Characterization of Diffusive Noise Fields Using Ambient Noise Interferometry, Spatial Gradients and Acoustic Bright Spots

Award Information
Agency: Department of Defense
Branch: Navy
Contract: N68335-10-C-0432
Agency Tracking Number: N10A-004-0723
Amount: $70,000.00
Phase: Phase I
Program: STTR
Awards Year: 2010
Solitcitation Year: 2010
Solitcitation Topic Code: N10A-T004
Solitcitation Number: 2010.A
Small Business Information
Rocky Mountain Geophysics, Inc.
167 Piedra Loop, Los Alamos, NM, 87544
Duns: 826538360
Hubzone Owned: N
Woman Owned: N
Socially and Economically Disadvantaged: N
Principal Investigator
 Steven Taylor
 President
 (505) 412-2841
 srt-rmg@comcast.net
Business Contact
 Steven Taylor
Title: President
Phone: (505) 412-2841
Email: srt-rmg@comcast.net
Research Institution
 University of California, San Diego
 Peter Gerstoft
 Marine Physical Laboratory, Sc
University of California
San Diego, CA, 92093
 (858) 534-7768
 Nonprofit college or university
Abstract
We propose to conduct a feasibility study for utilizing broadband sampling of the diffusive noise field in a dynamic environment. In ambient noise studies, the ability to resolve a wavefield is proportional to its time-bandwidth (TB) product. In a dynamic environment such as in the atmosphere or ocean, the nature of the impinging wave field is changing rapidly so that only short time segments can be used to model the ambient wave field thereby reducing the TB product. One way to counter the effect of a reduced time window is to increase the bandwidth of measurement. Our approach is to broaden the frequency spectrum used to characterize diffusive noise fields in dynamic environments by addition of Intensity Level Differences (ILD) caused by diffraction around a shadowing object to the more commonly used interferometric phase delay methods. Diffraction around a shadowing object can create acoustic bright spots that are easily detected. As an experimental test, we will use ambient noise data from existing infrasonic arrays and characterize the dynamic wavefield using passive interferometry and spatial gradiometry techniques. For spatial gradient techniques, the required sensor footprint is smaller and the wavefield can be mapped at higher resolution at closer ranges.

* information listed above is at the time of submission.

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