Multiple reference feedforward active noise control part II: Preprocessingand experimental results

Multiple reference active noise control (MRANC) has been applied to acousti cal fields with multiple noise sources to achieve low frequency noise reduc tion. The traditional control configuration feeds each reference signal int o a different control filter. This configuration has been widely adopted du e to its potential performance in a general multiple noise source environme nt. However, it entails the problem of ill conditioning when the reference signals are correlated. In this paper time domain analysis has been carried out to investigate the problem of ill conditioning for MRANC. To cope with the problem of ill conditioning, a reference signal preprocessing step is added to the conventional active noise control process. This preprocessing step essentially constructs a new set of reference signals, which preserve all the information of the original reference, but are uncorrelated with ea ch other. An adaptive decorrelation filter based on the Wiener filter theor y and Gram-Schmidt orthogonalization theorem is constructed to implement th e reference signal preprocessing step. Experiments based on sound transmiss ion through a vibrating plate have been conducted and the results presented are consistent with the theoretical analysis. (C) 2000 Academic Press.