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JP2000175297

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DESCRIPTION JP2000175297
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
speaker, and more particularly to a piezoelectric driven speaker mounted on a wall.
[0002]
2. Description of the Related Art As a conventional wall-mounted speaker, there is one disclosed
in Japanese Patent Application Laid-Open No. 54-111328. This will be described with reference
to FIG.
[0003]
The speaker 100 includes a diaphragm 101 and nine bimorph piezoelectric plates 102 to 110
attached to the diaphragm 101. The nine piezoelectric plates 102 to 110 are set so that the peak
values of the sound pressure frequency characteristics of the individual piezoelectric plates are
different by making the thickness and the area of the piezoelectric members different from one
another. The emitted sound waves obtain flat sound pressure characteristics over a wide
frequency band.
[0004]
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1
Further, by arranging the speaker 100 on a wall surface in the room, the wall surface can be
used as a speaker box, and the reproduction capability of the low frequency range is improved.
[0005]
However, the loudspeakers shown as the prior art have the following problems.
[0006]
That is, in the conventional example, a piezoelectric plate having a flat plate-like bimorph
structure is used as a sounding body, and the entire region from the high frequency band to the
low frequency band is reproduced. It is a speaker having directivity in the direction.
Therefore, when listening to the sound wave emitted from this speaker, when listening at a
position directly in front of the speaker, it is possible to listen to a sound wave having flat sound
pressure characteristics from the low range to the high range, When listening at a position
shifted in the direction, the sound waves emitted from the individual piezoelectric plates are
listened out of phase, and in particular, this phenomenon is felt when listening to the highpitched range, so listening in the room There is a problem that the listening condition (listening
environment) changes depending on the place (listening point).
[0007]
In addition, although the speaker of the conventional example uses a square piezoelectric plate as
a sounding body, the square piezoelectric plate often generates divided vibration at the time of
its vibration, and is deviated from the desired frequency characteristics, and reproduction The
sound pressure characteristics of the sound have deteriorated.
[0008]
Further, in the conventional speaker, the area and thickness of the piezoelectric plate for
reproducing the low frequency band are different from the area and thickness of the
piezoelectric plate for reproducing the high frequency band. The speaker functions as a speaker
that can hear a sound wave having flat sound pressure characteristics from the low range to the
high range for the first time.
03-05-2019
2
However, it is substantially difficult to arrange in a balanced manner the sounding bodies
composed of piezoelectric plates having different individual frequency characteristics, and
therefore, it was not possible to listen to a well-balanced reproduced sound with the conventional
speaker.
[0009]
Therefore, an object of the present invention is to solve the above-mentioned problems, and an
ideal reproduction sound can be heard regardless of the listening point, the sound pressure
characteristic of the reproduction sound is stable, and the reproduction is well-balanced. An
object of the present invention is to provide a speaker capable of listening to sound.
[0010]
[Means for Solving the Problems] In order to achieve the above object, in the loudspeaker
according to the present invention, a speaker for high band reproduction provided with a flat
plate and a piezoelectric element provided on the flat plate and having a hemispherical shell
shape, and high band reproduction And a sound-producing body for reproducing the lowfrequency range, which is formed of a plate-like piezoelectric element disposed at the periphery
of the sound-producing body.
[0011]
Further, the sound-producing body for low-frequency range reproduction is characterized by
comprising a disc-like piezoelectric element.
[0012]
In addition, a plurality of low-range reproduction sound producing bodies are characterized in
that a plurality of low-tone reproduction sound bodies are disposed in the periphery of the highrange reproduction sound production body.
[0013]
In addition, the high tone range playback sounding body is provided substantially at the center of
the flat plate, and the plurality of low tone range playback sounding bodies are symmetrical with
respect to the center of the high tone range playback sounding body, or the high tone range
playback sounding on the flat plate A straight line passing through the center of the body is a
symmetrical line, which is characterized by being symmetrically arranged at the periphery of the
tone reproducer.
03-05-2019
3
[0014]
Furthermore, the flat plate is characterized in that it is disposed in contact with the wall surface
of the construction.
