| 摘要 |
PROBLEM TO BE SOLVED: To provide a superdirectional sound device which is improved in efficiency of electroacoustic transduction. SOLUTION: The audio signal from an audible sound source is processed into a signal of a frequency band at least higher than the audio band through pulse-width modulation and a carrier level and the gain of a modulated signal are set through envelope processing in accordance with a value obtained from the level of the audio signal from the audible sound source. COPYRIGHT: (C)2007,JPO&INPIT
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