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JP2009290357

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DESCRIPTION JP2009290357
PROBLEM TO BE SOLVED: To provide a parametric speaker capable of obtaining a high
reproduction pressure reproduction sound in a desired range and position while achieving
downsizing of the entire device, and further providing an excellent assemblability and
maintainability. There is. SOLUTION: A plurality of ultrasonic transducers are mounted on the
same long substrate to constitute an ultrasonic transducer module, and a reflection plate is
provided at a position facing directly to each ultrasonic transducer of the ultrasonic transducer
module. . After the ultrasonic wave emitted from the ultrasonic transducer is reflected by the
reflection plate, the reflected sound is synthesized to reproduce an audible sound. [Selected
figure] Figure 4
パラメトリックスピーカー
[0001]
According to the present invention, when an ultrasonic wave modulated by an audible sound
signal or the like is emitted into air, a parametric characteristic that the modulated signal is
demodulated as an audible sound along an ultrasonic wave propagation path as a result of the
non-linear characteristic of air with respect to the ultrasonic wave It relates to a parametric
speaker using an array effect.
[0002]
Conventionally, as a device for generating an audible sound in a specific range of space, a
parametric speaker using non-linearity of air with respect to ultrasonic waves has been proposed.
03-05-2019
1
Patent Document 1 is an example. In this patent document 1, an audible sound signal source, a
carrier wave oscillator, a modulator, a power amplifier, and an ultrasonic transducer are
respectively provided, and amplitude modulation is performed on an ultrasonic wave generated
from the carrier wave oscillator with an audible range signal generated from the audible sound
signal source. The ultrasonic wave as an amplitude-modulated carrier wave is radiated from the
ultrasonic transducer through the power amplifier into the air, and the ultrasonic wave (primary
wave) radiated into the air has the carrier wave and upper and lower sideband waves. Can cause
non-linear interaction in the air, and the modulation signal can be self-demodulated along the
ultrasonic wave propagation path to obtain an effect that an audible sound (secondary wave) is
generated.
[0003]
Then, as a technique for improving the directivity of such a parametric speaker, ultrasonic
transducers that emit ultrasonic waves are arrayed and arranged on a curved surface (Patent
Document 2), or electroacoustic conversion is performed from an ultrasonic transducer. There
has been proposed a method (Patent Document 3) in which the emitted ultrasonic waves are
reflected by a curved surface. However, in the method of Patent Document 2, since there is no
countermeasure for the radiation emitted while spreading ultrasonic waves from the individual
ultrasonic transducers, the position determined by the curvature of the curved surface on which
the ultrasonic transducers are disposed There is a problem that the position of sound collection
extends over a wide range to some extent when the sound is collected. Since sound spreads at the
stage of emitting ultrasonic waves from the ultrasonic transducer, it is difficult to concentrate
ultrasonic waves emitted from multiple ultrasonic transducers in a narrow range even if they are
collected at a specific position, The further the position is from the ultrasound transducer, the
greater the problem.
[0004]
On the other hand, in Patent Document 3, ultrasonic waves are emitted from the ultrasonic
transducer toward the reflecting plate, and the ultrasonic radiation direction after reflection is
determined by the shape of the reflecting surface of the reflecting plate. The effects of the
ultrasonic radiation characteristics originally provided by the system can be eliminated at the
time of reflection by the reflector. Therefore, the radiation direction of the ultrasonic wave can be
03-05-2019
2
appropriately set by appropriately setting the shape of the reflecting plate to an elliptical shape
or a parabolic shape. However, since the system of this patent document 3 has a structure in
which an ultrasonic transducer is placed at the focal position using one reflector, it is difficult to
increase the number of ultrasonic transducers used. There is a problem that it is difficult to
increase the absolute amount of energy radiated from the acoustic transducer itself and it is
difficult to obtain an audible sound with high sound pressure. At the same time, there is also a
problem that the size of the entire speaker device increases. JP-B-1-15198 JP-A 2003-158788
JP-A 7-107588
[0005]
The present invention has been made to cope with the problems of the above-described prior
example, and while achieving the downsizing of the entire speaker device, it is possible to obtain
a high sound pressure reproduction audible sound in a desired range and position. The challenge
is to provide parametric speakers with excellent assemblability and maintainability.
