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JP2008187588

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This translation is machine-generated. It cannot be guaranteed that it is intelligible, accurate,
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DESCRIPTION JP2008187588
An electrical coupling between a noise cancellation signal and a musical tone signal is shallow,
the influence of the noise cancellation signal on the musical tone signal is reduced, and the
power amplification circuit of the noise cancellation signal and the power amplification circuit of
the musical tone signal become loads. Even without the sound quality is good, even without the
internal battery, you get headphones that perform noise cancellation operation. A speaker unit 5
driven by a tone signal, a power generation body generating electric power according to the
noise of the periphery, and a piezoelectric element 30 driving a frame 6 of the speaker unit 5 by
a power generation signal of the power generation body. The power generation body is a second
piezoelectric element 32 for driving the frame 6, and a sound receiving member 36 that vibrates
according to the surrounding noise is fixed to one surface of the second piezoelectric element 32.
The other surface of the second piezoelectric element 32 is a headphone housing 20 The second
piezoelectric element 32 generates power in accordance with the vibration of the sound receiving
member 36. [Selected figure] Figure 1
ヘッドホン
[0001]
The present invention relates to a headphone capable of reducing the sound pressure of noise
entering from the outside.
[0002]
With the spread of portable music players, headphones for personally listening to musical tones
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1
are also widely spread.
Portable music players are often used in towns with high noise levels, in vehicles such as trains
and buses, and external noises can be heard through headphones as well as musical tones
reproduced by the player. When listening to musical tones in the noise, the musical tones may be
overwhelmed by external noise, so the user increases the volume to listen to the musical tones,
raises the volume too much, and the sound leaks from the headphones to the surrounding
people. It can make you feel unpleasant. In addition, even if high-quality tones are reproduced by
headphones, the noise coming from the outside affects the tones, which may deteriorate the
quality of reproduced sounds that the user can hear.
[0003]
Therefore, noise cancellation type headphones in which the sound pressure of the noise is
reduced by canceling out the noise coming from the outside and the user's ear can almost hear
only the musical tone are becoming popular. The principle of the noise cancellation type
headphone is to detect noise coming into the headphone with a microphone, to generate
cancellation noise of the opposite phase to the detected noise signal, and to cancel the noise by
the cancellation noise. A typical noise cancellation type headphone is equipped with one speaker
and hence one voice coil. The noise signal collected by the microphone and converted into an
electrical signal is further passed through a filter or a delay circuit to generate a noise
cancellation signal in reverse phase to the noise signal, and this noise cancellation signal and the
desired musical tone signal are synthesized (addition After that, the power is amplified and input
to one voice coil of the one speaker.
[0004]
The sound output from the speaker is a synthesized signal of the noise cancellation signal and
the musical tone signal converted to sound, and the sound converted from the noise cancellation
signal cancels all or part of the external noise entering the headphones. The voice that comes
into the user's ear is almost only the voice into which the musical tone signal has been converted.
Alternatively, there is a method in which the noise cancel signal and the musical tone signal are
individually amplified in power, and then the noise cancel signal and the musical tone signal are
synthesized and the one voice coil is driven by the synthesized signal. However, since the two
power amplifiers are connected in series or in parallel to the voice coil, there is a disadvantage
that the two power amplifiers load each other.
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2
[0005]
FIG. 2 shows an example of a conventional noise cancellation type headphone. In FIG. 2, the
flange member 2 is coupled to the open end of the bottomed cylindrical headphone housing 1,
and the head pad 3 is fixed to the outer surface (left side in FIG. 2) of the flange member 2. .
When the user uses this headphone, the outer end face of the head pad 3 abuts on the side of the
head of the user, and the user's ear 13 is positioned in the space surrounded by the head pad 3.
The flange member 2 has a window hole at the center and is formed in a ring shape, and the
headphone unit 5 is fixed to the inner surface (right surface in FIG. 2) of the flange member 2 so
as to close the window hole. There is. The headphone unit 5 includes a flat petri dish-like base 6,
a flatter petri dish-like yoke 7 smaller in diameter than the base 6 fitted to the inner bottom of
the base 6, and a flat attached to the center of the inner bottom of the yoke 7. The magnet 8 has
a plate-like pole piece 9 fixed to the front end face of the magnet 8, a voice coil 10 wound in a
cylindrical shape, and a dome-shaped diaphragm 12.
