Research on an improved amplitude modulation method of audio directional loudspeaker

Abstract

Aimed at solving the harmonic distortion problem of the DSB (Double Side Band) method which is employed in audio directional loudspeaker, an improved amplitude modulation (AM) method is investigated. According to the parametric acoustic array principle and self-demodulation theory, the theoretical self-demodulation model of the improved AM method is established, and a conclusion that the variational phase in the improved AM method hardly affects the second pressure is drawn. Furthermore, the harmonic distortion of the improved AM method is analyzed theoretically and tested by experiments, and the results show that the improved AM method has a far smaller total harmonic distortion than the DSB method when their modulation factors are equal. However, the improved AM method can only be applied reasonably when the modulation factor is small, because its total harmonic distortion is notable when the modulation factor is high.