A comparative study of preprocessing methods in the parametric loudspeaker

The parametric loudspeaker is a directional sound reproduction device making use of the parametric sound generation. A sound beam is formed as a result of nonlinear interactions between ultrasonic beams. The parametric loudspeaker is advantageous in transmitting an equally narrow sound beam from a smaller emitter as compared to the conventional loudspeaker. Due to this advantage, parametric loudspeakers are readily applied in a variety of sound field control applications, such as creation of personal listening spots, spatial audio reproduction, and active noise control. However, there is a long concerned drawback of the parametric loudspeaker, whereby harmonic and intermodulation distortions are byproducts of the parametric sound generation. Hence, a comparative study of six preprocessing methods, including two proposed methods from this paper, is carried out. Harmonic and intermodulation distortions are demonstrated by experiments.