| 摘要 |
An echo detector has a correlator for correlating between an incoming signal and an echo signal, the correlator being arranged to operate recursively, the detector being arranged to detect the echo and the length of its delay from peaks in the correlation. Recursive operation means the computational load can drop from being proportional to N*N, to being proportional to 2N, where N is a number of samples in a correlation window. It also reduces computation delay. A filter at the inputs of the correlator suppresses low frequencies corresponding to the strongest components of pitch in human speech. Such filtering can remove periodic components which can mask a distinct peak of an echo. A classifier thresholds a ratio of highest and next highest correlation peaks beyond a time margin around the highest correlation peak, to reduce erroneous detections. It can classify two or more ratios simultaneously as distinct echoes.
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