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JPH11239394

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DESCRIPTION JPH11239394
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
superdirective speaker excellent in directivity by use of ultrasonic waves.
[0002]
2. Description of the Related Art It is known in the prior art to use ultrasound to achieve highly
directional superdirective speakers. For example, Japanese Patent Application Laid-Open No. 3159400 discloses a technique for forming a superdirective speaker with high directivity using an
audio signal and an ultrasonic wave. In this case, an ultrasonic wave having a predetermined
frequency is used as a carrier wave, and an electroacoustic transducer is disposed on a plane
where a modulation signal obtained by amplitude-modulating the ultrasonic wave with an audio
signal is placed on a plane. It is made to output as a sound via this electroacoustic transducer.
[0003]
Further, in Japanese Patent Application Laid-Open No. 3-296399, similarly, a modulation signal
obtained by amplitude-modulating an ultrasonic wave with an audio signal is output as sound
from a speaker in which a large number of ultrasonic transducers are arranged on a plane. There
is disclosed a technique in which such a speaker is vibrated or turned so that a predetermined
sound is transmitted only to a person at a predetermined position.
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[0004]
The block diagram of FIG. 6 shows the technology of the superdirective speaker disclosed in each
of the above-mentioned publications including a planar electroacoustic transducer.
[0005]
That is, the voice signal generated by the voice generator 10 and the high frequency signal
generated by the high frequency generator 50 are modulated by the amplitude modulator 20,
and this is amplified by the amplifier 30 to obtain a planar electroacoustic transducer 45. It
radiates as acoustic vibration by.
Acoustic vibration causes non-linear interaction in the process of being propagated through the
air as ultrasonic waves. Then, it is demodulated into superdirective sound consisting of low
frequency components, and can be heard by the listener.
[0006]
SUMMARY OF THE INVENTION However, in the case of the technique described in the abovementioned publication indicated in conjunction with FIG. 6, the following problems to be solved
remain.
[0007]
One problem is that the listener can not be given a high sound pressure to listen.
The reason is that since the electroacoustic transducer is configured in a planar shape, the
acoustic vibration energy does not converge, and the listener can only listen to a part of the
acoustic vibration.
[0008]
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In addition, one of the problems related to the above is that the configuration of the circuit
becomes complicated and the cost rises. That is, when it is required to output high sound
pressure sound from the superdirective speaker, the number of electroacoustic transducers is
increased to increase the overall output. At the same time, the amplification factor of the
amplifier 30 shown in FIG. 6 has to be increased, which complicates the circuit and is
disadvantageous in cost.
[0009]
On the other hand, the Technical Report of the Electronics and Information Communication
Society, "EA 94-37; 1994-08 pp. 25-pp. In 30 "Airborne sound source by parametric array beam",
there is reported a technology of reflecting acoustic vibration on a paraboloid to converge
acoustic vibration.
[0010]
However, in the case of this technology, the increase in size of the device becomes a problem.
That is, a method is adopted in which the acoustic vibration is converged by reflecting the
acoustic vibration output from the electroacoustic transducer on the parabolic surface. Therefore,
in addition to requiring an electroacoustic transducer, a reflector having a parabolic shape is
needed.
[0011]
Therefore, an object of the present invention is to solve each problem of the above-mentioned
prior art, and to provide a superdirective speaker capable of listening to high sound pressure to a
listener.
[0012]
SUMMARY OF THE INVENTION A superdirective speaker according to the present invention
modulates an audio signal generated by an audio generator and a high frequency signal
generated by a high frequency generator respectively by an amplitude modulator and amplifies it
by an amplifier. Accordingly, the electro-acoustic transducer emits acoustic vibration as an
acoustic vibration radiation plate, the electro-acoustic transducer comprising an acoustic
vibration radiation plate curved inward with a concave curved surface, and the acoustic vibration
radiation plate A plurality of electroacoustic transducers are arranged along a curved surface,
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and acoustic vibration outputted from each of the electroacoustic transducers is configured to
converge at a listening position at a predetermined distance.
