricity on the insulating layer 220U. A terminal 531U is in contact with the conductive layer
210U and is electrically connected thereto. The terminal 531U is also in contact with the surface
101U of the vibrating membrane 10 and is electrically connected thereto. That is, the terminal
531U is provided to apply a voltage to both the surface 101U and the conductive layer 210U.
Thereby, the charges supplied by the voltage from the bias power supply reach the respective
positions of the surface 111U of the vibrating portion 110 via the conductive layer 210U in
which the movement of the charge of a predetermined amount is faster than that of the surface
111. [Selected figure] Figure 3
Electrostatic transducer
[0001]
The present invention relates to an electrostatic electroacoustic transducer.
[0002]
By changing the voltage applied between the diaphragm and the electrodes arranged to face each
other at intervals and changing the electrostatic attractive force acting between them, the
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diaphragm is vibrated to output sound or Electrostatic transducers of the electrostatic type to
input are known.
In Patent Document 1, a diaphragm of an electrostatic electroacoustic transducer (electrostatic
speaker) is treated with a polymer film in an aqueous solvent solution containing a conductive
polymer monomer, a chemical oxidizing agent, and a dopant. Thus, there is disclosed a technique
using a conductive polymer layer formed on a polymer film.
[0003]
Japanese Patent Application Laid-Open No. 7-46697
[0004]
In an electrostatic electroacoustic transducer such as an electrostatic speaker or an electrostatic
microphone, the vibrating membrane and the electrode are disposed close to each other, and the
voltage applied between them is high. Discharge may occur during this period.
When a discharge occurs, a short circuit may occur between the vibrating membrane and the
electrode to generate abnormal noise. The frequency at which this abnormal noise occurs can be
suppressed as the surface resistance of the vibrating membrane increases. On the other hand, an
electrostatic electroacoustic transducer is operated after a sufficient charge is accumulated in a
vibrating film. As described above, when the surface resistance of the vibrating membrane is
increased, the time required for the charge accumulation on the vibrating membrane becomes
longer. That is, the time for which the user of the electrostatic electroacoustic transducer waits
until the start of use becomes longer. The present invention has been made in view of such
circumstances, and one of the objects thereof is an electrostatic electroacoustic transducer while
reducing generation of abnormal noise due to discharge between an electrode and a vibrating
membrane. To reduce the time it takes to become available.
[0005]
In order to solve the above-mentioned problems, the present invention is an electrode, and a
vibrating film disposed opposite to the electrode and spaced apart from the electrode, wherein
the vibration is caused by electrostatic attraction acting between the electrode and the electrode.
And a conductive film which is provided in contact with the surface of the vibrating portion on
the side facing the electrode and has a smaller surface resistivity than the surface and to which a
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bias voltage is applied. And an electrostatic electroacoustic transducer characterized by
comprising:
[0006]
In a preferred aspect, the surface resistivity of the surface of the vibrating portion is larger than
the volume resistivity of the conductive member.
In another preferred embodiment, the surface resistivity of the surface of the vibrating portion is
1 × 10 <11> Ω / □ or more. In another preferable aspect, the insulating member having an
insulating property provided on the electrode side of the conductive member is provided. In
another preferred embodiment, the insulating member is formed of a material that is an insulator
and an elastic body, has a breathability, and is provided with a cushion material provided
between the electrode and the conductive member, and the conductive member is formed of the
insulating member. It is bonded and fixed to the surface of the vibrating portion, and the
insulating member is fixed to the cushion material. In another preferable aspect, in the
conductive member, the surface of the vibrating portion has a bias potential at a predetermined
charging time constant, with the distance between the position farthest from the conductive
member and the conductive member on the surface of the vibrating portion. It is provided to be
less than or equal to the distance in the case.
[0007]
According to the present invention, the electrostatic type electroacoustic transducer can be used
while reducing the generation of abnormal noise due to the discharge between the electrode and
the vibrating film as compared with the configuration without the above vibrating film and
conductive member. The time it takes to become can be shortened.
[0008]
FIG. 1 is an external view of an electrostatic speaker according to an embodiment.
It is the figure which looked at the electrostatic-type speaker in the X-axis direction. It is a figure
which expands and shows the periphery of an adhesion member. It is a figure which shows the
cross section of an electrostatic type speaker. It is a figure which shows the electric constitution
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of an electrostatic type speaker. It is a figure which expands and shows the surface of the
vibrating membrane in FIG. It is a figure which shows the surface of the vibrating membrane in
which the adhesion member is not provided. It is a figure which shows the cross section of the
electrostatic-type speaker which concerns on a modification. It is a figure which shows the cross
section of the electrostatic-type speaker which concerns on a modification. It is a figure which
shows the cross section of the electrostatic-type speaker which concerns on a modification. It is a
figure which shows the cross section of the electrostatic-type speaker which concerns on a
modification. It is a figure which shows the electric constitution of the electrostatic-type speaker
which concerns on a modification. It is an external view of the electrostatic-type speaker which
concerns on a modification. It is a figure which expands and shows the periphery of the adhesion
member concerning a modification. It is a figure showing the electric composition of the
electrostatic type microphone concerning a modification.
[0009]
Embodiment In this embodiment, an example in which an electrostatic electroacoustic transducer
is applied as an electrostatic speaker that converts an acoustic signal (electric signal) into a
sound wave will be described. FIG. 1 is an external view of the electrostatic speaker 1 according
to the embodiment. FIG. 1 shows X, Y, and Z, which are coordinate axes of a three-axis
orthogonal coordinate system. The electrostatic loudspeaker 1 is provided with a vibrating
membrane 10, adhesive members 20U and 20L, cushion members 30U and 30L, spacers 35U
and 35L, and electrodes 40U and 40L as members. Below, about the member which attached "U"
and "L" to the end of a code | symbol, when not distinguishing each, description of "U" and "L" is
abbreviate | omitted and shown. In the electrostatic speaker 1, the electrode 40L, the cushioning
material 30L, the bonding member 20L, the diaphragm 10, the bonding member 20U, the
cushioning material 30U, and the electrode 40U are stacked in this order in the Z-axis direction.