[0006]
In order to solve the above problems, the present invention provides a plurality of ultrasonic
transducers for emitting ultrasonic waves modulated by an audible sound signal into a medium,
and a reflector for reflecting ultrasonic waves emitted from the ultrasonic transducers. And a
plurality of the ultrasonic transducers are mounted on the same long substrate for each of the
plurality of ultrasonic transducers to constitute an ultrasonic transducer module. We propose a
parametric speaker characterized in that the reflecting plate is provided for each transducer of
the ultrasonic transducer module.
[0007]
The ultrasonic transducer of the parametric speaker is preferably mounted in a direction in
which the ultrasonic waves after reflection are parallel to the surface of the long substrate, and
the cross-sectional shape of the reflection plate is substantially parabolic and parabolic. It is
desirable that the focal position and the position of the ultrasonic radiation surface of the
ultrasonic transducer substantially coincide with each other.
Further, a plurality of the reflecting plates facing the ultrasonic transducer module are disposed
along a curve, and the ultrasonic radiation surface of the ultrasonic transducer mounted on the
long substrate is made to face the reflecting plate and fixed. Is desirable.
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3
Furthermore, a plurality of ultrasonic transducer modules in which ultrasonic transducers are
mounted at predetermined intervals on a long substrate are disposed in parallel at predetermined
intervals, and a plurality of the reflecting plates are two-dimensionally opposed to each ultrasonic
transducer. It is desirable to place in
[0008]
According to the present invention, a plurality of ultrasonic transducers are mounted on the
same long substrate, a reflection plate is provided for each ultrasonic transducer, and the
ultrasonic waves emitted from the ultrasonic transducers are reflected by the reflection plate
Play an audible sound. According to this configuration, the ultrasonic wave emitted from the
ultrasonic transducer is once reflected by the reflection plate, and the reflection of each
ultrasonic transducer is reflected while taking advantage of the conventional structure of
facilitating adjustment of the ultrasonic radiation direction. By providing the plates, it is possible
to combine the reflected ultrasonic waves emitted from the plurality of reflectors into a
reproduction audible sound, and it is not necessary to use a reflector with a large external size
and it is used as one speaker The number of ultrasonic transducers can be increased. Therefore,
it is possible to realize a parametric speaker capable of reproducing an audible sound with high
reproduction sound pressure and controlling an audible area without increasing the external size
of the speaker device.
[0009]
In addition, the ultrasonic transducers are positioned at the focal point of the reflecting plate
corresponding to each ultrasonic transducer, and the ultrasonic radiation surface of the
ultrasonic transducers faces the reflecting plate in a plurality of ultrasonic waves. Since the
transducers are collectively mounted on the same long substrate, positioning of the reflection
plate and the ultrasonic transducer can be performed in plurals collectively, and the
assemblability can be improved. In addition, even when a failure or a defect occurs in the
ultrasonic transducer, it becomes possible to remove the entire long substrate and cope with the
repair of the failure occurrence part or to replace the entire long substrate, so that the
conventional ultrasonic Compared with the structure in which the transducers are arranged in an
array, it is possible to cope with partial repair or replacement.
[0010]
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4
In addition, since the cross-sectional shape of the reflection plate provided for each ultrasonic
transducer is substantially parabolic and the ultrasonic transducer is placed at the focal position
of the parabola, the ultrasonic waves after being reflected by the reflection plate are parallel I
will go forward. Therefore, by appropriately setting the directions of the individual reflectors, the
reflected sound waves are crossed at one point to cause a focal point to appear at an arbitrary
point, or a parallel beam-like audible sound generation region having no focal point is made to
appear. Etc., it becomes possible to easily set the characteristics of the entire speaker.