[0006]
The open side end face of the petri dish-like yoke 7 and the end face of the pole piece 9 are in
substantially the same plane, and a ring is formed between the outer peripheral face of the pole
piece 9 and the inner peripheral face on the open end side of the yoke 7 There is a gap, and the
voice coil 10 is in the gap. A magnetic field originating from the magnet 8 is formed in the ringshaped gap, and the voice coil 10 is present in the magnetic field. The diaphragm 12 is formed
with an edge portion having a cross-sectional arched shape so as to surround a dome portion at
the center portion, the outer periphery of the edge portion is fixed to the base 6, and the
diaphragm 12 is supported so as to vibrate in the front-rear direction. One end of the voice coil
10 is fixed to the boundary between the central dome portion and the edge portion of the
diaphragm 12, and the voice coil 10 is supported so as not to contact the yoke 7 or the pole
piece 9. A musical tone signal is input from the power amplifier (driver) of an external player to
the voice coil 10, and the voice coil 10 is driven back and forth according to the musical tone
signal. Be This sound reaches the user's ear 13 surrounded by the head pad 3 through the
central window hole of the flange member 2.
[0007]
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The above description is for a general headphone, and in the noise cancellation type headphone,
in the above configuration, a microphone for detecting surrounding noise and a noise
cancellation signal of the reverse phase of the noise detected by this microphone are generated A
signal processing circuit such as a synthesis circuit which synthesizes (adds) the generated noise
cancellation signal with the musical tone signal and inputs it to the voice coil 10 is added.
Various devices are applied to the position of the microphone and the configuration of the signal
processing circuit. In FIG. 2, M <b> 1 to M <b> 4 indicate various examples of the arrangement
position of the noise detection microphone. M1 is an example in which the microphone is
disposed inside the headphone, and is an example in which the front side of the microphone is
disposed in the space immediately before the diaphragm 12 toward the outside of the headphone
(left side in FIG. 2). M2 to M4 are examples in which the microphones are disposed outside the
headphones, M2 is disposed on the upper part of the flange member 2, M3 is disposed on the
lower part of the flange member 2, and M4 is disposed on the outer surface of the housing 1.
[0008]
In the noise cancellation type headphone, various measures are made to cancel external noise
more effectively. For example, the headphone described in Patent Document 1 has a small cavity
between the diaphragm (the diaphragm of the speaker) and the ear canal in order to reduce noise
while having a relatively constant frequency response, and the diaphragm And a feedback signal
based on the output of the microphone is coupled to the input electrical signal reproduced by the
headphone, and the combined signal is power amplified to drive the diaphragm. In the
conventional example shown in FIG. 2, the microphone is disposed at a position indicated by
reference numeral M1.
[0009]
In Patent Document 2, in order to enhance the noise cancellation effect, the synthesized sound in
the vicinity of the outer ear is picked up by a microphone, the synthesized sound is phaseinverted, and the phase-inverted speech signal and the musical tone signal from the sound source
are The invention relating to an active noise eraser is described which performs addition by an
addition circuit, adds a tone signal from a sound source to the addition result by a second
addition circuit, amplifies the addition result, and outputs the result from a speaker near the ear
canal. It is done. Patent Document 3 describes a headphone device in which a microphone unit is
disposed via a vibration isolation member in a headphone unit used for active noise control
headphones in order to enhance a noise cancellation effect. Although the inventions described in
Patent Documents 1 and 2 and the invention described in Patent Document 3 aim to improve the
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performance of the noise cancellation type headphone, they can not achieve the object of the
present invention described later. Also, the technical ideas are different.
[0010]
As known inventions related to the present invention, an active noise reduction signal processing
path for reducing active noise, a talk through signal processing path for providing a talk through
function, an active noise reduction signal processing path and a talk through signal processing
path A noise reduction headset provided with a switching element for disabling one or both has
been proposed (see Patent Document 4). Patent Document 4 describes that the switching element
disables the noise reduction signal path when the power supplied to the switching element is
insufficient for operating the noise reduction signal path. In this regard, although related to a
part of the effects of the present invention described later, the means for solving the problem is
completely different from the present invention.
