INDIVIDUAL DIFFERENCE OF ULTRASONIC TRANSDUCERS FOR PARAMETRIC ARRAY LOUDSPEAKER

A parametric array loudspeaker (PAL) consists of a lot of ultrasonic transducers in most cases and is driven by an ultrasonic which is modulated by audible sound. Because each ultrasonic transducer has each difference resonant frequency, there is the individual difference in ultrasonic transducers of a PAL in a manufacturing process. In this paper, two PALs are made of each set of transducers with large and small variance of resonant frequencies. Quality factor of PAL with the large variance of resonant frequencies is smaller than that of PAL with small variance, and the demodulated audible sound pressure level (SPL) is large and almost flat to 3 kHz in PAL with the large variance of resonant frequencies.