[0013]
In this case, the electro-acoustic conversion elements are arranged in an array form having
regularity with respect to the center of the acoustic vibration radiation plate, and as an array
form having regularity, the electro-acoustic conversion elements are annular with respect to the
center of the acoustic oscillation radiation plate. It can be in the form of a circular array or a
closely-spaced array form that is radially adjacent.
[0014]
Furthermore, the superdirective speaker according to the present invention is provided on the
front of the electroacoustic transducer, and is arranged along the curved surface of the acoustic
vibration radiation plate which is curved inward with a concave curved surface. And a listener
position recognition unit for detecting the position of the listener, and a position detection signal
of the listener received from the listener position recognition unit. A radiation plate shape control
means for variably controlling the curved shape by changing the curvature of the acoustic
vibration radiation plate so that the acoustic vibration outputted from the electroacoustic
transducer can be converged to the position of the listener corresponding to It can be provided
and configured.
[0015]
In this case, the listener position recognition means outputs an acoustoelectric converter that
converts the reflected wave of the acoustic vibration that reaches and reflects the listener into an
electrical signal, an ultrasonic modulation signal, and an output from the acoustoelectric
converter A delay detector for detecting a time delay from the difference between the two signals
based on the two signals of the electrical signal, and calculating the distance to the listener based
on the delay signal output from the delay detector And a distance calculator.
[0016]
In addition, the acoustic vibration radiation plate provided in the radiation plate shape control
means includes, for example, a plurality of connected sector blades forming a wedge shape, and
this sector blade is simultaneously expanded and contracted by an operation mechanism like a
diaphragm shutter mechanism. Operated to change the wedge curvature, it is possible to always
generate maximum and high sound pressure.
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[0017]
According to the above configuration, by freely changing the curved shape of the acoustic
vibration radiation plate according to the position of the listener, the listener can always hear a
high sound pressure at maximum.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the
superdirective speaker of the present invention will be described in detail with reference to the
drawings.
FIG. 1 is a block diagram showing the configuration of the first embodiment according to the
present invention.
A voice generator 10 is provided, and the voice signal generated here is to be modulated by an
amplitude modulator 20.
The voice generator 10 is a device that generates an electrical voice signal corresponding to the
voice that can be heard by the listener.
For example, a cassette tape player that converts audio information recorded in a cassette tape
into an electrical audio signal, a personal computer that converts audio information recorded in a
hard disk drive into an electrical audio signal, and the like are audio generators. 10 can be
configured.
[0019]
In addition, a high frequency generator 50 is provided, and the high frequency signal generated
here is similarly modulated by the amplitude modulator 20.
That is, in the case of the high frequency generator 50, a high frequency signal of the frequency
of the ultrasonic band can be generated, and can be configured as a clock oscillation circuit or
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the like as a specific example.
[0020]
Here, as the amplitude modulator 20, the input voice signal and high frequency signal can be
modulated into an amplitude modulation wave signal and output.
The amplitude modulation wave signal is amplified by the amplifier 30 to, for example, 20 to 40
volts (V).
If the voltage amount of the amplitude modulation wave signal is sufficiently large, the
installation of the amplifier 30 can be omitted.
[0021]
Further, the amplifier 30 amplifies the audio signal and the high frequency signal modulated in
the amplitude modulator 20, and generates an acoustic signal from the wedge-shaped acoustic
vibration radiation plate 42 provided in the electric / acoustic transducer 40 shown in FIGS.
Radiation output is possible as vibration.
[0022]
In the electro-acoustic transducer 40, as shown in FIG. 2, the wedge-shaped acoustic vibration
radiation plate 42 has a circular shape when viewed from the front of the traveling direction of
the acoustic vibration, and for example, 91 electroacoustic waves The conversion elements
(hereinafter, abbreviated as sound generation elements) 41 are arranged close to each other.
As shown in the cross-sectional view of FIG. 3 viewed from the lateral direction of the traveling
direction of the acoustic vibration, the sound emitting elements 41 are arranged along a wedgeshaped arc surface.
[0023]
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In the case of the first embodiment, the acoustic vibration radiation plate 42 of the electric /
acoustic transducer 40 is not limited to the illustrated shape. Of course, other shapes such as
square, rectangle and oval are also possible. Further, although the configuration is shown in
which 91 sound emitting elements 41 are arranged close to each other, the number may be any
number as long as it is one or more, and it is possible to freely arrange circularly.
