| 摘要 |
PURPOSE:To improve a converting efficiency by providing a carrier wave oscillator and a modulator to modulate a carrier wave by a sound signal, and an ultrasonic wave generator, driven by the output of the modulator, and using an intermittent wave or a waveform that the plural waves with a different amplitude are combined, as the waveform of a carrier wave. CONSTITUTION:A speaker 2 is constructed by arraying 1000 number of ultrasonic oscillators, the center frequency of which is 40 kHz, in a bee hive shape, and connecting all of them in parallel. At first, the carrier wave, shown in a figure, is generated by an optional waveform generator 5a, and is modulated by the sound signal, and is inputted to the speaker 2 through a power amplifier 6. In the figure, when a sound wave is emitted, because a voltage of 2<1/2> times of a continuous wave is impressed, the primary wave sound pressure level is 3 dB higher than the continuous wave. Because a secondary wave sound pressure is proportional to the square of the primary wave sound pressure, a secondary wave sound pressure level is 6 dB higher. On the other hand, when the sound wave is not emitted at all, the secondary wave is not generated as a matter of course, but it comes 3 dB higher on an average, compared with the time of the continuous wave. Namely, by driving by the waveform shown in the figure, the converting efficiency from electricity to sound is doubled. |
