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JP2012029082

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DESCRIPTION JP2012029082
An electronic device capable of highly directional sound reproduction is provided. An electronic
device 100 is provided opposite to a first vibration surface, an oscillation device 10 for
oscillating an ultrasonic wave 40 from a first vibration surface, a casing 20 having the oscillation
device 10 inside, and A waveguide 30 having an opening end 50 on the surface of a housing 20,
and a sound absorbing member 80 provided on an inner wall of the waveguide 30 in a region in
contact with at least the opening end 50. Thereby, the dispersion | variation in the angle to which
the ultrasonic wave 40 is radiated can be suppressed, and highly directional sound reproduction
| regeneration is attained. [Selected figure] Figure 1
Electronics
[0001]
The present invention relates to an electronic device using ultrasonic waves.
[0002]
A piezoelectric electroacoustic transducer is known as an electroacoustic transducer of a portable
device or the like.
The piezoelectric-type electroacoustic transducer generates an oscillation amplitude by using an
expansion and contraction motion generated by applying an electric field to the piezoelectric
vibrator. Moreover, the piezoelectric electroacoustic transducer does not require a large number
03-05-2019
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of members to generate vibration amplitude, which is advantageous for thinning. In addition,
there are some which are described, for example in patent documents 1-5 about technology
about a speaker, and it is indicated that improvement of a sound quality, a sound pressure, etc.
can be aimed at.
[0003]
The piezoelectric electroacoustic transducer may be used as a parametric speaker using
ultrasonic waves. The parametric speaker demodulates audible sound from modulated ultrasonic
waves using the air density phenomenon. Since ultrasonic waves are used, higher directivity can
be realized as compared with a normal speaker.
[0004]
JP-A-2000-125387 JP-A-2003-111194 JP-A-2007-060529 JP-A-08-331685 JP-A-11-136781
[0005]
It is desirable to improve the convenience of the electronic device equipped with the speaker.
For example, if sound can be transmitted only to the user, privacy can be protected. For that
purpose, it is required to develop an electronic device that enables highly directional sound
reproduction.
[0006]
An object of the present invention is to provide an electronic device capable of highly directional
sound reproduction.
[0007]
According to the present invention, there is provided an oscillation device for oscillating an
ultrasonic wave from a first vibration surface, a first vibration device provided opposite to the
first vibration surface and having a first open end on the surface of the housing. An electronic
device is provided, comprising: a waveguide; and a first sound absorbing member provided in an
inner wall of the first waveguide and in a region in contact with at least the first opening end.
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[0008]
According to the present invention, it is possible to provide an electronic device capable of highly
directional sound reproduction.
[0009]
FIG. 2 is a cross-sectional view showing the electronic device according to the first embodiment.
It is sectional drawing which shows the oscillation apparatus shown in FIG.
It is sectional drawing which shows the piezoelectric vibrator shown in FIG.
It is sectional drawing which shows the electronic device which concerns on 2nd Embodiment.
[0010]
Hereinafter, embodiments of the present invention will be described with reference to the
drawings. In all the drawings, the same components are denoted by the same reference numerals,
and the description thereof will be appropriately omitted.
[0011]
FIG. 1 is a cross-sectional view showing the electronic device 100 according to the first
embodiment. The electronic device 100 includes an oscillation device 10, a housing 20, a
waveguide 30, and a sound absorbing member 80. The electronic device 100 is, for example, a
mobile communication terminal, a laptop computer, or a small game device.
[0012]
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The oscillation device 10 oscillates the ultrasonic wave 40 from the first vibration surface. The
housing 20 has the oscillation device 10 inside. The waveguide 30 is provided to face the first
vibration surface. The waveguide 30 also has an open end 50 on the surface of the housing 20.
The sound absorbing member 80 is provided on the inner wall of the waveguide 30 at least in a
region in contact with the opening end 50. Hereinafter, the configuration of the electronic device
100 will be described in detail with reference to FIGS. 1 to 3.
