to step 304 where discrete cosine transform domain module 210 obtains a frame of n1 samples from sin signal 202 in one embodiment n1 may be a multiple of number of samples per frame next at step 306 echo canceller 200 computes a weighting window of length m where m is less than n1 such as hamming window tukey window and the like at step 308 echo canceller 200 performs a discrete cosine transform over the n1 samples and at step 310 echo canceller 200 obtains m coefficients from n1 u2212 m samples in the dct domain i e m u00d7 n1 u2212 m coefficients at step 312 echo canceller 200 selects k most significant coefficients from m u00d7 n1 u2212 m coefficients of step 310 where m n1 and k are integer values in one embodiment significant coefficients may be coefficients of highest energy coefficients with major peaks and or coefficients having more fluctuations next dct method 300 of fig3 moves to step 314 where echo canceller 200 obtains a frame of n2 samples from rout signal 204 in one embodiment n2 is usually greater than n1 and may be a multiple of number of samples per frame next at step 316 echo canceller 200 applies the weighting window of step 306 to the n2 samples from rout signal 204 at step 318 echo canceller 200 performs a discrete cosine transform over the n2 samples from rout signal 204 and at step 320 echo canceller 200 selects same k coefficients as those selected in step 312 next at step 322 echo canceller 200 applies normalized cross correlation to the k coefficients from sin signal 202 and the k coefficients from rout signal 204.