| 摘要 |
PROBLEM TO BE SOLVED: To obtain an acoustic device with a reproduced sound from an ultrasonic radiator always having the maximum sound pressure. SOLUTION: A super-directive acoustic device includes a modulator 7 for modulating an ultrasonic carrier signal by an input electric signal from a modulation signal source 1, an amplifier 8 for amplifying a signal obtained by the modulation of the modulator 7, and the ultrasonic radiator 9 for converting the signal amplified by the amplifier 8 into acoustic waves for acquiring an audible signal by a parametric action due to nonlinearity of ultrasonic limited amplitude acoustic waves. A means is provided, for detecting a change in a current signal flowing between the amplifier 8 and the ultrasonic radiator 9 to determine carrier signal frequency of the ultrasonic waves in the modulator 7. COPYRIGHT: (C)2005,JPO&NCIPI |
