Signal modeling of the conditioning stage of a parametric array loudspeaker by statistical design of experiments

Abstract

Parametric Array Loudspeaker is a directional sound technology that uses ultrasound amplitude modulation to generate audible sound in a specific propagation path. The mathematical modeling of this technology is an interesting problem that cannot be tackled analytically due to a nonlinear phenomenon associated with the production of sound from ultrasound, i.e. self-demodulation. Self-demodulation affects sound quality by both introducing undesired harmonic content and reducing drastically the intensity of low frequencies. The steps within the Digital Signal Processor having the greatest effect on self-demodulation at the conditioning stage of the ultrasonic signal were detected and empirical mathematical models that account for response variables such as the total harmonic distortion and the perceived intensity of the fundamental tone were elaborated by using statistical Design of Experiments. This methodology permitted the identification of the mono peak compressor as the variable with the largest influence with regard to the response variables.