HANNA: DESIGN OF TRANSMISSION LOSS EXPERIMENTS 



The schematic ray trace of Figure 9 shows a typical source- 

 receiver geometry and the four ray-paths belonging to the family of 

 rays having one bottom interaction. Explosive charges are used as 

 sources and the experimental design assumes that these four paths 

 are isolated by the signal processing. The basic analysis uses the 

 following relationship applied to these paths : 



RL = SL - TL - BL 



where RL = received level, 



SL = source level, 



TL = transmission loss, 



BL = bottom loss. 



The received level and source level are measured, the transmission 

 loss (excluding bottom loss) for the paths is estimated and bottom 

 loss is subsequently inferred. For the moment, it will be assumed 

 that there is no uncertainty in the measured received level or source 

 level (although the problem of source level measurements will be 

 touched upon later) . 



Transmission Loss Estimates 



Bottom- refracted Paths 



The examination here begins with the assumed transmission loss 

 model. In their data reduction, both organizations have assumed that 

 1) all four paths are of equal intensity at all ranges, and 2) the 

 contributions from all four paths combine on a power basis to yield 

 the total intensity. Based upon these assumptions, the total 

 spreading loss along the four paths is just 6 dB less than the loss 

 along any single path. Assumption 1) above is acceptable except for 

 ranges corresponding to small grazing angles on the bottom; at these 



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