A filtering method for separating a target speaker's voice from voice components from one other speaker comprising: receiving a first audio signal and a second audio signal, wherein each of the audio signals include voice signals emitted by a target speaker and one other speaker, wherein volumes of the voice signals included in the respective audio signals are different; transforming the first audio signal into a first transformed audio signal and the second audio signal into a second transformed audio signal in a frequency domain; generating a filtered signal (F2') by applying an adaptive FIR filter to the second transformed audio signal; and subtracting the filtered signal (F2') from the first transformed audio signal to obtain a target voice signal (F1') corresponding to the voice of the target speaker separated from the voice of the other speaker; characterized in that the method further comprises: receiving by a filter coefficient calculator the transformed audio signals, wherein the filter coefficient calculator calculates adaptive filter coefficients, wherein the adaptive filter coefficients are updated to minimize the level of a reference signal, the reference signal being generated by subtracting an update filter signal from the first transformed audio signal, the update filter signal being generated by convoluting the filter coefficients into the second transformed audio signal; calculating corrected adaptive filter coefficients (C2') by limiting a gain of the adaptive filter coefficients to 1.0 or less, wherein the limiting prevents the frequency components of the second audio transformed signal from being amplified by the FIR filtering; and using the corrected adaptive filter coefficients as coefficients of the FIR filter. receiving a first audio signal and a second audio signal, wherein each of the audio signals include voice signals emitted by a target speaker and one other speaker, wherein volumes of the voice signals included in the respective audio signals are different; transforming the first audio signal into a first transformed audio signal and the second audio signal into a second transformed audio signal in a frequency domain; generating a filtered signal (F2') by applying an adaptive FIR filter to the second transformed audio signal; and subtracting the filtered signal (F2') from the first transformed audio signal to obtain a target voice signal (F1') corresponding to the voice of the target speaker separated from the voice of the other speaker; characterized in that the method further comprises: receiving by a filter coefficient calculator the transformed audio signals, wherein the filter coefficient calculator calculates adaptive filter coefficients, wherein the adaptive filter coefficients are updated to minimize the level of a reference signal, the reference signal being generated by subtracting an update filter signal from the first transformed audio signal, the update filter signal being generated by convoluting the filter coefficients into the second transformed audio signal; calculating corrected adaptive filter coefficients (C2') by limiting a gain of the adaptive filter coefficients to 1.0 or less, wherein the limiting prevents the frequency components of the second audio transformed signal from being amplified by the FIR filtering; and using the corrected adaptive filter coefficients as coefficients of the FIR filter. receiving by a filter coefficient calculator the transformed audio signals, wherein the filter coefficient calculator calculates adaptive filter coefficients, wherein the adaptive filter coefficients are updated to minimize the level of a reference signal, the reference signal being generated by subtracting an update filter signal from the first transformed audio signal, the update filter signal being generated by convoluting the filter coefficients into the second transformed audio signal; calculating corrected adaptive filter coefficients (C2') by limiting a gain of the adaptive filter coefficients to 1.0 or less, wherein the limiting prevents the frequency components of the second audio transformed signal from being amplified by the FIR filtering; and