Underwater acoustics research at the Woods Hole Oceanographic Institution, 1930-1960

Author Posting. © Acoustical Society of America, 2016. This article is posted here by permission of Acoustical Society of America for personal use, not for redistribution. The definitive version was published in Proceedings of Meetings on Acoustics 23 (2016): 070013, doi:10.1121/2.0000214.The Woods Hole Oceanographic Institution (WHOI) was founded in 1930, and throughout its history has had a strong involvement in research into the science and applications of sound in the ocean. In terms of a brief history, three eras stand out: (1) pre-WWII, (2) WWII, and (3) the postwar years. This manuscript will focus on the history of the most influential and colorful, individuals and stories that arose during the war years. Provided are personal reminiscences, technical report details, and photos illustrating the achievements, and importance, in underwater sound research at WHOI during that time.This work was supported by ONR Grant N00014-14-1-0040/N00014-16-1-2361

Acoustic ducting, reflection, refraction, and dispersion by curved nonlinear internal waves in shallow water

Author Posting. © IEEE, 2010. This article is posted here by permission of IEEE for personal use, not for redistribution. The definitive version was published in IEEE Journal of Oceanic Engineering 35 (2010): 12-27, doi:10.1109/JOE.2009.2038512.Nonlinear internal waves in shallow water have been shown to be effective ducts of acoustic energy, through theory, numerical modeling, and experiment. To date, most work on such ducting has concentrated on rectilinear internal wave ducts or those with very slight curvature. In this paper, we examine the acoustic effects of significant curvature of these internal waves. (By significant curvature, we mean lateral deviation of the internal wave duct by more than half the spacing between internal waves over an acoustic path, giving a transition from ducting to antiducting.) We develop basic analytical models of these effects, employ fully 3-D numerical models of sound propagation and scattering, and examine simultaneous acoustical and oceanographic data from the 2006 Shallow Water Experiment (SW06). It will be seen that the effects of curvature should be evident in the mode amplitudes and arrival angles, and that observations are consistent with curvature, though with some possible ambiguity with other scattering mechanisms.This work was supported by E. Livingston and T. Pawluskiewicz of the U.S. Office of Naval Research (ONR) under Grant N00014–04-1–0146 and the ONR postdoctoral fellowship award Grant N00014-08-1-0204

Internal tidal modal ray refraction and energy ducting in baroclinic Gulf Stream currents

Author Posting. © American Meteorological Society, 2018. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 48 (2018): 1969-1993, doi:10.1175/JPO-D-18-0031.1.Upstream mean semidiurnal internal tidal energy flux has been found in the Gulf Stream in hydrodynamical model simulations of the Atlantic Ocean. A major source of the energy in the simulations is the south edge of Georges Bank, where strong and resonant Gulf of Maine tidal currents are found. An explanation of the flux pattern within the Gulf Stream is that internal wave modal rays can be strongly redirected by baroclinic currents and even trapped (ducted) by current jets that feature strong velocities above the thermocline that are directed counter to the modal wavenumber vector (i.e., when the waves travel upstream). This ducting behavior is analyzed and explained here with ray-based wave propagation studies for internal wave modes with anisotropic wavenumbers, as occur in mesoscale background flow fields. Two primary analysis tools are introduced and then used to analyze the strong refraction and ducting: the generalized Jones equation governing modal properties and ray equations that are suitable for studying waves with anisotropic wavenumbers.The Woods Hole research was supported by National Science Foundation Grant OCE-1060430 and by the Office of Naval Research Grants N00014-11-1-0701 and N00014-17-1-2624. The USM research was supported by ONR Grant N00014-15-1-2288 and National Science Foundation Grant OCE-1537449.2019-02-2

High-frequency side-scan sonar fish reconnaissance by autonomous underwater vehicles

