ELECTROSTATIC ULTRASONIC TRANSDUCER DRIVE CONTROL METHOD, ELECTROSTATIC ULTRASONIC TRANSDUCER, ULTRASONIC SPEAKER USING THE SAME, AUDIO SIGNAL REPRODUCTION METHOD, ULTRA-DIRECTIONAL ACOUSTIC SYSTEM, AND DISPLAY DEVICE

摘要

PROBLEM TO BE SOLVED: To provide a push-pull-type electrostatic ultrasonic transducer with an aim for improving the electro-acoustic energy conversion efficiency.;SOLUTION: A push-pull-type electrostatic ultrasonic transducer includes a first electrode 10A, having a through hole 14, a second electrode 10B having a through hole forming a pair with the through hole of the first electrode, and a vibration film 12 held between a pair of electrodes composed of the first and the second electrodes and having a conductive layer 121 to which a direct-current bias voltage is applied, and holds the pair of electrodes and the vibration film. If is the wavelength of the carrier wave, having a frequency shifted as a predetermined amount of frequency from the resonance frequency, which is the mechanical resonance frequency of the vibration film, thickness (t) of each of the pair of electrodes is set to (/4)n or roughly (/4)n (where is the wavelength of the ultrasonic wave, (n) is a positive odd number), and an alternating-current signal, which is a modulated wave, obtained by modulating the carrier wave in the ultrasonic frequency band with a signal wave in an audible frequency band, is applied between the pair of electrodes.;COPYRIGHT: (C)2007,JPO&INPIT