The Audio Spotlight system uses nonlinearly propagating ultrasound to create highly directional beams of sound in mid-air, which can be "shone" and "directed" much like light.
Developed by Dr. Pompei he was the first in the world to develop the mathematics and advanced engineering that allowed sound to be created literally from thin air with sound quality and reliability rivaling traditional loudspeakers.
The technique of using a nonlinear interaction of high-frequency waves to generate low-frequency waves was originally pioneered by researchers developing underwater sonar techniques dating back to the 1960's. These early acoustics researchers successfully derived the formal mathematical basis for this effect and developed innovative sonar systems with more directivity and bandwidth than would otherwise be available. They called this device a parametric array.
In 1975, the first publication appeared which demonstrated that these nonlinear effects indeed occur in air. While these researchers had not attempted to reproduce audio, they nonetheless proved that such a device may be possible.
Over the next two decades, several large companies, including Matsushita (Panasonic), NC Denon, and Ricoh attempted to develop a loudspeaker based on this principle, and published a paper describing one attempt in 1983. While they were successful in producing some sort of sound, problems with cost, feasibility, and extremely high levels of distortion (>50% THD) caused the almost total abandonment of the technology by the end of the 1980's.
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