an input unit to receive sound signals using a plurality of microphones;

a frequency splitter to split each sound signal received through the input unit into a plurality of narrowband signals;

an average spatial covariance matrix estimator which uses spatial smoothing to obtain a spatial covariance matrix for each frequency component of the sound signal, by which spatial covariance matrices for a plurality of virtual sub-arrays, which are configured in the plurality of microphones, are obtained with respect to each frequency component of the sound signal processed by the frequency splitter and an average spatial covariance matrix is calculated;

a signal source location detector to detect an incidence angle of the sound signal according to the average spatial covariance matrix calculated using the spatial smoothing;

a signal distortion compensator to calculate a weight for each frequency component of the sound signal based on the incidence angle of the sound signal and multiply the calculated weight by each frequency component, thereby compensating for distortion of each frequency component; and

a signal restoring unit to restore a sound signal using the distortion compensated frequency components,

wherein the spatial smoothing is performed according to an equation

where “p” indicates a number of the virtual sub-arrays, x_k⁽ⁱ⁾ indicates a vector of an i-th sub-array microphone input signal, “k” indicates a k-th frequency component in a narrowband, and R_k indicates an average spatial covariance matrix.