Stephen K. Mitchell
Appl. Res. Labs., Univ. of Texas at Austin, Austin, TX 78712
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.]