Abstract:Modulated onto the ultrasonic carrier and transmitted, the audio signal will generate the selfmodulation with the help of the air′s nonlinear effects and the good directivity can be obtained . In the applications of directional audio transmission, the biggest problem is how to improve the conversion efficiency. In this paper, we analyzed the parameters related to the efficiency of ultrasoundmodulated audio directional transmission by a detailed theoretical derivation and calculation.Through the analysis and calculation, we know that with the external environment remaining unchanged, the intensity and efficiency of directional audio sound can be influenced greatly by the change of the carrier frequency and frequency difference of the emitted ultrasonic sound, the change of the intensity of emitted ultrasonic sound as well as the change of the emission source area. So in the design of audio directional transmission system we should take the impact of these parameters into consideration.