Lee Chang-Min, Kwon Joong-Hak, Hwang Sang-Moon
The Journal of Mechanical Science and Technology, vol. 24, no. 9, pp.1763-1769, 2010

Abstract : With the advent of the mobile phone, Digital Multimedia Broadcasting (DMB) service for multimedia data communication will soon be realized. With regard to the acoustic aspects of this service, a smaller and lighter microspeaker also soon will be implemented in MP3 song players and speakerphones. The sound quality of such microspeakers, as evaluated with reference to total harmonic distortion (THD) is becoming more important. THD is the proportion of the higher-order frequency output response to a sinusoidal input signal. It is affected by uneven magnetic distribution and nonlinear responses of diaphragms. In this work, THD was analyzed in consideration of the coupling effects between mechanical vibration and electromagnetic exciting forces. Simulated THD results were compared with the experimental data. The THD in the lower frequency range increased due to the increased displacement of the voice coil and the elevated high-order component response of the sound pressure.

Keyword : Coupling effect; Microspeaker; Speedance; Sound pressure level (SPL); Total harmonic distortion (THD)