Active noise cancellation controller with fixed hybrid filters and a third adaptive filter

摘要

An active noise cancellation (ANC) controller for performing noise attenuation over a predetermined frequency range comprising two inputs (microphones) providing reference and error signals, and an output (loudspeaker), wherein a fixed feedback controller with a fixed infinite impulse response (IIR) filter, a fixed feedforward controller with a fixed IIR filter and an adaptive feedforward controller with a digital adaptive finite impulse response (FIR) filter provide a noise cancellation signal based on the input signals, characterised in that coefficients of the digital adaptive filter are determined by independently generating a set of initial coefficients for a plurality of sub-bands in the frequency domain and transforming these into the time domain. The controller is modelled in a numerical computing environment where each of the digital IIR filters is replaced with a respective adaptive FIR filter, and a simulated environmental noise signal causes the convergence of optimum filter coefficients. Discrete Fourier Transforms (DFTs) may be used and configured to use an inverse Fast Fourier Transform (FFT) algorithm. LMS, RLS or FXLMS algorithms may be used for the adaptive filter. The low-power arranged may be used in wireless ANC headphones.