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JP2013021448

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DESCRIPTION JP2013021448
Abstract: The present invention provides a superdirective speaker that widens the radiation angle
and makes the sound pressure level in the radiation angle range substantially uniform. A
plurality of array sound sources are formed by arraying a plurality of ultrasonic elements 41 for
converting an amplified signal output from a first amplifier 30 into ultrasonic waves, and
adjacent ones of the plurality of array sound sources are provided. The emitters 40 are provided
in which the phases of the arrayed sound sources are set to substantially opposite phases.
[Selected figure] Figure 1
Super directional speaker
[0001]
The present invention relates to a superdirective speaker that provides audible sound in a very
narrow area.
[0002]
A conventional superdirective speaker that obtains the non-linear phenomenon of air is
configured, for example, as follows.
First, an audio signal generated by an audio generator that generates an audible sound is
multiplied by an ultrasonic carrier signal from a high frequency generator in a multiplier.
Modulation is performed by the multiplication processing, a modulator and a high frequency
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1
generator constitute a modulator, and a modulation wave signal is obtained as an output thereof.
The modulated wave signal of the modulator is amplified by an amplifier, and ultrasonic elements
that emit ultrasonic waves are supplied to the emitters arranged in an array, and emitted as
sound waves from the emitters. The sound wave causes a non-linear interaction on the
assumption that the sound wave propagates in air as a finite amplitude sound wave which is a
strong ultrasonic wave, and the low frequency component which is the original audible sound is
self-demodulated and becomes audible. Here, the sound radiation pattern of the sound is
generated only in the front direction of the emitter, and not generated in the side direction and
the back direction of the emitter, so that the characteristic sound pressure distribution of the
parametric speaker is obtained.
[0003]
On the other hand, depending on the use environment of the superdirective speaker, it may be
desired to change the directivity angle. For example, Patent Document 1 describes a directional
sound source that extends the directivity angle of a superdirective speaker that provides audible
sound in a very narrow area. Specifically, a sound source unit including a plurality of ultrasonic
elements arranged in a multilayer annular shape is provided, and the directivity angle is changed
by changing the diameter of the sound source unit.
[0004]
Further, in Non-Patent Document 1, in order to reduce the ultrasonic sound pressure level
concentrated on the front of the emitter in the superdirective speaker, the sound source is
divided into two regions and the phase is shifted 180 ° between the center and the outside.
Methods of interference are described.
[0005]
Japanese Utility Model Laid-Open Publication No. 4-103091
[0006]
Satoshi Kikuchi, Hidetoshi Aiko, Tomoo Kamakura, Hideyuki Nomura, Shin-ichi Sakai, "Phase
Reversal Drive for Parametric Loudspeakers to Reduce the Sound Pressure of Carrier Ultrasound"
The Institute of Electronics, Information and Communication Engineers Technical Report
2008.11
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2
[0007]
However, in the above-described conventional superdirective speaker, for example, in the case of
an annular sound source, it is possible to change the directivity by changing the diameter of the
sound source unit, but in the case where the directivity is changed The radiation pattern to be
emitted is also a sharp unimodal pattern at the tip, and the hearing range is pinpointed, so that
when one listens to the sound of the superdirective speaker, it is unpleasant that only one ear
gets loud There was a problem of giving a sense of incongruity.
Further, at a short distance of the speaker, the sound pressure level of the ultrasonic wave at the
center of the front of the speaker is large, and there is also a concern that the ultrasonic
exposure of the large sound pressure level may affect the human body.
Further, in the superdirective speaker of Non-Patent Document 1, although the sound pressure
level of the ultrasonic wave in front of the emitter is reduced, the radiation pattern of the audible
sound is a sharp unimodal pattern as in the prior art, and the same problem as described above
Will remain.
[0008]
The present invention has been made to solve the above-described problems, and an object of the
present invention is to provide a superdirective speaker that widens the radiation angle and
substantially uniforms the sound pressure level in the radiation angle range.
