Effect of sound speed profile on the structure of long-range acoustic pulse

Using the deep-water sound propagation data from the experiments respectively conducted in the East Indian Ocean (EIO) and the South China Sea (SCS) with explosion sources near the sound channel axis (SCA), the long-range transmission loss (TL) and time arrival structure of acoustic pulses for different sound speed profiles (SSPs) are compared. It is found that there are some differences in the characteristics of TL and the difference in the time arrival structure of acoustic pulses is significant. In the EIO environment, sound energy transmitting along the SCA is relatively large, and the corresponding signals arrive first, whereas signals propagating off the SCA arrive late. In the full receiving depth, it shows a branch structure where the waveform near the SCA arrives earlier than other depths, which is totally different with the characteristics of the waveform in the SCS. Combined with the parametric mathematical model of deep-water sound channel, the influence mechanism of SSP on the time arrival structure of long-range pulse propagation is theoretically analyzed, which well explains the phenomenon observed in the two experiments. The reason lies in the difference of channel axis series parameters which determine the SSP in the SCA. The results can provide a reference for the application of communication sonar in the deep-sea remote environment.