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JP2007215119

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DESCRIPTION JP2007215119
An electro-acoustic transducer for use in a superdirective sound source for obtaining an audible
sound by utilizing a non-linear phenomenon of air, which has a simplified structure and can
obtain acoustic characteristics of high sound pressure is obtained. In an electro-acoustic
transducer that emits into air the modulated signal obtained by modulating an ultrasonic carrier
signal with an audio signal as an acoustic wave, a plurality of ultrasonic elements that are
oscillated by inputting the modulated signal, and a plurality of ultrasonic waves The device
includes the plurality of ultrasonic transducers and a single diaphragm that vibrates to emit
sound waves. [Selected figure] Figure 2
Electro-acoustic transducer
[0001]
The present invention relates to an electroacoustic transducer used in a superdirective sound
source that obtains an audible sound by utilizing a non-linear phenomenon of air.
[0002]
If a large diaphragm is used, resonance occurs at a low frequency, and it is necessary to use a
small diaphragm that is less likely to cause bending vibration even if the frequency is increased
because bending vibration is caused.
However, high sound pressure can not be obtained with a small diaphragm. Therefore, in order
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to obtain a high sound pressure, there is one having a resonator having a role of resonating with
the vibrator to raise the sound pressure level (for example, see Non-Patent Document 1).
[0003]
In addition, in order to obtain high sound pressure, there is one in which a plurality of ultrasonic
elements are arrayed (see, for example, Non-Patent Document 2).
[0004]
Nippon Ceramic Co., Ltd., "Airborne Ultrasonic Sensor Catalog", [online], [Search on November
17, 1999], Internet <http://www.nicera.co.jp> Masahide Yoneyama, 3 others "Nonlinear
Application of Parametric Action to Loudspeakers, Electroacoustics, 1981, EA 81-65
[0005]
Since the conventional electro-acoustic transducer is configured as described above, the
transducer for radiating the sound wave in the air is small, and even if it has the resonator, it is
impossible to obtain a sufficiently high sound pressure. was there.
In addition, when arraying a plurality of ultrasonic elements, the arrangement interval is
determined depending on the outer diameter of the case or base of each ultrasonic element, and
there is a problem that the electroacoustic transducers can not be densified.
[0006]
The present invention has been made to solve the above problems, and an electro-acoustic
transducer for use in a superdirective sound source that obtains an audible sound by utilizing a
non-linear phenomenon of air has a simplified structure and high acoustic pressure acoustic
characteristics. It is an object of the present invention to obtain an electroacoustic transducer
which can obtain
[0007]
An electro-acoustic transducer according to the present invention is an electro-acoustic
transducer that radiates a modulated signal obtained by modulating an ultrasonic carrier signal
with an audio signal as air waves into the air, comprising a plurality of ultrasonic elements that
receive the modulated signal and vibrate. A plurality of ultrasonic transducers are provided on
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the plurality of ultrasonic elements, and a single diaphragm that vibrates to emit a sound wave is
provided.
[0008]
According to the present invention, the vibration area is increased by the single diaphragm
provided on the plurality of ultrasonic elements, compared with the arrayed ultrasonic elements
each having the vibrator and the resonator, and the sound radiation is generated. Since the
efficiency is improved, there is an effect that high sound pressure can be obtained.
In addition, the resonator, the case, and the base in the conventional ultrasonic element are not
required, the assembly process is greatly simplified, and the cost for manufacturing can be
reduced.
In addition, since it is possible to omit a resonator having a large variation in resonance
frequency, it is possible to reduce the resonance variation.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, in order to explain the present
invention in more detail, the best mode for carrying out the present invention will be described
according to the attached drawings.
Embodiment 1 FIG. 1 is a block diagram showing the configuration of a superdirective sound
source using an electroacoustic transducer according to Embodiment 1 of the present invention.
The superdirective sound source according to the first embodiment of the present invention is
composed of a sound generator 10, an amplitude modulator 20, an amplifier 30, an
electroacoustic transducer 40 and a high frequency generator 50.
[0010]
The sound generator 10 outputs an audible sound to the amplitude modulator 20 as a sound
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signal. The high frequency generator 50 outputs the ultrasonic carrier signal to the amplitude
modulator 20. The amplitude modulator 20 generates a modulation signal obtained by
amplitude-modulating the ultrasonic carrier signal with the voice signal, and outputs the
modulation signal to the amplifier 30. The amplifier 30 amplifies the modulated signal output
from the amplitude modulator 20 and outputs the amplified signal to the electroacoustic
transducer 40. The modulated signal amplified by the amplifier 30 is emitted from the
electroacoustic transducer 40 into the air as a sound wave.
