**An alternative design for loudspeakers using
the non-linear interaction of sound waves.
Ratish J. Punnoose
When two sound waves having different frequencies interact, new sound waves whose frequencies correspond to the
sum and difference of the primary waves are created due to the non-linearity of the sound medium. An alternative kind
of loudspeaker can be designed on this principle. An ultrasound wave that has bee modulated with an audio signal is
radiated into air. Due to the nonlinearity of air, an audio signal is produced by the self-demodulation effect of the
ultrasound wave. This idea was first tested in 1975 when a single tone was created using this technique. This was
extended by creating a spotlight of sound. This work was done by Ricoh Company Ltd in 1983 as described in the
Journal of the Acoustical Society of America. There is work in progress in this area separately at MIT's media lab and a
private company "American Technolog Corporation" www.atcsd.com .