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JPH03252299

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DESCRIPTION JPH03252299
[0001]
FIELD OF THE INVENTION The present invention relates to ultrasonic parametric speakers.
PRIOR ART As typical examples of conventional ultrasonic parametric speakers, the following
exist, which will be described with reference to FIGS. 3 and 4. The ultrasonic parametric speaker
has the ultrasonic transducer 1 and the speaker box 5 as basic components. Specifically, the
ultrasonic transducer 1, the ultrasonic transducer fixing member 2, and the acoustic filter are
provided in the speaker box 5. 3 and the sound absorbing material 4 are accommodated. 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 fixed to a disk-shaped ultrasonic transducer fixing member
2. The acoustic filter 3 is a disc-like member made of foamed urethane or the like and is disposed
to face the ultrasonic transducer 1 with a predetermined interval, and the columnar sound
absorbing material 4 made of glass wool or the like is Covering the space. And the speaker box 5
is holding these each members. Here, a parametric phenomenon which is a kind of nonlinear
acoustic phenomenon of gas will be briefly described. When the speaker is driven at two
frequencies fl and h, fl and b (-order waves) cause interference due to non-linearity of the
medium (air), and the sum and difference frequency of these, that is, f. +f! A wave (secondary
wave) with and fi−fl is generated. Then, if ft and fz are made into ultrasonic waves and fl-f is
made to be an audio frequency, the generated audible sound can be heard, which is a parametric
phenomenon. However, in order to generate this phenomenon, it is necessary to make the -next
wave a sufficiently strong ultrasonic wave and to have a sufficient distance (effective array
length) capable of generating the second wave. The required strength and distance are
determined. As described above, the reason why a plurality of ultrasonic transducers 1 are used
is to generate sufficiently strong ultrasonic waves, and the acoustic filter 3 prevents the strong
ultrasonic waves from adversely affecting the human body. It is to do. [Problems to be Solved by
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the Invention] In the above-mentioned conventional ultrasonic parametric speaker, the acoustic
filter 3 is installed at a position which secures the effective array length and effectively absorbs
only the strong primary ultrasonic wave There is a problem that the depth dimension of the
speaker is increased as a result. The present invention has been made in view of the abovedescribed problems, and an object thereof is to miniaturize an ultrasonic parametric speaker
without shortening the effective array length required for generating a parametric phenomenon.
[Means for Solving the Problems] In order to solve the problems described above, the ultrasonic
parametric speaker of the present invention comprises an ultrasonic transducer and a speaker
box for housing the ultrasonic transducer, and an ultrasonic transducer is provided. In an
ultrasonic parametric speaker in which ultrasonic waves generated from the laser are affected by
parametric phenomena in nonlinear acoustic phenomena of gas, shortening the effective array
length of ultrasonic waves emitted from ultrasonic transducers in the speaker box (A reflection
member for reflecting light is attached. [Operation] According to the present invention, the
ultrasonic wave emitted from the ultrasonic transducer is reflected by the reflecting member, and
the effective path length necessary for the parametric phenomenon is generated including the
refracted path, so the depth of the speaker box Thus, the ultrasonic parametric speaker can be
miniaturized. An embodiment of the present invention will be described below with reference to
FIG. The members substantially the same as those of the conventional example are denoted by
the same reference numerals, and only differences from the conventional example will be
described. The difference from the conventional example is that a reflecting member comprising
the reflector 6 and the reflector 7 is attached. The reflector 6 and the reflector 7 are usually
formed of a metal or the like polished well so that the surface sufficiently reflects ultrasonic
waves. Then, assuming that the sound wave emitted from the ultrasonic transducer 1 travels
straight in the near-field sound field, the configuration such as the shape and the combination
position etc. is performed by the geometric sound ray method so that the sound wave is emitted
perpendicularly from the acoustic filter 3 It is determined. In the present embodiment, as shown
in the figure, the reflector 6 is formed in a substantially isosceles triangle in cross section, and
while the ultrasonic transducer 1 and the acoustic filter 3 face each other, the isosceles portion
serving as a sound reflection surface It is disposed to face the ultrasonic transducer 1. In
addition, the reflectors 7 are located on both sides of the ultrasonic transducer 1, and the
reflection surfaces thereof are disposed toward the reflector 6. By configuring as described
above, the ultrasonic waves emitted from the ultrasonic transducer 1 are reflected by the
reflector 6 and the reflector 7 to reach the acoustic filter 3 and the effective path required for the
parametric phenomenon including the refracted path thereof Produces an array length.
Therefore, the acoustic filter 3 can be brought closer to the ultrasonic transducer 1 by the
amount of the refracted path, and a compact ultrasonic parametric speaker in which the depth of
the speaker box 5 is reduced can be provided. The second embodiment of the present invention
is shown in FIG. 2. Similar to the first embodiment, substantially the same members as those of
the prior art are designated by the same reference numerals, and they are different from the
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2
prior art. Will be explained only.
The difference from the conventional example is that a reflector (reflection member) 8 is
provided to cause reflection of ultrasonic waves only once. In response to this, the shape of the
ultrasonic transducer fixing member 2 for fixing the ultrasonic transducer 1 also changes. That
is, while the ultrasonic transducer fixing member 2 is formed in a substantially hemispherical
shape and disposed so that the hemispherical surface is on the opposite side of the acoustic filter
3, the ultrasonic transducer 1 is fixed to the hemispherical surface There is. The above-described
reflector 8 has a concave reflection surface so that the ultrasonic wave emitted from the
ultrasonic transducer 1 projects perpendicularly to the acoustic filter 3, and this reflection
surface is on the ultrasonic transducer 1 side. It is arranged towards the As described above
(when configured, the ultrasonic wave emitted from the ultrasonic transducer 1 is reflected by
the reflector 8 and reaches the acoustic filter 3 to create the effective array length necessary for
the parametric phenomenon including its refracted path There is. Therefore, as in the first
embodiment described above, a compact ultrasonic parametric speaker with a reduced depth can
be provided. [Effects of the Invention] The ultrasonic parametric speaker according to the
present invention is configured as in 8 above, so that the ultrasonic wave emitted from the
ultrasonic transducer is reflected by the reflecting member, and the parametric phenomenon
including its refracted path Since the required effective array length is created, the depth of the
speaker box can be reduced, and the overall miniaturization can be achieved.
[0002]
Brief description of the drawings
[0003]
FIG. 1 is a sectional view showing one embodiment of the present invention, FIG. 2 is a sectional
view showing another embodiment of the present invention, FIG. 3 is a perspective view of a
conventional example, and FIG. FIG.
1- ultrasonic transducer 2 ultrasonic transducer fixing member 3 acoustic filter 4 sound
absorbing material 5 speaker box 6.7.8 reflector (reflecting member).
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