[0011]
FIG. 2 is a view showing the electro-acoustic transducer 40 according to Embodiment 1 of the
present invention, in which (A) shows a top view, and (B) shows an enlarged cross-sectional view
of line A-A in (A). Is shown. The electroacoustic transducer 40 comprises a piezoelectric ceramic
41 and a metal plate 42 constituting a vibrator, a holding member 43 for holding the vibrator, a
terminal 44 for supplying a modulation signal to the vibrator, and a holder It comprises a
substrate 45 for fixing the material 43 and the terminal 44, a vibrating plate 401 vibrated by the
vibrator, and a convex body 402 connecting the vibrator and the vibrating plate 401. Also,
although not shown, the terminal 44 is coupled to the vibrator by a conductive member to supply
a modulation signal. Note that reference numeral 421 in FIG. 2A indicates a joint between the
diaphragm 401 and the convex body 402.
[0012]
The ultrasonic element 46 is composed of the vibrator, the holding material 43, and the terminal
44. A plurality of ultrasonic elements 46 are arranged in a lattice form on the substrate 45, and
the diaphragm 401 is coupled to the plurality of ultrasonic elements 46 by a convex body 402.
The number of ultrasonic elements 46 disposed on the substrate 45 is determined by the size of
the ultrasonic elements themselves and the size of the substrate 45.
[0013]
As the diaphragm 401, it is possible to use one having a certain degree of strength and being
lightweight, such as a metal foil, a polymer resin sheet, FPR (fiber reinforced plastic), and the like.
In addition, the thickness of the diaphragm 401 may be a thickness that does not cause bending
vibration, for example, a thickness of several tens μm to several hundreds μm. Since the
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thickness at which bending vibration does not occur differs depending on the strength of the
diaphragm, the thickness at which bending vibration does not occur is determined according to
the strength of the diaphragm.
[0014]
Further, the shape of the metal plate 42 constituting the vibrator may be any shape such as a
square or a hexagon other than a circle.
[0015]
FIG. 3 is a cross-sectional view showing a shape usable as the convex body 402. As shown in FIG.
(A) is a rod-like body attached by penetrating the metal plate 42 from the piezoelectric ceramic
41, and shows a rod-like convex body 403 in which the upper end portion is expanded and the
area of the connecting portion with the diaphragm 401 is widened. . (B) shows a cylindrical
convex body 404 obtained by cutting a cylindrical body such as a cylinder short. (C) shows a
cone-shaped convex body 405 which is coupled with a small area to the upper central portion of
the metal plate 42 with a small area and coupled with a diaphragm 401 in a wide area in cross
section. Also, the diaphragm 401 may be directly coupled by an adhesive or the like dropped to a
small diameter at the center of the upper surface of the metal plate 42 of the vibrator without
having a convex body.
[0016]
Here, as a desirable structure of the convex body, the vibration of the metal plate 42 can be
transmitted to the diaphragm 401 without deformation, and the bonding area with the metal
plate 42 is small and the bonding area with the diaphragm 401 is large. It is desirable. That is,
the metal plate 42 generating the bending vibration and the convex body 402 are coupled to the
central portion of the upper surface of the metal plate 42 having the largest amplitude width of
the vibration, whereby the vibration amplitude of the diaphragm 401 is maximized. As for the
coupling between the projection 401 and the convex body 402, the deformation of the
diaphragm 401 at the joint portion between the diaphragm 401 and the convex body 402 is
reduced by increasing the coupling area, and the vibration of the vibrator is effectively
transmitted to the diaphragm 401. It will be transmitted.
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[0017]
Next, the operation will be described. When an audible sound is output as an audio signal to the
amplitude modulator 20 from the audio generator 10, the amplitude modulator 20 modulates
the ultrasonic carrier signal output from the high frequency generator 50 by amplitude
modulation with the audio signal. A signal is generated and output to the amplifier 30. The
amplifier 30 receiving the modulated signal amplifies the modulated signal and outputs the
amplified signal to the electroacoustic transducer 40. The modulated signal amplified by the
amplifier 30 is emitted from the electroacoustic transducer 40 into the air as a sound wave.
[0018]
Here, the process in which the modulation signal is emitted from the electroacoustic transducer
40 into the air as a sound wave will be described in detail using FIG. FIG. 4 is an enlarged crosssectional view for explaining an element according to Embodiment 1 of the present invention and
a vibration state thereof. First, the modulation signal amplified by the amplifier 30 is supplied to
the vibrator composed of the piezoelectric ceramic 41 and the metal plate 42 through the
terminal 44 (not shown). The piezoelectric ceramic 41 causes mechanical deformation
corresponding to the change in voltage due to the modulation signal, and the vibrator causes
bending vibration. The vibration generated by the bending vibration is transmitted to the
diaphragm 401 via the convex body 402, and when the diaphragm 401 vibrates, the modulation
signal is emitted as air into the air. At this time, the plurality of ultrasonic elements 46 disposed
on the substrate 45 cooperate to vibrate the diaphragm 401 in a uniform operation.
