各種マイクロフォンの特性に關する研究(其の一) : 振幅特性と周波數特性

概要

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The amplitude and frequency characteristics of microphones were measured strictly in a sound-proof chamber. The microphones used in the experiment were three condenser types, four electro-dynamic cones and one resistance type. As the source of sound, the cone speaker of moving coil type was excited by the valve oscillator of variable pitch. Its radiant energy was measured by the Rayleigh disc set in front of the source, its distance from source being more than 50 cm. In our experiments, the distance between the source and the microphone must be kept more than three metres, otherwise the standing wave appears between them. The output current in the microphone amplified by the resistance-capacity amplifier was measured. As for frequency characteristics, we made the experiments with different conditions: -1) The distance between the source and the microphone was varied from 3m. to 5m. 2) The sources of different nature were used. We found good coincidence between their results and moreover, the frequency characteristic obtained by the experiment was identical with that derived from the amplitude characreristic.
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