In the early 1980's, several Japanese companies, such as Nippon Columbia, Ricoh, and Matsushita, attempted to develop the parametric array for the reproduction of broadband audible sound. They typically deployed large arrays containing hundreds of piezoelectric transducers, such as the one to the right [3], to transmit simple AM modulated audible signals. While successful in reproducing sound, tremendous problems with cost, robustness, and extremely poor sound quality (up to 50% total harmonic distortion) caused them to abandon the technology as unfeasible. More recently in mid 1996, an American company produced their own version of this device and proclaimed it 'a revolution' in audio. In fact, this device, contrary to their claims and unbeknownst to the popular press, was very similar to those described in audio journals a decade earlier (shown to the left), and of course suffered from the very same problems of poor sound quality and lack of robustness that plagued the earlier researchers [4]. Since then, there has been no published evidence of progress towards a practical device. Background Since his days as a part-time musician and young acoustics engineer at Bose in the early 1990's, Mr. Pompei recognized that a key ingredient missing from audio reproduction was the ability to reliably spatialize sound. While in a natural environment, sound occurs all around us, giving us a tremendously strong impression of our environment, the reproduction of sound over loudspeakers, at best, provides a very vague and limited spatial impression. Similarly, what was missing from music, he decided, was the ability to choreograph musical instruments in space, just as you would dancers. While pursuing as a Master's student techniques related to '3D Audio' technologies, he realized that this method would simply not work in an uncontrolled acoustic environment - if the listener moved out of the small 'sweet spot', the illusion would vanish, and there were no practical remedies to this problem, so long as traditional loudspeakers were used. The solution, then, was to not rely on psychoacoustic illusions, but instead to create sound independently of the loudspeaker. One of several ideas he had at the time was the use of interacting ultrasound beams to produce audible sound. -96-