[0019]
Further, in FIG. 4, the displacement distribution of the vibration of the diaphragm 401 when the
diaphragm 401 is coupled to the vibrator composed of the piezoelectric ceramic 41 and the
metal plate 42 is indicated by reference numeral 411. Further, in FIG. 4, a displacement
distribution of vibration when the vibrator is mechanically resonated alone is shown by a
reference numeral 412 without providing the diaphragm 401. In the case where the diaphragm
401 is not provided, since the vibrator generates bending vibration as indicated by reference
numeral 412 in FIG. 4, the sound pressure does not increase. On the other hand, in the case
where the diaphragm 401 is provided, the plurality of ultrasonic elements 46 cooperate to
vibrate the diaphragm 401 in a uniform operation, so as shown by reference numeral 411 in FIG.
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The entire diaphragm 401 vibrates uniformly on a plane perpendicular to the vibration direction,
and flat amplitude characteristics can be obtained.
[0020]
As described above, the electro-acoustic transducer according to the first embodiment is an
electro-acoustic transducer that radiates a modulated signal obtained by modulating an
ultrasonic carrier signal with an audio signal into the air as a sound wave. And a plurality of
ultrasonic elements provided on the plurality of ultrasonic elements, and a single vibration plate
that vibrates to emit sound waves. The transducer attached to the sound element becomes a
single diaphragm, and the vibration area is increased and the sound radiation efficiency is
improved as compared to the array of a plurality of ultrasonic elements, so high sound pressure
can be obtained. There is an effect that can be done.
[0021]
In addition, the resonator, the case, and the base, which are attached to the conventional
ultrasonic element, are not required, the assembling process is greatly simplified, and the
manufacturing cost can be reduced.
Further, since there is no resonator having a large variation in resonance frequency, there is an
effect that the resonance variation is reduced. In addition, the vibration surface is the entire
diaphragm, so that flat amplitude characteristics can be obtained, and bending vibration of the
diaphragm is unlikely to occur as in the prior art, so that there is an effect that sound generation
efficiency is significantly improved. Further, in the resonant state of the vibrator, the amplitude
of the diaphragm is maximized, so that the generated sound pressure is also increased.
[0022]
The ultrasonic element may be disposed on the substrate and the diaphragm may be provided
while the base is provided. In addition, the electroacoustic transducer may be provided with a
cover which protects the diaphragm 401 and through which the sound wave emitted from the
diaphragm passes. In this case, it is possible to use the electroacoustic transducer even in the
place where there is a possibility of damage.
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[0023]
Second Embodiment FIG. 5 is a diagram showing the configuration of an electroacoustic
transducer according to Embodiment 2 of the present invention. In FIG. 5, the diaphragm is
removed from the electroacoustic transducer in order to show the arrangement of the ultrasonic
elements 46. Here, the feature of the electroacoustic transducer according to the second
embodiment lies in the arrangement of the ultrasonic elements 46. In the first embodiment, the
plurality of ultrasonic elements 46 are arranged in a lattice, and as shown in (A) of FIG. When the
diaphragm 401 does not have sufficient strength, the diaphragm 401 may cause bending
vibration at a portion not held by the ultrasonic element by the coupling portion 421.
[0024]
Therefore, in the second embodiment, the close-packed filling surface of the ultrasonic element
46 is formed on the substrate by shifting the coupling portion by half a pitch so as to be
positioned at the apex of the regular triangle. With this configuration, the space not coupled to
the coupling portion in the diaphragm can be narrowed, and the space that can be bent is
narrowed, so that bending vibration can be prevented.
[0025]
As described above, in the electroacoustic transducer according to the second embodiment, the
arrangement of the ultrasonic elements is arranged to be the closest packing surface, and the
space that may cause bending vibration is reduced. There is an effect that bending vibration
hardly occurs. Further, since bending vibration hardly occurs, there is an effect that the thickness
of the diaphragm can be reduced or a material with low strength can be used.
[0026]
It is a block diagram which shows an example of a structure of the super-directional sound
source which concerns on Embodiment 1 of this invention. FIG. 1A is a front view and a crosssectional view of an electro-acoustic transducer according to Embodiment 1 of the present
invention. It is a figure which shows the shape of the convex-shaped body which concerns on
Embodiment 1 of this invention. It is sectional drawing which shows the vibration state of the
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electroacoustic transducer which concerns on Embodiment 1 of this invention. It is a block
diagram which shows an example of the array method of the ultrasonic element which concerns
on Embodiment 2 of this invention.
Explanation of sign
[0027]
DESCRIPTION OF REFERENCE NUMERALS 10 sound generator, 20 amplitude modulator, 30
amplifier, 40 electroacoustic transducer, 41 piezoelectric ceramic, 42 metal plate, 43 holding
material, 44 terminal, 45 substrate, 46 ultrasonic element, 50 high frequency generator, 401
diaphragm , 402 convex body, 403 bar convex body, 404 cylindrical convex body, 405 cone
convex body, 411 diaphragm displacement distribution, 412 vibrator displacement distribution,
421 coupling portion.
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