In:
The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 116, No. 4_Supplement ( 2004-10-01), p. 2535-2535
Abstract:
The familiar mode-stripping and coupling processes are prevalent in shallow water, shaping the vertical directional content of noise from distributed sources and of signals from discrete sources. Directional patterns can help in the determination of the physical processes, including internal waves, controlling acoustic behavior in a given region. VLA beamformer output from the New England PRIMER and the South China Sea ASIAEX studies are shown. Beamformed output from moored source signals and of noise vary rapidly for ASIAEX, less so for PRIMER. Fluctuations of signal and noise directional content have limited coherence. Correlated fluctuations of these will not alter the signal/noise ratio for a given beam, whereas uncorrelated fluctuations will. Such correlation depends upon the distance between the mode-coupling structure and the receiver. Predictions of pattern variability are complex because many environmental degrees of freedom are involved. For example, mode coupling of distant sources will spread the pattern from near horizontal (low mode), but not always for nearby sources; mode coupling of noise will energize low angle beams, although most effectively near noise sources. Implications of waveguide characterization based on beam energy variability will be discussed and compared with direct environmental waveguide measurements and with other signal properties. [Work supported by ONR.]
Type of Medium:
Online Resource
ISSN:
0001-4966
,
1520-8524
Language:
English
Publisher:
Acoustical Society of America (ASA)
Publication Date:
2004
detail.hit.zdb_id:
1461063-2
Permalink