Modulation and demodulation of steerable ultrasound beams for audio transmission and rendering
Paper i proceeding, 2008

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. In this paper we describe the theoretical advantages of singlesideband (SSB) modulation versus a standard amplitude modulation (AM) scheme for the above-described application. We describe our near-field soundfield measuring experiments, and propose steering solutions for the array using two different types of transducers, piezoelectric or electrostatic, and the proper supporting hardware.


Mathias Barbagallo

Politecnico di Milano

Mendel Kleiner

Chalmers, Bygg- och miljöteknik, Teknisk akustik

Augusto Sarti

Politecnico di Milano

11th International Conference on Digital Audio Effects, DAFx 2008; Espoo; Finland; 1 September 2008 through 4 September 2008