ABSTRACT 



Surface duct acoustical transmission measurements were performed 

 in two areas of the Pacific Ocean. Three frequencies, three trans- 

 mitter depths and three receiver depths were employed . Both areas 

 demonstrated a persistent surface duct but they differed in that one 

 water mass was stable and the other unstable . Experimental trans- 

 mission loss curves gave good agreement with theoretical curves 

 based upon normal mode theory. It was not possible to distinguish 

 between the acoustic properties of the two areas either by the experi- 

 mental transmission loss data or by an analysis of the observed signal 

 variability . 



Arthur ZD.lMcJnr. 



