Patent ID: 7769193

Claim:
An ultrasonic speaker, comprising: an electrostatic ultrasonic transducer including: a first electrode that is formed with a plurality of holes; a second electrode that is formed with a plurality of holes, and forms a pair of electrodes with the first electrode; an oscillation film formed with a conductor layer that is sandwiched between the pair of electrodes, and the conductor layer receiving a direct-current bias voltage; and a retention member that retains the pair of electrodes and the oscillation film, wherein an alternating signal is applied between the pair of electrodes, and the pair of electrodes each have a thickness t of (λ/4)·n−λ/8≦t≦(λ/4)·n+λ/8, where λ denotes a wavelength of ultrasound, and n denotes a positive odd number); a signal source that generates a signal wave in an audio frequency band; a carrier wave supply unit that generates and outputs a carrier wave in an ultrasonic frequency band; and a modulation unit that modulates the carrier wave by the signal wave in the audio frequency band provided by the signal source, wherein the electrostatic ultrasonic transducer is driven by a modulation signal that is applied between the pair of electrodes and electrode layers formed to the oscillation film, and is provided by the modulation unit.