Sea-bed scattering and reflection contributions to the short-range acoustic impulse response: measurements and modelling

pp. 153-164, vol. 19, 2016

Sven Ivansson
Swedish Defence Research Agency, Sweden

Per-Axel Karlsson
Swedish Defence Research Agency, Sweden

Key words: ray-tracing; bistatic reverberation; beam-forming

Abstract: A short-range experiment in shallow water has been performed to assess the various contributions to the impulse response. A sound source emitted pulses, centered at 25 kHz, that were registered by an array some 50 m away. The impulse response recordings show initial isolated peaks, followed by long decaying spiky tails. A 3-D ray model, Rev3D, was used to model the measured time traces. The initial peaks were identified as direct and multi-path propagation arrivals, while the decaying tails arise from bistatic reverberation involving the bottom and the sea surface in an elliptical area, with the source and receiver positions as focal points. Beam-forming with the receiver array was applied to locate the parts of the bottom with the most significant contributions to the impulse response, and to suggest an improved reflection-coefficient as well as scattering-kernel values. Rev3D modelling with energy-density maps for selected time intervals, and time traces for energy-weighted averages of various parameters, such as the arrival angles at the array, was also applied for this purpose.

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© Polish Acoustical Society - Gdansk Department, Polish Academy of Sciences. This work is licensed under the Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported. (CC BY-NC-SA 3.0)