Effects of Directional Microphone and Transducer in Spatially Feedforward Active Noise Control System

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In this paper, an experimental study concerning the effects of a directional microphone and transducer in a duct active noise control (ANC) system in the presence of acoustic feedback is described. In the duct ANC system, a spatial feedforward system is used for broadband noise cancellation in ducts, where a non-acoustical reference is unavailable. In this structure, acoustic feedback that is known to be detrimental to the system stability and performance must be taken into account in the controller design. The algorithm of the proposed control system is based on the previous work by Roure (1985), Munjal and Eriksson, Hong and Bernstein (1998), and there exists some discusses for spatially feedforward structure. The algorithm is implemented on a digital signal processor (DSP), using finite impulse response (FIR) and infinite impulse response (IIR) filters. Experiments are carried out to evaluate the effects of a directional microphone and transducer in proposed the system for reducing the noise at the broadband noise source. The results of the experiment indicated that the proposed system with a directional microphone and loudspeaker improved the ANC system attenuation performance in the presence of acoustic feedback.
2001-10-15