20 
FREQUENCY, C 
TIME, SECONDS 
AG UM mCEm Oke Sonagrams showing the Low Frequency 
Groan sound. A. Groan from shallow hydrophone 
(between sec 4 and 7). B. Same groan with 
changed time and frequency scales (resulting 
from different tape playback speed). C. Same as 
Bonly from the deep hydrophone, arriving 4 sec 
earlier. LG SCrORG WOTUZOREBGL LURE 88 jVirOl- 
ably from equipment hum. WDE OBGLGICGH SerbOGosORS 
Lite AL Tal Conan Ta OY TCH TCH Celanc CH iam CHI VORTAUIS He 