[0011]
Hereinafter, preferred embodiments of the present invention will be described based on the
drawings. FIG. 1 is an explanatory view showing the appearance of the present invention. As
shown, the parametric speaker according to the present invention incorporates a speaker drive
circuit inside the main casing 1, and an opening for generating sound is formed in the front of
the casing, and the opening is covered with a woven fabric.
[0012]
FIG. 2 is a block diagram showing an entire configuration including a drive circuit of a parametric
speaker according to an embodiment of the present invention. 11 is an audible sound signal
input unit to which an audio signal such as an audio signal or a music signal is input, 12 is an
AGC (auto gain control) circuit that automatically limits the amplitude of a signal input to the
audible sound signal input unit A carrier wave signal generating unit for generating a pulse
signal for obtaining a 40 kHz reference carrier signal which is a frequency of an ultrasonic band,
14 is an audio signal outputted from the audible sound signal input unit 11 to the carrier wave
outputted from the carrier wave signal generating unit 13 Pulse width modulation unit for pulse
width modulation. A low pass filter 15 cuts an audio sound frequency or more of the modulated
signal output from the pulse width modulation unit 14, and the cutoff frequency can be set as
appropriate. In this embodiment, the cutoff frequency is set to 10 kHz, and the generation of
spurious to the modulated signal is suppressed while cutting the treble band which is hard to
hear even when demodulated. An acoustic output unit 16 includes a plurality of ultrasonic
transducers arranged in an array, receives a modulated signal input through a low pass filter 15,
and emits the ultrasonic waves as air to a medium.
03-05-2019
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[0013]
In the above configuration, the audio signal input to the audible sound signal input unit 11 may
be stored in a storage device inside the device to be used as an audio sound source, but it is also
possible to use an audio sound source existing outside the device is there. If the signal
transmission terminal of the external audio source and the external signal input terminal (not
shown) of this device are connected by a signal cable, and the audio signal sent out through the
signal cable is input to the audible sound signal input unit 11 good. The carrier signal generation
unit 13 generates a pulse signal of at least 160 kHz, and when pulse width modulation is
performed by the pulse width modulation unit 14, one cycle of the 40 kHz reference carrier is
configured by four pulses.
[0014]
Next, the operation of the pulse width modulation unit 14 will be described based on FIG. FIG. 2
shows a state in which an audio signal of 4 kHz is output from the audible sound signal input
unit 11. First, an audio signal of 4 kHz is sampled at a sampling frequency of 40 kHz (FIG. 2 (a)),
and is quantized by 10 bits (1024 steps). The digitized audio signal is pulse width modulated
onto a 40 kHz carrier wave composed of four pulses per cycle as shown in FIG. 2 (b). The
modulated signal shown in FIG. 2B generated in this way is sent to the sound output unit 16
through the low pass filter 15, and drives the piezoelectric element of the ultrasonic transducer
arranged inside the sound output unit in the state of the digital signal. And perform
electroacoustic conversion. As described above, in the parametric speaker according to the
present invention, an audio signal input as an analog signal is digitalized, and then pulse width
modulation is performed on a pulse-like carrier in an ultrasonic frequency band, and the pulse
width is modulated. The system which drives an oscillator directly is adopted.
[0015]
Next, the configuration of the sound output unit 16 will be described in detail with reference to
FIG. Fig.4 (a) is explanatory drawing which looked at the sound output part 16 from the front,
and FIG.4 (b) is explanatory drawing which showed the LL cross section of Fig.4 (a). The
reference numeral 21 denotes an ultrasonic transducer, and seven ultrasonic transducers are
mounted on the long substrate 22 at a predetermined interval to constitute an ultrasonic
transducer module 23. As shown in the figure, a pair of lead terminals 21a and 21b led out from
the ultrasonic transducer 21 abut on and fixed to one side and the other side of the substrate so
03-05-2019
6
as to straddle the long substrate 22, lead terminals 21a The ultrasonic waves are mounted so
that the ultrasonic waves emitted from the side opposite to the side from which 21 b is derived
are emitted parallel to the plane of the long substrate 22. The reflection plate 24 is disposed at a
position facing the ultrasonic transducer module 23 configured as described above. The
reflecting plate 24 is provided corresponding to each of the seven ultrasonic transducers
constituting the ultrasonic transducer module 23, and the reflecting plate 24 is provided to the
ultrasonic radiation surface 21c of the ultrasonic transducer. The reflecting surface of is made to
face and fixed.
