1. A method for separating a target voice from a plurality of other voices having different directions of arrival, comprising: disposing a first and a second voice input device at a predetermined distance from one another and upon receipt of voice signals at said devices calculating discrete Fourier transforms for said signals; calculating a weighted CSP (cross-power spectrum phase) coefficient from said two transformed signals, each assigned its own weight coefficients, each value of said weight coefficients for frequency components of the Weighted CSP that are affected by other speeches other than the target speech being smaller than each value of the weight coefficients for other frequency components of the Weighted CSP; performing gain control on the power spectrum based on the weighted CSP coefficient or moving average thereof; estimating a speech section of said target voice by using weighted CSP coefficient or moving average thereof; clipping a speech section out of the power spectrum obtained by the gain control, based on the estimated speech section; and separating a target voice when received by said devices from other voice signals in a spectrum by using said calculated weighted CSP coefficient.