“…These algorithms perform two tasks: i) computing y (n) as the response of an adaptive filter, W , to x (n) and ii) updating the weight vector of W , w (n), by using an update equation, e.g. the FxLMS update equation [15] given by w (n + 1) = w (n) + μe (n) s (n) ⊗ x (n) (1) where ⊗ denotes the linear convolution, μ is the step-size and s (n) is the impulse response of S. ANC systems can attenuate the noise propagating in a duct by about −20dB in practice [1], [3], [7], [9]. However, they cannot significantly attenuate the noise propagating in free space.…”