The use of airborne ultrasonics for generating audible sound beams

A device known as a parametric array employs the nonlinearity of the air to create audible sound from inaudible ultrasound, resulting in an extremely directive, beamlike wide-band acoustical source. This source can be project ed about an area much like a spotlight, and creates an actual spatialized s ound distant from the transducer. A basic theoretical analysis of the airbo rne parametric array is outlined and verified experimentally, and future ch allenges are discussed.