| 摘要 |
PROBLEM TO BE SOLVED: To reduce THD, and to equalize frequency characteristics. SOLUTION: A system for modulating an ultrasonic wave carrier beam using an audio input signal is proposed. An audio signal is divided into frequency bands, and each frequency of these different bands is to be treated individually. Concretely, different modulation methods are to be used corresponding to respective divided frequency bands. And each aperture size of different converters is to be used in relation to each different frequency signal. A frequency equalizer is further provided within each frequency band. Finally, a relatively small amplitude modulation degree (one or a plurality of indexes) is to be used in response to a signal in a low frequency band. COPYRIGHT: (C)2006,JPO&NCIPI |
