Estimating the sound speed of a shallow-water marine sediment from the head wave excited by a low-flying helicopter

The Journal of the Acoustical Society of America
Dieter A Bevans, Michael J Buckingham

Abstract

The frequency bandwidth of the sound from a light helicopter, such as a Robinson R44, extends from about 13 Hz to 2.5 kHz. As such, the R44 has potential as a low-frequency sound source in underwater acoustics applications. To explore this idea, an experiment was conducted in shallow water off the coast of southern California in which a horizontal line of hydrophones detected the sound of an R44 hovering in an end-fire position relative to the array. Some of the helicopter sound interacted with seabed to excite the head wave in the water column. A theoretical analysis of the sound field in the water column generated by a stationary airborne source leads to an expression for the two-point horizontal coherence function of the head wave, which, apart from frequency, depends only on the sensor separation and the sediment sound speed. By matching the zero crossings of the measured and theoretical horizontal coherence functions, the sound speed in the sediment was recovered and found to take a value of 1682.42 ± 16.20 m/s. This is consistent with the sediment type at the experiment site, which is known from a previous survey to be a fine to very-fine sand.

References

Feb 12, 2005·The Journal of the Acoustical Society of America·Michael J Buckingham
Feb 4, 2006·The Journal of the Acoustical Society of America·Michael J Buckingham, Eric M Giddens
Jan 18, 2007·The Journal of the Acoustical Society of America·Peter H Dahl, Jee Woong Choi
Oct 12, 2007·The Journal of the Acoustical Society of America·Michael J Buckingham
Nov 7, 2014·The Journal of the Acoustical Society of America·Michael J Buckingham
Aug 1, 2016·The Journal of the Acoustical Society of America·John Gebbie, Martin Siderius

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Citations

Mar 3, 2018·The Journal of the Acoustical Society of America·Martin SideriusPeter Gerstoft
Apr 3, 2020·The Journal of the Acoustical Society of America·Jie LiJun Fan
Jan 1, 2021·The Journal of the Acoustical Society of America·Jie LiJun Fan

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