In addition, on both end sides of the electrostatic speaker 1 in the Y-axis direction, spacers 35L
and 35U are overlapped instead of the cushioning material 30 and the bonding member 20,
respectively. The spacers 35L and 35U respectively have surfaces in contact with members
adjacent in the Z-axis direction, and the normal lines of those surfaces are all along the Z-axis
direction. Further, in FIG. 1, the thickness of the electrostatic speaker 1, that is, the length in the
Z-axis direction is shown larger than the lengths in the X-axis direction and the Y-axis direction in
order to facilitate understanding of the shape of each part. ing. That is, the electrostatic
loudspeaker 1 is actually thinner than that shown in FIG. 1 and has a sheet-like shape as a whole.
[0010]
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(Structure and Structure of Each Part of Electrostatic Speaker 1) The electrode 40 is a film made
of a synthetic resin having insulation and flexibility, such as PET (polyethylene terephthalate,
polyethylene terephthalate) or PP (polypropylene, polypropylene). It is the member which vapordeposited the metal which passes electricity on one side of a member, and formed the electric
conduction film. The electrode 40 is rectangular when viewed from a point on the Z-axis, and has
a plurality of holes penetrating from the surface on the cushion material 30 side to the surface
on the back side. In the electrode 40, these holes allow sound waves to pass from the cushion
material 30 side to the back side thereof. In the drawings, the illustration of the holes is omitted.
The cushion material 30 is a sponge-like member formed using an insulator as a material, and is
rectangular when viewed in the Z-axis direction. The cushion material 30 separates the vibrating
membrane 10 from the electrode 40. The cushioning material 30 is also an elastic body, and is
deformed when an external force is applied, and returns to its original shape when an externally
applied force is removed. In addition, the cushion material 30 is a member having a porous
inside and air permeability, and a sound transmitted by the air present inside the cushion
material 30. The cushion material 30 has the same length in the X-axis direction and the length
in the Y-axis direction as the electrode 40. The cushion members 30U and 30L all have the same
length in the Z-axis direction. The cushion material 30 may be in various forms such as a sheet or
non-woven fabric as long as the vibration film 10 and the electrode 40 are separated and sound
can be transmitted.
[0011]
The spacer 35 is a member formed of insulating plastic. The length of the spacer 35 in the X-axis
direction is the same as that of the electrode 40, and the length in the Z-axis direction is the same
as the total length of the cushioning material 30 and the bonding member 20 in the Z-axis
direction. Further, the spacers 35U and 35L have the same length in the Z-axis direction. The
vibrating film 10 is, for example, a film-like member formed of a synthetic resin having insulating
properties and flexibility, such as PET or PP. Also, a surfactant is applied or added to the
vibrating film 10. An antistatic agent is formed on the surface of the vibrating film 10 by the
action of the surfactant. The vibrating membrane 10 has a surface resistivity of 1 × 10 <11> Ω
/ □ or more measured by the JIS method due to this antistatic agent. The vibrating membrane
10 has a thin film shape with a thickness of about several μm, so it freely deforms when it
receives an external force. The vibrating film 10 has a rectangular shape when viewed in the Zaxis direction, and the length in the X-axis direction and the length in the Y-axis direction are the
same as those of the electrode 40 and the cushion material 30.
[0012]
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The bonding member 20 is a member provided between the vibrating membrane 10 and the
cushion material 30 and bonded to each of them. Hereinafter, the details of the bonding member
20 will be described with reference to FIGS. 2 to 4. FIG. 2 is a view of the electrostatic speaker in
the X-axis direction. The bonding member 20U is bonded to the surface 101U of the cushioning
material 30U side of the vibrating membrane 10 (in other words, the side facing the electrode
40). Further, the bonding member 20U is bonded to the surface 301U on the vibrating film 10
side of the cushion material 30U. The bonding member 20L is bonded to the surface 101L of the
vibrating membrane 10 on the cushion material 30L side. Further, the bonding member 20L is
bonded to the surface 301L of the cushioning material 30L on the vibrating film 10 side. In FIG.
2, nine ends of the bonding member 20 in the X-axis direction are shown. The bonding members
20 are provided such that the distance between these end portions is T1. In the present
embodiment, T1 is 50 mm. Spacers 35 are provided on both sides of the bonding member 20
and the cushion member 30 in the Y-axis direction. The spacer 35 is bonded to the electrode 40
and the vibrating membrane 10 on both sides in the Z-axis direction. The vibrating membrane 10
is fixed to the electrode 40 on both sides in the Y-axis direction by a spacer 35. Terminals 531
(531U, 531L) for applying a voltage to the diaphragm 10 are provided in contact with the
surface 101 between the spacer 35 on the Y axis direction side and the adhesive member 20.
[0013]
FIG. 3 is an enlarged view of a portion III of FIG. The portion III shows the periphery of the
portion of the bonding member 20 where the terminal 531 is provided. The bonding member
20U has a conductive layer 210U (conductive member) and an insulating layer 220U (insulating
member). The insulating layer 220U is formed of a highly insulating material. This material is, for
example, a synthetic resin such as PET or polyethylene, or a natural resin such as rubber, and is a
material having a volume resistivity of 1 × 10 <8> Ωcm or more measured by the JIS method.
The insulating layer 220U is bonded to the surface 301U of the cushioning material 30U,
whereby the bonding member 20U is fixed to the cushioning material 30U. The conductive layer
210U is a layer formed by vapor-depositing a metal that conducts electricity on the insulating
layer 220U. This metal is, for example, copper or aluminum, and is a metal having a volume
resistivity of 1 × 10 4 or less Ω cm or less measured by the JIS method. The conductive layer
210U is formed to have the same width as the insulating layer 220U. The conductive layer 210U
is bonded to the surface 101U of the vibrating membrane 10, whereby the bonding member 20U
is fixed to the vibrating membrane 10. The conductive layer 210U is electrically connected to the
surface 101U of the vibrating membrane 10. In addition, a terminal 531U is in contact with the
conductive layer 210U and is electrically connected thereto. The terminal 531U is also in contact
with the surface 101U of the vibrating membrane 10 and is electrically connected thereto. That
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is, the terminal 531U is provided to apply a voltage to both the surface 101U of the vibrating
membrane 10 and the conductive layer 210U. The conductive layer 210L, the insulating layer
220L, and the terminal 531L included in the bonding member 20L have the same configurations
as the conductive layer 210U, the insulating layer 220U, and the terminal 531U, respectively, so
the description will be omitted.
