Patent ID: 7899197
Filing Date: 2011-03-01
Classification: H04R

Abstract:
1. An ultrasonic speaker comprising: an electrostatic transducer which is driven by a boosted driving signal by boosting a modulated signal obtained by modulating a carrier wave with an acoustic signal in an audio frequency band and includes an output transformer T which connects the electrostatic transducer to a secondary side winding thereof in parallel and boosts the modulated signal, and a resistor R and a coupling capacitance C an audio frequency signal source which generates a signal wave in an audio frequency band; a carrier wave signal source which generates and outputs a carrier wave in an ultrasonic frequency band; a modulator which modulates the carrier wave with the signal wave in the audio frequency band; and a power amplifier which amplifies the signal modulated by the modulator and applies the amplified signal to the primary side winding of the transformer T through the resistor R and the coupling capacitance C wherein, when the load capacitance of the electrostatic transducer is CL(F) and a rated carrier wave frequency of the electrostatic transducer is fc(Hz), the self-inductance L