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



angle while the vessel is in a horizontal position or to measure the 

 angle at each end of the pitching motion. If the latter plan is pur- 

 sued the average of the two angles gives the correct value. 



Errors Introduced by Shelving Bottom Can be Eliminated. 



A consideration of Fig. 5 shows that the errors introduced by 

 shelving of the sea-bottom can be eliminated if a hydrophone and a 

 sound-source are placed in both the bow and the stern of a vessel 



D'Ci-H 



METHOD FDR aiMINATING ERROR DUE TD aHELUING BOTTDM 



Fig. S- 



Let (Sj) and (H^) represent a sound-source and hydrophone re- 

 spectively, located near the bow of the vessel and (^a) and (//o) 

 another sound-source and hydrophone located near the vessel's stern. 

 Sound from {S^ and {S^^ reflects from the same portion of the 

 sea-bottom, making angles with the horizontal at (//o) and {H^ of 

 *2 and $1 respectively. 



If (2L) is the horizontal distance between {^S^ and {H^ and 

 between (^'o) and (Hj), then 



and 

 Thence 



Z) = C+ (2L — X) tan$i, 

 D = C + Z tan $,. 



L' = C + 2L 



tan $1 • tan $2 

 tan $i -f~ tan $2 



