Patent ID: 9681225
Date: 2017-06-13
CPC Classifications: H04R,H04S

Claim:
1. In a parametric loudspeaker system comprising a modulator for modulating an ultrasonic carrier signal with an audio signal, at least one driver amplifier for amplifying the ultrasonic carrier signal, and one or more ultrasonic transducers for directing the ultrasonic carrier signal through air along a selected projection path, a method of modulating the ultrasonic carrier signal, comprising: receiving the audio signal at the parametric loudspeaker system, the audio signal having, for a duration of the audio signal, low audio signal levels, intermediate audio signal levels, and high audio signal levels; for the intermediate audio signal levels, modulating, by the modulator, the ultrasonic carrier signal with the audio signal at under-modulation; for the low audio signal levels, reducing a predetermined modulation offset to obtain a reduced ultrasonic signal level; and for the high audio signal levels, modulating, by the modulator, the ultrasonic carrier signal with the audio signal at maximum modulation.