| 摘要 |
PURPOSE:To attain the acoustic reproduction utilizing the nonlinear parametric operation of air by reproducing a pulse code modulating signal by an ultrasonic wave element. CONSTITUTION:A signal subject to pulse code modulation from an input signal 1 at an A/D converter 2 is formed as 4 bits; signals 5-8 in order from the lower bit. An oscillator 4 has an oscillating frequency nearly equal to the resonance frequency of ultrasonic wave elements 21-24. The signal of the oscillator 4 and the signals 5-8 are processed for operation by multipliers 9-12. The signals subject to processing operation are amplified by amplifiers 13-16 and the weighting depending on each bit is conducted by level control elements 17-20. The resonance frequency of the ultrasonic wave elements 21-24 and the reference frequency (the frequency of the oscillator 4 in this case) included in the signal 5-8 are set nearly equal by applying the signals to the ultrasonic wave elements 21-24. |
