ACCELERATED NOISE INTERFEROMETRY-BASED PASSIVE ACOUSTIC CHARACTERIZATION OF THE LITTORAL OCEAN

Acoustic remote sensing of the ocean traditionally relies on controlled sound sources and active sonars. Alternatively, the seabed and the water column can be characterized acoustically in a surreptitious and environmentally friendly way using noise interferometry. Noise interferometry exploits ambient sound as a signal to probe the environment. Empirical acoustic Green's functions are retrieved from cross-correlations of diffuse noise that is measured concurrently by spatially separated hydrophones. Continuous, multi-day noise-averaging periods were employed in the past to capture noise from numerous noise sources. Long averages achieved maximum diffusivity of ambient sound and retrieved the Green's function with high accuracy required for ocean remote sensing. However, usefulness of the long averaging times is limited by rapid variations in the acoustic propagation environment, e.g., due to internal gravity waves and tides. Using the data acquired in the Shallow Water 2006 experiment on the continental shelf off New Jersey, this thesis focuses on accelerating the noise-interferometry process by judiciously selecting periods where ambient sound is sufficiently diffuse. The goal is to reduce the total time needed for passive acoustic characterization of the seabed and increase the time resolution of acoustic measurements of the water-column properties, thus extending the applications of noise interferometry in naval operations.

Department dc:contributor.department

Oceanography (OC)

Grantor dc:publisher

Monterey, CA; Naval Postgraduate School

Year dc:date.issued

2021

Author dc:creator

• Shen, Yi-fan

Advisors dc:contributor.advisor

• Godin, Oleg A.
• Olson, Derek

Statement dc:rights

• Copyright is reserved by the copyright owner.

Handle dc:identifier.uri

https://hdl.handle.net/10945/68384

OAI identifier oai:identifier

oai:calhoun.nps.edu:10945/68384