Page 50 - \Winter 2015

TECHNICAL COMMITTEE REPORT
Andone C. Lavery
Postal:
Department of Applied Ocean Physics and Engineering Woods Hole Oceanographic Institution Woods Hole, MA 02536 USA
Email:
alavery@whoi.edu
Acoustical Oceanography
The Technical Committee (TC) on Acoustical Oceanography (TCAO) was found- ed in 1991 and is made up of scientists and engineers interested the development and use of acoustical techniques to understand the physical, biological, geological, and chemical parameters and processes that occur in the ocean, broadly described here as “oceanography.” This requires a fundamental knowledge of the physics of the generation, scattering, and propagation of sound in a spatially and temporally complex and dynamic ocean. Combining this fundamental understanding with knowledge of the underlying oceanography, allows relevant parameters to be re- motely inferred at scales often unachievable by more traditional oceanographic sampling techniques.
There is strong overlap in the areas of interest to the TCAO and the TCs on Un- derwater Acoustics (TCUW) and Animal Bioacoustics (TCAB). This overlap is highlighted in a recent Acoustics Today article on the effects of climate change on acoustical oceanography, animal bioacoustics, and underwater sound (Kloepper and Simmons, 2014). There is also significant overlap with the TCs on Signal Pro- cessing, Physical Acoustics, Atmospheric Acoustics, and Biomedical Acoustics, as is evidenced by the number of co-sponsored special sessions at ASA meetings. As with many areas of acoustics, the majority of researchers in acoustical oceanogra- phy have not received formal training in acoustics, but instead, “ended up” in the field with backgrounds rooted in a broad array of disciplines. The highly inter- disciplinary nature of the research is considered one of the primary strengths and distinguishing characteristics of the TCAO.
An area of research in the TCAO that has received sustained attention is the area of geoacoustic inversion, an area of research with particular synergy with the TCUW. The general approach is to estimate geoacoustic parameters by comparing mod- eled predictions with measurements, such as transmission loss. In general, the ability to predict transmission loss, particularly in shallow waters typical of conti- nental shelves, is severely constrained by the lack of knowledge of the geoacoustic properties of the bottom, such as sediment layer thicknesses, sound-speed profiles, etc. Since the inception of the TCAO, significant progress has been made in the development of active and passive inversion methods for seabed characterization that complement and extend the capabilities of conventional techniques such as seismic reflection imaging and coring. In 2014 alone, at least ten papers involving different aspects of geoacoustic inversion have been published in the Journal of the Acoustical Society of America and Express Letters, including papers on the contin- ued development of “passive” geoacoustic inversion methods that exploit ambient ocean noise (Yardim et al., 2014).
Though there is heavy overlap with other TCs in some areas, there are certain areas of research that are almost exclusively studied by members of the TCAO, such as seismic oceanography. The prestigious Munk Award, granted for significant origi- nal contributions to the understanding of physical processes related to sound in the sea, was awarded in 2013 to Steven Holbrook, who was honored as the father of
48 | Acoustics Today | Winter 2015, volume 11, issue 1 ©2015 Acoustical Society of America. All rights reserved.