Separability of scattering and reflection parameters in reverberation inversion

Abstract

A premise of reverberation inversion is that one can separate geoacoustic reflection properties from scattering properties since their effects on reverberation are distinguishable. Some doubt has been cast on this premise in the case of long range reverberation by the fact that simple theory suggests that the two are inseparable for many scattering laws, even in a refracting environment. Instead a recent paper [Harrison, C.H.,

Nielsen, P.L., J. Acoust. Soc. Am., 121, 108-119, (2007)] has shown that by modifying the directionality of the source or receiver one can effectively alter the propagation in situ whilst leaving the scattering law unchanged. In particular, using a dipole directivity results in a

different dependence of reverberation on range, and therefore provides an additional

measurement. Dividing this 'dipole reverberation' by the usual 'monopole reverberation'

yields a quantity that clearly does not depend on the strength of the scattering (although it does depend on its angle behaviour). One can therefore separate geoacoustic and scattering properties. This idea has been tested on experimental data and could, in principle be applied to dipole-steered horizontal triplet arrays.