Research On Micro-loudspeaker Array Systems

With the rapid development of portable communication devices, more and more attention has been paid to the sound focusing ability of the loudspeaker systems. Due to the space limitation, only small size loudspeaker array can be installed in the portable devices. In this thesis, the algorithms for small size loudspeaker array are investigated. The robustness of the near-field sound focusing strategy of the small size array is highlighted. A multi-channel acoustic echo cancellation system suitable for array processing is also proposed.The acoustic contrast method is a commonly-used strategy for array processing. The robustness of this method is improved by averaging the cost function with consideration of the acoustic disturbance. The performance of the robust algorithm is analyzed using disturbed acoustic models as well as the head scattering model. Experiments are conducted in the anechoic chamber. Another highly robust focusing method based on inverse transfer function is also experimentally evaluated.A two-head scattering model is established for the two listener scenario, and the influence of different listener positions on the sound focusing performance is investigated.A multi-channel acoustic echo cancellation system that is suitable for the micro loudspeaker array is introduced. An efficient post filter which aims to suppress both the residual echo and background noise is proposed based on the coherence between the error signal and the echo estimation of the adaptive filter. This post filter also has the advantage to be easily combined with multi-channel adaptive filters.