| 摘要 |
PURPOSE: An audio equipment is provided to minimize influence of a demodulation processing and transfer characteristics of a transducer for an audible signal by obtaining a second ultrasonic signal by modulating a first ultrasonic signal by the audible signal by a modulator, transducing the second ultrasonic signal into a ultrasonic pressure wave by the transducer and simultaneously correcting demodulation characteristics of a nonlinear medium and the transfer characteristics of the transducer by correcting the audible signal. CONSTITUTION: The audible signal(28) is formed as the digital second ultrasonic signal(30) by digitally modulating the first ultrasonic signal(29) form a ultrasonic signal source(13) by the modulator, formed as an analog ultrasonic signal(31) by performing digital/analog conversion by a DAC(14), it is emitted as an inaudible ultrasonic pressure wave by a ultrasonic transducer(15). The inaudible ultrasonic pressure wave is mutually acted with the air (nonlinear medium), self-demodulated and the modulated audible signal can be heard. A transducing effect of the ultrasonic transducer(15) is changed for different frequency and depth of demodulation by a square root arithmetic unit(11). According to the change, a transducer response filter(8) is experientially decided and the audible signal(28) is corrected.
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