Signal and noise levels in numerical scattering chamber snapshots
Swift, Stephen A.
Little, William S.
Stephen, Ralph A.
MetadataShow full item record
A study was carried out to quantify the level of numerical noise in numerical scattering chamber (NSC) calculations and to compare these noise levels with signal levels of body waves, interface waves and ambient noise. The amplitudes of signal and noise in snapshots from the numerical scattering chamber were quantified at 50 and 65 periods for a few reference models. Models with homogeneous subseafloor structure were studied to determine the level of numerical noise; models with a wavenumber-correlation length product of one were examined to determine signal levels. Models were run with both Higdon and telegraph equation absorbing boundaries since the numerical noise within the grid depends on the boundary formulation. Amplitudes were measured along data traces obtained at a grid depth of 3.33 λw and at the seafloor. Forward traveling head waves had typical amplitudes of ±125 but may reached ±250 near the direct wave. Diffraction amplitudes were observed up to ±300. Stoneley wave amplitudes ranged from ±800 up to ±20,000. Numerical noise levels were less than ±25 in most areas of the water and less than ±350 along most of the seafloor. Regardless of the absorbing boundary type, however, there was a region of noise extending up to 15 λw behind the first seafloor reflection at 3.33 λw in which noise levels range from ±100 up to ±600. In this region it is difficult to resolve signal from systematic numerical noise.
Suggested CitationWorking Paper: Swift, Stephen A., Little, William S., Stephen, Ralph A., "Signal and noise levels in numerical scattering chamber snapshots", 1995-05, DOI:10.1575/1912/9326, https://hdl.handle.net/1912/9326
Showing items related by title, author, creator and subject.
Stephen, Ralph A.; Swift, Stephen A. (Acoustical Society of America, 1994-08)A numerical scattering chamber (NSC) has been developed to compute backscatter functions for geologically realistic seafloor models. In the NSC, solutions are computed to the elastic (or anelastic) wave equation by the ...
Three-dimensional numerical modeling of sound propagation and scattering in the deep ocean with elastic bottoms [poster] Udovydchenkov, Ilya A.; Stephen, Ralph A.; Komatitsch, Dimitri; Xie, Zhinan; Tromp, Jeroen (2014-02-25)A challenging problem in bottom-interacting ocean acoustics and marine seismology is to accurately describe environmental variability in a computationally feasible model. Wave field predictions are often difficult in ...
Stephen, Ralph A. (Acoustical Society of America, 2000-03)Gaussian beams provide a useful insonifying field for surface or interface scattering problems such as encountered in electromagnetics, acoustics and seismology. Gaussian beams have these advantages: (i) They give a finite ...