Oceans of noise - Whale and Dolphin Conservation Society

5.0 145
Tug pulling loaded barge 1.0
170
Miles et al. 1989
5.0
161
34m (twin diesel engine)
workboat
0.63 159 Malme et al. 1989
Tanker (135m)
0.43
169
Buck and Chalfant 1972;
Tanker (179m)
0.06
180
Ross 1976;
Supertanker (266m) 0.008
187
Thilele and Ødengaard
Supertanker (340m) 0.007
190
1983
Supertanker (337m) 0.007
185
Containership (219m) 0.033
181
Buck and Chalfant 1972;
Containership (274m) 0.008
181
Ross 1976;
Freighter (135m)
0.041
172
Thilele and Ødengaard
1983
3.3. Oil and gas exploration
3.3.1. Seismic surveys
During seismic surveys, high intensity, low frequency sounds are directed through the earth's
crust and are reflected at the geological boundaries defining different strata. The reflected sound
is processed to provide information about the structure and composition of geological formations
below the sea bed and to identify potential hydrocarbon reservoirs (Figure 3.3). During marine
seismic surveys, the sound source, usually an array of airguns, is towed at 4-6 knots at a depth of
4-10 m (McCauley 1994, Gulland and Walker 1998), and reflected signals are recorded using
arrays of hydrophones several kilometres long. Shots are fired at approximately 6 - 20 second
intervals along pre-determined routes (commonly called “transect” lines or legs). Each transect
line can be several hours long, and surveys can last several months and can consist of hundreds of
transects.
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