[0014]
FIG. 4 is a view showing a cross section of the adhesive member 20U taken along the line IV-IV in
FIG. In addition, since this cross section is a cross section of the conductive layer 210U, FIG. 4
shows the conductive layer 210U. The vibrating portion 110 includes the fixed portions 121 and
122 at both end sides in the Y-axis direction and the vibrating portion 110 sandwiched
therebetween. The vibrating portion 110 vibrates by electrostatic attraction acting between the
fixed portions 121 and 122 with the electrode 40 in a state where the fixed portions 121 and
122 are fixed to the electrode 40 by the spacer 35. The conductive layer 210U is provided over
the entire surface 111U of the vibrating portion 110 among the surface 101U of the vibrating
membrane 10. Conductive layer 210U is entirely bonded to surface 111U. The conductive layer
210U has a linear shape of nine lines each in the X-axis direction and the Y-axis direction, and
has a grid shape of 9 rows × 9 columns. The linear portions aligned in the Y-axis direction are
provided at intervals of the length T1 as shown in FIG. 2, and the linear portions aligned in the Xaxis direction are similarly length T1. It is provided at intervals. Thus, the conductive layer 210 is
a lattice-like layer having linear portions. A plurality of square rectangular regions 112t are
formed on the surface 111U by the conductive layer 210U provided in such a shape. The
terminal 531U is provided on the fixed portion 121, and extends linearly in the X-axis direction.
[0015]
(Electrical Configuration of Electrostatic Loudspeaker 1) FIG. 5 is a diagram showing an electrical
configuration of the electrostatic loudspeaker 1. As shown in FIG. The drive unit 500 is
connected to the electrostatic speaker 1. The drive unit 500 includes a transformer 510, an
amplification unit 520, and a bias power supply 530. The amplification unit 520 amplifies and
outputs an acoustic signal (that is, an electrical signal input in the direction of the arrow A1
shown in FIG. 5) input to one terminal on the input side. In addition, the other terminal of the
input side of the amplification unit 520 is grounded. One terminal Q1 on the input side of the
transformer 510 is connected to one terminal on the output side of the amplification unit 520 via
the resistor R1. The other terminal Q2 of the input side of the transformer 510 is connected to
the other terminal of the output side of the amplification unit 520 via the resistor R2. One
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terminal Q4 on the output side of the transformer 510 is connected to the conductive film of the
electrode 40U. The other terminal Q5 on the output side of the transformer 510 is connected to
the conductive film of the electrode 40L. The terminal Q3 at the middle point of the transformer
510 is connected to the ground GND serving as the reference potential of the drive unit 500 via
the resistor R3. With such a configuration, a voltage according to the acoustic signal input to the
amplification unit 520 is applied to the conductive film of the electrode 40U via the transformer
510, and a voltage having the opposite polarity to this voltage is the transformer The conductive
film of the electrode 40L is applied through 510.
[0016]
The bias power supply 530 is a DC power supply, and the negative pole is connected to the
ground GND which is the reference potential of the drive unit 500. In addition, the positive pole
of the bias power supply 530 is connected to the vibrating membrane 10 and the bonding
member 20U via the resistor R4 and the terminal 531U, and connected to the vibrating
membrane 10 and the bonding member 20L via the resistor R4 and the terminal 531L. There is.
The bias power supply 530 applies a positive voltage to the vibrating film 10. Since the vibrating
film 10 forms a capacitor with the electrodes 40 arranged apart from each other, a positive
charge is accumulated until the surface 101 becomes a bias potential by the voltage applied from
the bias power supply 530 (ie, Capacitor is charged). At this time, the bias power supply 530
applies a voltage directly to the vibrating membrane 10 and applies a voltage to the vibrating
membrane 10 via the adhesive member 20. In this configuration, the electrostatic speaker 1
operates as a push-pull electrostatic speaker by applying a voltage corresponding to the acoustic
signal input to the amplification unit 520 to the electrodes 40 (40U and 40L). Do.
[0017]
(Operation of Electrostatic Speaker 1) Next, the operation of the electrostatic speaker 1 will be
described. First, the electrostatic speaker 1 is referred to as a potential (hereinafter referred to as
a “bias potential”) in which the surface 101 of the diaphragm 10 is determined before the
acoustic signal is input. A direct current bias is applied to the vibrating membrane 10 by the bias
power source 530 until the Thereby, the surface 101 of the vibrating membrane 10 has a
potential of +500 V, for example. Subsequently, when an acoustic signal is input to the
amplification unit 520, a voltage corresponding to the input acoustic signal is applied from the
transformer 510 to the electrode 40U and the electrode 40L. Then, when a potential difference is
generated between the electrode 40U and the electrode 40L due to the applied voltage, the
vibrating film 10 between the electrode 40U and the electrode 40L is drawn to the side of either
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the electrode 40U or the electrode 40L. Electrostatic force works.
[0018]
For example, in accordance with the acoustic signal, a negative voltage is applied to the electrode
40U, the surface potential becomes -100 V, a positive voltage is applied to the electrode 40 L,
and the surface potential becomes +100 V. . In this case, the potential difference between the
vibrating membrane 10 and the electrode 40L is 400 V (500 V-100 V), as compared to the
potential difference between the vibrating membrane 10 and the electrode 40 U being 600 V
(500 V + 100 V). As a result, the electrostatic attraction acting between the electrode 40U and
the electrode 40L is larger than the electrostatic attraction acting between the electrode 40L and
the electrode 40L, and the diaphragm 10 is displaced toward the electrode 40U. In addition,
when the voltage applied to the electrodes 40U and 40L changes, and the potentials on these
surfaces become opposite to the above (−40V for the electrode 40U and + 100V for the
electrode 40L), this time between the electrode 40U and the electrode 40U The electrostatic
attraction acting between the electrode 40L and the electrode 40L is larger than the electrostatic
attraction acting at the above, and the vibrating membrane 10 is displaced toward the electrode
40L. As described above, the vibrating portion 110 of the vibrating membrane 10 is displaced
toward the electrode 40 U or the electrode 40 L according to the acoustic signal, and vibrates as
the direction of displacement changes sequentially. Then, a sound wave corresponding to the
state of this vibration, specifically, the frequency and the amplitude is generated from the
vibrating portion 110 of the vibrating film 10. The generated sound wave passes through the
cushion material 30 and the electrode 40 and is emitted to the outside of the electrostatic
speaker 1.
