Directional propagation of audio signal is a new technology to control the propagation of sound. Ultrasonic wave which is amplitude modulated by an audio signal is radiated from a transducer into the air. Because of nonlinearity of the air, AM sound wave is self-demodulated and an audio signal is produced in the air. The sound beam id produced.Firstly, the property of propagation of sound wave and ultrasonic wave is introduced. The sound pressure and directional plot and nonlinearity effect while sound wave...