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JPS60117900

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DESCRIPTION JPS60117900
[0001]
TECHNICAL FIELD The present invention relates to a piezoelectric speaker. 2. Description of the
Related Art In recent years, with the development of ceramic technology, piezoelectric speakers
utilizing the piezoelectric effect of ceramic have come to be used. Hereinafter, a conventional
piezoelectric speaker will be described. FIG. 1 is a cross-sectional view of a conventional
piezoelectric speaker, in which ▪ indicates a case, and 1-1 indicates a projection provided on the
inner bottom surface of the housing 1 to support the plate-like piezoelectric element 2, 3-1.3-2.
Are each a terminal, 4-1.4-2 is a straight line connecting the piezoelectric element 1 and the
terminal 3-1. 3-2, respectively, 5 is a central part of the piezoelectric element 2 and an outer
peripheral part is a housing l The diaphragm attached to the step 1-2 of the inner circumference
of the peripheral barrel, 6 is fixed to the opening of the housing 1 to hold the outer peripheral
part of the diaphragm 5 and is integrally formed with 6 6-2 is a ripple provided with a plurality
111i1 to hold 6-1. FIG. 2 shows sound pressure frequency characteristics of the conventional
piezoelectric speaker, and fr1, fr2 and fr3 are the frequencies of primary resonance, secondary
resonance and tertiary resonance of the piezoelectric element 2, respectively. Although the
piezoelectric element 2 oscillates only at the resonance frequency, since the diaphragm 5 is
divided and resonated, wide band reproduction can be obtained. However, since the frequency is
low between fr1 and fr2, split resonance of cone paper does not occur. For this reason, the
conventional piezoelectric speaker has a single-peak and a second-order resonance. It was a
frequency characteristic with a smooth portion of tertiary resonance. FIG. 3 shows a frequency
characteristic of a speaker system in which the above-mentioned piezoelectric speaker and
woofer are combined to form a 21J7A. As described above, in the speaker system using the
conventional piezoelectric speaker, the sound pressure of the piezoelectric speaker frl and the
sound pressure of the woofer overlap to cause a large peak. SUMMARY OF THE INVENTION It is
an object of the present invention to provide a piezoelectric speaker which can lower the sound
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pressure due to the -next resonance. In the piezoelectric speaker according to the present
invention, a resonator resonating with the primary resonance frequency of the piezoelectric
element is disposed in at least one of the front position of the diaphragm or the space formed by
the housing and the diaphragm. Thereby reducing the sound pressure of the next resonance.
Description of the Embodiment FIG. 4 shows a cross-sectional view of a piezoelectric speaker
according to an embodiment of the present invention. In the figure, the same parts as those in
FIG. In FIG. 4, 7 is a hollow walled cavity, 7-1 is a hole made in a hard wall, and 7-2 is a support
for holding a resonator.
A resonator having a hole 7-1 in a cavity 7 surrounded by a wall 11411 is known as a Helmholtz
resonator. Assuming that the internal volume of the cavity 7 is V, the cross-sectional area of the
hole 7-1 is S, the length p of the hole 7-1 is C, and the speed of sound of air is C, the resonance
frequency 10 of this resonator is fo = c / 7T ■ It is expressed by / 2π. That is, the resonant
frequency can be freely changed by the internal volume V of the cavity 7 and the cross-sectional
area S of the hole 7-1 and the length l. In 4th M, the dimensions of the air / 1ii 11 and the hole 71 are set to be the same frequency as the primary resonance frequency fr1 of the piezoelectric
speaker. "The operation of the piezoelectric speaker according to the embodiment configured as
described above will be described. The reflection of the sound from the diaphragm 5 has the
same frequency characteristic as that of the conventional piezoelectric speaker shown in FIG.
However, since the resonator is in front of the diaphragm 5, the resonance frequency of the
resonator, that is, the sound pressure of the primary resonance frequency of the piezoelectric
speaker is absorbed by the resonator, and the overall frequency characteristic is the fifth. As
shown in the figure, the sound pressure of the primary resonance is low. FIG. 6 shows a sound
pressure frequency characteristic diagram of the two-way speaker system constituted by the
piezoelectric speaker of the above embodiment and the U-no, and unlike FIG. 3, the sound
pressure in frl is suppressed and the frequency characteristic is flat. It has become. As described
above, according to this embodiment, it is possible to obtain smooth sound pressure frequency
characteristics with good connection by a simple configuration in which a resonance box is
provided in front of the diaphragm of the piezoelectric speaker. Although the resonator 7 is
disposed in front of the diaphragm 5 in the above embodiment, it may be disposed in the space
formed by the diaphragm 5 and the housing 1. Also, it is needless to say that by installing both
on both sides, the sweetness will be better. According to the piezoelectric speaker of the present
invention, by providing the resonator at the front position of the diaphragm and / or at least one
of the space formed by the housing and the diaphragm, the sound pressure by the next
resonance And the peak in the sound pressure frequency characteristic when the two-way
speaker system is configured with the woofer.
[0002]
Brief description of the drawings
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2
[0003]
1 is a cross-sectional view of a conventional piezoelectric speaker, FIG. 2 is its sound pressure
frequency characteristic diagram, and FIG. 3 is a sound pressure frequency characteristic
diagram of a conventional two-way speaker system composed of a piezoelectric speaker and a
woofer. FIG. 4 is a cross-sectional view of a piezoelectric speaker according to an embodiment of
the present invention, FIG. 5 is its sound pressure frequency characteristic diagram, and FIG. 6 is
a two-way speaker system composed of the piezoelectric speaker according to the embodiment
and a woofer. It is a sound pressure frequency-characteristics figure.
1-housing, 1-1-projection, 2 piezoelectric element, 3-1 -3-2-electrode, 5- diaphragm, 6-imaging
temporary presser and horn, 6- 1 -I co-riser, 7- Cavity, 7-1 per square □ 汝 v (Hz) □ mill 7
collection (Hz) Fig. 3-2 3-2 1-1 1 1 □ frequency wave (Hz)--a wave ffl () (2 (2) )
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