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BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
microphone which obtains an output having two properties from one microphone.
2. Description of the Related Art A conventional microphone is one that is obtained by a
piezoelectric effect or obtained as a single signal for capacitance change.
SUMMARY OF THE INVENTION In a conventional microphone in which only a single signal is
obtained, it has been difficult to easily obtain a signal that causes the operation of an electrical
feedback circuit.
SUMMARY OF THE INVENTION Electrodes are provided on both sides of a piezoelectric film
(plate), and the principle is shown in FIG. , 03, and an electrode 2 obtained by applying a
conductive treatment to a conductive object or a nonconductive object is provided at the position
of the front surface or the back surface facing each other.
Although the film (plate) 1 and the case for housing the electrodes are omitted in the drawing, a
film that can obtain a suitable back pressure if noise cancellation type due to anti-phase is
obtained due to the characteristics of the microphone It is free to apply the conventional
technique, for example, by providing an opening so that sound pressure in reverse phase can be
obtained from the back surface of the plate.
The feature of the present invention is shown in FIG. 2 as its electrical principle diagram, in
which the signal S1 obtained by the piezoelectricity and the electrode (01 or 03) applied to the
piezoelectric film (plate) are opposed to each other. Configuration in which at least three
electrodes are overlapped substantially vertically with respect to the front as shown in the
principle diagram of FIG. 1 for the purpose of obtaining a signal S2 based on a capacitance
change .DELTA.C caused by a change in gap with the electrode 2 And a microphone.
BEST MODE FOR CARRYING OUT THE INVENTION As a piezoelectric film (plate), an inorganic
one such as PVF2 ↓ or the like, or an inorganic ferroelectric piezoelectric material using such an
adhesive It is possible to freely select one obtained by mixing and filling a powder of No. 1 and
forming a film, a thin film of a piezoelectric body formed by a deposition method, and further a
thin film obtained by a bulk method. With regard to the electrode 2, a target sensitive frequency
band etc. is calculated, and an electrode having an appropriate aperture ratio is prepared and
arranged as shown in the figure. I will explain in detail about the implementation. As a film
(plate), a piezoelectric film finished to 100 μm or less is selected as an electrode, a metal having
good workability is selected, as shown in FIG. 1, a minimum not to electrically short the electrode
facing the electrode of the film (plate) Put in the case with a limited gap. In order to prevent an
electrical short circuit between the electrode of the film (plate) and the opposing electrode, it is
free to sandwich an insulating film therebetween. The drawings are omitted.
As an example for improving the sensitivity of the capacitance change ΔC, opposing electrodes 2
are provided on both sides of the film (plate) 1 as shown in FIG. 4 based on the principle of the
present invention. That is, when the piezoelectric film (plate) is changed by the sound pressure P
from the front to the rear due to the sound pressure P, the capacitance between the electrodes
01 and 2 on the front side changes -ΔC while the opposing electrodes 03 and 2 of the back
example are This produces a change of + ΔC. The signal change source of the 2ΔC capacity
change generated by these differential methods is used as the signal generation source -S2 and +
S2 signals and the signal S1 generated from the piezoelectric film (plate) 1 itself as two unique
signals. It can be extracted.
Industrial Applicability The microphone of the present invention can be used in many acoustic
devices that use an electrical feedback signal to improve fidelity.
Brief description of the drawings
1 schematically illustrates the principle of the present invention.
2 shows the principle of the present invention electrically.
FIG. 3 shows an example for extracting a change in capacitance as an electric signal, and the
cases where resistances are added in parallel or in series are respectively shown in FIGS.
Fig. 4 is a schematic view of an embodiment utilizing the principle of the microphone of the
present invention, in which members such as a housing are omitted, and a plurality of
piezoelectric films (plates) 02 provided with electrodes 01 and 03 on both sides A case is shown
in which the conductive electrodes 2 provided with the holes 21 are respectively disposed, and
the capacitance change amount is doubled based on the principle of differential displacement.
Explanation of sign
01, 03 Electrode 02 provided on piezoelectric film (plate) Piezoelectric film (plate) 1 Piezoelectric
film provided with electrode 2 Conductive electrode 21 Aperture P provided on electrode Sound
pressure Indicates the direction of the signal S2 generated from the piezoelectric film S2
generated by the capacitance change