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DESCRIPTION JP2006013903

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DESCRIPTION JP2006013903
PROBLEM TO BE SOLVED: To provide an acoustic lens capable of maintaining the lens shape for
a long time and reducing the escape of filling gas, and an ultrasonic speaker using the same.
SOLUTION: The acoustic lens 1 changes the traveling direction of sound waves at the interface
between different gases separated by a rubber film 10, and the lens of a desired sound wave is
supported by supporting the rubber film 10 by a support structure 11. It is configured to
maintain the shape for exerting the function. [Selected figure] Figure 2
Acoustic lens and ultrasonic speaker using the same
[0001]
The present invention relates to an acoustic lens that changes the traveling direction of sound
waves in gas, and more particularly to an acoustic lens suitable for focusing and diverging
ultrasonic waves and an ultrasonic speaker using the same.
[0002]
Conventionally, as an acoustic lens for changing the traveling direction of (air) sound waves,
there is a system that uses reflection by a substance with high acoustic impedance to realize the
focusing of sound waves by giving characteristics to the structure of a reflecting material (for
example, Patent Document 1).
Further, as an acoustic lens using a rubber balloon, there is one in which the inside of the balloon
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is filled with a gas heavier than air (such as carbon dioxide) or a light gas (such as helium) and
the refraction of sound waves at the balloon boundary. JP 2002-44773 A
[0003]
In the case of the acoustic lens using the latter rubber balloon, it is necessary to increase the
pressure of the filling gas in order to form the shape. However, the higher the pressure, the
easier the internal gas can permeate (that is, it is easy to escape) through the rubber membrane,
and it is difficult to maintain the shape for a long time.
[0004]
The present invention has been made in view of such circumstances, and it is an object of the
present invention to provide an acoustic lens capable of maintaining the lens shape for a long
time and reducing the loss of filling gas and an ultrasonic speaker using the same. To aim.
[0005]
In order to achieve the above object, the acoustic lens of the present invention is an acoustic lens
that changes the traveling direction of the sound wave at the interface between different gases
separated by a film, which is desired by supporting the film by a support structure It is
characterized in that it is configured to maintain the shape for exerting the lens function of the
acoustic wave.
In the acoustic lens of the present invention configured as described above, the support structure
supports the shape of the film filled with gas for exerting the lens function of the desired sound
wave. Therefore, compared to the conventional acoustic lens in which the film shape is
maintained by the pressure of the filling gas, the removal of the filling gas can be reduced.
[0006]
The acoustic lens of the present invention is characterized in that the shape of the acoustic lens
is a shape capable of obtaining a lens effect. In the acoustic lens of the present invention having
the above configuration, for example, the shape that can obtain lens effects such as a spherical
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shape, a hemispherical shape, or a shape in which a paraboloid, a convex surface, and a concave
surface are partially formed is the shape of the acoustic lens. Selected as Therefore, by using the
acoustic lens of the present invention, the sound wave emitted from the sound source can be
converged or diverged in a desired direction depending on the application.
[0007]
The acoustic lens of the present invention is characterized in that the support structure is a
polyhedral frame structure. The acoustic lens of the present invention having the above
configuration is realized by a polyhedral frame structure. Therefore, a free shape can be selected
as the shape of the acoustic lens while considering the influence of the frame.
[0008]
The acoustic lens of the present invention is characterized in that the film is bonded to the
support structure. In the acoustic lens of the present invention configured as described above,
the film in the shape of the acoustic lens is bonded to the support structure. Therefore, the
tension of the membrane can be maintained to prolong the life of the membrane.
[0009]
In the acoustic lens of the present invention, the film is a rubber film. In the acoustic lens of the
present invention having the above configuration, the shape of the acoustic lens is formed of a
rubber film. Therefore, the shape of the acoustic lens can be freely formed so as to obtain a
desired lens effect.
[0010]
The ultrasonic speaker according to the present invention comprises a signal source for
generating a signal wave in an audible frequency band, a carrier wave supply means for
generating and outputting a carrier wave, and a modulation means for modulating the carrier
wave with the signal wave. An ultrasonic speaker driven by a modulation signal output from the
modulation means, an ultrasonic transducer for converting the modulation signal into a sound
wave of a finite amplitude level and emitting the sound wave into a medium, any one of the
above-mentioned inventions And an acoustic lens according to the present invention.