[0013]
As shown in FIG. 1, the electronic device 100 further includes a waveguide 35 and a sound
absorbing member 85. The oscillation device 10 oscillates the ultrasonic wave 45 from a second
vibration surface which is constituted by a surface opposite to the first vibration surface. The
waveguide 35 is provided to face the second vibration surface. The waveguide 35 also has an
open end 55 on the surface of the housing 20. The sound absorbing member 85 is an inner wall
of the waveguide 35 and provided at least in a region in contact with the opening end 55.
[0014]
As shown in FIG. 2, the oscillation device 10 includes a piezoelectric vibrator 60, a vibrating
member 72, and a support member 70. The vibrating member 72 restrains the piezoelectric
vibrator 60. The support member 70 supports the vibrating member 72. The oscillation device
10 further includes a control unit 74 and a signal generation unit 76. The signal generation unit
76 is connected to the piezoelectric vibrator 60 and generates an electrical signal to be input to
the piezoelectric vibrator 60. The control unit 74 is connected to the signal generation unit 76,
and controls the generation of the signal by the signal generation unit 76 based on the
information input from the outside. Since the oscillation device 10 is used as a speaker, the
information input to the control unit 74 is an audio signal.
[0015]
In the present embodiment, the oscillation device 10 is used as a parametric speaker. Therefore,
the control unit 74 inputs a modulation signal as a parametric speaker via the signal generation
unit 76. When used as a parametric speaker, the piezoelectric vibrator 60 uses a sound wave of
20 kHz or more, for example, 100 kHz as a transport wave of a signal. In the oscillation device
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10, for example, a plurality of piezoelectric vibrators 60 and a plurality of vibration members 72
are provided in an array. Thereby, the directivity of the ultrasonic waves 40 and 45 which the
oscillation apparatus 10 emits can be improved. The piezoelectric vibrator 60 and the vibration
member 72 may be singular.
[0016]
FIG. 3 is a cross-sectional view showing the piezoelectric vibrator 60 shown in FIG. As shown in
FIG. 3, the piezoelectric vibrator 60 includes a piezoelectric body 62, an upper electrode 64, and
a lower electrode 66. The piezoelectric vibrator 60 has, for example, a circular shape, an elliptical
shape, or a rectangular shape. The piezoelectric body 62 is sandwiched between the upper
electrode 64 and the lower electrode 66. The piezoelectric body 62 is made of a material having
a piezoelectric effect, and is made of, for example, lead zirconate titanate (PZT), barium titanate
(BaTiO3) or the like. The thickness of the piezoelectric body 62 is preferably 10 um to 1 mm. If
the thickness is less than 10 μm, the piezoelectric body 62 is made of a brittle material, and thus
breakage or the like is likely to occur. On the other hand, when the thickness exceeds 1 mm, the
electric field strength of the piezoelectric body 62 is reduced. Therefore, the energy conversion
efficiency is reduced.
[0017]
The upper electrode 64 and the lower electrode 66 are made of, for example, silver or a silver /
palladium alloy. The thickness of the upper electrode 64 and the lower electrode 66 is preferably
1 to 50 μm. If the thickness is less than 1 um, uniform molding becomes difficult. On the other
hand, when it exceeds 50 um, the upper electrode 64 or the lower electrode 66 becomes a
constraining surface with respect to the piezoelectric body 62, and the energy conversion
efficiency is lowered.
[0018]
The vibrating member 72 is made of a material having a high elastic modulus with respect to the
ceramic material, and is made of, for example, phosphor bronze or stainless steel. The thickness
of the vibrating member 72 is preferably 5 to 500 μm. The longitudinal elastic modulus of the
vibrating member 72 is preferably 1 to 500 GPa. If the longitudinal elastic modulus of the
vibrating member 72 is excessively low or high, the characteristics and reliability as a mechanical
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vibrator may be impaired.
[0019]
The waveguide 30 is formed by providing a waveguide 22 connecting the first vibration surface
and the open end 50. The waveguide 35 is formed by providing the waveguide 24 connecting the
second vibration surface and the open end 55. The waveguides 30 and 35 are provided
perpendicular to the first and second vibration planes.