[0019]
In the electrostatic loudspeaker, the distance between the vibrating membrane 10 and the
electrode 40 is a few mm (or 1 mm or less), and when the vibrating membrane 10 vibrates, this
distance is further shortened. On the other hand, since the potential difference between the
vibrating membrane 10 and the electrode 40 is a unit of several hundred volts to several
thousand volts, the air existing between them may cause dielectric breakdown and discharge may
occur. . When a discharge occurs here, the noise emitted from the electrostatic speaker may be
mixed with an unusual noise such as "plucking". This discharge is more likely to occur as the
surface resistivity of the surface of the vibrating membrane is lower. For example, when the
voltage applied to the electrode changes in a state where the vibrating membrane is bent and
displaced toward the electrode, a portion close to the electrode (for example, a central portion of
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the vibrating membrane, hereinafter referred to as "proximal portion"). The more electrostatic
attraction is, the more electric charge tends to collect in the vicinity. Here, if the surface
resistivity of the surface of the vibrating film is low, charges of the same amount will be collected
in the proximity part more quickly if charges of the same amount are compared with the case
where the surface resistivity is high. The potential difference at the proximity portion also
becomes large, and discharge tends to occur. In the electrostatic loudspeaker 1, the surface
resistivity of the surface 101 including the surface 111 of the vibrating portion 110 is 1 × 10
<11> Ω / □ or more as described above. For this reason, in the electrostatic speaker 1,
compared to the case where the surface resistivity of the surface of the vibrating film is lower
than this, it takes a longer time for the same amount of charge to move to the above close
portion. As a result, when the same time has elapsed, the potential difference at the proximity
portion becomes smaller, so that the discharge is less likely to occur.
[0020]
On the other hand, when the surface resistivity of the surface of the vibrating film is large, the
time required for the surface to reach the bias potential becomes longer when a bias voltage is
applied, as compared to the case where the surface resistivity is small. In other words, the time
constant of charge determined by the above-described capacitor formed by the diaphragm and
the electrode and the resistors R3 and R4 connected to the capacitor becomes large. Hereinafter,
this time constant is referred to as "charging time constant". FIG. 6 is a diagram for explaining
the movement of charge in the vibrating film in which the adhesive member 20 is not provided.
FIG. 6A shows the vibrating membrane 10x in which the terminal 531x from the bias power
source 530 is provided only on the fixed portion 121 side. In the vibrating membrane 10x, the
position most distant from the terminal 531x in the vibrating section 110 is a point P1x at the
end on the fixing section 122 side. In the vibrating film 10x, in order for the charge (plus charge
in the case of this embodiment) supplied from the terminal 531x to reach the point P1x by the
voltage applied from the bias power supply 530, the charge vibrates the surface 111 It must
move by T2, which is the length of 110 in the Y-axis direction. FIG. 6B shows the vibrating
membrane 10y in which the fixed portion 121 is provided with the terminal 531y and the fixed
portion 122 is provided with the terminal 532y. In the vibrating membrane 10y, the position
most distant from any of the terminals 531y and 132y in the vibrating portion 110 is the center
point P1x in the Y-axis direction of the vibrating portion 110. In the vibrating film 10y, in order
for the charges supplied from the terminals 531y and 132y to reach the point P1y by the voltage
applied from the bias power supply 530, the charges move the surface 111 by T3, which is half
the length T2. There must be.
[0021]
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On the other hand, in the vibrating film 10, since the terminal 531 connected to the bias power
supply 530 is also connected to the surface 111 of the vibrating portion 110 via the conductive
layer 210 of the adhesive member 20, the conductive layer 210 is moved The charge that has
been transferred reaches each position of the vibrating portion 110 faster than the charge
moving on the surface 111 of the vibrating portion 110. FIG. 7 is a diagram for explaining the
movement of charge in the vibrating film 10. FIG. 7A shows a cross section of the conductive
layer 210U similar to FIG. The volume resistivity (1 × 10 <−4> Ωcm or less) of conductive layer
210U is, as described above, the surface resistivity (1 × 10 <11> Ω / □) of surface 101U
including surface 111 of vibrating portion 110. Since the digits differ by 15 digits or more, the
inside of the conductive layer 210U is referred to as a predetermined amount of charge
(hereinafter referred to as "predetermined amount of charge" even in consideration of differences
in dimensions. The time required for the movement of the movable portion 110 is much shorter
than the time for the charge of the predetermined amount to move on the surface 111U of the
vibrating portion 110. For this reason, on the surface 111U, the time taken for the
predetermined amount of charge moved from the terminal 531 to reach is approximately
determined by the distance for the charge to move in the conductive layer 210U. In the vibrating
portion 110, the position at which the distance from the conductive layer 210U is the largest is a
point P1 which is the center of each rectangular area 112t. FIG. 7A shows one of a plurality of
points P1 as an example.
