| 摘要 |
PURPOSE:To generate an audible band sound wave by synthesizing two ultrasonic waves having respectively different frequency, radiated to space in respectively prescribed directions, respectively modulated to prescribed waveforms, and inputted in the two directions at their intersecting point. CONSTITUTION:Sine wave signals in ultrasonic wave bands having respectively different frequency f1, f2 are generated from sine wave oscillators 1, 2 and the waveforms of these sine wave signals are modulated by waveform modulators 3, 4 under the control of a modulation signal outputted from a waveform modulation controller 5 so that a required audible band sound wave can be obtained. The waveform-modulated sine wave signals are radiated to space as ultrasonic waves by speakers 6, 7 to be electric-acoustic conversion means in variable radiation directions and synthesized at their intersecting point on the radiation directions. Thus, the audible band sound wave (f1 to f2 frequency) can be generated. |
