A controller composed of a nonrecursive filter and a recursive filter is used to approximate the ideal controller for a spatially feedforward duct ANC problem. The nonrecursive part represents the dynamics of the transducer, whereas the recursive part is in the form of a comb filter. The parameters of the comb filter are obtained from the impulse response of the controller by using the least-square method. The comb filter is then cascaded with the nonrecursive part implemented as either a fixed filter or an adaptive filter. In the latter approach, two types of LMS-based algorithms are used. The proposed algorithms are implemented on the platform of a digital signal processor. Experimental results showed that the approximated controller attained 17 dB maximal attenuation in the frequency band 200∼600Hz.

Issue Section:
Technical Papers
Keywords:
active noise control, feedforward, least mean squares methods, comb filters, acoustic signal processing, controllers, recursive filters
Topics:
Algorithms, Control equipment, Feedforward control, Filters, Ducts, Noise control
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