Characteristics of oil industry dredge and drilling sounds in the Beaufort Sea

As part of a general study of underwater industrial noises and their effects on bowhead whales, sounds from drilling and dredging operations were measured in the shallow waters (<50 m) of the Canadian Beaufort Sea during August of each year from 1980–1984. The measurements were made from a vertical string of hydrophones at depths of 3, 9, and 18 m suspended from a sparbuoy. Sound sources included drillships logging and drilling, drilling at a caisson‐retained island, transfer dredges, and hopper dredges. Results are presented in spectrum graphs, as sound pressure levels in third‐octave and octave bands, and as overall levels in the 20‐ to 1000‐Hz band. Most energy from these sources was below 1000 Hz. The weakest drilling/dredging sounds measured came from a drillship performing logging operations (122–125 dB re:1 μPa, 20–1000 Hz, range 0.17 km). The strongest sounds came from a hopper dredge underway with a damaged propeller (150 dB, range 0.46 km). Measured data were used to derive regression equations for received sound level versus range. In these shallow waters, the overall noise (20‐ to 1000‐Hz band) from most drilling and dredging operations would be at levels below the median ambient noise (99 dB) at ranges greater than 30 km.