Bottom reverberation in shallow water: Coherent properties as a function of bandwidth, waveguide characteristics, and scatterer distributions

Abstract

Shallow water presents a difficult, reverberation-limited environment for active SONAR operations. It is important to understand the predictable structure of shallow-water reverberation in order to aid the design of processors and detectors which work properly in these environments. In this paper, the temporal characteristics of monostatic reverberation are predicted as a function of source bandwidth, source–receiver depth, and the propagation characteristics of range-independent shallow water. Results show that at early time, reverberation can be highly coherent across a vertical line array, violating the homogeneous noise assumption, while at late time the reverberation becomes increasingly uncorrelated. This is shown to be due to the insonification of independent bottom patches at late time. It is also shown that this decorrelation of the reverberation is dependent both on the propagation characteristics of the particular shallow-water environment, the correlation length scale of the scatterers, and the bandwidth of the source, with high-bandwidth sources causing decorrelated reverberation sooner than low-bandwidth sources. The results also show that there are several identifying characteristics in reverberation time series which may be useful for identifying the types of scatterers which cause reverberation during particular experiments.

Advanced Applications for Underwater Acoustic Modeling

“…The scattering process itself can be modeled either as a parametric scattering strength such as Lambert's law or via perturbation theory. The model includes coherent propagation to and from the scattering patch [84][85][86][87]. (Also, unpublished notes by K.D.…”

Method of coupled mode for long-range bottom reverberation

“…For bi-static cases, Ellis and Crowe in 1991 [17] discussed a kind of three dimensional function and on the basis of this function, Liu [18] proposed the bi-static reverberation theory However, all the mentioned work mainly focuses on the incoherent part of the reverberation intensity. In recent years, LePage shows the temporal characteristics of mono-static reverberation [19], and the coherent ray-mode reverberation theory is used to explain the observed oscillation phenomenon of reverberation intensity by Li et al [20]. The stable structure of range-frequency interference for shallow water bottom reverberation had also been investigated [21].…”

Scattering and Reverberation Uncertainty in Shallow Water Environments due to Environmental Variability

“…Estimates of reverberation uncertainty were built upon a coherent model for reverberation developed at SACLANTCEN [2]. The results showed that bottom uncertainty induced uncertainty most strongly in the late time multipath arrivals, whereas oceanographic uncertainty most strongly affected axially propagating earlier arrivals.…”