An Observer for Phased Microphone Array Signal Processing with Nonlinear Output

Acoustic arrays have become an important testing tool in noise identification for industry applications, where the typical beamforming algorithm has been adopted as a classical processing technique. In most practical cases the beamforming computations have to be conducted off-line due to the excessive computational requirements. An alternative algorithm with a real-time capability is proposed. The algorithm is similar to a classic observer while array processing is performed in the frequency domain. The performance of this observer-based algorithm is studied here through comparing with the typical beamforming method, particularly for a case of coherent noise sources. In this paper it is shown that the observer-based algorithm could resolve the coherence restriction between the background noise and the signal of interest. The proposed algorithm is also beneficial for its capability of operating over sampling blocks recursively. The convergence rate of this recursive algorithm is fast enough to satisfy the requirements for practical cases. The experimental efforts could be saved extensively as any testing defects could be revealed instantaneously and corrected on site. In addition, this innovative approach provides an alternative perspective, from which many techniques already developed in control and filtering could be extended to this new application area of array processing.