[0011]
JP-A-6-343195 JP-A-9-54592 JP-A 5-36991 JP-A 2006-14307
[0012]
An object of the present invention is to solve the problems of the conventional noise cancellation
headphone.
That is, in the conventional noise cancellation headphone, since the signal for canceling noise
and the musical tone signal are electrically synthesized and combined, and the signal passes
through the signal processing circuit, the musical tone signal is affected by the noise canceling
signal and the sound quality is improved. to degrade. Further, when it is bad, the sound quality
difference occurs between the case where the noise cancellation operation is performed and the
case where the operation is not performed, which causes the user to feel discomfort. Further,
since the conventional noise cancellation headphone has a built-in power supply battery for
performing the noise cancellation operation, there is a problem that the weight of the headphone
becomes heavy and a problem that the noise cancellation can not be performed when the power
supply battery is exhausted.
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[0013]
The present invention reduces the influence of the noise cancellation signal on the musical tone
signal by making the electrical coupling relationship including the magnetic coupling between
the noise canceling signal and the musical tone signal and the electrostatic coupling as shallow as
possible, thereby reducing the noise cancellation signal. An object of the present invention is to
provide a noise cancellation type headphone in which the power amplification circuit and the
power amplification circuit for a musical tone signal do not become loads to each other, and
additionally, the sound quality is excellent. The present invention also enables noise cancellation
without using a built-in battery, and a headphone of a noise cancellation method that can solve
the problem of heavy weight and the problem of being unable to cancel noise due to battery
exhaustion as in the prior art. Intended to provide.
[0014]
The present invention comprises a speaker unit driven by a tone signal, a power generation body
generating electric power according to the noise of the surroundings, and a piezoelectric element
driving a frame of the speaker unit by a signal generated by the power generation body. The
most major feature. The power generation body is a second piezoelectric element different from
the piezoelectric element that drives the frame, and a sound receiving member that vibrates
according to the surrounding noise is fixed to one surface of the second piezoelectric element,
and the other surface of the second piezoelectric element is a headphone housing Preferably, the
second piezoelectric element is configured to generate electricity in accordance with the
vibration of the sound receiving member.
[0015]
The speaker unit reproduces only musical tone signals input from a sound source such as a
player. The power generator generates power according to the noise in the vicinity, and drives
the piezoelectric element by this power generation signal. By driving the piezoelectric element,
the frame of the speaker unit is mechanically vibrated. If the sound generated by this mechanical
vibration is in opposite phase to the noise intruding into the headphone, the noise infiltrating
into the headphone can be canceled and the user's ear, It is possible to transmit the reproduced
sound of the tone signal without noise or less noise.
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[0016]
The piezoelectric element for noise cancellation and the speaker unit driven by the tone signal
are equivalent to being mechanically connected in series in the frame of the speaker unit. Since
the diaphragm of the speaker unit is extremely movable, the acousto-mechanical impedance of
the speaker unit is low. On the other hand, the piezoelectric element is made of, for example,
piezoelectric ceramic, and the material itself is hard and hard to move, and the acoustomechanical impedance is high. Therefore, it is a structure equivalent to the speaker unit being
mechanically connected in series to the piezoelectric element having high acousto-mechanical
impedance. On the other hand, since the electrical drive system of the speaker unit and the
electrical drive system of the piezoelectric element are electrically separated and the electrical
coupling is shallow, the musical tone signal is less affected by the noise cancellation signal, and
the sound quality is high. Can reproduce the tone signal.
[0017]
The piezoelectric element for noise cancellation is driven by the power generation signal from
the power generation body according to the surrounding noise, and thus does not require a
power supply for the noise cancellation operation. Therefore, it is not necessary to incorporate a
power supply battery for noise cancellation in the headphones, and it is possible to reduce the
weight of the headphones and eliminate the problem that the noise cancellation operation can
not be performed due to the battery consumption. If the sound insulation effect of the
headphones is enhanced, the driving force of the piezoelectric element for canceling the noise
may be small, and hence the output of the power generator may be small.
