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BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional front view of a conventional
ultrasonic ceramic microphone, FIG. 2 is a sectional front view of an embodiment of the
ultrasonic ceramic microphone according to the present invention, and FIG. FIG. 4 is a
comparison diagram of the directivity of the ultrasonic ceramic microphone of the prior art and
the present invention. 1 ······· Piezoelectric ceramic vibrator, 2 ······ Metal diaphragm, 3
······································ Terminal plate, 5 ····· · Elastic adhesive, 8 · · · · · · · · · · · · · · · · cylindrical case, 9 ·
· · · · throat portion 10 · · · · · · · · · · 11 · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · ·
· · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · Terminals · 17.18
· · · · · · · lead wire.
[Detailed description of the invention] The present invention is to provide an ultra sweat wave)
sehook micro ono capable of omnidirectional transmission / reception in an ultra-blind wave-L-l]
kli'i used indoors. There are 1 (5) fish. First, a conventional microphone of this type will be
described with reference to FIG. Reference numeral 1 denotes a piezoelectric ceramic vibrator,
which is bonded to a metal diaphragm 2 to form a bimorph vibrator 83 is a conical or frustoconical resonance, a child, which is attached to the central portion of the bimorph vibrator II-) , 4
is a terminal board, and the bimorph vibrator is attached to the central convex portion of the
terminal board 4 through an elastic adhesive 6. 6 is a case having a mesh-like screen 7 fixed at
one end hole and the other end opened, and the bimorph transducer and terminal plate are
housed in the case 6 vc to constitute an ultrasonic ceramic microphone . In this conventional
microphone, the transmission sensitivity radiated from the screen 7 of the case 6 or the
reception sensitivity as the receiver has a pointing angle, and the open hole diameter of the case
6 configured by the screen end; It has directivity determined by the wavelength of sound. For
example, in the case of using a 40 KHz sound, the sound pressure or sensitivity had a half angle
or directivity angle of 60. ;) Also, if the hole diameter of case 6 is increased, ultrasonic waves
(20H1! Side lobes, which is a characteristic of 143 KH2 or more). The present invention provides
an ultrasonic ceramic microphone which ameliorates the conventional drawbacks as described
above, suppresses the sound pressure of frontal radiation sound waves, and provides uniform
sound pressure and sensitivity at a stereo directivity angle of 0 to 186. It is. Hereinafter, an
embodiment of the present invention will be described. It will be described with reference to the
drawing of FIG. A conical or frusto-conical resonator 3 made of metal or resin is bonded to the
central part of a pi-self oscillator formed by bonding the piezoelectric ceramic vibrator 1 and the
metal diaphragm 2 to form a 111-piece resonator. Do. Reference numeral 8 is a cylindrical case
for housing the composite resonator, 9 is a four-part slit t, θ) and a portion provided on the
central part of the upper surface 1 o of the case 8 so as to project to the external force. It is
attached to the attachment portion 11 of the throat portion e via the elastic adhesive 5.
Reference numeral 12 denotes a bottom surface of the case 8 which is set to have a conical
shape whose central portion is close to the surface 10. The shape of the bottom surface 12) is
influenced by the standing wave resonance of the air generated in the case 8 to prevent
interference with the signal sound waves, 0954 and therefore a conical shape is optimum, but a
spherical or conical shape The trapezoid also has its effect fl) ll :). An opening port 13 is provided
around the side of the case 8 and is a port for inputting and outputting sound.
It is desirable that the aperture 13 be large at the base of the acoustic impedance of the free
sound field and the sound field in the case. A dividing plate 14 divides the internal space in the
case 8 into four equal parts, and simultaneously connects the top surface 1 o and the bottom
surface 12. The separating plate 14 is set to a length from the periphery of the throat portion 9
of the central portion of the case 8 to the opening 13 of the case 8. The separating plate 14
shows the effect as a reflecting plate, and two or more plates are sufficient. In the embodiment of
the present invention, the mesh screen is not employed for the aperture L "13 and the throat
portion 9, but it may be employed for the purpose of internal protection by external impact or
the like. 15.16 is a terminal for electric signal output, 17.18 is a lead wire which connects the
terminal 16.16 and the bimorph N- ≦ − motion 0 electrode 7 according to the structure of J or
more, Due to the structure where the opening 09660 is broken on the side of the glass, the
incident from the front is reflected on the bottom of the glass and is not reflected as an incident
wave, but it is incident from the side of the case due to the diffraction effect of the smoke, and
the output is A sound wave that can be taken out and that is incident from the side direction can
be taken out by receiving a direct wave from the case opening by the horn-shaped sound
collecting shape comprising the dividing plate and the bottom face provided in the case It is.
Therefore, it is possible to obtain uniform sensitivity in the stereo orientation of 0 to 180.
Further, the throat portion is installed in the case to guide the throat portion VC sound wave by
the conical bottom surface shape, and the slope shape can significantly reduce the occurrence of
the standing wave in the case. Also, it was clarified that housing the composite resonator in the
front part i [: throat part is largely due to the effect that the direct incident wave and the indirect
incident wave due to diffraction and reflection have the same sensitivity. FIG. 4 is a comparison
of the directivity of the microphone of the prior art and the present invention. 9 shows that the
characteristics of the micro-tens of the present invention and that the characteristics of the
microphone according to the present invention are excellent as is apparent from FIG. 976. As
described above, according to the present invention, stable pointing is achieved. It is possible to
obtain an ultrasonic ceramic microphone exhibiting high sensitivity and high sensitivity.
Therefore, in the circuit design, the voltage fluctuation due to the remote control operation angle
is small, so that the design of the amplification factor and the S / N ratio of the circuit can be