Modal inversion results for geoacoustic properties in the SWAT experiments

Bottom sediment properties at sites on the New Jersey Shelf and in the East China Sea were studied in the Shallow Water Acoustic Technology (SWAT) experiments. In these experiments, a source towed at constant depth transmitted low-frequency cw signals, which were measured on a bottom-moored vertical line array. The Hankel transform was applied to the acoustic field measured on the resulting synthetic aperture horizontal array created at each receiver depth. The horizontal wave number spectra, with peak positions corresponding to the modal eigenvalues, were observed to be slightly different among the different receiver depths, partially due to noise and range dependency. Thus stochastic mode inversion was exploited by using all of the observed peak positions for estimation of the geoacoustic properties. The sound field simulated using the inversion results agrees well with the measured one for each receiver depth.