Environmental mismatch in shallow-water matched-field processing: Geoacoustic parameter variability

The effects of variations in geoacoustic environmental parameters on the performance of a matched-field localization processor in shallow water were investigated. The SUPERSNAP propagation model was used to generate a reference acoustic pressure field and to simulate an ‘‘experimentally detected’’ field due to an acoustic ‘‘source.’’ These were then correlated using a maximum-likelihood estimator for selected degrees of mismatch of environmental parameters. It was found that small perturbations in a downward-refracting summer water sound-speed profile of ±1σ (i.e., ±1 standard deviation) from average measured values caused severe degradation in localization performance, with predictions of source range and depth becoming highly unstable. However, similar perturbations of an almost isospeed winter profile caused comparatively little degradation. Similarly, perturbations in the sediment sound-speed profile of up to ±1σ from average measured values were possible while still giving stable and reliable estimates of source location. The processor also appeared to be relatively insensitive to mismatch of sediment density and attenuation. The source was correctly localized even when the density and attenuation deviated by significantly more than ±1σ from average measured values.