SSB Modulation of the Ultrasonic Carrier for a Parametric Loudspeaker

The parametric loudspeaker takes advantage of the non-linearity property of the air to create new frequency sound components, which can be used to reproduce audible sound from the ultrasonic waves generated by the transducer. Compared with the traditional loudspeaker, the audible sound from the transducer of the parametric loudspeaker has very sharp directivity pattern, which makes its possible to create a sound beam. The problem is also from the non-linearity interaction, which brings great harmonic distortion to the audible sound. As a result of that, many signal processing methods have been proposed to reduce THD (total harmonic distortion), including square-rooter method, DSB (double sideband) modulation, and SSB (single sideband) modulation etc. In this paper, the SSB modulation used in parametric loudspeaker has been analyzed in detail and its testing results are also included, which show that SSB modulation has great advantage over the other processing methods.