### ASA 125th Meeting Ottawa 1993 May

## 2aAO8. Statistics of shipping noise vertical directionality in shallow
water.

**Stephen K. Mitchell
**

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*Appl. Res. Labs., Univ. of Texas at Austin, Austin, TX 78712
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Even a cursory examination of ambient noise from a region of moderate or
high shipping density shows that one of the most important features of noise in
the frequency region from approximately 10 to 1000 Hz is its variability. A
useful statistical summary of a noise time series n((theta),t), where
n((theta),t) is the beam noise level from a vertical array steered in direction
(theta) is the sample distribution function D[sub n](L). D[sub n](L) is
computed from data as the fraction of time for which the noise n((theta),t) is
less than or equal to L. A practical problem is to use known shipping densities
for an area, together with a description of the acoustic propagation
environment, to predict the distribution, D[sub n](L). In this paper, an
approach is presented for modeling the distribution function of vertical beam
noise, and to demonstrate a comparison with experimental data from a
shallow-water region. [This work is supported by the Office of Naval Research,
Code 23, through Block RL3B.]