Author Posting. © The Author(s), 2016. This is the author's version of the work. It is posted here by permission of NRC Research Press for personal use, not for redistribution. The definitive version was published in Canadian Journal of Fisheries and Aquatic Sciences 74 (2017): 240-255, doi:10.1139/cjfas-2015-0301.A dichotomy between depth penetration and resolution as a function of sonar frequency, draw resolution, and beam spread challenges fish target classification from sonar. Moving high-frequency sources to depth using autonomous underwater vehicles (AUVs) mitigates this and also co-locates transducers with other AUV-mounted short-range sensors to allow a holistic approach to ecological surveys. This widely available tool with a pedigree for bottom mapping is not commonly applied to fish reconnaissance and requires the development of an interpretation of pelagic reflective features, revisitation of count methods, image-processing rather than wave-form recognition for automation, and an understanding of bias. In a series of AUV mission test cases, side-scan sonar (600 and 900 kHz) returns often resolved individual school members, spacing, size, behavior, and (infrequently) species from anatomical features and could be intuitively classified by ecologists — but also produced artifacts. Fish often followed the AUV and thus were videographed, but in doing so removed themselves from the sonar aperture. AUV-supported high-frequency side-scan holds particular promise for survey of scarce, large species or for synergistic investigation of predators and their prey because the spatial scale of observations may be similar to those of predators.AUV missions were funded by an Office of Naval Research grant to the Woods Hole Oceanographic Institution and Rutgers University. The field work was supported by the Office of Naval Research under grant N00014-11-1-0160

Impacts of ocean warming on acoustic propagation over continental shelf and slope regions

Author Posting. © The Oceanography Society, 2018. This article is posted here by permission of The Oceanography Society for personal use, not for redistribution. The definitive version was published in Oceanography 31(2), (2018):174–181, doi:10.5670/oceanog.2018.219.Gradients of heat and salt affect the propagation of sound energy in the ocean. Anticipated changes in oceanic conditions will alter thermohaline conditions globally, thus altering sound propagation. In this context, we examine changes in shallow- water propagation. Because these waters are close to the surface, they will be the earliest to change as the atmospheric state and radiative conditions change. We compare current and possible future propagation patterns near fronts and across fronts on continental shelves. Changes in sound pathways between the deep ocean and coastal regions are also examined, including an example from the Arctic Ocean.GG was supported by the Office of Naval Research under grants N00014-16-1-3071 and N00014-16-1-2774

Preliminary acoustic and oceanographic observations from the winter Primer experiment

A joint acoustics and physical oceanography experiment was conducted in the winter of 1997 on the shell break and continental slope south of New England in the Middle Atlantic Bight (figure 1). This experiment, Primer4, provided a seasonal contrast to the previous summer Primer3 experiment and had the same goals and tasks: to study the thermohaline variability and structure of the shelfbreak front and its effects on acoustic propagation. To accomplish the linked oceanographic and acoustic objectives of this experiment, a combination of measurements (fig 2) were made. Seasoar hydrography, shipboard ADCP measurements, Satellite IR sea surface temperature field observations, and AXT drops were employed to study the larger scale oceanographic fields. To study the finer scale, which includes internal waves, a number of rapid-sampling thermistor strings and current meters, including a moored, upward looking ADCP, were deployed. The acoustics components consisted of three 400 Hz tomography transceivers, a 224 Hz source and two hydrophone arrays. To study the geoacoustic parameters in the bottom a number of SUS charges were also deployed. The field setup was approximately the same for both the summer 1996 and winter 1997 experiments; however the weather conditions and the thermal structure of the mixed layer were radically different. This report is dedicated to the data from the Winter 1997 Primer4 experiment.Funding was provided by the Offce of Naval Research under Contract No. NOOOl4-98-10413

Low-frequency broadband sound source localization using an adaptive normal mode back-propagation approach in a shallow-water ocean

Author Posting. © Acoustical Society of America, 2012. This article is posted here by permission of Acoustical Society of America for personal use, not for redistribution. The definitive version was published in Journal of the Acoustical Society of America 131 (2012): 1798-1813, doi:10.1121/1.3672643.A variety of localization methods with normal mode theory have been established for localizing low frequency (below a few hundred Hz), broadband signals in a shallow water environment. Gauss-Markov inverse theory is employed in this paper to derive an adaptive normal mode back-propagation approach. Joining with the maximum a posteriori mode filter, this approach is capable of separating signals from noisy data so that the back-propagation will not have significant influence from the noise. Numerical simulations are presented to demonstrate the robustness and accuracy of the approach, along with comparisons to other methods. Applications to real data collected at the edge of the continental shelf off New Jersey, USA are presented, and the effects of water column fluctuations caused by nonlinear internal waves and shelfbreak front variability are discussed.The SW06 experiment was supported by the Office of Naval Research

Merging multiple-partial-depth data time series using objective empirical orthogonal function fitting