[0022]
In FIG. 7B, the W portion in FIG. 7A (one rectangular area 112t including the point P1 and its
surrounding area) is shown enlarged. The charge reaching the point P1 moves from the
conductive layer 210U to the surface 111U at the center of any side of the rectangular area
112t. Then, the charge moves on the surface 111U by a half length T4 of T1, which is the length
of one side of the rectangular area 112t, and reaches the point P1. That is, in the vibrating
membrane 10, compared to the vibrating membrane 10x shown in FIG. 6, the distance for
moving the charge on the surface 111U is half the dimension (T1) of the vibrating portion 110 in
the Y axis direction and half of one side of the rectangular area 112t. The difference with the
dimension (T4) is short. Further, in the vibrating film 10, compared to the vibrating film 10y
shown in FIG. 6, the distance in which the charge moves on the surface 111U is half the
dimension (T2) of the vibrating portion 110 in the Y axis direction and one side of the
rectangular region 112t. The difference with the half dimension (T4) is short. Therefore, the time
required for the predetermined amount of charge to move from the terminal 531 to the point P1
in the electrostatic speaker 1 is the same as the amount of charge from the terminals 531x and
531y in the electrostatic speaker including the vibrating films 10x and 10y. Compared to the
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time required to move to the points P1x and P1y, the amount of charge of this amount is
generally shortened by the time required to move the above-described differences. The points P1,
P1x, and P1y indicate positions where the time required for the predetermined amount of charge
moving from each terminal to reach in each electrostatic type speaker is the largest. That is, in
the electrostatic speaker 1, the time required for the predetermined amount of charge to spread
to the vibrating portion 110 is shorter than that of the electrostatic speaker including the
vibrating films 10x and 10y. (Ie, the charging time constant of the vibrating portion 110 also
decreases).
[0023]
As described above, in the electrostatic speaker 1, by setting the surface resistivity of the surface
101 of the vibrating membrane 10 to 1 × 10 <11> Ω / □, it is possible to use a vibrating
membrane having a surface resistivity smaller than this. Also, the charge does not easily move on
the surface 111, and the occurrence of discharge between the electrode 40 and the vibrating film
10 can be reduced. Further, in the electrostatic speaker 1, as compared with the electrostatic
speaker in which the adhesive member 20 having the conductive layer 210 is not provided on
the surface 111, the time required for the vibrating membrane 10 to become a bias potential by
the bias voltage is shortened. (Ie, the charging time constant can be reduced). This time is, in
other words, the time required to use the electrostatic speaker 1.
[0024]
Further, in the electrostatic speaker 1, the insulating layer 220 is provided on the side (electrode
40 side) opposite to the side in contact with the surface 111 with respect to the conductive layer
210, and the conductive layer 210 is an insulating layer. It is fixed to the cushioning material 30
via the layer 220. Thereby, even if the cushioning material 30 is deformed by the vibration of the
vibrating membrane 10 and the vibrating membrane 10 and the electrode 40 come in contact
with each other through the porous inside of the cushioning material 30, short circuit can be
prevented. Further, in the electrostatic speaker 1, the entire conductor and the surface 111 are
bonded. When there is a portion where the vibrating membrane and the bonding member 20 are
not bonded, when the vibrating membrane 10 vibrates, in that portion, when the vibrating
membrane 10 and the bonding member 20 once separate and come in contact again, a collision
noise occurs. Although this may occur, in the electrostatic speaker 1, the entire conductor and
the surface 111 are bonded, so that such a collision noise is not generated.
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[0025]
[Modifications] The embodiment described above is only an example of implementation of the
present invention, and various applications and modifications are possible as follows, and it is
also possible to combine them as required.
[0026]
(Modification 1) In the embodiment described above, the vibrating membrane 10 has a surface
resistivity of 1 × 10 <11> Ω / □ or more, but the surface resistivity is more than this. Even
small ones may be used.
In the electrostatic speaker, the possibility of the occurrence of discharge between the electrode
and the vibrating membrane changes depending on the magnitude of the voltage applied
between them, the distance between them, the state of air, and the like. Even if the surface
resistivity of the vibrating membrane 10 is 1 × 10 <11> Ω / □, the above-described abnormal
noise may not occur depending on other conditions. In short, the vibrating membrane may have
a surface resistivity larger than the volume resistivity (or surface resistivity) of the conductive
layer 210. In other words, the vibrating membrane may be provided with the above-described
conductive layer in which the predetermined amount of charge moves faster than the surface of
the vibrating membrane so as to be in contact with the surface. Thus, the conductive layer 210
can move a predetermined amount of charges faster than the surface 101, and the time until the
surface 101 is charged by the charges supplied via the conductive layer 210 can be shortened. In
the electrostatic type speaker, the occurrence of the discharge is reduced as the surface
resistivity of the vibrating film is larger unless the other conditions are changed. Therefore, the
surface resistivity is preferably 1 × 10 <11>. It is good that it is more than Ω / □.
[0027]
(Modification 2) In the embodiment described above, the adhesive member 20 is formed as a
member in the shape shown in FIG. 4 and then adhered to the vibrating membrane 10 and the
cushion material 30 respectively, but it is possible to use other methods It may be adhered. For
example, it may be a double-sided tape having a conductive layer and an insulating layer as in the
adhesive member 20, or an adhesive that functions as a conductive layer is applied to the
vibrating film 10, and an adhesive that functions as an insulating layer is applied thereon. It may
be applied and adhered to the cushion material 30. The conductive layer 210 and the insulating
layer 220 may be formed as separate members (for example, a conductive member and an
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insulating member). In this case, the conductive film is bonded to the surface 111 of the vibrating
portion 110 on the vibrating film 10 side, and bonded to the insulating member on the electrode
40 side. In addition, the insulating member has a condition that the electrode 40 side is adhered
to the cushion material 30.
[0028]
(Modification 3) In the embodiment described above, the whole of the bonding member 20 is
bonded to the vibrating portion 110, but only a part of the bonding member 20 may be bonded
or may not be bonded at all. In short, the bonding member 20 may be provided to be in contact
with the surface 111 of the vibrating portion 110 when the vibrating portion 110 is not
vibrating. As a result, charge is supplied from the conductive layer 210 to the surface 111, and
the charging time constant of the vibrating portion 110 is smaller than in the case where the
adhesive member 20 is not provided.
[0029]
(Modification 4) Although the adhesion member 20 has the insulating layer 220 in the abovedescribed embodiment, it may be an adhesion member that does not have this. In this case, the
bonding member is a member formed only of the conductive layer 210 (conductive member).
The adhesive member, that is, the conductive layer 210 is fixed to the cushion 30 by directly
adhering to the cushion 30. Even in this case, the adhesive member functions as a member that
reduces the charging time constant as the conductive layer 210 supplies the charge to the
surface 111 of the vibrating portion 110. In short, in the electrostatic speaker, the conductive
member may be provided in contact with the surface 111 to move the predetermined amount of
charges faster than the surface 111.
