Patent ID: 7620172

Claim:
An adaptive filter system for eliminating noise and echo mixed in voice signal, the system comprising: a first signal adaptive filter estimating the noise in the voice signal according to a reference noise; a first subtractor subtracting the noise estimated by the first adaptive filter from the voice signal to obtain the voice signal without the noise, wherein an order of the first adaptive filter is bounded by a first interval N 1 , the first adaptive filter estimates a noise vector ew1[n] mixed in the voice signal represented as a voice vector S 1 [n] at n (time domain) according to a first formula: ew ⁢ ⁢ 1 ⁡ [ n ] = ∑ i = 0 N ⁢ ⁢ 1 - 1 ⁢ ⁢ W ⁢ ⁢ 1 ⁡ [ n ] ⁡ [ i ] * N ⁡ [ n - i ] , where W 1 [n][i] indicates i-order coefficient of the first adaptive filter at time interval n, and N[n−i] indicates the reference noise expressed as a reference noise vector at n−i, subsequently, the voice signal without the noise expressed as S 3 [n] is obtained according to a second formula of: S 3 [n]=S 1 [n]−ew 1 [n] where S 1 is the voice signal, an undated step size ε(n) of the first adaptive filter is calculated according to a third formula of: ɛ ⁡ ( n ) = ɛ δ + N ⁢ ⁢ 1 ⁢ σ S ⁢ ⁢ 1 2 ⁡ [ n ] where σ S1 2 [n] is an estimated value of short time energy and obtained from either one of: σ S ⁢ ⁢ 1 2 ⁡ [ n ] = ( 1 - β ) ⁢ σ S ⁢ ⁢ 1 2 ⁡ [ n - 1 ] + β ⁢ ⁢ S ⁢ ⁢ 1 2 ⁡ [ n ] ; ⁢ or σ S ⁢ ⁢ 1 2 ⁡ [ n ] = 1 N ⁢ ⁢ 1 ⁢ ∑ i = 0 N ⁢ ⁢ 1 - 1 ⁢ ⁢ S ⁢ ⁢ 1 2 ⁡ [ n - i ] = σ S ⁢ ⁢ 1 2 ⁡ [ n ] + 1 N ⁢ ⁢ 1 ⁢ ( S ⁢ ⁢ 1 2 ⁡ [ n ] - S ⁢ ⁢ 1 2 ⁡ [ n - N ⁢ ⁢ 1 ] ) ; where 0<ε<2, δ is a positive value and in an order of magnitude with ε, β is a constant between 0 to 1; a second adaptive filter estimating the echo in the voice signal according to a remote voice signal, wherein an order of the second adaptive filter is bounded by a second interval; and a second subtractor subtracting the echo estimated by the second adaptive filter from the voice signal without the noise to produce a clean voice signal.