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Projects

3D acoustic propagation modeling

Collaborators:
Y. T. Lin and Arthur Newhall

A suite of split-step Fourier propagation codes have been developed to study sound in the complex time-varying three dimensional ocean.

Ocean Acidification and Acoustic Absorption

Collaborators:
Ilya Udovydchenkov, Scott Doney, Ivan Lima

Noise levels in a future more acidic ocean have been simulated. There results indicate that decreased absorption causes a slight increase in noise level (it must), but the effect is very small for the low frequencies that carry for long distances.. This is because little sound is absorbed at low frequencies. Instead, the sound waves propagate freely until they encounter the seabed and are absorbed.

That being said, there are special places in the world's ocean where sound of higher frequencies that are absorbed can propagate without seabed interaction and may be usable at longer distances in a lower-pH ocean.

Integrated Ocean Dynamics and Acoustics (IODA)

Long Term Goal: IODA is an integrated ocean fluid physics and acoustics study with the goal of creating a broadly applicable and portable continental shelf-area acoustic prediction capability that includes the effects of internal and surface gravity waves as well as effects of subtidal large-scale processes.

Objective: The objective is to improve ocean physical state and acoustic state predictive capability. Specific short-term project objectives are the completion of targeted studies of the relevant oceanographic processes, acoustic propagation processes, and acoustic scattering processes, plus the development of improved computational tools for the physical regimes identified to be important.

The motivation for the project is that regional environmental modeling and acoustic or sonar modeling can occur in disconnected fashion. If the environmental models are optimized for other purposes, they may not provide environmental inputs that are essential to predictive acoustic models. Research into what the relevant environmental factors are, and how to best model them, and how to pass the information to acoustic models are important thrusts of the project.

Internal Tides

Research into the factors that cause variations in the ocean's internal tides, which are generates by the surface tide interacting with the seabed, and the groups of small scale nonlinear internal waves that they can spawn. The generation mechanisms and propagation behavior of these tidal-frequency internal gravity waves are the major study topics.

 

 

 

Ocean Acoustic Propagation and Coherence Studies

ONR-sponsored research program on the details of how ocean dynamical features and the seabed boundary work in tandem to complicate underwater sound fields.

Seabed Characterization Experiment

ONR-sponsored research program to investigate the properties of a silty seabed and how sounds interacts with it. WHOI placed fixed equipment on the seabed, moored equipment, mobile assets, and made ship surveys. Image shows split-beam echo-sounder image of an ocean salinity/temperature front. see https://wwwext.arlut.utexas.edu/sbcex/

Arctic Acoustics "CANAPE"

WHOI Collaborators YT Lin and Weifeng Gordon Zhang.

ONR-sponsored Canadian Basin Acoustic Propagation Experiment in the area north of Alaska. Ducted transmissions from deep wter sound sources (Scripps Inst.) were received on the continental slope by WHOI receivers. The ducting is subject to variable flow and water mass conditions that are a subject of study. An ASA article was published examining the role of climate change and the carbon cycle on the ducted sound effect.