Separability of seabed reflection and scattering properties in reverberation inversion

Abstract

Separation of scattering properties (Lambert's mu) from reflection properties (the reflection loss angle derivative alpha) presents difficulties in the geoacoustic inversion of long range reverberation in isovelocity water, and here it is shown that there is still a problem in a refracting environment. An alternative technique is proposed where reverberation is modified by altering the source or receiver

beam pattern, for instance, using a triplet array or ring source, to provide a dipole and monopole

pattern. Combinations of these two measures of reverberation then conveniently determine alpha and mu

independently of other unknown quantities from long (or short) range data, in fact even from a

single range. In addition the short range ratio of the two quantities determines the critical angle

independently. The effects of refraction and other source or receiver beam patterns, including a

horizontal beam and a tilted beam, are investigated by using analytical techniques. To enhance the

credibility of these findings and demonstrate the benefits of the approach an example is posed as a

standard inversion problem using a cost function based on both types of reverberation. Finally the technique is applied to some experimental data by forming simultaneous monopole and dipole beams in the vertical plane. Cop. 2007 Acoustical Society of America. [DOI: 10.1121/1.2384966]