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[0011]
In the ultrasonic speaker of the present invention having the above configuration, the carrier
wave generated by the carrier wave supply means is modulated by the modulation means with
the signal wave of the audible frequency band generated by the signal source.
The ultrasonic transducer is driven by the modulation signal output from the modulation means,
and the ultrasonic transducer converts the modulation signal into a sound wave of a finite
amplitude level and emits it into the medium. At this time, the acoustic wave (acoustic signal)
emitted by the ultrasonic transducer is converged or diverged by any one of the above-described
acoustic lenses provided opposite to the vicinity of the sound wave emitting surface in the
ultrasonic transducer. Therefore, in the ultrasonic speaker of the present invention, the output
acoustic signal is converged or diverged in a desired direction. Thereby, when applying to the
ultrasonic speaker system carrying a plurality of ultrasonic speakers, a desired acoustic effect
can be obtained.
[0012]
The ultrasonic speaker according to the present invention comprises a signal source for
generating a signal wave in an audible frequency band, a carrier wave supply means for
generating and outputting a carrier wave, and a modulation means for modulating the carrier
wave with the signal wave. An ultrasonic speaker driven by a modulation signal output from the
modulation means, and an ultrasonic transducer for converting the modulation signal into a
sound wave of a finite amplitude level and emitting the sound wave into a medium, wherein the
sound wave of the ultrasonic transducer A cylinder which is in communication with the front of
the radiation surface and extends in the sound wave radiation direction, and which has a first
film forming a boundary with the outside at the outlet of the cylinder; And a second film disposed
between the first film and the sound wave emitting surface at a predetermined distance from the
first film and formed by the first film and the second film. The room with different ambient gas
and specific gravity And having a gas-filled means that.
[0013]
The ultrasonic speaker according to the present invention having the above-mentioned
configuration is in communication with the front surface of the sound wave emitting surface of
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the ultrasonic transducer, and has a cylindrical body extended in the sound wave emitting
direction.
In this cylinder, a first film forming a boundary with the external world at the outlet of the
cylinder, and a space between the first film and the first film and the sound wave emitting
surface at a predetermined distance. A second film to be disposed is provided, and a gas sealing
means for filling a gas having a different specific gravity from the ambient gas is attached to the
chamber formed by the first film and the second film. . Therefore, by filling the gas having
different specific gravity from the external world by the gas sealing means, the curvature of the
curved surface formed by one or both of the first and second films is changed by the filling
pressure of the gas sealing means. For example, by adjusting the curvature, an ultrasonic speaker
provided with an acoustic lens having a desired lens function such as a concave lens or a convex
lens can be realized.
[0014]
Further, in the ultrasonic speaker according to the present invention, the first film is provided so
as to be attached to a support structure, and the inside of the chamber is filled with the gas by
the gas sealing means so that the second film has a desired curvature. It is characterized by
setting. In the ultrasonic speaker of the present invention having the above configuration, the
first film is attached to a support structure, and the gas is introduced into the chamber formed of
the first film and the second film by the gas sealing means. By filling, the second film is set to the
desired curvature. Therefore, an ultrasonic speaker provided with an acoustic lens having a
desired lens function can be realized by adjusting only the curvature of the curved surface
formed by the second film without changing the shape of the first film. it can.
[0015]
Further, in the ultrasonic speaker according to the present invention, the tension of the first film
is attached to and fixed to the cylindrical body so as to be larger than the tension of the second
film, and the gas sealing means To set the second film to a desired curvature. In the ultrasonic
speaker according to the present invention having the above configuration, the first membrane is
attached to and fixed to the cylindrical body so that the tension of the first membrane is larger
than the tension of the second membrane. By filling the gas, the second film is set to a desired
curvature. Therefore, without providing the support structure, only the curved surface formed by
the second film is set to a desired curvature without changing the shape of the first film, and an
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acoustic lens having a desired lens function is provided. An ultrasonic speaker can be realized.
[0016]
Further, in the ultrasonic speaker according to the present invention, the second film is provided
to be attached to the support structure, and the inside of the chamber is filled with the gas by the
gas sealing means so that the first film has a desired curvature. It is characterized by setting. In
the ultrasonic speaker of the present invention having the above configuration, the second film is
attached to the support structure, and the gas is introduced into the chamber formed of the first
film and the second film by the gas sealing means. The filling sets the first film to the desired
curvature. Therefore, an ultrasonic speaker provided with an acoustic lens having a desired lens
function can be realized by adjusting only the curvature of the curved surface formed of the first
film without changing the shape of the second film. it can.
