Ocean Ambient Noise Studies for Shallow and Deep Water Environments
Abstract
The objective of this research is to study the ocean ambient noise field by means of new physics-based processing techniques, to determine ways to exploit noise for environmental characterization and to improve sonar-system performance. Effective performance prediction of active and passive sonar systems relies on accurate modeling of sound propagation in the environment of the target and receiver. In shallow littoral water, propagation is affected by interaction with the acoustic waveguide boundaries, i.e. the sea surface and the seabed. The seabed reflection loss in particular is a primary contribution to the transmission loss, and is included in shallow-water propagation models as a power reflection loss coefficient, a function of frequency and grazing angle. A simple passive technique for estimating the bottom loss by beamforming the ambientnoise field using a vertical line array has been developed by Harrison and Simons [Harrison, 2002]. The advantages of passive bottom-survey techniques include simpler measurement requirements, decreased risk of counter-detection, and minimal environmental impact. However, beamforming has some inherent limitations, which affect in particular the angular resolution: All other array parameters being equal, the angular resolution improves when the array length increases. With increasing interest for short arrays, which can be more easily deployed (even on autonomous underwater vehicles) and potentially eliminate array-mismatch errors due to geometric deformation of the array, poor angular resolution becomes a matter of concern. In recent work, we have proposed a physics-based processing technique for improving the angular resolution of short arrays and investigated its application to measured data as well as its limitations [Publications #1 and #2].
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 30, 2013
- Accession Number
- ADA599171
Entities
People
- Lanfranco Muzi
- Martin Siderius
Organizations
- Portland State University