[0015]
As a result, since the high tone range reproducing sounding body is formed of a hemispherical
shell-like piezoelectric element, the sound wave in the high tone range is emitted as a spherical
wave, and is emitted as a so-called omnidirectional sound wave.
Further, although the low frequency range reproducing sounding body is formed of a flat platelike piezoelectric material, when the piezoelectric material is small, non-directional sound waves
of the low frequency range are also emitted.
Thus, the sound waves emitted from the entire speaker are non-directional sound waves all over
the high range to the low range.
[0016]
Further, since the low frequency range reproducing sounding body has a disk shape, it does not
generate divided vibration, and a desired sound pressure characteristic can be stably obtained.
[0017]
In addition, since a plurality of sound-producing bodies for low-frequency range reproduction are
provided, sufficient low-frequency reproduction capability is provided even as a speaker using a
piezoelectric element.
[0018]
In addition, a hemispheric shell-like high tone reproduction speaker is placed at the center of the
flat plate, and the flat low tone reproduction speaker is placed symmetrically around it, so the
symmetrical low tone reproduction speaker is It functions as a so-called dipole, emitting a
spherical wave that coincides with the center of the high-range reproduction sound generator.
03-05-2019
4
[0019]
Further, by using the speaker in contact with the wall surface, the wall surface functions as a
large baffle, so that the bass range can be reproduced more efficiently.
[0020]
BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be
described in detail with reference to the drawings.
[0021]
In FIG. 1 and FIG. 2, the speaker 10 includes the high-frequency range reproducing sounding
body 1 formed of a hemispherical shell-like piezoelectric element (hereinafter abbreviated as
"high-pitched sounding body 1").
Further, the speaker 10 includes two sound producing members 2 for reproducing the low tone
range of a bimorph structure in which two disk-shaped piezoelectric elements are laminated
(hereinafter, abbreviated as "low tone sound producing member 2").
The piezoelectric elements constituting the high-pitched sounding body 1 and the low-pitched
sounding body 2 are mainly composed of Ag̶Pd on both sides of a hemispherical shell-like or
disk-like piezoelectric body mainly composed of lead zirconate titanate (PZT). An electrode is
formed.
[0022]
The high-pitched sounding body 1 is attached to, for example, a rectangular flat plate 3 made of
wood or the like via a supporting member 4 made of an elastic material such as silicone rubber.
Similarly, the two low-pitched sounding bodies 2 are supporting members 5. Are attached to the
flat plate 3 via
[0023]
Here, the treble-sounding body 1 is disposed substantially at the center of the flat plate 3, and
03-05-2019
5
the two bass-sounding bodies 2 are symmetrically disposed so as to sandwich the treblesounding body 1.
That is, with the vertical line passing through the center of the treble-sounding body 1 as the
symmetry line, the two bass sounding bodies 2 are arranged symmetrically.
Also, the two bass sound producing bodies 2 have the same frequency characteristics.
[0024]
In the speaker 10 configured as described above, since the high-tone sounding body 1 is formed
of a hemispherical-shell-like piezoelectric element, so-called breathing movement is generated
when an audio signal is applied to the electrodes formed on the outer surface and the inner
surface, High sound waves of spherical waves are emitted from the outer surface.
Here, since the high-pitched sound producing body 1 is hemispherical, sound waves in the high
frequency band are reproduced from the frequency characteristic unique to the shape, and the
low frequency band is not reproduced due to the presence of a so-called cutoff frequency.
Therefore, only the sound wave in the high frequency band, that is, only the high sound is
emitted by the spherical wave from the high sound producing body 1, and it becomes a speaker
that reproduces the non-directional high sound.
[0025]
Further, in the speaker 10, since the disk-like piezoelectric element is used as the low-pitched
sound producing body 2, the divided vibration is not generated, and the sound pressure
characteristic in the low-pitch range can be stably obtained.
And since the sound wave of the low frequency band, ie, the low frequency band, has a long
wavelength, when the piezoelectric element is small, a non-directional sound wave is emitted
even with a flat sounding body.
03-05-2019
6
The low-pitched sound generator 2 is designed to have a thickness and an area so that lowpitched sound can be reproduced.
