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Timothy F. Duda
Address:
Applied Ocean Physics and Engineering Department Woods Hole Oceanographic Institution MS 11 Woods Hole, Massachusetts 02543 USA
Email:
tduda@whoi.edu
Julien Bonnel
Address:
Applied Ocean Physics and Engineering Department Woods Hole Oceanographic Institution MS 11 Woods Hole, Massachusetts 02543 USA
Email:
jbonnel@whoi.edu
Emanuel Coelho
Address:
Applied Ocean Sciences 11006 Clara Barton Drive Fairfax Station, Virginia 22039
USA
Email:
emanuel.coelho@ appliedoceansciences.com
Kevin D. Heaney
Address:
Applied Ocean Sciences 11006 Clara Barton Drive Fairfax Station, Virginia 22039
USA
Email:
kevin.heaney@ appliedoceansciences.com
Computational Acoustics in
Oceanography: The Research Roles
of Sound Field Simulations
Simulation of underwater sound to understand processes is an indispensable tool in modern oceanography.
Lobsters, icebergs, and submarines have little in common except that they produce sound, like many other marine occupants. Noisy occupants include animals (from shrimp to whales), geophysical phenomena (from earthquakes to storms), and man’s devices (from ships to energy turbines). Together, they create an underwater cacophony, now called the marine soundscape (Miksis-Olds et al., 2018). Interest- ingly, even silent things (such as a piece of muddy seabed or a parcel of warm water) may impact the soundscape because they affect the sound propagation.
Although sound provides a great deal of information about the underwater envi- ronment, unraveling and using the underwater clamor is not at all simple. In particular, one needs to understand the sound propagation. An excellent tool for understanding is computer modeling.
Computing simulated sound fields to understand sensed underwater sound is now a common practice in ocean science and engineering. The value for naval defense activities is perhaps obvious, but these simulations are finding a growing number of research applications. Applications include inversion and inference, study of marine fauna, system performance predictions, improved source localization, and improved navigation.
Accurate, detailed simulations of underwater sound can also motivate research expeditions by uncovering propagation behavior that may be difficult to tease out of sparse untargeted acoustic datasets but that are visible in computer simulations and then provable with targeted data collection. For our purposes, simulations mean computed predictions of spatial sound fields (amplitude and phase) from specified sources or sound pressure time series predictions for known emitted waveforms.
Sound Field Structure
Figure 1 shows an example computed field of harmonic 1,100-Hz sound refract- ing away from a layering anomaly in a shallow sea. The highly structured field that results from sound undergoing dispersion and refraction in this deceptively simple environment is of typical complexity for underwater sound. Underwater sound computation uses many approaches, partly because the complexity does not yield to any single approach (Jensen et al., 2011). In this article, we explore how the oceanographic community (as opposed to sonar system users) came to adopt computed sound simulation as a primary tool, what research it enables, and to what research it is indispensable.
28 | Acoustics Today | Fall 2019 | volume 15, issue 3 ©2019 Acoustical Society of America. All rights reserved. https://doi.org/10.1121/AT.2019.15.3.28