CONCLUSIONS 
Principal conclusions from analyzing the sounds in 
the recorded samplings of 192 hours, from both deep water 
and shallow water, are: 
1. The Rhythmic Grunt sound was the cause of the 
raised level of the minimum ambient background noise in 
the 100-c/s-to-160-c/s frequency region at the deep hydro- 
phone just before midnight. 
2. In shallow water the peaks in the minimum am- 
bient noise levels in the 160-c/s-to-1000-c/s frequency 
region at 2000 and 0400 hours were due to the Click Chorus 
sound. 
3. The Motorboating sound is one of the agents 
responsible for the ambient noise hump at the shallow 
hydrophone during the hours around midnight. 
A dominant sound feature, which may have played a 
part in the base ambient noise levels at any hour and at 
either hydrophone, was the widely varied Barking sound. 
Furthermore, although at first ignored as an irrelevant 
and hardly heard, low-frequency disturbance, the 20 c/s 
Long Pulses were found to be an omnipresent fundamental 
in the symphony of sound in the San Nicolas Basin. 
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