[0017]
Further, in the ultrasonic speaker according to the present invention, the tension of the second
film is attached to and fixed to the cylindrical body so as to be larger than the tension of the first
film, and the gas sealing means To set a desired curvature of the first film. In the ultrasonic
speaker according to the present invention having the above configuration, the second
membrane is attached and fixed to the cylindrical body so that the tension of the second
membrane is larger than the tension of the first membrane. By filling the gas, the first film is set
to a desired curvature. Therefore, without providing a support structure, only the curved surface
formed by the first film is set to a desired curvature without changing the shape of the second
film, and an acoustic lens having a desired lens function is provided. An ultrasonic speaker can be
realized.
[0018]
Moreover, the ultrasonic speaker of the present invention is characterized in that the gas has a
specific gravity greater than that of the external gas. In the ultrasonic speaker having the above
configuration, the inner surface is in communication with the front surface of the sound wave
emitting surface of the ultrasonic transducer, and is formed in the chamber formed of the first
film and the second film in a cylinder extending in the sound wave emitting direction. As the gas
filled by the gas sealing means, one having a specific gravity greater than that of the external gas
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(for example, air) is used. Therefore, by filling the chamber formed of the first film and the
second film with a gas whose specific gravity is heavier than that of the external gas, either the
first film or the second film, or both of them can be used. The curved surface to be formed can be
set to a desired curvature, and hence an ultrasonic speaker equipped with an acoustic lens
having a desired lens function can be realized.
[0019]
The ultrasonic speaker according to the present invention comprises a signal source for
generating a signal wave in an audible frequency band, a carrier wave supply means for
generating and outputting a carrier wave, and a modulation means for modulating the carrier
wave with the signal wave. An ultrasonic speaker driven by a modulation signal output from the
modulation means, and an ultrasonic transducer for converting the modulation signal into a
sound wave of a finite amplitude level and emitting the sound wave into a medium; A first
membrane which is in communication with the front of the surface and extends in the sound
wave radiation direction, and which forms a boundary with the external world at the outlet of the
cylindrical body; And a second film disposed between the first film and the sound wave emitting
surface at a predetermined distance, and a gas disposed between the second film and the sound
wave emitting surface. And a partition wall to be sealed; First and chamber formed in the second
film, and having the second membrane and the gas charging means for filling the second
different specific gravity of gas chamber formed by the partition wall.
[0020]
The ultrasonic speaker having the above configuration is in communication with the front
surface of the sound wave emitting surface of the ultrasonic transducer and has a cylindrical
body extended in the sound wave emitting direction.
In this cylinder, a first film forming a boundary with the external world at the outlet of the
cylinder, and a space between the first film and the first film and the sound wave emitting
surface at a predetermined distance. A second film to be disposed, and a partition disposed
between the second film and the sound wave emitting surface and sealing a gas are provided, and
the first film and the second film are provided. In the first chamber formed in the above, and in
the second chamber formed by the second film and the partition, gas sealing means for filling gas
of different specific gravity is attached. Therefore, by adjusting the pressure of the gas filled in
the first chamber and the second chamber by the gas sealing means, it is formed in one or both
of the first film and the second film. The curved surface can be set to a desired curvature, and
hence an ultrasonic speaker equipped with an acoustic lens having a desired lens function can be
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realized.
[0021]
Further, in the ultrasonic speaker according to the present invention, the first film is provided so
as to be attached to the support structure, and the pressure difference between the first chamber
and the second chamber is adjusted by the gas sealing means. It is characterized in that the film
of No. 2 is set to a desired curvature. In the ultrasonic speaker having the above configuration,
the first film is attached to a support structure, and the second film is adjusted by adjusting a
pressure difference between the first chamber and the second chamber by the gas sealing means.
Is set to the desired curvature. Therefore, an ultrasonic speaker provided with an acoustic lens
having a desired lens function can be realized by adjusting only the curvature of the curved
surface formed by the second film without changing the shape of the first film. it can.
[0022]
Hereinafter, embodiments of the present invention will be described in detail with reference to
the drawings. An exemplary configuration of an acoustic lens according to an embodiment of the
present invention is shown in FIG. An acoustic lens according to an embodiment of the present
invention is an acoustic lens that changes the traveling direction of the sound wave at the
interface between different gases separated by a film, and the desired sound wave is obtained by
supporting the film by a support structure. It is characterized in that it is configured to maintain
the shape for exerting the lens function. FIG. 1A schematically shows a structure in which the
rubber film 10 having the lens shape of the acoustic lens 1 (or 1A) is supported by the support
structure 11 by being filled with a gas. 1 (B) shows the external appearance of a state in which
the lens shape of the acoustic lens is supported by the frame structure of the polyhedron.
