Various surveys have measured the near-field power of such events and they are huge: a large tanker generates up to 200 dB, active sonar hits 180, dredging and drilling 185. Research by Linda Weilgart of Dalhousie University in Canada estimates that active naval sonar in the Pacific affects 3.9 million square miles of ocean.

George Michelsen Foy, Zero Decibels, loc. 355