Condenser microphone utilizable at high temperature and intense radioactive rays. The microphone has a tension ring and a backplate, both of which are made of a metal having a small coefficient of linear expansion relative to the other parts of the microphone. The tension ring is fitted to a tension ring holder, and the backplate is mounted on the tension ring holder
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The microphone of the piezo-electric ceramic type, however, has a sensitivity of as low as -105 to -120 dB under the conditions of a high-temperature atmosphere. Therefore, the microphone of the piezo-electric ceramic type is not capable ofdetecting sound of small levels when it is used in a high-temperature atmosphere condition. Microphones of other types are not utilizable at high temperatures as a matter of course. Therefore, the conventional microphones are not capable of detectingsound of small levels when they are used as sensors under high-temperature atmosphere conditions.
An object of the present invention is to solve the above-mentioned problems inherent to the conventional art.Another object of the present invention is to provide an improved condenser microphone which can be used under the conditions of high temperature and radioactive rays.Another object of the present invention is to provide an improved microphone which is capable of detecting sound of small levels under the condition of high temperature.According to the present invention, there is provided a condenser microphone having resistance against high temperature and radioactive rays.
The microphone has a first cylindrical body having a bottom end member at its one end, a second cylindrical body threadedly engaged at its one end to the other end of the first cylindrical body, ring means threadedly engaged with the other end ofthe second cylindrical body, a vibration membrane
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The microphone structural body has tensionmeans for imparting a tension to the vibration membrane, a backplate which has an upper surface spaced from
insanity workout dvds the vibration membrane, and an insulator between the tension means and the backplate so that a unitary structure of the microphone structural bodyis formed. In the present invention, the tension means and the backplate are made of a metal having a small coefficient of linear expansion relative to the other elements such as the ring means and first and second cylindrical bodies.
In an embodiment of the invention, the
cheap p90x tension means has a tension ring contacted with the vibration membrane, and a holder for holding the tension ring. The holder is threadedly engaged with the second cylindrical body and connected to thebackplate through the insulator. Preferably, the insulator is a glass insulator of aluminosilicate. In a further embodiment of the invention, the ring means has a first ring threadedly engaged with the aforementioned second cylindrical body and asecond ring fixed to the first ring with the circumferential end of the vibration membrane being secured firmly therebetween.
In a further preferred embodiment of the invention, the height from the upper end of the insulator to the upper end of thebackplate is set smaller by about 40 to 50 μm than the height from the upper end of the insulator to the upper end of the tension ring so that a gap of about 40 to 50 μm is maintained between the vibration membrane and the backplate when a tensionis imparted to the membrane by the tension ring.
According to the present invention, the tension imparted to the vibration membrane decreases as the temperature rises, and the effect of creep is restrained. Further, the gap changes very little between the vibration membrane and the backplateAccordingly, there is obtained a microphone which is highly sensitive and which exhibits good frequency characteristics under the conditions of high temperatures and intense radioactive rays. At a temperature of 300° C., for instance, themicrophone exhibits a sensitivity of -74. -.3 dB, and frequency characteristics of . -.5 dB over a range of 500 to 10 KHz. Therefore, the present invention makes it possible to detect low amplitude sounds that could not be detected so far under hightemperature atmosphere conditions.
While condenser microphone has been described with respect to a preferred embodiment, it should be apparent to those skilled in the art that numerous modifications may be
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