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The present invention relates to a method of driving rl-power squisker. In general, in a
piezoelectric speaker, a cone paper is attached to a piezoelectric pie self plate in which a
piezoelectric ceramic handle such as P / Ku is bonded to a diaphragm of a metal plate or the like
to transmit bending vibration of the piezoelectric bimorph plate to the sheet. One that emits
sound from paper, or one that pastes a piezoelectric bimorph plate on a vibrating membrane and
vibrates an IJ T vibrating membrane together with a piezoelectric bimorph plate to make blue out
of the vibrating membrane and so on. Such a piezoelectric speaker has a high resonance Q
specific to the piezoelectric effect and generates a lot of harmonic vibration, so that a peak "C" is
often found in a high range on the sound j frequency characteristic. Therefore, the sound quality
is sharp in high-pitched and kinkinned, which is undesirable when used as an ordinary speaker.
Also, when a piezoelectric speaker is used as a voice synthesizer, the harmonic components of
the voice signal formed by the voice synthesizer 81 are strongly reproduced, and in some cases C inserts a high cut filter to generate a harmonic of the voice signal. The wave component had to
be removed. With regard to the problem G3 of the piezoelectric speaker described above, various
attempts have been made to improve the size of the piezoelectric speaker itself and its peripheral
circuits to improve it, but 1-minute results have not been obtained yet. The present invention is
intended to solve the above-mentioned problems from the method of driving a piezoelectric
speaker, and the peak on the high frequency side can be effectively suppressed by simple means
without using a high cut filter or the like. The purpose of the present invention is to provide a
method of driving a piezoelectric speaker that can reproduce a mellow sound. That is, the present
invention pays attention to the fact that the impedance characteristics of the piezoelectric
speaker have negative characteristics with respect to the frequency because they are capacitive,
and that the It tlj speaker is of the electrode drive type, utilizing these characteristics -C1
piezoelectric The above object is achieved by means of extremely simple 41 means of inserting a
resistor in series with a speaker and driving -C. Hereinafter, the embodiment of the present
invention will be revised with reference to the drawings. FIG. 1 is a diagram for explaining the
driving method of the present invention. In FIG. 1, reference numeral 1 denotes a piezoelectric
ceramic speaker, and a resistor 2 is inserted in series with the speaker 1. The drive circuit 3 is
connected to both ends of the line 1. The signal from the drive circuit 3 is divided into C1 series
resistor 2 applied to the speaker 1 through the series resistor 2 and the impedance of the
speaker 1 and C ′, and the speaker 1 is driven by the divided voltage.
On the other hand, the impedance of the piezoelectric ceramic speaker 1 is capacitive, and its
frequency characteristic shows a negative characteristic in which the impedance decreases as the
frequency becomes higher, as shown in FIG. The voltage applied to the piezoelectric ceramic biforce 1 decreases as the frequency increases, and the pressure level is also suppressed
accordingly. The value of the series resistor 2 may be set equal to (L) the impedance of the
electric ceramic loudspeaker at the lower limit frequency f1 of the small product frequency band
as one standard. In this case, 1. The amount of attenuation of the sound pressure level at each
frequency of the F electric ramix pee force is as shown in Table 1. As apparent from Table 1, as
the frequency increases, the amount of attenuation also decreases significantly. Specifically,
when the unnecessary frequency is 4 K +-17 or more and the impedance value at 4 KH 2 of the
piezoelectric resistive speaker is 250 Ω, the resistor 2 having a resistance value close to 250 Ω
is connected. The M It-frequency characteristic in this case is as shown by the characteristic a
shown in FIG. In practice, the final resistance value is set by adjusting the resistance value while
comparing the sound pressure-frequency characteristic obtained by inserting the resistor 2 with
the desired frequency characteristic. In FIG. 3, as the resistance value decreases, the
characteristics become like, and conversely, as the resistance value increases, it becomes like the
characteristic C. Characteristics (j shows characteristics when the piezoelectric ceramic speaker is
driven by the conventional method without connecting the resistor 2). As apparent from FIG. 3,
according to the present invention, the sound pressure level on the high frequency side can be
reduced, and particularly the peak of the harmonics can be largely suppressed by the simple
means of inserting one resistor 2. It becomes possible to reproduce a mellow sound. In addition,
the slope of the frequency characteristic on the side of the Gf ° C., IOI region can be adjusted to
a desired value by changing the value of the resistance. In addition, when used in a speech
synthesizer, a high-cut filter that is normally inserted is not necessary.
Brief description of the drawings
FIG. 1 is a diagram for explaining an embodiment of the present invention, FIG. 2 is an
impedance-frequency characteristic diagram of piezoelectric remix bee force used in the
description of the present invention, and FIG. 3 is a prior art and based on the present invention
It is a sound pressure level-frequency characteristic view of a piezoelectric ceramic speaker.
1 is a piezoelectric ceramic speaker, 2 is a resistor, and 3 is a speaker drive circuit. Patent
application applicant 祠 Inc. ((1 plant No. 1? Fig. 7 Fig. 5I 1575-
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