Fundamentals of Shallow Water Acoustics

Abstract

In 2001 the Office of Naval Research began a program to publish a selected monograph series in the field of underwater acoustics. The series publishes in-depth reviews and analysis on the state of understanding of the physics of sound in selected areas of research.The monograph series covers the most important topics in underwater sound in an in-depth, critical, scholarly, and comprehensive fashion. It is intended to provide researchers with an understanding of the physics of underwater sound, based on both theory and experiment. The discussion of important unanswered questions is encouraged. Topics of particular importance in the field are low-frequency sound in the deep ocean, shallow-water acoustics, and ambient noise.

Shipping noise in a dynamic sea: a case study of grey seals in the Celtic Sea

“…The common approach to calculating acoustic TL is to consider a two-dimensional (2D) problem (range and depth) assuming that the azimuthal dependence is small and the source is treated as an omnidirectional monochromatic point, a single point where source energy is 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 10 concentrated and sound energy radiates spherically through all directions (Katsnelson, et al, 2012). A transect (A in Fig.…”

“…Key factors affecting sound propagation are the oceanographic and geomorphological characteristics of the surrounding region. Underwater acoustic signals do not propagate along a straight line, instead sound waves experience multiple reflections from the sea surface and seabed (Katsnelson et al, 2012). Furthermore, meso-scale features (e.g.…”

A Volunteer Computing Project for Solving Geoacoustic Inversion Problems

“…M, where τm(f ) denotes the arrival time of m-th modal component [19,23] of a pulse acoustical signal as a function of frequency f (M is the total number of modes that can be filtered from the data). The curves t = τm(f ) in the two-dimensional time-frequency space are called dispersion curves [20]. The experimental dispersion curves can be obtained from a pulse signal recorded by a single receiver (hydrophone) [8,10].…”

“…Note that probably the most important advantage of the dispersion-based inversion schemes is their ability to provide some information on the medium using single-hydrophone measurements. By contrast, more conventional geoacoustic inversion methods [20] usually require the deployment of a vertical or horizontal array of receivers (which makes the experiment much more expensive and complicated). The lack of spatial diversity of the measurements in this case is compensated for by the frequency diversity.…”

“…The project is based on the popular platform BOINC (Berkley Open Infrastructure for Network Compuitng [3]). The notion of geoacoustic inversion refers to a variety of techniques in underwater acoustics that can be used for the reconstruction of water column and bottom parameters from acoustic data [20]. While previously the data for the geoacoustic inversion was mostly obtained using expensive receiver arrays, recently it was shown that a single-hydrophone recording of a broadband pulse signal can be also successfully used for estimating the acoustical parameters of sea bottom [8][9][10].…”