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