[0030]
(Modification 5) In the embodiment described above, the conductive layer 210 is a metal having
a volume resistivity of 1 × 10 <-4> Ω cm or less, but it is not limited to this. For example, the
conductive layer 210 included in the bonding member may be formed of a material other than a
metal, and may have a volume resistivity greater than 1 × 10 <-4> Ωcm. In short, the conductive
layer 210 only needs to have conductivity such that a predetermined amount of charge moves
faster when the same voltage is applied as compared to the surface 111 of the vibrating portion
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110. Thereby, the charging time constant of the vibrating portion 110 can be made smaller than
in the case where the adhesive member is not provided.
[0031]
(Modification 6) Although the rectangular area 112t is formed on the surface 111 of the
vibrating portion 110 in the above-described embodiment, it may not be formed. For example, on
the surface 111, linear adhesive members may be provided side by side so as not to overlap each
other. FIG. 8 is a view showing a cross section of the electrostatic loudspeaker 1a according to
the present modification. In FIG. 7, as in the cross section shown in FIG. 4, a cross section of the
conductive layer 210Ua included in the electrostatic speaker 1a is shown. The conductive layer
210Ua is formed in a straight line along the Y-axis direction. Further, on the surface 111U, a
plurality (9) of conductive layers 210Ua are provided spaced apart by a length T1 in the X-axis
direction. In this case, the position on the surface 111 where the distance from the conductive
layer 210Ua is the largest is a linear region L1 located at an equal distance from each conductive
layer 210Ua (ie, T4 which is half of T1). In FIG. 8, one of the plurality of areas L1 is shown as an
example. In the region L1, the distance from the conductive layer 210Ua is T4 at any position,
and the charge time constant of the vibrating portion 110 can be reduced as described with
reference to FIG.
[0032]
(Modification 7) Aside from the adhesion member 20Ua having the conductive layer 210Ua
according to the modification 6, an adhesion member not having the conductive layer may be
overlapped. FIG. 9 is a view showing a cross section of an electrostatic loudspeaker 1b according
to this modification. The electrostatic loudspeaker 1b has the same configuration as the
electrostatic loudspeaker 1a shown in FIG. 8 except that it has an adhesive member 230Ub not
having a conductive layer. Note that FIG. 9 shows a cross section of the bonding member 230Ub,
unlike FIG. The bonding members 230Ub are a plurality of linear members, and are disposed
closer to the cushion member 30 than the bonding members 230Ua, crossing the bonding
members 230Ua. Thus, the adhesive members provided on the surface 111U may include those
not having the conductive layer. Even in this case, the charge time constant can be reduced due
to the charge supplied from the adhesive member having the conductive layer (in this example,
the adhesive member 20Ua) as compared with the case where the adhesive member is not
provided.
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[0033]
(Modification 8) The bonding members are provided on the surface 111U so as to be in the form
of a lattice in the embodiment described above, and a plurality of lines in the Y axis direction in
Modification 7; It may be provided. FIG. 10 is a view showing a cross section of an electrostatic
loudspeaker 1c according to the present modification. In the electrostatic loudspeaker 1c, only
the shape of the connection member including the conductive layer 210Uc differs from the
electrostatic loudspeaker 1 according to the embodiment. The conductive layer 210Uc is
provided on the surface 111U with one end in contact with the terminal 531U and the other end
facing the center of the vibrating portion 110 so as to draw a spiral. In this case, the position
where the distance from the conductive layer 210Uc is the largest in the vibrating portion 110 is
a linear region at an equal distance (T5 shown in FIG. 10) from the conductive layers 210Uc on
both sides in the region sandwiched by the conductive layers 210Uc. It is L2. In FIG. 10, one of
the plurality of regions L2 is shown as an example. The region L2 has a distance T5 from the
conductive layer 210Uc at any position, and is shorter than the lengths T2 and T3 shown in FIG.
Similarly, the charging time constant of the vibrating unit 110 can be reduced.
[0034]
FIG. 11 is a view showing a cross section of an electrostatic loudspeaker 1d according to the
present modification. In electrostatic speaker 1d, an adhesive member including conductive
layers 210Ud formed in a plurality of straight lines along a direction oblique to the Y-axis
direction and the X-axis direction is provided on surface 111 of vibrating portion 110. ing. In
addition to the terminal 531U, the fixed portion 122 is provided with a terminal 532U on the
surface 111. Each conductive layer 210Ud is provided to be electrically connected to either of
the terminals 531U or 132U. In this figure, a region L3 corresponding to the region L2 in FIG. 10
and a distance T6 corresponding to the distance T5 are shown. Since the distance T6 is shorter
than the lengths T2 and T3 shown in FIG. 6, the charging time constant of the vibrating portion
110 can be reduced in the electrostatic speaker 1d as described with reference to FIG.
[0035]
In short, in the electrostatic speaker, the adhesion member formed in a linear shape is provided
on the surface 111 of the vibrating portion 110, and the adhesion member is the distance
between the position on the surface 111 most distant from the self member and the self member
Should be arranged so as to fall within the defined range. The range of the distance referred to
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here is at least shorter than the distance between the terminal provided on the vibrating film 10
(such as the terminal 531 described above) and the position on the surface 111 of the vibrating
portion 110 that is most distant from the terminal Just do it. Further, the number of bonding
members may be one or plural. In any case, desirably, the directions in which the adhesive
members extend are the same (that is, portions parallel to each other), hereinafter referred to as
"parallel portions". In the case of), it is preferable that their parallel parts be arranged at equal
intervals. The charging time constant of the vibration unit 110 described above depends on the
time required for the predetermined amount of charge to reach the position farthest from the
adhesive member. For this reason, when the distance between the parallel parts is not constant,
the place where the distance between the parallel parts is narrow does not contribute to
shortening the charging time constant. In other words, even if the distance between the parallel
portions is made equal to that at a wider distance, the charging time constant does not change.
And the area which the adhesion member covers the surface 111 of the vibration part 110 can
be made small, so that the space | interval of parallel parts is enlarged. Here, as the area of the
portion covered with the adhesive member on the surface 111 is increased, the surface 111
exposed to the electrode 40 decreases and the magnitude of the electrostatic attraction acting
between the electrode 40 and the vibrating film 10 Depends on the electrical characteristics of
the adhesive member. This state may affect the manner of vibration of the diaphragm 10, that is,
the characteristics of the sound output. Such effects can be reduced by configuring the adhesive
member as described above.
[0036]
Moreover, in the embodiment and modification which were mentioned above, although the
conductive layer was linear at all, the part which is not linear may be included. For example, in
the conductive layer, the portion connected to the terminal may be plate-shaped, or a part of the
portion in contact with the vibrating portion may be plate-shaped. In addition, the conductive
layer may not include a linear portion. For example, the conductive layer may be provided in
such a shape that the rectangular rectangular area 112t shown in FIG. 4 is a circular area. In this
case, desirably, the bonding member has an area such that the above-mentioned characteristics
affected by the covering member 111 covering the surface 111 of the vibrating portion 110 fall
within the range permitted as an electrostatic speaker, and It is preferable that the charging time
constant of the vibration unit 110 be smaller than that in the case where the (conductive layer in
particular) is not provided. Therefore, the bonding member may have, for example, a linear
conductive layer or a conductive layer including a linear portion so that the surface 111 is easily
exposed to the electrode 40 side. Also, in any case, the conductive layer included in the adhesive
member has a surface 111 of the vibrating portion 110 with a predetermined charging time
constant at the surface 111 of the vibrating portion 110 and a distance from the position farthest
from the conductive layer to the conductive layer. It is preferable that they be provided so as to
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be equal to or less than the case where 111 is a bias potential. In the electrostatic speaker, by
providing such a conductive layer, the charging time constant of the vibrating portion 110 can be
made shorter than a predetermined charging time constant. For example, in an experiment by the
inventor, when the distance is 50 mm or less, the charge time constant is several tens of seconds,
and can be kept within the intended charge time constant.
[0037]
More specifically, the points P1 and the regions L1, L2 and L3 shown in the above-described
embodiment and modification are the distances T4, T4, T5 and T6 from the respective
conductive layers T2 and T3 shown in FIG. Although it is shorter than this, it has been confirmed
by the experiments of the inventors that if this dimension is 50 mm or less, the capacitor formed
by the vibrating membrane and the electrode is charged in several tens of seconds. Therefore, it
is desirable that the bonding members be provided such that the distance from the conductive
layer to the position farthest from the conductive layer on the surface 111 is 50 mm or less.
[0038]
(Modification 9) In the electrostatic loudspeaker 1, the electrical connection between the
conductive layer 210 and the terminal 531 may be disconnected after the surface 111 of the
vibrating portion 110 becomes a bias potential. FIG. 12 is a diagram showing an electrical
configuration of an electrostatic loudspeaker 1e according to the present modification. The
electrical configuration shown in FIG. 12 differs from that shown in FIG. 5 only in the
configuration of the terminals connected to the vibrating membrane 10 and the adhesive
member 20. The electrostatic loudspeaker 1e includes terminals 533U and 533L for connecting
the vibrating membrane 10 and the bias power supply 530, and terminals 534U and 534L for
connecting the adhesive member 20 and the bias power supply 530. The terminals 534U and
534L respectively have switches 535U and 535L for switching the presence / absence (on / off)
of electrical connection. In addition, the vibration unit 110 is provided with a sensor of a
measuring device (not shown) that measures the potential of the surface 111. The switch 535 is
electrically connected (turned on) when power is supplied to the electrostatic speaker 1e, and is
disconnected when the measurement result by the measuring apparatus reaches the bias
potential described above (see FIG. Works as if it were turned off). In such an electrostatic
speaker 1 e, after the surface 111 becomes a bias potential, the charge does not move from the
conductive layer 210 to the vibrating portion 110 via the terminal 534 as compared with the
case where the switch 535 is not provided. , Charge transfer on the surface 111 is delayed.
Thereby, compared with the case where the switch 535 is not provided, the electrostatic speaker
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1 e can suppress the occurrence of discharge in the case where the potential of the surface 111
fluctuates at the time of sound emission.
[0039]
(Modification 10) In the embodiment described above, the electrostatic speaker 1 has a push-pull
configuration in which the diaphragm 10 is sandwiched between the pair of electrodes 40.
However, the configuration of the electrostatic speaker 1 is not limited to this configuration. It is
not limited. For example, a single-type configuration in which one cushion material 30 is
sandwiched between the vibrating membrane 10 and one electrode 40 may be used. FIG. 13 is an
external view of an electrostatic speaker 1 f according to this modification. The electrostatic
loudspeaker 1 f differs from the electrostatic loudspeaker 1 in that the adhesive 1 f has one
bonding member 20 f, one cushioning material 30 f and one electrode 40 f. The electrostatic
speaker 1f emits sound when the vibrating membrane 10 vibrates due to a change in
electrostatic attraction acting between the vibrating membrane 10 and the electrode 40f. Even in
this case, since the bias voltage is applied to the surface of the electrostatic speaker 1f through
the conductive layer of the adhesive member 20f, the charging time constant is made smaller
than when the adhesive member 20f is not provided. It can be made smaller.
[0040]
(Modification 11) In the embodiment described above, the bonding member includes the linear
insulating layer 220 having the same width as the conductive layer 210. However, the present
invention is not limited thereto. A plate having a width wider than the conductive layer 210 The
insulating layer may be provided. FIG. 14 is an enlarged view of the periphery of the bonding
member 20g according to the present modification. The bonding member 20g has a conductive
layer 210 (210U, 210L in the figure) and an insulating layer 220g (220Ug, 220Lg in the figure).
In the insulating layer 220g, the width in the Y-axis direction is wider than the conductive layer
210, and a portion of the surface on the vibrating film 10 side where the conductive layer 210 is
not vapor-deposited protrudes toward the vibrating film 10 and adheres to the surface 101 .
Therefore, the whole of the conductive layer 210, including the side surface (the surface normal
to the Y-axis direction), is covered with the insulating layer 220g. Thereby, even if the vibrating
portion 110 vibrates and the conductive layer 210 and the electrode 40 approach each other, the
insulating layer 220 g is always sandwiched between the side surface of the conductive layer
210 and the electrode 40, A short circuit or a discharge can be prevented from occurring
between this side surface and the electrode 40.
