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DESCRIPTION JPH03277100

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DESCRIPTION JPH03277100
[0001]
FIELD OF THE INVENTION The present invention relates to ultrasonic parametric speakers.
PRIOR ART The following exist as typical examples of conventional ultrasonic parametric
speakers, which will be described based on FIGS. 3 and 4. The ultrasonic parametric speaker is
configured such that the ultrasonic transducer 1, the ultrasonic transducer fixing member 2, the
acoustic filter 3, and the sound absorbing material 4 are accommodated in the speaker box 5. In
addition, the speaker box 5 has a cylindrical shape for fishing and is housed in a box shown by a
dot-and-dash line. More specifically, a plurality of ultrasonic transducers 1 are used to generate
strong ultrasonic waves, and they are disposed in a state of being uniformly distributed in the
disk-shaped ultrasonic transducer fixing member 2 . The acoustic filter 3 is formed in a disk
shape of urethane or the like, disposed to face the ultrasonic transducer 1 with a predetermined
interval, and a columnar sound absorbing material 4 made of glass wool or the like is used as the
space. Covering. And the speaker box 5 is holding these each members. Here, to explain the
parametric phenomenon which is a kind of non-linear acoustic phenomenon of gas briefly,
driving 6 Sveakers at two frequencies of f + and fz, fl and 12 (-order wave) are caused by the nonlinearity of medium (air) Interference occurs to generate a wave (secondary wave) having these
sum and difference frequencies, that is, f + f, f, and -f. Therefore, if rl and rl are made into
ultrasonic waves and rt-rl is made to be an audio frequency, the generated audible sound can be
heard, which is a parametric phenomenon. Then, a plurality of ultrasonic transducers 1 are used
as described above so that the primary wave is a sufficiently strong ultrasonic wave to generate
this phenomenon, and the acoustic filter 3 passes the strong ultrasonic waves to adversely affect
the human body. In order not to [Engagement to be solved by the invention] The ultrasonic
parametolink speaker uses an ultrasonic wave with excellent directivity as the next wave, so the
secondary wave generated thereby is also an audible sound, but it is also directional It will be
excellent in sex. However, in the above-described conventional ultrasonic parametric link
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speaker, since the plurality of ultrasonic transducers 1 are disposed in a state of being evenly
distributed to the ultrasonic transducer fixing member 2, they are emitted from them The sound
pressure distribution of the entire ultrasonic wave is constant. In such a case, a side lobe is
generated, which has the property of deteriorating the directivity of the ultrasonic wave, and the
secondary wave generated thereby is also deteriorated in the directivity, and the abovementioned ultrasonic balametolink The problem arises that the feature of excellent speaker
directivity can not be sufficiently exhibited.
The present invention has been made in view of the above-mentioned problems, and its object is
to improve the directivity by preventing the side lobe from being generated from the primary
wave emitted from the ultrasonic transducer, and hence to improve the directivity. -The
directivity of the secondary wave generated from the next wave is also improved, and the feature
is to sufficiently exhibit the directivity of the ultrasonic parametric speaker. (Means for Solving
the Problems) In order to solve the problems described above, in the ultrasonic balammetric
speaker according to the present invention, ultrasonic waves emitted from a plurality of
ultrasonic transducers are parametric in non-linear acoustic phenomena of gas. In the ultrasonic
parametric speaker that is affected by the phenomenon, the number of the ultrasonic transducers
is increased in the central portion and in the peripheral portion so that the sound pressure
distribution of the ultrasonic waves approaches the Gaussian distribution. It is a structure.
(Operation) According to the present invention, the sound pressure distribution of the ultrasonic
waves (-next wave) emitted from the plurality of ultrasonic transducers approaches a Gaussian
distribution which is theoretically said to have zero side lobes. Since the number of ultrasonic
transducers is increased in the central part and in the peripheral part, the generation of side
lobes from the next wave is prevented to improve directivity. The directivity of the secondary
wave generated from the next wave can also be improved. An embodiment of the present
invention will be described below with reference to FIG. The difference from the conventional
example is the configuration of the ultrasonic transducer 1, and the members substantially the
same as those of the conventional example are assigned the same reference numerals, and only
the different points will be described. The plurality of ultrasonic transducers 1 are not disposed
in a state of being evenly distributed to the ultrasonic transducer fixing member 2 as in the
conventional example, and the number thereof is increased as the number increases in the
central portion and in the peripheral portion. It is set up. More specifically, the sound pressure
distribution of the ultrasonic waves (-next wave) emitted from the plurality of ultrasonic
transducers 1 is a Gaussian distribution (so-called normal distribution) G which is theoretically
said to have zero side lobes. In order to get close, the ultrasonic transducers 1 are arranged in
such a way that the intervals are narrow or dense in the central part of the ultrasonic transducer
fixing member 2 and the intervals become gradually wider or coarser toward the peripheral part.
It is arranged in the state and less. [Effects of the Invention] The ultrasonic parametric speaker
according to the present invention is configured as described above, so that side lobes are
prevented from being generated from ultrasonic waves (-next wave) emitted from a plurality of
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ultrasonic transducers. Since the directivity of the secondary wave generated from the next wave
can be improved as well, it becomes possible to sufficiently exhibit the feature of excellent
directivity of the ultrasonic parametric speaker.
[0002]
Brief description of the drawings
[0003]
FIG. 1 is a cross-sectional view showing an embodiment of the present invention, FIG. 2 is a
perspective view of a conventional example, and FIG. 3 is a cross-sectional view of the same.
1-Ultrasonic transducer, 2-Ultrasonic transducer fixing member, 3-Acoustic filter 4-Sound
absorbing material, 5-Speaker box, G-Gaussian distribution.
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