A subtracter subtracts {HEAD ~ the estimated wraparound speech signal ai d′} from the input speech signal “bi” to generate {TAIL ~ an echo cancellation signal “ei}” 
A subtracter subtracts { HEAD ~ the estimated wraparound speech signal ai d′ } from the input speech signal “ bi ” to generate { TAIL ~ an echo cancellation signal “ ei } ”
OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH