Patent ID: 8041049

Claim:
A method for controlling output from an ultrasonic speaker, comprising: modulating carrier waves by signal waves that generates signal waves in an audio frequency band outputted from a signal source; and driving an ultrasonic transducer by the modulated waves, wherein signal processing is applied to the signal waves in the audio frequency band according to an angle formed between a first plane that contains a sound wave emitting axis of the ultrasonic transducer and that is normal to a reference floor plane and a second plane that contains an axis indicating a listener's front direction and that is normal to the reference floor plane such that frequency characteristics of a signal sound in the audio frequency band which is self-demodulated when emitted from the ultrasonic speaker are made flat for each angle in a predetermined range of angles formed between the first plane containing the sound wave emitting axis and the second plane containing the axis indicating the listener's front direction, and wherein the predetermined range of angles ranges from 90 degrees to −90 degrees, a 0 degree midpoint of the predetermined range corresponding to an orientation of the listener in which the listener's front direction faces the ultrasonic transducer.