[0009]
The superdirective speaker according to the present invention comprises a plurality of array
sound sources formed by arraying a plurality of ultrasonic elements for converting the amplified
signal output from the first amplifier into ultrasonic waves, and the plurality of array sound
sources Among them, an emitter is provided in which the phases of adjacent arrayed sound
sources are set to substantially opposite phases.
[0010]
According to the present invention, interference between arrayed sound sources makes it
possible to expand the directivity angle, whereby the sound pressure level in the directivity angle
range becomes uniform, and the sound pressure level of ultrasonic waves in front of the emitter
can be reduced. .
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[0011]
FIG. 1 is a block diagram showing a configuration of a superdirective speaker according to a first
embodiment.
FIG. 2 is a diagram showing a detailed structure of an emitter of the superdirective speaker
according to the first embodiment.
FIG. 6 is a diagram showing a polar pattern of the superdirective speaker according to the first
embodiment.
FIG. 5 is a diagram showing the arrangement of ultrasonic elements of the superdirective speaker
according to Embodiment 1 and the polar pattern thereof.
FIG. 7 is a diagram showing another configuration example of the emitter of the superdirective
speaker according to the first embodiment. FIG. 7 is a diagram showing another configuration
example of the emitter of the superdirective speaker according to the first embodiment. FIG. 10
is a block diagram showing a configuration of a superdirective speaker according to Embodiment
2. FIG. 10 is a block diagram showing another configuration of the superdirective speaker
according to Embodiment 2. It is a figure which shows the example of arrangement ¦ positioning
of the annular ¦ circular shaped sound source of the super-directional speaker by other structure.
[0012]
Embodiment 1 FIG. 1 is a block diagram showing the structure of a superdirective speaker
according to a first embodiment of the present invention. The superdirective speaker 100
according to the first embodiment includes an audio generator 10 generating an audio signal
indicating an audible sound, an amplitude modulator 20 inputting an audio signal to generate an
amplitude modulation signal, and amplifying an amplitude modulation signal An amplitude
modulation signal amplified by the first amplifier 30 and the first amplifier 30 is converted into
an ultrasonic wave and the emitter 40 emits the sound as acoustic vibration (sound) into the air.
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Further, the amplitude modulator 20 inputs a high frequency generator 21 for generating a
signal indicating a carrier wave in the ultrasonic band, and an ultrasonic carrier wave signal from
the high frequency generator 21 and an audio signal from the voice generator 10; It comprises a
multiplier 22 which performs multiplication processing of these signals.
[0013]
In the emitter 40, as shown in FIG. 1, a plurality of ultrasonic elements 41 for emitting ultrasonic
waves are annularly arranged. Each ultrasonic element 41 has a "+" phase or a "-" phase. FIG. 2 is
a diagram showing the detailed structure of the emitter of the superdirective speaker according
to the first embodiment of the present invention. In the example of FIG. 2, the plurality of
ultrasonic elements 41 have annular sound sources 50a, 50b and 50c which are three concentric
circles different in radius, and these annular sound sources 50a, 50b and 50c are multilayered to
form a multilayer circle An annular sound source 50 is configured. The annular sound sources
50a, 50b, and 50c are arranged such that the ultrasonic elements 41 are adjacent to both sides
of the center circles 51a, 51b, and 51c. Further, adjacent annular sound sources 50a and 50b
and adjacent annular sound sources 50b and 50c are connected so as to have opposite phases.
For example, when the annular sound source 50 a is in the + phase, the annular sound
source 50 b is connected to be the − phase, and the annular sound source 50 c is connected
to be the + phase. By alternately connecting the adjacent annular sound sources 50a, 50b,
50c in this manner, the adjacent annular sound sources 50a, 50b, 50c have opposite phases, and
the sound emitted from the emitter 40 is It interferes and the pointing angle spreads.
[0014]
The center circles 51a, 51b, 51c of the annular sound sources 50a, 50b, 50c are spaced apart by
a predetermined distance, but the high frequency generator 21 generates the separation distance
between the center circle 51a and the center circle 51b. By setting the frequency to be twice or
less of the wavelength determined by the frequency to be made, the directivity angle of the
sound emitted from the emitter 40 can be expanded, and the sound pressure level within the
range of the directivity angle can be made uniform.
