Passive geoacoustic inversion using waveguide characteristic impedance: A sensitivity study

Abstract

It is difficult to apply existing active geoacoustic inversion techniques to passive acoustics in the sense of dealing unknown source signature, track, appearance and duration for traditional measurement systems. The capacity of a vector in simultaneously measuring the pressure and vector fields may lead to a novel method for passive geoacoustic inversion. This paper discusses the feasibility of using the "vertical waveguide characteristic impedance", i.e., the ratio of pressure over vertical particle velocity for passive geoacoustic inversion. Such impedance is independent of source spectrogram but highly correlated with source range due to the transmission loss and phase difference between the pressure and vertical particle velocity during propagation. Through numerical studies, the vertical waveguide characteristic impedance is demonstrated to be high sensitive to bottom geoacoustic parameters, e.g., sound speeds, attenuation coefficients and densities of the seabed. Promising results suggest the vertical waveguide characteristics impedance can give a good resolution for the bottom geoacoustic properties using passive acoustic sources, i.e., surface ship. © 2013 Acoustical Society of America.