Possible physical mechanisms for two features of ambient noise observed in shallow water in the Pacific are explored. These features are (a) non-Gaussian distribution of the probability density function, and (b) the fact that probability density function plots whose X scales are normalized by the standard deviation of the power decibel levels of each hydrophone are independent of depth. The results of the analysis show that variation in multipath interference of distant shipping noise is an unlikely cause of the observed features. Predictions based on source depth variations caused by wave action when a dominant noise source (such as the hull of a large ship) is located close to the surface agree with the observed features. A parametric match to the experimental probability density functions has been found with the use of non-Gaussian random noise. Future studies are recommended to explore the distributions in other oceanic regions and for other frequency bands, and to identify the underlying ambient noise mechanisms.
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