Tuned feedforward LMS filter with feedback control

  • US 20040264706A1
  • Filed: 05/10/2004
  • Published: 12/30/2004
  • Est. Priority Date: 06/22/2001
  • Status: Active Grant
First Claim
Patent Images

1. A method of tuning an adaptive feedforward noise cancellation algorithm, comprising the acts of:

  • providing a feedback active noise reduction (ANR) circuit, for providing an ANR error signal;

    providing a feedforward LMS tuning algorithm including at least first and second time varying parameters wherein said feedforward LMS tuning algorithm includes the formulas;

    γ

    k=WkTXk Wk+1

    kWk

    kXkek; and

    adjusting said at least first and second time varying parameters as a function of instantaneous measured acoustic noise, a weight vector length and measurement noise variance, wherein said time varying parameters include;

    μ

    k
    =

    μ

    o


    λ

    k
    (Xk+Qk)T

    (Xk+Qk)
    λ

    k
    =

    (Xk+Qk)T

    (Xk+Qk)
    -2

    L





    σ

    q2
    (Xk+Qk)T

    (Xk+Qk)
    wherein Xk=Xk+Qk is a measured reference signal;

    Qk is measurement noise, including electronic noise and quantization noise;

    σ

    q2 is the known or measured variance of the measurement noise;

    L is the length of the LMS weight vector Wk; and

    ek is an error signal which is the net result of both the feedforward method and the feedback circuit.

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