AI4BIENT-N0ISE MODELS 



R. C. Cavanagh 

 Office of Naval Research (AESD) 



Ambient-noise prediction schemes are viewed in terms of 

 three basic components: (a) submodels which characterize 

 source locations, levels, and coupling mechanisms, (b) a 

 propagation submodel which calculates the acoustic field 

 at the receiver generated by each source, and (c) an 

 algorithm for combining the fields at the receiver. The 

 results of a survey of noise models in operation today 

 suggest a division into two classes: 



• The POINT MODEL is intended to estimate the 

 noise field at a discrete point in space and 

 time; it thus requires detailed source infor- 

 mation and precise transmission loss from 

 each source to the receiver 



• The FIELD MODEL predicts the noise field 

 averaged over receiver location and time 

 and, hence, permits averaging both the source 

 positions and transmission loss. 



Applications and advantages of each type are discussed. 



Serious limitations in present noise-prediction capa- 

 bilities are shown to be related to the ship-source sub- 

 model and to the proper treatment of propagation in the 

 range-dependent ocean environment. 



My task is to give an overview of our present-day capabilities 

 in the area of ambient-noise prediction modeling. I will discuss 

 where we are now and where we are headed. 



During this conference we have spent time discussing the effects 

 of the medium on signal transmission. When we come to the subject 

 of ambient noise, the problem must be an order of magnitude more 

 difficult since it involves the propagation of signals from many 

 sources . 



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