DRIVE CONTROL METHOD OF ELECTROSTATIC-TYPE ULTRASONIC TRANSDUCER, ELECTROSTATIC-TYPE ULTRASONIC TRANSDUCER, ULTRASONIC SPEAKER USING ELECTROSTATIC-TYPE ULTRASONIC TRANSDUCER, AUDIO SIGNAL REPRODUCING METHOD, SUPERDIRECTIONAL ACOUSTIC SYSTEM, AND DISPLAY

摘要

A push-pull-type electrostatic-type ultrasonic transducer includes a first electrode having through holes, a second electrode having through holes each of which is paired with the corresponding through hole of the first electrode, and an oscillation film sandwiched between a pair of the first and second electrodes and having a conductive layer to which direct current bias voltage is applied. When a wavelength obtained from a resonance frequency at a mechanical oscillation resonance point of the oscillation film is λ, a thickness t of the respective fixed electrodes is (λ/4)·n or substantially (λ/4)·n (where λ: wavelength of ultrasonic wave, n: positive odd number). AC signals as modulation waves produced by modulating carrier waves in an ultrasonic frequency band by signal waves in an audio frequency band are applied between a pair of the electrodes.