Development of an adaptive delay filter for active periodic noise control
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An adaptive delay filter (ADF) for active periodic noise control (APNC) system has been developed in this thesis. An ADF consists of one variable delay and gain, which has the benefit of simplicity that saves computational cost Theoretical analysis and computer simulations prove that the APNC system using ADF is an effective technique to cancel the narrowband noise, especially in the higher sampling frequency case. When the primary noise contains several harmonic components, a multiple-channel APNC system can be established by connecting several ADFs in parallel. The traditional APNC system uses an adaptive FIR filter and an off-line secondary path modeling technique. This technique does not have the ability to track the time-varying secondary path. By connecting an ADF in parallel with the secondary path and employing a step-size control algorithm, a robust APNC system was developed. The robust APNC system has the ability to estimate the delay of the time-varying secondary path. Computer simulations using a sweep sinewave at different speeds show that this robust APNC system performs better than the traditional APNC system. The capability of on-line secondary path delay estimation for the robust APNC system is verified by computer simulations.