The Acoustic Ecology of Geophysical Surveys

OCR advisory board member and acoustic ecologist Jim Cummings sent us a New York Times article about life aboard geophysical research vessel (RV) Marcus G. Langseth wherein marine geologist Bernard Coakley writes about the acoustic environment aboard the vessel after winding down a survey operation.

He writes that while a lot of the compressors, airguns, sub-bottom profiling sonar, 12kHz scanning sonar, and the drone of the engines have subsided, the ship-board noise is still too loud to hear the evening movie selection in the crew lounge.

In speaking about the subsiding noise he mentions that the airgun array – which every 13 seconds for a month, and over 5,300 km of track data generated explosions and received seafloor reflections which “shook the aft end of the ship.”

Marcus G. Langseth, Research Vessel

What Coakley doesn’t mention – although it is implied in the setting, is that the noises he is enduring are only the incidental noises of the equipment and operations used for their scientific surveys. The intentional noises used in the surveys are purpose-focused into the ocean, and are by dint of this considerably louder in the water.

Of course the RV Langseth is only a research vessel, towing the relatively small arrays used in an academic context. Surveys conducted for the fossil fuel industry are often considerably louder than academic operations because in principal and in practice they are much better funded and are in turn looking for “deeper pockets” of hydrocarbons.

Industrial Survey Vessel

While the larger ships are probably much less noisy on board due to there being more “elbow room,” given that there are over 40 industrial surveys occurring world-wide at any given time, their contribution to global ocean noise has become a leading feature in the acoustic ecology of the sea.

Global Seismic Survey Ops.

Yet another great reason to wean ourselves from oil.