[0020]
The sound absorbing member 80 is formed only in the vicinity of the opening end 50 of the
inner wall of the waveguide 30. Further, the sound absorbing member 85 is formed only in the
vicinity of the opening end 55 of the inner wall of the waveguide 35. The sound absorbing
members 80 and 85 are made of, for example, a sound absorbing material such as urethane or
fiber glass wool. The thickness of the sound absorbing members 80, 85 in the radial direction of
the waveguides 30, 35 is, for example, 1 mm or less. The width of the sound absorbing members
80 and 85 in the axial direction of the waveguides 30 and 35 is, for example, 1 cm.
[0021]
Next, the principle that enables highly directional sound reproduction will be described. As
shown in FIG. 1, a part of the components of the ultrasonic wave 40 oscillated from the
oscillation device 10 is absorbed by the sound absorbing member 80 provided on the inner wall
of the waveguide 30. Therefore, only the component of the ultrasonic wave 40 that passes near
the center of the waveguide 30 is emitted from the open end 50. Further, a part of the
components of the ultrasonic wave 45 oscillated from the oscillation device 10 is absorbed by
the sound absorbing member 85 provided on the inner wall of the waveguide 35. Therefore, only
the component of the ultrasonic wave 45 which passes near the center of the waveguide 35 is
emitted from the open end 55. Thereby, the dispersion | variation in the angle from which the
ultrasonic waves 40 and 45 are radiated can be suppressed. Therefore, highly directional sound
reproduction is possible.
[0022]
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Next, the effects of the present embodiment will be described. In the electronic device 100
according to the present embodiment, the sound absorbing members 80 and 85 are provided on
the inner walls of the waveguides 30 and 35 through which the ultrasonic waves 40 and 45 pass.
Ultrasonic waves are more directional than audible sound waves. Also, ultrasonic waves are more
easily absorbed by the sound absorbing member than audible sound waves. For this reason, the
dispersion | variation in the angle to which an ultrasonic wave is emitted can be suppressed and
high directivity can be implement | achieved. Therefore, it is possible to provide an electronic
device that enables highly directional sound reproduction.
[0023]
Further, since the ultrasonic wave is easily absorbed by the sound absorbing member, the
directivity can be improved even if the sound absorbing member is thin. Thus, the electronic
device can be miniaturized. Further, waveguides 30 and 35 are provided on the first vibration
surface and the second vibration surface of the oscillation device 10, respectively. Therefore, the
ultrasonic waves 40 and 45 oscillated from both the first vibration surface and the second
vibration surface can be used, and sound can be reproduced with high efficiency. In addition,
waveguide 30 is perpendicular to the first plane of oscillation and waveguide 35 is perpendicular
to the second plane of oscillation. The ultrasonic waves 40 and 45 emitted from the oscillation
device 10 have many components perpendicular to the first vibrating membrane and the second
vibrating membrane, so that acoustic reproduction can be performed with higher efficiency.
[0024]
FIG. 4 is a cross-sectional view showing the electronic device 102 according to the second
embodiment, which corresponds to FIG. 1 according to the first embodiment. The electronic
device 102 according to the present embodiment is the same as the electronic device 100
according to the first embodiment except for the configurations of the sound absorbing members
80 and 85.
[0025]
As shown in FIG. 4, the sound absorbing member 80 is provided on the entire inner wall of the
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waveguide 30. Further, the sound absorbing member 85 is provided on the entire inner wall of
the waveguide 35.
[0026]
Also in this embodiment, the same effect as that of the first embodiment can be obtained.
Further, since the area capable of absorbing the ultrasonic waves 40 and 45 is increased,
directivity can be further enhanced as compared with the first embodiment.
[0027]
Although the embodiments of the present invention have been described above with reference to
the drawings, these are merely examples of the present invention, and various configurations
other than the above can also be adopted.
[0028]
Reference Signs List 10 oscillator 20 housing 22 waveguide 24 waveguide 30 waveguide 35
waveguide 40 ultrasonic 45 ultrasonic 50 opening end 55 opening end 60 piezoelectric vibrator
62 piezoelectric body 64 upper electrode 66 lower electrode 70 support member 72 vibration
Member 74 Control unit 76 Signal generation unit 80 Sound absorption member 85 Sound
absorption member 100 Electronic device 102 Electronic device
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