MODULATION AND DEMODULATION OF STEERABLE ULTRASOUND BEAMS FOR AUDIO TRANSMISSION AND RENDERING TEMPLATES FOR DAFX-08, FINLAND, FRANCE (original) (raw)

Nonlinear effects in ultrasound propagation can be used for generating highly directive audible sound. In order to do so, we can modulate the amplitude of the audio signal and send it to an ultrasound transducer. When played back at a sufficiently high sound pressure level, due to a nonlinear behavior of the medium, the ultrasonic signal gets self-demodulated. The resulting signal has two important characteristics: that of becoming audible; and that of having the same directivity properties of the ultrasonic carrier frequency.