[0023]
When gases having different specific gravities are separated at the membrane boundary,
refraction occurs because the velocity of sound is different between the boundaries. For example,
if the inside of the membrane is filled with a gas (for example, carbon dioxide) with a high
specific gravity (relative to air), the speed of sound in the inside of the membrane becomes
slower (the speed of sound in the gas is inversely proportional to the square root of the
molecular weight of the gas ). Conversely, when the gas with a low specific gravity (for example,
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helium) is filled, the speed of sound in the membrane becomes faster. In the case of refraction
due to the difference in the speed of sound, refraction is made in the direction in which the angle
of refraction is smaller than the incident angle at the interface where the speed of sound slows
down.
[0024]
The acoustic lens 1 shown in FIG. 1A is formed into a spherical shape by filling a balloon made of
a rubber film 10 with carbon dioxide which is a gas having a heavier specific gravity than air as a
gas forming the outside. When a sound wave having high directivity such as ultrasonic waves is
emitted from the sound source 2 toward the acoustic lens 1, this sound wave enters the acoustic
lens 1, and the sound wave is refracted at points X1 and X1 'at the interface with the external
world. Do. At this time, in the balloon filled with carbon dioxide, the propagation speed of the
sound wave is slower than in the air in the outside world, so the refraction angles β1 and β1 ′
become smaller than the incident angles α1 and α1 ′, respectively.
[0025]
Then, when the sound wave exits the acoustic lens 1, it refracts from the inside of the acoustic
lens 1 to the air which is the outside world at points X2 and X2 'at the interface with the outside
world. At this time, the refraction angles β2 and β2 ′ become larger than the incident angles
α2 and α2 ′, respectively, for the reason described above, and the sound wave emitted from
the sound source 2 becomes a plane wave by passing through the acoustic lens 1. Therefore, the
acoustic lens 1 shown in FIG. 1A functions as a convex lens for the sound wave. When the sound
source in FIG. 1A is a plane wave, the sound wave can be converged.
[0026]
Further, an acoustic lens 1A shown in FIG. 1B is formed into a spherical shape by filling helium
having a lighter specific gravity than air as a gas forming the outside on a balloon made of a
rubber film 10. When a sound wave having high directivity such as ultrasonic waves is emitted
from the sound source 2 toward the acoustic lens 1A, the sound wave enters the acoustic lens
1A, and the sound wave is refracted at points X10 and X10 'at the interface with the external
world. Do. At this time, in the balloon filled with helium, the propagation speed of the sound wave
is faster than in the air in the outside world, so the refraction angles β10 and β10 'become
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larger than the incident angles α10 and α10', respectively.
[0027]
Then, when the sound wave exits the acoustic lens 1A, it refracts from the inside of the acoustic
lens 1A to the air which is the outside world at points X11 and X11 'at the interface with the
outside world. At this time, the refraction angles β11 and β11 ′ respectively become smaller
than the incident angles α11 and α11 ′ for the reason described above, and the sound wave
emitted from the sound source 2 changes so as to diverge by passing through the acoustic lens 1
. Therefore, the acoustic lens 1A shown in FIG. 1B functions as a concave lens for the sound
wave.
[0028]
For example, as shown in FIG. 2, the acoustic lenses 1 and 1A described above are formed by
covering the support structure 11 of the frame structure with the rubber film 10, and the shape
of the rubber film filled with gas is the support structure 11 Support to maintain the lens shape.
Usually, when the balloon shape is formed by the pressure of the filling gas like a rubber balloon,
the internal air pressure becomes high, the filling gas easily permeates the rubber film, and it is
difficult to maintain the balloon shape for a long time. However, since the support structure 11
as shown in FIG. 2 is formed inside the balloon made of the rubber film 10 and the structure is
supported by the structure, it is not necessary to increase the internal air pressure to maintain
the shape. Thereby, the rubber membrane permeation of the filling gas is reduced.
[0029]
Therefore, compared to the conventional acoustic lens in which the film shape is maintained by
the pressure of the filling gas, the removal of the filling gas can be reduced. The acoustic lens is
realized by a polyhedral frame structure. Therefore, a free shape can be selected as the shape of
the acoustic lens while considering the influence of the frame.