[0018]
Hereinafter, an embodiment of a headphone according to the present invention will be described
with reference to FIG. The same components as in the conventional headphone shown in FIG. 2
are denoted by the same reference numerals.
[0019]
In FIG. 1, the tubular headphone housing 20 has a partition wall 21 at an axial intermediate
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portion, and the front side (left side in FIG. 1) and the rear side of the partition wall 21 are
cylindrical portions 22 and 24, respectively. The headphone unit 5 is incorporated in the front
cylindrical portion 22, and the power generator 32 that generates electric power according to
the surrounding noise is incorporated in the rear cylindrical portion 24. A ring-shaped head pad
3 is fixed to the open end of the front cylindrical portion 22. When the user uses this headphone,
the outer end face of the head pad 3 abuts on the side of the head of the user, and the user's ear
13 is positioned in the space surrounded by the head pad 3.
[0020]
The headphone unit 5 is fixed to the inside of the headphone housing 20 via a ring-shaped
support 35. The headphone unit 5 includes a flat petri dish-like frame 6, a flatter petri dish-like
yoke 7 smaller in diameter than the frame 6 fitted to the inner bottom of the frame 6, and a flat
fixed to the center of the inner bottom of the yoke 7. The magnet 8 has a plate-like pole piece 9
fixed to the end face of the magnet 8, a voice coil 10 wound in a cylindrical shape, and a domeshaped diaphragm 12. The outer peripheral side front end (left end in FIG. 1) of the frame 6 of
the headphone unit 5 is circular, and the inner peripheral side rear end surface of the support 35
is bonded to this front end surface by adhesion or the like. The cross-sectional shape of the
support 35 is arched, and the outer peripheral surface of the support 35 is fixed to the inner
peripheral surface of the headphone housing 20 by adhesion or other appropriate means. The
support 35 is made of a material that is flexible and hard to pass sound waves so as to allow the
headphone unit 5 to move back and forth relative to the headphone housing 20 by the expansion
and contraction of the piezoelectric element 30 described later. There is.
[0021]
An open side end face of the petri dish-like yoke 7 and an end face of the pole piece 9 are in
substantially the same plane, and a ring-shaped gap is formed between the outer peripheral face
of the pole piece 9 and the open end side inner peripheral face of the yoke 7 The voice coil 10 is
in the gap. A magnetic field originating from the magnet 8 is formed in the ring-like gap, and a
voice coil 10 in which a thin conductive wire is wound in a cylindrical shape is present in the
magnetic field. The diaphragm 12 is formed with an edge portion having a cross-sectional arched
shape so as to surround a dome portion at the center portion, the outer periphery of the edge
portion is fixed to the frame 6, and the diaphragm 12 is supported so as to vibrate in the frontrear direction. One end of the cylindrical voice coil 10 in the axial direction is fixed in a cantilever
manner to the boundary between the central dome portion and the edge portion of the
diaphragm 12 so that the voice coil 10 does not contact the yoke 7 or the pole piece 9 It is
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supported by the diaphragm 12. When a musical tone signal is input to the voice coil 10 from
the power amplifier (driver) of an external player, the voice coil 10 is driven back and forth
according to the musical tone signal, and the diaphragm 12 vibrates accordingly, and the voice
from the diaphragm 12 is produced. Is emitted. The headphone unit 5 is disposed with the
diaphragm 12 directed to the open end side of the tubular portion 22 of the headphone housing
20 so that the sound reaches the user's ear 13 surrounded by the head pad 3.
[0022]
One surface of the piezoelectric element 30 is fixed to the front surface side (left surface side in
FIG. 1) of the frame 6 of the speaker unit 5 and the partition wall 21 of the headphone housing
20, and the other surface of the piezoelectric element 30 is one surface of the elastic sheet 40
The other side of the elastic sheet 40 is fixed to the rear end face of the frame 6 of the speaker
unit 5. In other words, the frame 6 of the speaker unit 5 is coupled to the headphone housing 20
with the elastic sheet 40 and the piezoelectric element 30 interposed. More specifically, the
piezoelectric element 30 is disposed between the frame 6 of the speaker unit 5 and the
headphone housing 20, one surface side of the piezoelectric element 30 is coupled to the frame
6, and the other surface side of the piezoelectric element 30 is headphone An elastic sheet 40 is
interposed between the other surface of the piezoelectric element 30 and the frame 6 and
functions as a mechanical filter. The partition plate 21 and the piezoelectric element 30, the
piezoelectric element 30 and the elastic sheet 40, and the elastic sheet 40 and the frame 6 are
fixed, for example, by adhesion.
