Methods and Results of Acoustic Calibration of Shallow Sea Local Zones

Belov A. I., Kuznetsov G. N.

The estimation of the waveguide transfer function is required to measure the mentioned noise level of marine objects with a given accuracy and to perform matched filtering of the received signals for assessment of the depth and distance to the object in passive mode. The paper analyzes and discusses the methodology developed by the use of various technical means for acoustic calibration of local zones of shallow water and getting adequate models of ground with parameter estimation in the areas of the receiving antenna, in the area of traffic or towing of the source, as well as along the path of signals propagation. The information received, together with an evaluation of the vertical distribution of sound velocity allows us to give an analytical description of the waveguide transfer function according to the distance, the operating frequency, the depth of the transmitter and receiver. The results of comparison of different methods and of experimental estimation of the model parameters of the ground in homogeneous and inhomogeneous waveguides are presented. The advantage of applying the Wigner method to estimate the parameters of normal waves is proved. A comparison of different models is performed, their adequacy is estimated by calculating the correlation ratio between the experimental and theoretical dependences of sound field, as well as by assessing the noise with absolutely calibrated source noise which was known. Practical recommendations are given, the methods of the interference field structure prediction and of providing the consistent estimates of the noise of the source are justified.

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