Influence of enclosure wall vibration on the frequency response of miniature loudspeakers

The miniature loudspeaker is widely used in consumer electronic products. The unwanted vibration of the enclosure wall of the loudspeaker could add to the overall acoustic output and cause distortion of the frequency response. An experimental miniature loudspeaker model with a low-damping enclosure wall was constructed. The vibration of the enclosure wall plate was simulated with an acoustical analogous circuit, in which the wall plate was modeled as a separate branch in parallel with the back cavity air volume. The acoustic frequency response of the enclosure wall was simulated with combined finite element method and boundary element method (FEM–BEM). The vibration and acoustic measurements validated the effectiveness of the simulation methods. Finally, the frequency response of a production type miniature loudspeaker was measured before and after modification. Distortion up to ±15 dB on the frequency response curve was observed around 7.8 kHz. With damping material applied to the enclosure wall, the distortion was largely suppressed.