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