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[0041]
(Modification 12) In the embodiment described above, the terminal 531 is in the form of a
straight line in contact with the surface 101 and the conductive layer 210. However, the present
invention is not limited to this. It may be in contact with these at a point. In short, this terminal
only needs to be capable of applying a voltage to the surface 101 and the conductive layer 210,
and the larger the area in contact with these, the more the amount of charge that can be supplied
per unit time increases. The constant can be reduced.
[0042]
(Modification 13) In the above-described embodiment, the electrostatic speaker 1 has a size such
that one side of a rectangle is approximately 500 mm when viewed from the Z-axis direction, but
even a smaller one is larger It may be. For example, the length in the Y-axis direction may be
several meters, and the length in the X-axis direction may be several tens cm. In addition,
although the electrode 40, the cushion member 30, and the vibrating membrane 10 have a
rectangular shape as viewed from the Z-axis direction in the above-described embodiment, the
present invention is not limited to this. It may be in the form of
[0043]
(Modification 14) In the embodiment described above, both ends of the vibrating film 10 in the
Y-axis direction are fixed to the electrode 40 by the spacer 35, but only one end may be fixed.
The spacer 40 may not be fixed to the electrode 40 without providing the spacer 35. In the latter
case, the terminal 531 is desirably provided closer to the end of the surface 101 because the
entire vibrating membrane 10 vibrates. Further, the terminal 531 is fixed to, for example, the
cushion member 30 without directly contacting the terminal 531 with the surface 101. Then, a
part of the conductive layer 210 may be separated from the surface 101 without being bonded
to the surface 101, and a part of the conductive layer 210 may be connected to the terminal 531.
Thus, the influence of the terminal 531 on vibration can be reduced. In this case, it is desirable
that the conductive layer 210 be provided on the surface of the vibrating portion of the vibrating
membrane 10 (in this case, the entire surface 101 of the vibrating membrane 10). As a result, the
charging time constant can be reduced in the entire vibrating portion of the vibrating membrane
10. In other words, it is desirable that the conductive layer 210 be provided at least on the
surface of the vibrating portion of the vibrating membrane 10.
18-04-2019
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[0044]
(Modification 15) In the embodiment and the modification described above, an example has been
described in which the electrostatic electroacoustic transducer is applied to an electrostatic
speaker that converts an acoustic signal (electric signal) into sound (acoustic). Electrostatic
transducers of the electrostatic type may be applied to electrostatic microphones that convert
sound (sounds) into acoustic signals (electrical signals). FIG. 15 is a diagram showing the
electrical configuration of an electrostatic microphone 1M according to this modification. In the
configuration shown in FIG. 15, the electrostatic microphone 1M has the same configuration as
the above-described electrostatic speaker 1 of FIG. The driving unit 500M is connected to the
electrostatic microphone 1M. The drive unit 500M has the same configuration as the drive unit
500 of FIG. 5 described above, but the transformation ratio of the transformer 510 and the
resistance values of the resistors R1 to R4 may be appropriately adjusted. Further, in the drive
unit 500M, the direction of the acoustic signal input to and output from the amplification unit
520 is opposite to that in FIG. 5, and the acoustic signal is output in the direction of the arrow
A2.
[0045]
When a sound wave is generated outside the electrostatic microphone 1M, the vibration film 10
is vibrated by the sound wave, and the distance between the vibration film 10 and the electrode
40 changes according to the vibration, so the vibration is generated. A change in the capacitance
between the membrane 10 and the electrode 40 will occur. Since the vibrating membrane 10 is
connected to the bias power supply 530 via the resistor R4, the charge remains constant even if
the capacitance changes. When the vibrating membrane 10 vibrates, the distance between the
vibrating membrane 10 and the electrode 40 becomes short (or long), whereby the capacitance
between the vibrating membrane 10 and the electrode 40 becomes large (or small). In this case,
the potential of the electrode 40 is changed such that the potential difference between the
vibrating membrane 10 and the electrode 40 is small (or large). This change in the potential of
the electrode 40 is supplied to the transformer 510 as a voltage output proportional to the
displacement of the vibration, that is, as an acoustic signal via the terminal Q4 and the terminal
Q5. Then, the transformer 510 transforms this acoustic signal and inputs it to the amplification
unit 520, and the amplification unit 520 amplifies this acoustic signal and outputs it to a speaker,
a computer or the like (not shown).
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[0046]
According to this modification, generation of discharge between the electrode 40 and the
vibrating film 10 is reduced rather than using a vibrating film having a surface resistivity smaller
than that of the vibrating film 10 as in the embodiment described above. Can. Further, as
compared with an electrostatic microphone in which the adhesive member 20 having the
conductive layer 210 is not provided on the surface 111, the time required for the electrostatic
microphone to be available, which is an electrostatic electroacoustic transducer, is shortened. be
able to.
[0047]
By the way, although the electrostatic microphone 1 </ b> M supplies the acoustic signal to the
transformer 510 of the drive unit 500 </ b> M in this modification, the acoustic signal may be
supplied to other than the transformer 510. For example, when the impedance of the
transformer 510 is low, the load characteristics of the electrostatic microphone 1M may lower
the frequency characteristics at low frequencies. In such a case, the electrostatic microphone 1 </
b> M may suppress the deterioration of the frequency characteristic at a low frequency by
supplying the acoustic signal to the amplification unit 520 whose impedance is higher than that
of the transformer 510.
[0048]
DESCRIPTION OF SYMBOLS 1 ... electrostatic type speaker (electroacoustic transducer of
electrostatic type), 10 ... vibrating film, 20 ... adhesive member, 30 ... cushion material, 40 ...
electrode, 101, 111 ... surface, 110 ... vibration part, 121, 122 ... fixed portion 210 conductive
layer 220 insulating layer 301 surface 500 drive portion 510 transformer 520 amplification
portion 530 bias power supply 531 532 533 534 terminals 535 535 Switch, 1 M: electrostatic
microphone (electro-acoustic transducer of electrostatic type), 500 M: driving unit
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