A parametric array PMUT loudspeaker with high efficiency and wide flat bandwidth

A previous study demonstrated that a piezoelectric micromachined ultrasonic transducer (PMUT) could be used to construct a PA loudspeaker, and developed a prototype. In this paper, we describe the performance of a PA loudspeaker fabricated using a more developed package. Our PA loudspeaker consists of an array of PMUTs with two resonance frequencies and uses an `out-of-phase´ driving technique, resulting in high power efficiency (up to 71%) and a wide flat radiation bandwidth. We also describe the characteristics of the PA sound, which depend on the method used to modulate the audible signal.