VARIABILITY OF ECHOES 



375 



50 MSEC 



SECOND ECHO 

 PRINCIPAL ECHO 



S- TYPE SUBMARINE AT 100 FT DEPTH 



50 MSEC 



^fstecHo 



J4t ECHO 



aiMomufc 



a*o eato 



/oms ptif& 



f-oms pif^ir 



B 



S- TYPE SUBMARINE AT 90 FT DEPTH 



Figure 9. Double echoes. 