[0023]
One of the features of the embodiment of the headphone according to the present invention is
that the piezoelectric element 30 is provided and the second piezoelectric element 32 for
generating a signal to be applied to the piezoelectric element 30 is provided. The second
piezoelectric element 32 has a central hole in a ring-shaped support wall 26 integrally formed in
parallel with the partition plate 21 radially inward from the inner peripheral surface of the rear
side cylindrical portion 24 of the headphone housing 20. It is fixed so as to close the The second
piezoelectric element 32 constitutes a power generation body that generates electric power
according to the noise in the vicinity, and the sound receiving member 36 is fixed to one surface
side (the outer side surface on the right side in FIG. 1). The sound receiving member 36 has a
function of collecting noise in the vicinity of the headphones, vibrating in response to the noise,
and transmitting the vibration to the second piezoelectric element 32, so that this function can be
effectively exhibited. Made of a material that vibrates easily in response to noise, that is, a
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material that is light in weight and highly rigid. Also, the sound receiving member 36 has a
conical sound receiving portion, and the area of the sound receiving portion is larger than the
area of the surface facing the sound receiving portion of the second piezoelectric element 32,
and The vibration is devised to be concentrated and transmitted to the second piezoelectric
element 32. In the example shown in FIG. 1, the sound receiving member 36 is formed in a flat
truncated cone shape, and the flat surface of the top of the truncated cone is fixed to the second
piezoelectric element 32. The illustrated sound receiving member 36 is a member obtained by
forming a plate-like member into a truncated cone shape, but it may be a member formed
integrally with a material having a small mass, for example, a foamed resin. The outer periphery
of the second piezoelectric element 32 of the cylindrical portion 24 of the headphone housing 20
can be vibrated relative to the headphone housing 20 through the flexible edge member 38 so
that the second piezoelectric element 32 can vibrate relative to the headphone housing 20. It is
coupled to the inner circumferential surface.
[0024]
The power generation output by the second piezoelectric element 32 is electrically connected to
be applied to the piezoelectric element 30. The piezoelectric element 30 is a generally used
piezoelectric element, and vibrates (extends and contracts) in the axial direction of the
headphone housing 20 when the power generation output of the second piezoelectric element 32
is applied. It is desirable that the second power generation element 32 can generate electric
power by the vibration of air and therefore has a low mechanical impedance. For example, a
piezoelectric bimorph may be used. The piezoelectric element 30 is mechanically vibrated by
being driven by the power generation signal of the second piezoelectric element 32, and drives
the frame 6 of the speaker unit 5. The support 35 is formed into a cross-sectional arch shape,
while a material that allows mechanical vibration of the frame 6 of the speaker unit 5 with
respect to the headphone housing 20 is selected by the piezoelectric element 30 being driven
and mechanically vibrated. It is done. When the support body 35 allows the frame 6 to vibrate,
the entire speaker unit 5 is driven by the piezoelectric element 30 and vibrates.
[0025]
According to the embodiment described above, the speaker unit 5 is driven by the musical tone
signal input from the player or the like to reproduce the musical tone. The piezoelectric element
30 receives the output signal of the second piezoelectric element 32 as a power generation body
to be generated according to the surrounding noise, that is, a noise signal, and is driven by the
noise signal to vibrate. The whole vibrates. The piezoelectric element 30 and the second
07-05-2019
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piezoelectric element 32 are electrically connected such that the vibration is in the opposite
phase to the noise entering into the headphone, and the vibration caused by the driving of the
piezoelectric element 30 is This cancels all or part of the noise intruding into the headphones,
and only the musical tone reaches the user's ear, or the noise level is lowered.
