Coherence of Sound Using Navy Sonars
Abstract
LONG-TERM GOALS. The long-term goal of this research is to understand and predict the temporal and spatial coherence of broadband sound in the ocean at low frequencies. OBJECTIVES. We will compare broadband acoustic signals at basin-scales with predictions for spatial coherence. Degradation of coherence will be modeled using spectra of internal waves in the ocean. APPROACH. Data will be collected from a variety of Navy sonars. Traditional means to process the signals will be done including beamforming, coherent averaging (when dealing with periodic signals), correcting for Doppler shifts (when dealing with mobile sonars), and matched filtering (when a replica with the emitted waveform is available). The data will be interpreted using rays and the sound speed insensitive parabolic approximation (Tappert et al. 1995) . The acoustic models will be used in conjunction with oceanographic models that contain the best available digital data sets for bathymetry, sound speed fields that vary with range and depth, and internal waves. Spatial coherence will be modeled using the sound speed insensitive parabolic approximation and spectra of internal waves. A secondary goal of this contract is to theoretically quantify which regions in the ocean significantly affect temporal and spatial coherence. Theories of diffraction are used and developed for this purpose as well as to understand how to predict the scattering of waves in general.
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 30, 2006
- Accession Number
- ADA630908
Entities
People
- John L. Spiesberger