Author Posting. © IEEE, 2010. This article is posted here by permission of IEEE for personal use, not for redistribution. The definitive version was published in IEEE Journal of Oceanic Engineering 35 (2010): 710-721, doi:10.1109/JOE.2010.2052875.In this paper, a method for merging partial overlapping time series of ocean profiles into a single time series of profiles using empirical orthogonal function (EOF) decomposition with the objective analysis is presented. The method is used to handle internal waves passing two or more mooring locations from multiple directions, a situation where patterns of variability cannot be accounted for with a simple time lag. Data from one mooring are decomposed into linear combination of EOFs. Objective analysis using data from another mooring and these patterns is then used to build the necessary profile for merging the data, which is a linear combination of the EOFs. This method is applied to temperature data collected at a two vertical moorings in the 2006 New Jersey Shelf Shallow Water Experiment (SW06). Resulting profiles specify conditions for 35 days from sea surface to seafloor at a primary site and allow for reliable acoustic propagation modeling, mode decomposition, and beamforming.This work was supported by the U.S. Office of Naval Research (ONR) under Grants N00014-04-1-0146 and N00014-05-1- 0482, theONRPostdoctoral FellowshipAward under Grant N00014-08-1-0204, and by E. Livingston and T. Pawluskiewicz. The work of P. F. J. Lermusiaux and P. J. Haley was supported by the ONR under Grants N00014-07-1-1061, N00014-07-1-0501, and N00014-08-1-1097 to the Massachusetts Institute of Technology

A three-dimensional underwater sound propagation model for offshore wind farm noise prediction.

Author Posting. © Acoustical Society of America, 2019. This article is posted here by permission of Acoustical Society of America for personal use, not for redistribution. The definitive version was published in Journal of the Acoustical Society of America 145(5), (2019):EL335-EL340, doi: 10.1121/1.5099560.A three-dimensional underwater sound propagation model with realistic ocean environmental conditions has been created for assessing the impacts of noise from offshore wind farm construction and operation. This model utilizes an existing accurate numerical solution scheme to solve the three-dimensional Helmholtz wave equation, and it is compared and validated with acoustic transmission data between 750 and 1250 Hz collected during the development of the Block Island Wind Farm (BIWF), Rhode Island. The variability of underwater sound propagation conditions has been investigated in the BIWF area on a temporal scale of months and a spatial scale of kilometers. This study suggests that future offshore wind farm developments can exploit the seasonal variability of underwater sound propagation for mitigating noise impact by scheduling wind farm construction during periods of high acoustic transmission loss. Discussions on other applications of soundscape prediction, planning, and management are provided.The authors would like to acknowledge Captain Ken Houlter and First Mate Ian Hanley of the WHOI R/V Tioga. The authors would also like to acknowledge Dr. Steven Crocker from the Naval Undersea Warfare Center in Newport, Rhode Island for the design of the tetrahedral hydrophone array. Study concept, oversight, and funding under the Real-time Opportunity for Development Environmental Operations (RODEO) were provided by the U.S. Department of the Interior, Bureau of Ocean Energy Management, Environmental Studies Program, Washington, DC under Contract No. M16PD00025. The Program Manager at BOEM is Dr. Mary Boatman. The prime contractor for this work is HDR, Inc. (Program Manager Anwar Khan).2019-11-0

Passive time reversal acoustic communications through shallow-water internal waves

Author Posting. © IEEE, 2010. This article is posted here by permission of IEEE for personal use, not for redistribution. The definitive version was published in IEEE Journal of Oceanic Engineering 35 (2010): 756-765, doi:10.1109/JOE.2010.2060530.During a 12-h period in the 2006 Shallow Water Experiment (SW06), binary phase shift keying (BPSK) signals at the carrier frequencies of 813 and 1627 Hz were propagated over a 19.8-km source–receiver range when a packet of strong internal waves passed through the acoustic track. The communication data are analyzed by time reversal processing followed by a single-channel decision feedback equalizer. Two types of internal wave effects are investigated in the context of acoustic communications. One is the rapid channel fluctuation within 90-s data packets. It can be characterized as decreased channel coherence, which was the result of fast sound-speed perturbations during the internal wave passage. We show its effect on the time reversal receiver performance and apply channel tracking in the receiver to counteract such fluctuation. The other one is the long-term (in the scale of hours) performance degradation in the depressed waveguide when the internal waves passed through the acoustic track. Even with channel tracking, the time reversal receiver experiences average 3–4-dB decrease in the output signal-to-noise ratio (SNR). Such long-term performance degradation is explained by the ray approximation in the depressed waveguide.This work was supported by the U.S. Office of Naval Research (ONR) Code 322OA under Grants N00014-07-1-0546 and N00014-06-1019