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JPS60106294

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DESCRIPTION JPS60106294
[0001]
INDUSTRIAL FIELD OF THE INVENTION The present invention relates to a loudspeaker, and
more particularly to an ultrasonic transducer array for superdirective loudspeakers effective for
explanation of exhibition halls and guidance broadcasting of station homes. A speaker for audio
sound waves using nonlinear parametric action of ultrasonic waves is attracting attention as a
new type of speaker because superdirectivity can be obtained. However, to obtain a sound
pressure of 1, for example, 90 dB / m, which can be obtained with a normal conductive speaker
using this method, 165 dB / m; [a transducer that emits extremely strong ultrasonic waves of is
necessary. FIG. 1 is a block diagram of a conventional ultrasonic transducer array. In FIG. 1,
reference numeral 1 denotes an ultrasonic transducer (transducer) using a bimorph structure of
a piezoelectric element, which has an outer diameter of 16 + 1111. The efficiency is about 112
dB / m. In order to generate a parametric action, a large number of ultrasonic transducers 1 are
arranged in a plane on the baffle plate 2 and used in an array. FIG. 2 is a diagram showing the
relationship between the number of ultrasonic transducers 1 and the sound pressure at the
listening point separated by a distance of 1 m on the axis of the array obtained in this manner,
which is the number of ultrasonic transducers 1 The maximum sound pressure of 132 dB can be
obtained when the number is 61. However, the sound pressure does not rise even if the number
is further increased. The cause of this is that if the diameter of the array is increased, the phases
from the ultrasonic transducers 1 at the listening point will not match. Therefore, it is necessary
to accurately adjust the phase of each ultrasonic transducer 1 through a phase matching unit
with a gain control in order to match the phase, which makes it difficult to adjust the phase as
the number increases. It has the disadvantage that the degree of failure due to the breakage of
the ultrasonic transducer 1 increases. SUMMARY OF THE INVENTION The present invention has
been made in view of the above-mentioned drawbacks, and by arranging the horns to which the
ultrasonic transducers are attached so as to focus in the radiation direction, the number of
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ultrasonic imaging movers is reduced to achieve high sound. It is an object of the present
invention to provide an ultrasonic transducer array which obtains pressure and realizes sharper
directivity. SUMMARY OF THE INVENTION In order to achieve the above object, the ultrasonic
transducer array of the present invention has a plurality of horns on which ultrasonic
transducers are attached, and the central axis of each horn is focused in the radial direction, And
each horn is arranged so that the sound wave radiation center of the ultrasonic transducer forms
a part of one spherical shape, and p5, thereby enhancing the sound pressure at the listening
point to realize sharp directivity. Can.
Description of the Embodiment FIG. 3 is a block diagram of an ultrasonic transducer array
according to an embodiment of the present invention. In FIG. 3, reference numeral 3 denotes an
ultrasonic transducer, whose sound emitting surface is attached to the focal point of the
paraboloid of the horn 4. 06 are 19 horns 4 on the axis of the sound emitting surface. The
support frame 6 is mounted on a wooden baffle 6 with a spherical support frame mounted to
focus on a .5 m position. An alternating current signal modulated with an audio signal is applied
to each of the ultrasonic transducers 3 through the amplifier 7 and the phase matching unit 8
which mainly performs phase adjustment due to manufacturing variations of the ultrasonic
transducers 3. 9 is a modulator connected to each phase matching unit 8; 10 is a signal source of
the modulation wave of the modulator 9. By configuring as above, the sound pressure at 0.6 m
on the axis emitted from one horn 4 is 130 dB / m, and the ultrasonic vibration in the state
without horn 4 is 14 dB compared to the sound pressure of child 1 It can be improved. When the
19 ultrasonic transducers 3 are driven in parallel, the sound pressure at the on-axis 0.5111 is
155 dB / m'i. In order to obtain the same sound pressure with the ultrasonic transducer 1
without using the horn 4 as in the prior art, the ultrasonic transducers are arranged in a
spherical shape, and about 70 ultrasonic transducers 1 are arranged. It was necessary, and it was
very time-consuming to adjust the phase because it had to be perfectly in phase. Next, another
embodiment of the present invention will be described with reference to FIG. In FIG. 4, reference
numeral 11 is a para-polonic horn, 12 is an ultrasonic transducer, and 13 is a support of the
ultrasonic transducer 12. Seven ultrasonic transducers 12 are mounted on the support 13 in a
spherical shape. The center of the spherical surface is made to coincide with the focal point F of
the parabola. As a result, the sound pressure at the focal point F is about 8 dB higher than when
one ultrasonic transducer 12 is used, and the synthetic sound pressure is also further enhanced
when a large number of horn arrays are arranged as shown in FIG. It can be raised. Also, even if a
plurality of ultrasonic wave imaging moving elements 12 are used in one loosely policed horn 11
as described above, the size can be smaller than the horn opening, and the overall size becomes
large. There is no. As described above, according to the present embodiment, an array is formed
so that each horn opening forms a part of one spherical surface such that the central axis of the
ultrasonic transducer + * V attached horn focuses in the radiation direction. Therefore, high
sound pressure can be generated with a small number of ultrasonic transducers, and since there
are few ultrasonic transducers, the number of circuit parts such as phase matching units can be
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reduced, and the time required for adjustment can be greatly shortened. it can.
Further, the directivity angle characteristic is narrower than when the ultrasonic transducers
alone are arranged side by side, and superdirectivity can be realized. Furthermore, a higher
sound pressure can be obtained by attaching a plurality of ultrasonic transducers to one horn as
a driver. Effects of the Invention As described above, according to the ultrasonic transducer array
of the present invention, ultrasonic waves are generated. The sound emission centers of the
respective horns form one 1m-shaped part so that the central axes of the horns attached with the
transducers are focused in the radial direction, and the wavelengths at the focal points are
arranged to be the same. Therefore, it is possible to generate high sound pressure with a small
number of ultrasonic transducers, and since there are few ultrasonic transducers, the number of
circuit parts such as a phase matching unit can be reduced, and the time required for adjustment
can be greatly shortened. The directivity angle characteristic is narrowed, superdirectivity can be
realized, and the effect is great.
[0002]
Brief description of the drawings
[0003]
FIG. 1 is a block diagram of a conventional ultrasonic transducer array, FIG. 2 is a diagram
showing the relationship between the number of ultrasonic transducers and the sound pressure,
and FIG. 3 is an ultrasonic wave according to an embodiment of the present invention. FIG. 4 is a
block diagram of a transducer array, and FIG. 4 is a block diagram of an ultrasonic transducer
array according to another embodiment of the present invention.
3.12 и и и и и и и и и и и и и и и и и и и и и и и и ultrasonic transducer, 4 и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и
и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и ultrasonic transducer, 4 и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и
и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и ultrasonic transducer, 4 и и и и и и и и и и и и и.
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