1. A speech enhancement method, comprising: obtaining a speech signal using at least one input microphone; calculating a whitening filter using a silence interval in the obtained speech signal; applying the whitening filter to the obtained speech signal to generate a whitened speech signal in which noise components present in the obtained speech signal are whitened; estimating a clean speech signal by applying a multi-channel filter to the whitened speech signal; and outputting the clean speech signal via an audio device, wherein the calculating step comprises: iteratively updating the whitening filter as an FIR filter sequence using NS noise samples from the obtained speech signal, NS being a positive integer, and wherein the step of iteratively updating the whitening filter comprises updating the matrix FIR filter sequence W p (k) using the iterative equation: W p ⁡ ( k + 1 ) = ( 1 + μ ) ⁢ c ⁡ ( k ) ⁢ W p ⁡ ( k ) - μ ⁢ c ⁡ ( k ) d ⁡ ( k ) ⁢ U ~ p ⁡ ( k ) , ⁢ 0 ≤ p ≤ L ⁢ ⁢ where ⁢ ⁢ d ⁢ ( k ) = 1 n ⁢ ∑ i = 1 n ⁢ ∑ j = 1 n ⁢ ∑ p = 0 L ⁢  g ijp ⁡ ( k )  , ⁢ and ⁢ ⁢ c ⁡ ( k ) = 1 d ⁡ ( k ) ( 26 ) are gradient scaling factors, i, j, k, and p are integers, μ is a real number, L is the integer length of the FIR filter, n is a number of microphones, k is an iteration index, μ is a step size, g()is a scaling function where g ijp are elements of a coefficient matrix G vp (k) that defines Ũ p (k), or using the iterative equation: W p ⁡ ( k + 1 ) = ( 1 + μ ) ⁢ c ⁡ ( k ) ⁢ W p ⁡ ( k ) - μ ⁢ c ⁡ ( k ) d ⁡ ( k ) ⁢ U p ⁡ ( k ) , ⁢ where ⁢ ⁢ d ⁢ ( k ) = 1 n ⁢ ∑ i = 1 n ⁢ ∑ j = 1 n ⁢ ∑ p = 0 L ⁢  g ijp ⁡ ( k )  , ⁢ and ⁢ ⁢ c ⁡ ( k ) = 1 d ⁡ ( k ) ( 20 ) are gradient scaling factors, i, j, k, and p are integers, μ is a real number, n is a number of microphones, k is an iteration index, μis a step size, g( )is a scaling function where g ijp are elements of a coefficient matrix G p (k) that defines U p (k).