On Friday Scientific American online published an article about ocean noise pollution research. The article covers the work of Chris Clark who has been doing some fabulous passive acoustic monitoring of Right whales in the Stellwagen Banks National Marine Sanctuary – which also happens to encompass the busy shipping lanes to and from Boston Harbor.
While there is nothing new in the article that folks on this mail list don’t already know, it does include a neat visual of Chris’ work. He has synchronized a large array of autonomous hydrophones in the sanctuary. The output of this array allows tracking of sound sources such as the Right whales, and also the transit of ships through the sanctuary.
Chris also introduces the idea that noise impacts should be considered in terms of acoustic habitat rather than looking at mitigation from the standpoint of the noise levels of individual sound sources. In this context noise makers would need to consider their contribution to the entire soundscape.
Heretofore what scant noise criteria that does exist is predicated on sources not exceeding a specific threshold – usually a level just shy of what will cause measurable compromise to a target animal’s hearing. By considering the habitat, noise criteria might be set at a threshold where the noise overlaps and masks biologically significant signals.
This is heading in the right direction. The US Navy has been setting their mitigation as if animals were ‘input devices,’ setting maximum exposure levels based on “recoverable thresholds” i.e.: how much the system can endure and recover.
We’ve always maintained that animals are not isolated from their environment. As Chris Clark’s work gets broader coverage in popular media perhaps regulations will be crafted around a more holistic model.