パラメトリックスピーカーにおける生成音の位相シミュレーション

Abstract

The phase of sound waves in a strong ultrasonic wave is simulated using the Khokhlov-Zabolotskaya-Kuznetsov equation，which is solved as a transformed beam equation using the Richtmyer method. The simulation is applied to a parametric speaker using amplitude modulation and self-demodulation with a circular configuration. The characteristics of the generated audio waveform are compared with those of plane and spherical ones. The phase of the generated waveform is different from those of plane and spherical waves. However，the generated waveform shows similar characteristics to those of a spherical one within a few degrees of the sound axis. This similarity decreases with increasing distance from the axis，and the phase converges to that of a plane wave. From the viewpoint of the phase，the audio waveform generated by the parametric speaker can be regarded as a narrow wave generated at a virtual point source located at the rear of the speaker.