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

## 2aUW14. A normal-mode theory of shallow-water reverberation.

**Renhe Zhang
**

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*State Key Lab. of Acoust., Chinese Acad. of Sci., Beijing 100080, People's
Republic of China
*

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**Guoliang Jin
Dinghua Guan
Wenhua Li
Xinfang Qiu
**

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**
*Shanghai Acoust. Lab., Chinese Acad. of Sci., Shanghai 200032, People's
Republic of China
*

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*
Shallow-water reverberation is mainly caused by bottom scattering, and is
much more complicated than the deep-water one. Ray theory can be used for
calculating short-range reverberation simply by ignoring the water
inhomogeneity, but is not suitable for long-range reverberation due to effects
of refraction and multipath transmission. Assuming that the scattering sources
are homogeneously distributed on the bottom and regarded as the secondary sound
sources with certain directivity, by using the WKBZ approximation a normal-mode
theory suitable for long-range reverberation is developed. Because the effects
of the complex eigenvalues on the mode incident field have been considered, the
theory is better than the former ones. The given expressions of reverberation
intensity have explicit physical meaning and concise form so that they are
easily used for numerical calculation and analytical discussion. Both theory
and experiment show that the reverberation in inhomogeneous shallow water has
obvious depth dependence and there exists the relationship: I[sub R](r,z[sub
1],z[sub 2])=[I[sub R](r,z [sub 1],z[sub 1])xI[sub R](r,z[sub 2],z[sub 2])][sup
1/2]. Some experimental results are given that are consistent with theory.