A study on compensating for the distortion of the parametric array loudspeaker with changing nonlinearity

The parametric array loudspeaker (PAL) is a type of directional loudspeakers, which incurs notable distortion due to its nonlinear sound principle. Many preprocessing methods have thus been proposed to compensate for the nonlinear distortion or to linearize the PAL. In this paper, we present recent results of linearizing the PAL upon changing nonlinearity. The varying input amplitude of the PAL causes change in the amplitude of the modulated ultrasonic carrier and results in the consequent change of nonlinearity. The experiment results show that the performance of the previous linearization system is much degraded when the input amplitude is different from the sine sweep used for the Volterra filter identification. Moreover, it is also observed that when the input amplitude is very large, the identification accuracy of the Volterra filter also decreases