Patent ID: 8379879

Claim:
An active noise reduction system having a microcontroller unit (MCU) for receiving an audio input signal a(n) and a noise interference signal d(n) and calculating an audio broadcasting signal y(n) according to a Feedback Filtered-X Least-Mean-Square algorithm, the active noise reduction system comprising: a first operation unit for receiving the audio input signal a(n) and the audio broadcasting signal y(n), a firs reference signal y 2 ( n ) being analyzed with an analytic function of y 2 ( n )=y(n)+a(n); a first error operation unit for receiving the noise interference signal d(n) and the audio broadcasting signal y(n), a first error signal e(n) being analyzed with an analytic function of e ⁡ ( n ) = d ⁡ ( n ) - ∑ m = 0 M - 1 ⁢ Sm * y ⁢ ⁢ 2 ⁢ ( n - m ) ; a second error operation unit for receiving the first error signal e(n) and the audio input signal a(n), a second error signal e 2 ( n ) being analyzed with an analytic function of e ⁢ ⁢ 2 ⁢ ( n ) = e ⁡ ( n ) + ∑ m = 0 M - 1 ⁢ Sm ′ ⁢ a ⁡ ( n - m ) ; a second operation unit for receiving the second error signal e 2 ( n ) and the audio broadcasting signal y(n), a first noise prediction signal x(n) being analyzed with an analytic function of x ⁡ ( n ) = e ⁢ ⁢ 2 ⁢ ( n ) + ∑ m = 0 M - 1 ⁢ Sm ′ ⁢ y ⁡ ( n - m ) ; a first adaptive operation unit for receiving the first noise prediction signal x(n), the audio broadcasting signal y(n) being analyzed with an analytic function of y ⁡ ( n ) = μ ⁢ ∑ l = 0 L - 1 ⁢ Wl ⁡ ( n ) _ ⁢ x ⁡ ( n - l ) , wherein μ is a convergence factor; and a second adaptive operation unit for receiving the first noise prediction signal x(n), a second noise prediction signal x′(n) being analyzed with analytic function of x ′ ⁡ ( n ) ≡ ∑ m = 0 M - 1 ⁢ Sm ′ ⁢ x ⁡ ( n - m ) , wherein S′m and Wl are functions of a Least-Mean-Square algorithm, the definition of S′m being S′m(n+1)=S′m(n)+μa(n−m)e 2 ( n ) and the definition of Wl being Wl(n+1) = Wl(n) +x′(n−1)e 2 ( n ), Sm being a function of a sound field transfer caused during a sound conduction of the active noise reduction system.