[0030]
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In addition, the lens shape of the acoustic lens 1 (1A) is not limited to a spherical shape, and a
hemispherical shape or a shape such as a shape in which a paraboloid, a convex surface or a
concave surface is formed in a part Is selected. Therefore, by using the acoustic lens of the
present invention, the sound wave emitted from the sound source 2 can be converged or
diverged in a desired direction depending on the application.
[0031]
In the acoustic lens according to the embodiment of the present invention, the film (in the
present embodiment, the rubber film) 10 in the shape of the acoustic lens may be bonded to the
support structure 11. By this configuration, the tension of the membrane can be maintained, and
the life of the membrane can be prolonged. Furthermore, in the acoustic lens according to the
present embodiment, a rubber film is used as a film in the shape of the acoustic lens. Therefore,
the shape of the acoustic lens can be freely formed so as to obtain a desired lens effect.
[0032]
Next, the configuration of the ultrasonic speaker according to the embodiment of the present
invention provided with the above-described acoustic lens is shown in FIG. In the figure, the
ultrasonic speaker includes sound waves radiated from an audio frequency wave oscillation
source 21, a carrier wave oscillation source 22, a modulator 23, a power amplifier 24, an
ultrasonic transducer 25 and an ultrasonic transducer 25 ( And an acoustic lens 26 for
converging or diverging the acoustic signal).
[0033]
The audio frequency wave oscillation source 21 has a function of generating a signal in the audio
frequency band. The carrier wave oscillation source 22 has a function of generating a carrier
wave in an ultrasonic frequency band. The carrier wave oscillation source 22 is configured to be
able to change the frequency of the carrier wave. The modulator 23 has a function of AMmodulating a carrier wave supplied from the carrier wave oscillation source 22 with a signal
wave output from the audio frequency wave oscillation source 21 and outputting a modulation
signal to the power amplifier 24. Also, the ultrasonic transducer 25 is driven by a modulation
signal output from the modulator 23 through the power amplifier 24, converts the modulation
signal into a sound wave of a finite amplitude level and emits it into the medium, It has a function
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of reproducing a signal sound (reproduction signal).
[0034]
In the above configuration, the carrier wave in the ultrasonic frequency band output from the
carrier wave oscillation source 22 is modulated by the modulator 23 by the signal wave output
from the audio frequency wave oscillation source 21 and the modulation signal amplified by the
power amplifier 24 The ultrasonic transducer 25 is driven. As a result, the modulated signal is
converted to a sound wave of a finite amplitude level by the ultrasonic transducer 25 and this
sound wave is converged or diverged by the acoustic lens 26 and emitted into the medium (in
air) to cause nonlinear effects of the medium (air). The tone of the original audio frequency band
is reproduced by. The acoustic lens 26 has the function of a convex lens with respect to the
sound wave in the configuration example of FIG. 3, but is not limited to this, and may be an
acoustic lens having a function of a concave lens having a function of diverging the sound wave.
Also, a plurality of acoustic lenses may be provided in consideration of the acoustic effect.
[0035]
The reproduction range of the reproduction signal in the audio frequency band is a beam-like
range from the ultrasonic transducer 25 in the emission axis direction. Here, the "reproduction
range of the reproduction signal" includes both the distance that the reproduction signal reaches
from the sound wave emission surface of the ultrasonic transducer in the radiation axis direction,
and the beam width (beam emission angle) of the ultrasonic beam, By changing the wave
frequency, the reproduction range can be changed. The audio frequency wave oscillation source
21 corresponds to the signal source of the present invention, the carrier wave oscillation source
22 corresponds to the carrier wave supply means of the present invention, and the modulator 23
corresponds to the modulation means of the present invention.
[0036]
The ultrasonic transducer 25 is, for example, an electrostatic transducer that can emit an
acoustic signal (ultrasound) in a wide frequency band. The ultrasonic transducer 22 may not be
of the electrostatic type as long as it can oscillate a wide frequency band acoustic signal. The
specific configuration of the ultrasonic transducer 25 is shown in FIG. The ultrasonic transducer
of the electrostatic type shown in FIG. 4 uses a dielectric 31 (insulator) such as PET (polyethylene
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terephthalate resin) having a thickness of about 3 to 10 μm as a vibrator. For the dielectric 31,
an upper electrode 32 formed as a metal foil such as aluminum is integrally formed on the upper
surface thereof by a process such as evaporation, and a lower electrode 33 formed of brass is
formed on the lower surface of the dielectric 31. It is provided to contact the part. The lower
electrode 33 is connected to the lead 52 and fixed to a base plate 35 made of Bakelite or the like.