[0026]
The piezoelectric element 30 driven by the noise cancellation signal and the speaker unit 5
driven by the tone signal are equivalent to being mechanically connected in series by the frame 6
of the speaker unit 5. Since the diaphragm 12 of the speaker unit 5 is configured to be extremely
movable, the acousto-mechanical impedance of the speaker unit 5 is low. On the other hand, the
piezoelectric element 30 is made of, for example, piezoelectric ceramic, and the material itself is
hard and hard to move, and the acousto-mechanical impedance is high. Therefore, it has a
structure equivalent to that in which the speaker unit 5 is mechanically connected in series to the
piezoelectric element 30 having high acousto-mechanical impedance, and the movement of the
diaphragm 12 viewed from the headphone housing 20 depends on the musical tone signal. At the
moment when the direction of vibration and the direction of vibration by the piezoelectric
element 30 coincide, the amplitude is large, and the amplitude decreases if the directions of the
two vibration are opposite to each other. In other words, the movement of the diaphragm 12 of
the speaker unit 5 by the piezoelectric element 30 and the movement of the diaphragm 12 by
the drive of the speaker unit 5 are mechanically and serially overlapped, and noise intruding into
the headphone By configuring the phase and the phase of the sound component generated by the
drive of the piezoelectric element 30 to be opposite to each other, the noise entering the
headphone is canceled by the drive of the piezoelectric element 30.
[0027]
In the embodiment shown in FIG. 1, the acoustic impedance, sound pressure, voltage, etc. of each
part are defined as follows. P1: sound pressure of noise component PL: sound pressure of noise
component entering the headphone F1: amount of force received by the sound receiving member
36 by the noise component S1: sound receiving area of the sound receiving member 36 ZPZ1:
impedance of the second piezoelectric element X1 The amount of movement of the second
piezoelectric element 32 by F1: e1: The generated voltage of the second piezoelectric element
[0028]
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The amount of force F1 received by the sound receiving member 36 by the noise component is
F1 = S1 · P1. The amount X1 of movement of the second piezoelectric element 32 by the amount
of force F1 is: X1 = (1 / jω) (F1 / ZPZ1). As the second piezoelectric element 32 moves by X1,
the voltage e1 generated by the second piezoelectric element 32 becomes e1 = AX1 (where A is a
constant).
[0029]
Since the frequency component of noise leaking between the earpad 3 and the human body and
reaching the ear is in a low frequency range, in the illustrated embodiment, between the
piezoelectric element 30 for noise cancellation and the frame 6 of the speaker unit The elastic
sheet 40 is interposed between the The elastic sheet 40 functions as a mechanical low pass filter
or high cut filter that mechanically connects the piezoelectric element 30 and the frame 6 of the
speaker unit, and effectively removes or reduces noise in a low frequency region effective for
noise cancellation. can do.
[0030]
As described above, according to the embodiment of the present invention, the electrical drive
system by the tone signal of the speaker unit 5 and the electrical drive system of the piezoelectric
element 30 for noise cancellation are electrically separated, Since the electrical connection is
shallow, the musical tone signal is less affected by the noise cancellation signal, and the musical
tone signal can be reproduced with high sound quality. The signal applied to the piezoelectric
element 30 for noise cancellation is an output signal of the second piezoelectric element 32
which generates electric power in response to the noise in the periphery, so that a noise
cancellation is possible without the need for a power supply battery for the noise cancellation
operation. The weight of headphones can be reduced. The sound receiving member 36 has a
conical sound receiving portion, the area of the sound receiving portion is larger than the area of
the second piezoelectric element 32, and the vibration of the sound receiving member 36 is
concentrated and transmitted to the second piezoelectric element 32. Therefore, the second
piezoelectric element 32 can efficiently generate a signal for canceling the ambient noise.
[0031]
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It is a longitudinal cross-sectional view which shows the Example of the headphone which
concerns on this invention. It is a longitudinal cross-sectional view which shows the example of
the conventional headphone.
Explanation of sign
[0032]
Reference Signs List 5 speaker unit 6 frame 10 voice coil 12 diaphragm 20 headphone housing
30 piezoelectric element 32 second piezoelectric element 35 support 36 sound receiving
member 40 elastic filter
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