The transitional zone in the ocean is the channel connecting the shallow water and deep water. In the transitional zone, the sloping bottom widely exists and affects the sound propagation significantly.
Previous researches about source range estimation are mainly concentrated in shallow water and the primary means are match-field process, waveguide invariant process and warping transform process. Source range estimation in the transitional zone has been an important issue to be considered, whereas relevant research is insufficient.
Researchers from the Institute of Acoustics of the Chinese Academy of Sciences propose an approach of source range estimation in an ocean environment with sloping bottom recently.
The approach is based on matching the depth structure of pulse waveform between the received and simulated signals. For the explosive sources in the experiment with two depths, the mean relative errors of range estimation are both less than 7%, which show that this algorithm is effective.
Their research results have been published in Chinese Physics Letters (Volume 34, June 2017).
In a slope environment, the depth structures of pulse waveforms are utilized to estimate source range. Researchers delay the pulse signals recorded by all the channels, then superpose all delayed signals and suppose that all signals are received by the first channel. This step transforms the two-dimensional pulse waveform (depth and temporal distribution) into one-dimensional (temporal distribution), which not only reserves the distribution structure of pulse waveform but also provides more information for range estimation.
From comparisons between the experimental and numerical pulse waveforms, it is observed that the depth structures agree well. Besides, the depth structures of pulse waveform are different when the source ranges are changed. Accordingly, source range is able to be estimated through matching the depth structure of pulse waveform.
When the source depth is 200 m and range is 5.2 km, after correlated process of the experimental data and the numerical data, the cross-correlation coefficient versus source range can be obtained. Afterwards, the range corresponding to the maximum value of the correlation coefficient is 5.3 km, which is the estimated source range.
Applying the algorithm to all the experimental data in the propagation track, results show the mean relative error is 5.21%, which reveals that this algorithm is effective for source range estimation.
However, due to the errors of bottom parameters in the complicated environment with a slope bottom, range estimation would have bad performance in some special ranges.
WU Zuyong, ZHANG Renhe, QIN Jixing, PENG Zhaohui, MENG Zhou. Source Range Estimation Based on Pulse Waveform Matching in a Slope Environment. Chinese Physics Letters (Volume 34, June 2017). DOI: 10.1088/0256-307X/34/7/074301
Institute of Acoustics, Chinese Academy of Sciences, 100190 Beijing, China