Simultaneous Online Modeling of the Secondary Path and Neutralization of the Feedback Path in an Active Noise Control System

Regular paper

Werner Reich

Hochschule Offenburg

Wednesday 3 june, 2015, 08:40 - 09:00

0.7 Lisbon (47)

This paper proposes a new method for modeling the secondary path and neutralizing the feedback path for a feedforward single channel active noise control (ANC) system in a duct, during its online operation. Using white noise with fixed variance for this purpose is the most widely used method but in the final stage the noise adds up to the residual error and reduces the performance of the ANC system. In the proposed method a gain scheduling strategy is used to control the variance of the injected white noise. The variance is in turn controlled by the convergence of feedback path neutralization filter and secondary path modeling filter. Instead of the traditional Least Mean Squared (LMS) algorithm, the Normalized Least Mean Squared (NLMS) algorithm is used in the proposed method. This ensures robustness of the system in practical situations where the power of the signal can vary any time. The algorithm is tested in a MATLAB/Simulink environment. Custom Simulink blocks like Fx_NLMS block were designed using Level-2 S- Functions from Simulink. Simulations show that the proposed method ensures reduced steady state error at the error microphone and provides an excellent steady state performance even if the power of input noise is varied.

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