### ASA 126th Meeting Denver 1993 October 4-8

## 2pAO5. Spectral integral formalism of wave propagation in a
range-dependent waveguide.

**Dajun Tang
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*Woods Hole Oceanogr. Inst., Woods Hole, MA 02543
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**Yue-Ping Guo
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*MIT, Cambridge, MA 02139
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This work is the study of acoustic wave propagation in a range-dependent
waveguide, where either the interfaces or the medium parameters are functions
of horizontal dimensions. For a range-independent, i.e., horizontally
stratified, problem where the wave equation can be solved using separation of
variables, the well-established wave-number spectrum formulation has been
proved to be a powerful technique. When such a spectrum is known, the modal
structure and its continuous component will completely determine the wave
behavior in the waveguide. More importantly, knowledge of the spectral
information can be used in inversion techniques to estimate environment
parameters through acoustic probing. At the ASA Ottawa meeting [Tang and Guo,
J. Acoust. Soc. Am. 93, 2284(A) (1993)], Tang and Guo presented the spectrum
formalism and an application of the formalism to an ideal wedge. Here the
approximate spectral formalism is further developed for more general weakly
range-dependent problems. Special attention is paid to the ``transition
regions'' of the waveguide where the discrete part of the spectrum borders the
continuous part of the spectrum. Near such regions, different parts of the
spectrum interact strongly with each other, resulting in apparent changes of
the acoustic fields. Some examples will be discussed to elucidate the
advantages of this approach.