Directional Loudspeaker

Project Leader: Xiao Qin

According to the nonlinear acoustics, modulated airborne ultrasound will start a self-demodulation process along the propagation in the air. The sound pressure level of demodulated wave(the desired audible sound) is proportion to the 2nd time-derivative of the modulating envelope squared. Thus, the demodulation process forms a virtual sound source array along the propagation axis. Since ultrasound is directional, and it attenuates more quickly, only audible sound exists after a certain distance (parametric array length)

 A Directional Loudspeaker system can be roughly divided into three major parts: Transducer (usually piezoelectric materials such as PVDF and PZT), Power Amplifier and Digital Signal Processing Unit (DSP).

On the left is a photo of our Directional Loudspeaker System prototype.