[0015]
FIG. 3 is a diagram showing a polar pattern of the superdirective speaker according to the first
embodiment of the present invention.
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Region A in FIG. 3 indicates the sound pressure level when the distance between the center circle
51a and the center circle 51b and the distance between the center circle 51b and the center
circle 51c are separated within a range of twice the predetermined wavelength or less. Region B
indicates the sound pressure level when separated by a range of twice or more of the
predetermined wavelength, and region C indicates the sound pressure level of the conventional
superdirective speaker. In the region B, the directivity angle is expanded compared to the region
C, or the sound pressure level in the desired directivity angle range P-Q is not uniform. On the
other hand, in the region A, the directivity angle is wider than in the region B and the region C,
and the sound pressure level in the desired directivity angle range P-Q is uniform.
[0016]
Next, the arrangement of the ultrasonic elements 41 in the annular sound sources 50a, 50b, and
50c will be described. FIG. 4 is a view showing the arrangement of the ultrasonic elements
constituting the emitter of the superdirective speaker according to the first embodiment of the
present invention and the polar pattern thereof. 2 shows an annular sound source in which the
ultrasonic elements 41 are disposed adjacent to both sides of the center circles 51a, 51b, and
51c, but in FIG. 4, the ultrasonic elements 41 are simply arranged in a line. Sound as a circular
toroidal sound source. 4 (a) shows the case where the centers of the ultrasonic elements 41 are
not positioned on the axis X passing through the center of the emitter 40, and FIG. The case
where it arrange ¦ positions so that the center of the sound wave element 41 may be located is
shown.
[0017]
Polar patterns in the case of adopting the configuration of FIG. 4A are shown in the area D of FIG.
4C, and polar patterns in the case of employing the configuration of FIG. 4B are shown in the
area E of FIG. It shows. In the region E, side lobes E ′ are formed compared to the region D. This
is because when the centers of the ultrasonic elements 41 are aligned on the axis X, that is, in a
straight line, the interference of ultrasonic waves is concentrated to generate unnecessary side
lobes. As apparent from these, when the center of the ultrasonic element 41 of one annular
sound source of the multilayer annular sound source 50 is located on the axis X passing through
the center O of the emitter 40, the one annular ring The occurrence of unnecessary side lobes
can be suppressed by arranging the centers of the ultrasonic elements forming the other on-ring
sound sources excluding the sound source not to be located on the axis X.
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[0018]
FIGS. 5 and 6 are diagrams showing other configuration examples of the emitter of the
superdirective speaker according to the first embodiment of the present invention. FIG. 5 shows a
multilayer rectangular annular sound source 52 configured by layering a plurality of rectangular
annular sound sources in which ultrasonic elements 41 are arranged in a rectangular annular
shape. Also, in addition to the one shown in FIG. 5, it may be arranged in a ring shape of a
polygon such as a hexagon. The same performance can be obtained even when the arrangement
of the ultrasonic elements 41 is arranged in a rectangular, hexagonal or other polygonal annular
structure.
[0019]
FIG. 6A shows a multilayer linear sound source 53 in which a plurality of linear sound sources in
which the ultrasonic elements 41 are linearly arranged are multilayered in the lateral direction of
the emitter 40. FIG. 6 (b) shows the polar pattern. In the configuration shown in FIG. 6A, the
ultrasonic elements 41 adjacent to each other in the lateral direction of the emitter 40 are
arranged so as to be alternately different. Therefore, as shown in FIG. 6B, in the area F of the
polar pattern by the ultrasonic element 41 in the lateral direction of the emitter 40, the sound
pressure level in the front near 0 ° tends to slightly decrease. The angle spreads, the directivity
angle of the radiation pattern spreads, and the sound pressure level in the directivity angle range
P-Q becomes substantially uniform. On the other hand, in the vertical direction of the emitter 40,
the adjacent ultrasonic elements 41 are arranged so as to have the same polarity. Therefore, as
shown in FIG. 6 (b), the area G of the polar pattern by the ultrasonic element 41 in the
longitudinal direction of the emitter 40 becomes a unimodal pattern having a sharp directional
angle similar to the prior art, and the sound pressure in the directional angle range PQ The level
is not uniform.