[0026]
Further, in the speaker 10, since a plurality of bass sound producing members 2 are provided, a
bass tone reproducing capability sufficient as a speaker using a piezoelectric element is provided,
and the hemispherical shell-like high sound producing body 1 is disposed at the center of the flat
plate 1. Since the two flat sounding bodies 2 having the same characteristics are arranged in a
symmetrical manner around the periphery, the bass sounding body 2 functions as a so-called
dipole.
That is, the sound waves in the low frequency band emitted from the two bass sound producing
bodies 2 become spherical waves coinciding with the central point of the high sound producing
body 1 which is the central point thereof, like a dipole antenna.
Therefore, the speaker 10 is a completely nondirectional speaker of a point sound source
emitting a spherical wave.
[0027]
Next, a loudspeaker 20 according to a second embodiment of the present invention will be
described with reference to FIG.
The same components as those of the speaker 10 shown in the first embodiment are designated
by the same reference numerals, and the description thereof is omitted.
[0028]
In the speaker 20, two low frequency sound producing bodies 6 having different frequency
03-05-2019
7
characteristics from the low frequency sound producing body 2 are disposed on the flat plate 1
vertically symmetrically with the high sound producing body 1 interposed therebetween as the
low frequency range reproducing sound producing body. Like the low-pitched sounding body 2,
the low-pitched sounding body 6 also has a bimorph structure in which two piezoelectric
elements 2 are laminated, and is attached to the flat plate 1 via the support member 7.
[0029]
In the speaker 20 configured as described above, the disk-like low-pitched sounding members 2
and 6 are supported by the support members at the periphery of the disk, and in this case, the
resonance of the disk-shaped bimorph piezoelectric element Since the frequency is proportional
to the thickness and inversely proportional to the square of the radius, it is possible to set
different resonance frequencies in the low frequency band by arbitrarily selecting the thickness
and the radius.
[0030]
And in this speaker 20, while two bass sounding bodies 2 function as a dipole, two bass sounding
bodies 6 play a function as a dipole different from the bass sounding body 2, and all the dipoles
are high sounding bodies 1 Since a spherical wave coincident with the center point of the
speaker is to be emitted, the reproduced sound in the bass region is further thickened, resulting
in a completely omnidirectional speaker.
[0031]
In the loudspeakers 10 and 20 described above, the entire wall surface can be used as a large
baffle by arranging the flat plate 1 so as to abut on the wall surface 8 as shown in FIG. It
becomes a speaker to be reproduced.
[0032]
In the loudspeakers shown in the above embodiments, two or four bass sound producing
members are shown, but the number is not particularly limited.
However, as described above, it is preferable that there be an even number in order to exhibit a
function as a dipole by arranging two bass sounding bodies having the same frequency
characteristic in a symmetrical manner.
03-05-2019
8
[0033]
Also, although the low-pitched sounding body has a disk shape, it may have a square plate shape.
However, as described in the section of the prior art, it is preferable to use a disk-shaped
piezoelectric element because a square plate-shaped piezoelectric element is likely to generate
divided vibrations.
[0034]
As described above, in the loudspeaker according to the present invention, since the sound wave
in the high range is emitted as a spherical wave, it is emitted as a so-called non-directional sound
wave, and non-directivity is also emitted from the sound generator for low range reproduction.
The sound waves emitted from the entire speaker are non-directional sound waves over the
entire range from the high range to the low range.
Thereby, the listener can listen to the sound wave which does not feel distortion or phase delay
regardless of the listening point.
[0035]
In addition, desired sound pressure characteristics can be stably obtained without generating
divided vibration, and can have sufficient bass reproduction capability as a speaker using a
piezoelectric element.
[0036]
In addition, the hemispheric shell-like high tone reproduction sounding body is disposed at the
center of the flat plate, and the even number of flat plate-like low tone reproduction sound bodies
are arranged symmetrically in the periphery, so that it is symmetrical for the low tone
reproduction The sounding body functions as a so-called dipole, and a spherical wave coinciding
with the center of the sounding body for high-range reproduction is emitted, and the speaker
becomes a completely nondirectional speaker of a point sound source.
03-05-2019
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[0037]
Further, by using the speaker in contact with the wall surface, the wall surface functions as a
large baffle, so that the bass range can be reproduced more efficiently.
03-05-2019
10
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