Deducing environmental properties from broadband matched-mode processing ambiguity surface striations generated from baleen whale data

Abstract

Numerous multi-year shallow-water recordings of several species of baleen whale have been obtained from shallow-water arctic environments, including the Bering Sea. When non-linear time sampling is applied to the single-hydrophone data, these broadband signals yield individual normal mode arrivals, which in turn permit incoherent matched-mode processing (MMP) techniques to be applied for source localization and geoacoustic inversion. When continuously broadband MMP ambiguity surfaces are constructed from pairs of modes and plotted as a function of range and frequency, both the mainlobe and sidelobes form striations that embed information about the type and amount of environmental mismatch present between the modeled and true environment. These striations are useful for identifying bandwidths of inversion-quality data within whale calls. Acoustic invariant theory explains how mismatched waveguide replicas from simple environmental models, when applied to sufficiently low-frequency data, produce ambiguity s...