The near field, Westervelt far field, and inverse-law far field of the audio sound generated by parametric array loudspeakers

The near and far fields of traditional loudspeakers are differentiated by whether the sound pressure amplitude is inversely proportional to propagating distance. However, audio field generated a parametric array loudspeaker (PAL) more complicated, in this article it proposed be divided into three regions: field, Westervelt inverse-law field. In experiences strong local effects an efficient quasilinear solution presented. negligible so that equation used, simpler adopted. It found boundary between for lies at approximately a2/? – ?/4, where transducer radius ? ultrasonic wavelength. At large radii high frequencies, moves close PAL can estimated closed-form formula. holds than 10 meters away from most cases. With classification, convenient apply appropriate prediction models different regions.