“…Such signals have been analyzed in the time domain, frequency domain, or time-frequency/scale domain. Signal averaging, auto-and cross-correlation matched filtering, autoregressive analysis, order statistics, frequency spectrum analysis, split spectrum processing ͑SSP͒, 1,2 wavelet transform ͑WT͒, 3 and model-based optimization algorithms 4,5 have all been used to analyze ultrasonic signals. In this paper we have no intention of reviewing all these techniques.…”