HAYES— U. S. NAVY MV TYPE OF HYDROPHONE. 375 



6^ — R — H are nearly equal. The reflection at (P), being from a 

 rare to a dense medium, introduces a change of phase of one half 

 the wave-length and as a result the sound which travels directly 



^i//ft7ce of -Sea 



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w 



If Pf? a J// 



TTJen XPe7 t ^ ^ PH 



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gorTomof3ea 



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Mutual CflNCELLATiDN df Direct and Surfhce-Rcflected Rays 



Fig. I. 



from (5') to (H) and that which is reflected from the surface will 

 give almost complete interference at the receiver (H) and only the 

 sound reflected from the bottom (0) will be heard. 



T 



Surrace or /he Sea 



INflVEDlSTDFJTIDN DUE TD PRESSURE RELEASE AT SURFACE 



Fig. 2. 



Referring to Fig. 2, the surface of the water represented by the 

 horizontal line is a region of pressure release and as a result the rare 



