State Key Lab. of Acoust., Chinese Acad. of Sci., Beijing, 100080, People's Republic of China
It was observed that the pulse signals in shallow water with a thermocline have regular multipath structures, which are strongly dependent on the depths of source and receiver. When both the source and receiver are located above the thermocline, the received signal consists of a train of almost equispaced wave packets and the time interval T between packets is related to the speed-profile parameters. When the source is below the thermocline and the receiver is above, the received signal consists of a train of wave packets with time intervals (tau) and (T-(tau)), where (tau) is dependent on the distance from the source to the bottom. The formulas of intervals T and (tau) were deduced by the ray theory, and the calculated values of T and (tau) are consistent with measured ones. The normal-mode theory was used to model the waveforms of pulse signals, and the effects of speed-profile, geoacoustic parameters, signal parameters, and source and receiver depths on waveform structure were studied.