[0037]
Further, a lead 53 is connected to the upper electrode 32, and the lead 53 is connected to a DC
bias power supply 50. A DC bias voltage for attracting the upper electrode of about 50 to 150 V
is constantly applied to the upper electrode 32 by the DC bias power supply 50 so that the upper
electrode 32 is attracted to the lower electrode 33 side. An alternating current signal source 51
corresponds to the output (AC 50 to 150 Vp-p) of the power amplifier 24 in FIG. The dielectric
31 and the upper electrode 32 and the base plate 35 are crimped by the case 30 together with
the metal rings 36, 37 and 38 and the mesh 39.
[0038]
On the surface of the lower electrode 33 on the dielectric 31 side, a plurality of microgrooves of
about several tens to several hundreds of μm having an uneven shape are formed. Since this
minute groove becomes an air gap between the lower electrode 33 and the dielectric 31, the
distribution of capacitance between the upper electrode 32 and the lower electrode 33 changes
minutely. The random minute grooves are formed by manually roughening the surface of the
lower electrode 33 with a file. In the electrostatic ultrasonic transducer, the frequency
characteristics of the ultrasonic transducer become wide band by thus forming an infinite
number of capacitors having different air gaps in size and depth.
[0039]
In the ultrasonic transducer 22 configured as described above, the modulation signal (the output
of the power amplifier 24) is applied between the upper electrode 31 and the lower electrode 33
in a state where a DC bias voltage is applied to the upper electrode 32. There is. By the way, the
frequency characteristic of the resonance type ultrasonic transducer is, for example, 40 kHz at
the center frequency (resonance frequency of the piezoelectric ceramic) and for the maximum
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sound pressure at a frequency of ± 5 kHz with respect to the center frequency which is the
maximum sound pressure. It is -30 dB. On the other hand, the frequency characteristics of the
broadband oscillation type ultrasonic transducer of the above configuration are flat from 40 kHz
to 100 kHz, and are about ± 6 dB at 100 kHz as compared to the maximum sound pressure.
[0040]
According to the ultrasonic speaker of the present invention configured as described above, the
ultrasonic transducer 25 converts the modulation signal output from the modulation 23 through
the power amplifier 24 into a sound wave of a finite amplitude level and emits it into the
medium. At this time, the acoustic wave (acoustic signal) emitted by the ultrasonic transducer is
converged or diverged by an acoustic lens 26 provided in the ultrasonic transducer 25 so as to
face the vicinity of the sound wave emitting surface. Therefore, in the ultrasonic speaker of the
present invention, the output acoustic signal is diverged or converged in a desired direction.
Thereby, when applying to the ultrasonic speaker system carrying a plurality of ultrasonic
speakers, a desired acoustic effect can be obtained.
[0041]
Next, an example of a specific configuration of the ultrasonic speaker according to the
embodiment of the present invention provided with an acoustic lens is shown in FIG. FIG. 5
shows the configuration of the main part of an ultrasonic speaker provided with an acoustic lens.
In the figure, reference numeral 25 denotes an ultrasonic transducer that constitutes an
ultrasonic speaker, and the configuration of the ultrasonic speaker itself is the same as that
shown in FIG. 3 and FIG.
[0042]
In FIG. 5, the ultrasonic speaker is in communication with the sound wave emitting surface front
surface 25A of the ultrasonic transducer 25 and has a cylindrical body 100 extended in the
sound wave emitting direction. In the cylindrical body 100, a first film 101 forming a boundary
with the external world at an outlet portion of the cylindrical body 100, and the first film 101
and the acoustic wave radiation at a predetermined distance from the first film 101. A second
film 102 disposed between the surface 25A and the surface 25A is provided. In addition, a
cylinder 104 filled with a gas (in the present embodiment, carbon dioxide) different in specific
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gravity from the ambient gas (air) is attached to a chamber 103 formed of the first film 101 and
the second film 102. The first film 101 and the second film 102 are both rubber films in this
embodiment. Further, the cylinder 104 is filled with carbon dioxide, and the cylinder 104
corresponds to the gas sealing means of the present invention.