[0020]
Thus, by configuring the array sound source in which the ultrasonic elements 41 are linearly
arranged, the radiation pattern by the ultrasonic elements 41 in the lateral direction of the
emitter 40 and the radiation pattern by the ultrasonic elements 41 in the vertical direction of the
emitter 40 Are different, and superdirective speakers having different pointing angles depending
on the arrangement direction of the emitters 40 can be obtained. Of course, the ultrasonic
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elements 41 adjacent to each other in the lateral direction of the emitter 40 may be arranged to
have the same polarity, and the ultrasonic elements 41 adjacent to each other in the vertical
direction to the emitter 40 may be arranged alternately differently. .
[0021]
As described above, according to the first embodiment, the multilayer annular sound source 50
in which the annular sound sources 50a, 50b, and 50c are multilayered is provided, and adjacent
annular sound sources are arranged in substantially opposite phase. Therefore, the directivity
angle can be expanded by the interference between the annular sound sources. Furthermore, the
sound pressure level in the range of the directivity angle becomes uniform, and the sound
pressure level of the ultrasonic wave in front of the emitter can be reduced.
[0022]
Further, according to the first embodiment, for example, in the annular sound sources 50a and
50b adjacent to each other, the distance between the central circle 51a and the central circle 51b
is twice or less the wavelength determined by the frequency generated by the high frequency
generator 21. The sound pressure level of the ultrasonic wave in the directivity angle range can
be made uniform.
[0023]
Further, according to the first embodiment, when the center of the ultrasonic element 41 forming
one annular sound source is located on the axis X passing through the center O of the emitter 40,
the other annular sound sources are selected. The arrangement is made so that the center of the
ultrasonic element 41 to be formed is not located on the axis X, so the generation of unnecessary
side lobes can be suppressed.
[0024]
Second Embodiment
In the first embodiment, a configuration is shown in which adjacent annular sound sources are
connected so as to have opposite phases, but in the second embodiment, a configuration is
provided in which means for switching the phase of adjacent annular sound sources is provided.
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FIG. 7 is a block diagram showing the configuration of the superdirective speaker according to
the second embodiment. A phase shifter 60 and a second amplifier 31 are additionally provided
to the superdirective speaker 100 shown in FIG. The phase shifter 60 and the second amplifier
31 are provided downstream of the amplitude modulator 20. The phase shifter 60 can freely
adjust the phase of the signal subjected to multiplication processing in the multiplier 22. In the
configuration shown in FIG. 7, the signal of + phase output from the multiplier 22 is adjusted
to a signal of − phase by the phase shifter 60, amplified by the second amplifier 31, and
output to the emitter 40. doing. As described above, by providing the phase shifter 60 capable of
changing the phase angle, the phase can be set arbitrarily, and if the phase is set to 0 °, the
narrow directivity as in the prior art can be obtained, and the directivity angle Can be obtained.
[0025]
FIG. 8 is a block diagram showing another configuration of the superdirective speaker according
to the second embodiment. In FIG. 8, the changeover switch 70 is provided at the subsequent
stage of the phase shifter (antiphase) 61 that adjusts the phase to the antiphase. The phase
shifter (anti-phase) 61 adjusts the signal input from the multiplier 22 to an anti-phase signal. The
changeover switch 70 is a switch for receiving the signal from the multiplier 22 and the signal
adjusted to be in the reverse phase by the phase shifter (reverse phase) 61 and arbitrarily
selecting the output signal. In the configuration shown in FIG. 8, the switch 70 receives the +
phase signal output from the multiplier 22 and the − phase signal output from the phase
shifter (anti-phase) 61. When the signal of + phase outputted from the multiplier 22 is
selected by the changeover switch 70 and is outputted to the second amplifier 31, it becomes a
conventional single peak pattern. On the other hand, when the signal of − phase outputted
from the phase shifter (negative phase) 61 is selected by the changeover switch 70 and
outputted to the second amplifier 31, a radiation pattern having uniform sound pressure level in
the directivity angle range is obtained. be able to.
