Active acoustic noise control in ducts

In this paper existing classical and advanced techniques of active acoustic noise cancellation (ANC) in ducts are collected and compared. The laboratory plant used in experience showed a linear behaviour and so the advanced techniques were not used. Due to delay on the plant, the feedback classical techniques could not be applied. The best results were obtained with the modified filtered-reference LMS (MFX-LMS) and filtered-u techniques. A very important conclusion is that the quadratic normalisation is needed to maintain the algorithms always stable. In this paper 18dB of attenuation of white noise and 35 dB of attenuation of tonal noise were achieved. Thus, ANC can be applied in a real situation resulting in important noise attenuations.