[0043]
Therefore, a curved surface formed by filling the pressure of the cylinder 104 with one or both of
the first and second films 101 and 102 by filling the cylinder 104 with carbon dioxide, which is a
gas having a specific gravity different from that of the ambient air. The curvature of the lens can
be changed, and by adjusting the curvature, an acoustic lens having a desired lens function such
as, for example, a concave lens or a convex lens can be formed, and thus an acoustic lens having
a desired lens function Can be realized.
[0044]
Alternatively, the first film 101 may be attached to the support structure 105, and the chamber
103 may be filled with the gas to set the second film 102 to a desired curvature.
In the ultrasonic speaker according to the embodiment of the present invention configured as
described above, the first film 101 is attached to the support structure 105 provided at the outlet
of the cylindrical body 100, and the first film 101 and the first film 101 are By filling the gas
(carbon dioxide) into the chamber 103 formed of the two films 102, the second film 102 is set to
a desired curvature. Therefore, an acoustic lens having a desired lens function can be formed by
adjusting only the curvature of the curved surface formed by the second film 102 without
changing the shape of the first film 101. Therefore, an ultrasonic speaker equipped with an
acoustic lens having a desired lens function can be realized.
[0045]
In the ultrasonic speaker according to the embodiment of the present invention, the tension of
the first film 101 is attached to and fixed to the cylindrical body 100 so as to be larger than the
tension of the second film 102. The second film 102 may be set to a desired curvature by filling
the gas (carbon dioxide). In the ultrasonic speaker according to the embodiment of the present
invention configured as described above, the gas sealing means is attached and fixed to the
cylindrical body so that the tension of the first film is larger than the tension of the second film.
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The second film is set to a desired curvature by filling the chamber with the gas. Therefore,
without providing the support structure 105, an acoustic lens having a desired lens function by
setting only the curved surface formed by the second film 102 without changing the shape of the
first film 101 to a desired curvature. An ultrasonic speaker with an acoustic lens with the desired
lens function can thus be realized.
[0046]
Next, another example of the specific configuration of the ultrasonic speaker according to the
embodiment of the present invention provided with an acoustic lens is shown in FIG. This
configuration example differs from the configuration example shown in FIG. 5 in that the second
film 102 is provided so as to be attached to the support structure 105, and the cylinder 104 is
formed of the first film 101 and the second film 102. The first film 101 is set to a desired
curvature by filling the inside of the chamber 103 with the gas (carbon dioxide).
[0047]
In the ultrasonic speaker of the present invention having the above configuration, the second film
102 is attached to the support structure 105, and the gas (in the chamber 103 formed by the
first film 101 and the second film 102 by the cylinder 104) The first film 101 is set to a desired
curvature by filling it with carbon dioxide. Therefore, an acoustic lens having a desired lens
function is formed by adjusting only the curvature of the curved surface formed by the first film
101 without changing the shape of the second film 102. Therefore, an ultrasonic speaker
equipped with an acoustic lens having a desired lens function can be realized.
[0048]
In the ultrasonic speaker according to the embodiment of the present invention, the tension of
the second film 102 is attached to and fixed to the cylindrical body 100 so as to be larger than
the tension of the first film 101. The first film 101 may be set to a desired curvature by filling the
gas (carbon dioxide).
[0049]
In the ultrasonic speaker of the present invention having the above configuration, the second
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membrane 102 is attached and fixed to the cylindrical body 100 so that the tension of the
second membrane 102 becomes larger than the tension of the first membrane 101. By filling the
gas (carbon dioxide), the first film 101 is set to a desired curvature.
Therefore, without providing a support structure, without changing the shape of the second film
102, only the curved surface formed by the first film 101 is set to a desired curvature, and an
acoustic lens having a desired lens function is obtained. It can be formed. Therefore, an
ultrasonic speaker equipped with an acoustic lens having a desired lens function can be realized.
[0050]
Further, in the ultrasonic speaker according to the present invention, the first speaker 101 and
the second film 102 are formed in the cylindrical body 100 which is in communication with the
front surface of the sound wave emitting surface of the ultrasonic transducer and extends in the
sound wave emitting direction. As the gas filled in the chamber with a cylinder, a gas (for
example, carbon dioxide) whose specific gravity is heavier than that of the external gas (for
example, air) is used. Therefore, the curved surface formed of one or both of the first film 101
and the second film 102 is set to a desired curvature by filling the chamber 103 with a gas
having a specific gravity greater than that of the ambient gas. It is possible to realize an
ultrasonic speaker with an acoustic lens which has the desired lens function.