[0024]
In addition, since the sound emitting elements 41 may be arranged along a curve, for example,
they can be arranged freely as if they are parabolic or circular arcs. Although the configuration of
the sound emitting element 41 is not particularly limited, for example, a ceramic piezoelectric
element can also be used.
[0025]
Next, the operation and action of the first embodiment having the above configuration will be
described.
[0026]
The propagation direction of the acoustic vibration is shown by a solid line in FIG. 3 and
propagates while giving the largest acoustic energy in the vertical direction of the sound emitting
element 41.
Thus, the acoustic vibrations converge and overlap at point A, giving the listener a maximum
sound pressure at point A. This acoustic vibration causes non-linear interaction in the process of
being propagated through the air as ultrasonic waves, and is demodulated into superdirective
voice composed of low frequency components and the like, and can be heard by the listener.
[0027]
Therefore, the sound signal generated by the sound generator 10 and the high frequency signal
generated by the high frequency generator 50 are modulated by the amplitude modulator 20,
amplified by the amplifier 30, and acoustic vibration radiation provided to the electric / acoustic
transducer 40. The plate 42 converts it into acoustic vibration and radiates it into the air.
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[0028]
The frequency band of the acoustic vibration output by the sounding element 41 may be any
ultrasonic band of 20 kHz or more.
By using a relatively low ultrasound band around 40 kHz, the listener listens to higher sound
pressure. Also, by using a relatively high ultrasound band of 100 kHz to 300 kHz, the listener
listens to more directional speech. FIG. 4 is a block diagram showing the configuration of the
second embodiment according to the present invention. In this case, the listener position
recognition means 60 and the curved surface shape control means 70 are provided. That is, the
voice signal generated by the voice generator 10 and the high frequency signal generated by the
high frequency generator 50 are respectively modulated by the amplitude modulator 20,
amplified by the amplifier 30, and acoustic vibration radiation of the electric / acoustic
transducer 40 The plate 42 emits radiation as acoustic vibration. The acoustic vibration causes
non-linear interaction in the process of propagating through the air as ultrasonic waves, and is
demodulated into superdirective voice consisting of low frequency components and is heard by
the listener.
[0029]
The listener position recognition means 60 recognizes the position of the listener listening to the
acoustic vibration and notifies the curved surface shape control means 70 of the position
information. The curved surface shape control means 70 changes the shape of the electroacoustic transducer 40 according to the position information of the listener, and adjusts the
convergence point of the acoustic vibration to the position of the listener.
[0030]
Here, FIG. 5 is an example showing the configuration of the listener position recognition means
60. As shown in FIG. The acoustic / electrical converter 61 converts the acoustic vibration, i.e.,
the reflected wave, which the acoustic vibration reaches the listener and reflects, into an
electrical signal. The delay detector 62 receives the electrical signal converted from the reflected
wave and the ultrasonic modulation signal, and detects a time delay from the difference between
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the two signals. The distance calculator 63 calculates the distance from the time delay.
[0031]
For example, when the listener is positioned at point A in FIG. 3, the acoustic vibration radiation
plate 42 of the electric / acoustic transducer 40 is variably curved so that the acoustic vibration
converges to the point A. When the listener is located at a distance closer to point A or at a
longer distance, the curved shape of the acoustic vibration radiation plate 42 of the
electroacoustic transducer 40 changes, and the convergence point is brought closer. It is possible
to go far. As a mechanism of the acoustic vibration radiation plate 42, the curvature can be
varied by expanding and contracting a plurality of sector blades like a diaphragm shutter.
[0032]
Also, a technique known as an application of the prior art, for example, an ultrasonic filter for
removing the adverse effect of ultrasonic waves on human hearing, and determining the
presence or absence of a reflected wave from a listener and switching an audio input signal It is
obvious that by applying to the present invention, etc., they also have their original effects
without losing the effects of the present invention.
[0033]
As described above, in the superdirective speaker according to the present invention, by making
the electroacoustic transducer a curved surface structure, generation of high sound pressure
becomes possible by convergence of acoustic vibration energy, High sound pressure can be given
to the listener.
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