[0016]
Here, the relationship of the arrangement position of the ultrasonic transducer 21 and the
reflection plate 24 will be described. FIG. 5 is an explanatory view showing a state in which the
ultrasonic transducer 21 and the reflection plate 24 are respectively mounted at regular
positions. The reflection surface 24a of the reflection plate 24 is formed in a parabolic shape in
its cross-sectional shape, and the ultrasonic radiation surface 21c of the ultrasonic transducer is
positioned at the position where the focal point of the parabola is formed. The ultrasonic waves
radiated from the ultrasonic radiation surface 21c in a fan-like manner are reflected at the
reflection surface 24a and become parallel waves having the same traveling direction. In this
embodiment, the ultrasonic waves reflected by the reflecting surface 24a become parallel beamshaped traveling waves, and a part thereof is reflected again to the reflecting plate 24 side by
hitting the cross section of the ultrasonic transducer 21 and the long substrate. Mostly, they are
emitted toward the outside of the present parametric speaker, and become effective ultrasonic
waves that contribute to the generation of audible sound based on the parametric array effect.
Incidentally, the directivity of the reflected ultrasonic waves can be improved by increasing the
size of the reflection plate (the area of the reflection surface 24a) relative to the size of the
ultrasonic transducer (the diameter of the ultrasonic transducer). Although possible, it also leads
to a reduction in the energy per unit area of the reflected ultrasound. On the other hand, if the
size of the reflector is reduced, the directivity of the reflected ultrasonic waves is reduced, but the
energy density of the ultrasonic waves after reflection can be increased. The directivity in this
case is closely related to the ratio of the wavelength of the sound wave to be reflected to the
diameter of the reflecting surface, and it is known that the smaller the ratio, the closer to the
ideal reflection closer to the light reflection. In this embodiment, the ultrasonic radiation angle
from the ultrasonic transducer is set to about 90 degrees, and the ultrasonic radiation range
formed by this 90 degrees is set on the condition that the diameter dimension of the reflection
plate is included, and at the same time As a result of considering the ratio of the wavelength of
ultrasonic waves (about 8 to 9 mm because the frequency is 40 kHz) and the diameter of the
reflecting surface, the diameter of the reflecting plate is 30 mm.
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[0017]
With the above configuration, the arrangement interval of the seven ultrasonic transducers on
the long substrate constituting the ultrasonic transducer module 23 becomes substantially the
same as the diameter dimension of the reflecting plate 24, and the seven reflecting plates The
ultrasonic transducer modules 23 are arranged in a straight line in close contact with the
positions of the ultrasonic transducer modules 23 that are directly opposed to each other. Then,
as shown in FIG. 4A, the ultrasonic transducer modules 23 are arranged in parallel in seven rows
(rows) via the mounting stays 25, and the ultrasonic transducers are mounted on the respective
ultrasonic transducer modules 23. As a whole, an array-like array of 7 vertical × 7 horizontal is
formed. As a result, an acoustic output unit 16 in which a total of 49 ultrasonic transducers are
arranged at equal intervals in the vertical and horizontal directions is configured by seven
ultrasonic transducer modules. With this structure, it is not necessary to adjust the mounting
position of the ultrasonic transducer and the reflection plate one by one, and seven ultrasonic
vibrations are generated using a jig for mounting the transducer for each ultrasonic transducer
module. The children can be implemented collectively while aligning the mounting angle.