[0051]
Next, still another example of the specific configuration of the ultrasonic speaker according to
the embodiment of the present invention provided with an acoustic lens is shown in FIG. This
configuration example differs from the configuration example shown in FIG. 5 in the outlet
portion of the cylindrical body 100 in the cylindrical body 100 which is in communication with
the front surface of the sound wave emitting surface of the ultrasonic transducer and extends in
the sound wave emitting direction. A first film 101 forming a boundary with the external world,
and a second film 102 disposed between the first film 101 and the sound wave emitting surface
25A at a predetermined distance from the first film 101; And a partition 110 disposed between
the second film 102 and the sound wave emitting surface 25A for sealing a gas, and a first
chamber formed of the first film 101 and the second film 102. 103, cylinders 104A and 104B for
filling gas of different specific gravities in the second chamber 108 formed by the second film
102 and the partition wall 110 are attached.
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[0052]
Here, in the present embodiment, the cylinder 104A is filled with carbon dioxide, and the
cylinder 104B is filled with air. The partition 110 is composed of a rubber film 106 and a
support structure 107 to which the rubber film is fixed.
[0053]
Therefore, by adjusting the pressure of the gas filling the first chamber 103 and the second
chamber 108 with the cylinders 104A and 104B filled with the gases having different specific
gravities, the first film 101 and the second film can be obtained. The curved surface formed on
one or both of the surfaces 102 can be set to a desired curvature, and hence an ultrasonic
speaker equipped with an acoustic lens having a desired lens function can be realized.
[0054]
Further, the ultrasonic speaker of the present invention is provided so as to attach the first film
101 to the support structure 105 fixed to the outlet of the cylindrical body 100 in FIG. 7, and the
first chamber 103 is provided by cylinders 104A and 104B. The second film 102 may be set to a
desired curvature by adjusting the pressure difference between the second chamber 108 and the
second chamber 108.
[0055]
In the ultrasonic speaker configured as described above, the first film 101 is attached to the
support structure, and the second film is adjusted by adjusting the differential pressure between
the first chamber 103 and the second chamber 108 with the cylinders 104A and 104B. The
curved surface formed by 102 is set to the desired curvature.
[0056]
Therefore, an acoustic lens having a desired lens function can be formed by adjusting only the
curvature of the curved surface formed by the second film 102 without changing the shape of
the first film 101, and hence the desired lens. An ultrasonic speaker equipped with an acoustic
lens having a function can be realized.
[0057]
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A versatile application is possible as an acoustic lens that can change the traveling direction of a
sound wave.
For example, (1) in the case of diffusing the ultrasonic component outputted from the ultrasonic
speaker (light gas (helium) filling), (2) an ultrasonic diagnostic apparatus by realizing the
ultrasonic wave focusing function in ultrasonic medical treatment Can be applied to applications
such as (3) reduction of ambient noise (divergence of external sound), etc.
[0058]
Explanatory drawing which shows the structural example of the acoustic lens which concerns on
embodiment of this invention.
Explanatory drawing which shows an example of the support structure of the acoustic lens
shown in FIG.
FIG. 1 is a block diagram showing the configuration of an ultrasonic speaker according to an
embodiment of the present invention.
FIG. 4 is a view showing the configuration of an ultrasonic transducer that constitutes the
ultrasonic speaker shown in FIG. 3; Explanatory drawing which shows an example of a structure
of the principal part of the ultrasonic speaker which has an acoustic lens which concerns on
embodiment of this invention. Explanatory drawing which shows the other example of a
structure of the principal part of the ultrasonic speaker which has an acoustic lens which
concerns on embodiment of this invention. Explanatory drawing which shows the further another
example of a structure of the principal part of the ultrasonic speaker which has an acoustic lens
which concerns on embodiment of this invention.
Explanation of sign
[0059]
DESCRIPTION OF SYMBOLS 1 ... acoustic lens, 2 ... sound source, 10 ... rubber film, 21 ... audio
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frequency wave oscillation source, 22 ... carrier wave oscillation source, 23 ... modulator, 25 ...
ultrasonic transducer, 25A ... sound wave emitting surface, 26 ... acoustic lens , 100: cylinder,
101: first film, 102: second film, 103: indoor, 104: cylinder, 11, 105: support structure
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