[0026]
As described above, according to the second embodiment, since the phase shifter 60 for
adjusting the phase of the signal subjected to multiplication processing in the multiplier 22 is
provided, the phase of the ultrasonic element 41 can be set arbitrarily. It is possible to obtain a
superdirective speaker whose directivity angle can be switched.
[0027]
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Further, according to the second embodiment, the phase shifter (antiphase) 61 which adjusts the
phase of the signal subjected to multiplication processing in the multiplier 22 to the opposite
phase, the signal output from the multiplier 22 and the phase shifter (inverse Phase switch 61
configured to optionally select an output signal from two input signals with the signal output
from phase 61, so that a radiation pattern with uniform sound pressure levels in the unimodal
pattern and directivity angle range And can be switched.
[0028]
In the above-described first and second embodiments, the configuration in which the ultrasonic
elements 41 are formed into an array is shown, but the present invention is not limited to the
configuration in which the ultrasonic elements 41 are provided. -Various electro-acoustic
conversion methods having a film-shaped diaphragm such as an electrostatic type can be applied.
Further, the type and size of the ultrasonic element 41 disposed in the emitter 40 can be
appropriately changed as long as the reproduction frequency characteristic in the ultrasonic
band is the same.
[0029]
Moreover, in Embodiment 1 and Embodiment 2 mentioned above, in order to make adjacent
annular ring-shaped sound source 50 into reverse phase, although the structure which connects
the ultrasonic element 41 alternately to + pole and-pole was shown, connection is A phase
difference of a distance corresponding to approximately 1⁄2 wavelength of the wavelength
determined by the frequency generated by the high frequency generator 21 is provided in the
same annular pole 50 adjacent to each other, and the phase is shifted 180 ° in the sound
radiation direction. It may be configured.
This makes it possible to obtain the same effect as changing the connection alternately.
[0030]
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Moreover, although the structure which provides an electrical phase difference to the adjacent
annular ring-shaped sound source 50 was shown above, you may shift and arrange ¦ position the
position of each annular ring-shaped sound source 50 physically. FIG. 9 is a diagram showing an
arrangement example of the annular sound source of the superdirective speaker according to the
first or second embodiment. FIG. 9 (a) shows an example in which each annular sound source
50a, 50b, 50c is shifted by about a half wavelength (180 °), and FIG. 9 (b) is a circle with
respect to the annular sound source 50a, 50c. An example is shown in which the annular sound
source 50b is arranged by being shifted by a distance of approximately 1⁄2 wavelength (180 °).
[0031]
The wavelength can be calculated by the following equation (1). Wavelength = wave propagation
speed / frequency (1) The wave propagation speed is the speed of sound (340 m / sec), and the
frequency is an ultrasonic carrier. When the ultrasonic carrier is calculated at 40 kHz, the
wavelength is calculated as the following equation (1) ′. Wavelength = 340 [m / sec] / 40 [kHz]
= 8.5 [mm] ... (1) ́
[0032]
In the scope of the invention, the present invention allows free combination of each embodiment,
or modification of any component of each embodiment, or omission of any component in each
embodiment. .
[0033]
DESCRIPTION OF SYMBOLS 10 voice generator, 20 amplitude modulator, 21 high frequency
generator, 22 multiplier, 30 1st amplifier, 31 2nd amplifier, 40 emitter, 41 ultrasonic element,
50 multilayer annular ring sound source, 50a, 50b, 50c Annular sound source, 51a, 51b, 51c
center circle, 52 multilayer rectangular ring sound source, 53 multilayer linear sound source, 60
phase shifter, 61 phase shifter (antiphase), 70 switch, 100 super-directional speaker.
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