The Nonlinear Distortion of Directional Loudspeaker
A directional audible sound could be generated from the nonlinear interaction of ultrasound in the propagation medium. The demodulated audible signal is proportional to the second time derivative of the square of the ultrasound envelope, described in Berktay s Far-field solution, which is nonlinear to the process of sound reproduction. Double Side-Band modulation (DSB) is proposed to amplitude-modulate the ultrasound carrier with audio signal. Total harmonic distortion (THD) is calculated for signal with single frequency firstly, and it increases with the increase of the modulation index. However, its more complex for input with two frequencies or multi-frequency. Except for the interaction between the modulated ultrasound and the carrier, the intermodulation distortion (IMD) is generated from the interaction of modulated signal with multi-frequencies. Hence, Single Side Band modulation (SSB) is proposed for reducing the THD and IMD. There is no 2nd harmonic frequency or higher frequencies for input with single frequency. And the amplitudes of harmonics are only related to the modulation index for input with two frequencies or wideband. SSB is recommended to reduce THD or IMD.
Ying Wang Limei Xu Min Chen Leon Xu Cao Yang Jian Ma
Institute of Astronautics & Aeronautics, University of Electronic Science and Technology, Chengdu, S Nokia Research Center, Beijing Economic and Technological Development Area, No.5 Dong Huan Zhonglu,
国际会议
2008 International Conference on Audio，Language and Image Processing(2008国际声音、语言、图像过程大会)
镇江
英文
17-21
2008-07-07（万方平台首次上网日期，不代表论文的发表时间）