Ambient-Noise Prediction. Volume 2. Model Evaluation with IOMEDEX Data

Abstract : Ambient sea noise for frequencies 20 < or = F < or = 120 Hz is due principally to shipping and should therefore be predictable from knowledge of all ships. Volume I describes a point-source model of noise in this frequency band developed at NRL to predict statistical as well as dynamic ambient noise levels. The model uses shipping information and transmission-loss data as inputs. This volume reports on a test of the model using data taken in the Mediterranean Sea; ambient-noise values computed using the NRL model are compared with noise measurements made by five midwater hydrophones over a 12- hour period. Results of the test indicate that, in areas of high shipping density, the point method of computing ambient noise from known shipping and transmission loss is valid. However, it is shown that errors in the computed time series of noise arising from uncertainties in the inputs may be expected to be almost as large as fluctuations in the measured noise. Hence, a statistical noise calculation, easy to implement and yielding compact results, is as useful in many applications as a rigorous dynamic calculation.