Further, the mounting stay 25 and the ultrasonic transducer module are detachably fixed by
fixing means such as screws, and when a failure or a defect occurs in the ultrasonic transducer,
the ultrasonic transducer module is removed. It can respond to repair and replacement.
[0018]
Incidentally, in the structure shown in FIG. 4, the ultrasonic transducers 21 and the reflection
plate 24 are arranged on a plane to form an array. Therefore, when driven by the drive circuit
shown in FIG. 2, the ultrasonic waves emitted from the two-dimensional pair of 49 ultrasonic
transducers and reflectors travel in the direction perpendicular to the plane in which the
reflectors are arranged. It becomes parallel beam-like traveling waves, and as a result, it radiates
like a beam ahead of the main body casing 1 with a cross-sectional area corresponding to the
opening area of the opening 2 shown in FIG. And enable the generation of directional audible
sound waves.
[0019]
Next, another embodiment of the sound output unit 16 will be described based on FIG. FIG. 6
shows a structure in which the reflecting plate 24 disposed opposite to the ultrasonic transducer
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8
is disposed on the spherical surface, and the ultrasonic transducer mounted on the long substrate
22 of the ultrasonic transducer module 23 is also a reflection of the reflecting plate 24 It is
attached facing the surface. When the sound output unit 16 shown in FIG. 6A is viewed from the
front, it is confirmed as an array in which seven ultrasonic transducers and seven reflectors are
arranged in the vertical and horizontal directions, as in the example shown in FIG. In the state
where the array array is viewed from the side as shown in FIG. 6 (b) showing the M-M cross
section in FIG. 6 (a), the reflection plate 24 is disposed along the spherical surface, The child 21
is also mounted on the long substrate 22 at an angle corresponding to the curve of the spherical
surface. In addition, with regard to the ultrasonic transducer modules stacked in seven stages, it
is fixed so that the seven transducers mounted on the module face the reflecting plate while
giving an angle according to the curve of the spherical surface to the mounting stay 25 keeping.
When the acoustic output unit 16 of this configuration is driven by the drive circuit of FIG. 2, the
ultrasonic waves emitted from the 49 ultrasonic transducer / reflector pairs become convergent
traveling waves traveling toward the center of the spherical surface, It converges at the center of
the sphere and then diverges. In this case, a high sound pressure portion is obtained before and
after the convergence to the center of the spherical surface, and efficient demodulation occurs to
generate a relatively small high sound pressure audible sound region. Also, in the area after the
emission, the audible sound sounds as if it were at the center of the spherical surface, and a
virtual sound source can be set in the air. Also in this embodiment, it is possible to assemble
seven ultrasonic transducers together by using a jig for mounting the transducers for each
ultrasonic transducer module and mount them while adjusting the mounting angle, and
assemblability Can be improved. In addition, the mounting stay 25 and the ultrasonic transducer
module 23 are detachably fixed to facilitate handling when a failure or a defect occurs in the
ultrasonic transducer.
[0020]
It is explanatory drawing which shows the external appearance of this invention Example. FIG. 1
is a block diagram showing an entire configuration of an embodiment of the present invention. It
is an explanatory view showing pulse width modulation operation of an example of the present
invention. It is an explanatory view showing the composition of the sound output part concerning
the present invention example. It is explanatory drawing which shows the positional relationship
of an ultrasonic transducer | vibrator and a reflecting plate. It is an explanatory view showing the
composition of the sound output part concerning the example according to the present invention.
Explanation of sign
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[0021]
DESCRIPTION OF SYMBOLS 1 main body casing 2 opening 11 audible sound signal input part 12
AGC circuit 13 carrier wave signal generation part 14 pulse width modulation part 15 low pass
filter 16 acoustic output part 21 ultrasonic transducer 21a, 21b lead terminal 21c ultrasonic
radiation surface 22 long substrate 23 ultrasonic transducer module 24 reflector 24a reflective
surface 25 mounting stay
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