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High Quality Directional Audio System

Highly directional audible sound can be reproduced by the nonlinear interaction of finite amplitude AM ultrasound waves in the air. Due to the nonlinear process, however, the reproduced audible sound does not quite match the level of the traditional speaker in sound quality. There are mainly two reasons for this, namely, high harmonic and non-harmonic distortions and -12 dB/oct dependence for the low frequency response. In this paper, new methods for improving the sound quality are proposed and verified. Furthermore, a technique of forming desirable sound beam shapes is also discussed.