Statistical Measures of Beam Output Noise Due to Shipping

In a band of rather low frequencies, almost all of the ambient noise in the ocean is generated by ship traffic. If the output of a beamformer in this band of frequencies is squared and averaged, the result would be found to fluctuate in a random manner. This quantity can be regarded as a random variable Y characterized by a probability density function. This paper presents an algorithm for the calculation of the probability density function of Y, which is organized according to shipping routes in an acoustic basin and the types of ships on those routes. One of the inputs required by the algorithm is a set of source characteristic functions, one for each type of ship. Additional required inputs include the beam pattern of the array, transmission loss functions, ocean route envelopes, and average numbers of ships on those routes.