Underwater Noise

Over the past ten years there has been an increase in the number of cetacean strandings worldwide which have coincided with military exercises taking place in various areas.

Sound carries so well underwater that animals can be affected over great distances, and there is evidence that active sonar exposure can have an impact on some cetacean species, in particular beaked whales. When exposed to such loud noise they may experience gross damage to ears and body tissue.

Most military sonar is not a gentle ping but can create a massive blast of noise, reach 235 decibels and travel hundreds of miles through the ocean. One scientist analysing underwater acoustic data reported that a single low frequency sonar signal deployed off the coast of California could be heard over the entire North Pacific Ocean.

There is no dispute that some underwater activities can injure or kill marine mammals. The US Navy has acknowledged that its use of sonar activities in early 2000 off the Bahamas resulted in the deaths of many beaked whales. There has also been a number of mass beaked whale strandings around the Canary Islands coincident with military sonar activities, particularly mid-frequency sonar. The Marine Connection is concerned not only about the potential impact of underwater noise on cetaceans but the wider marine environment.

UK Underwater Noise Report

With sound in the sea being such an issue, a short-life UK Working Group to address the topic was formed in 2004.Membership of the Group included individuals from government departments, conservation bodies including Marine Connection, the research community and industry. The report of the Group was presented to The Inter-Agency Committee on Marine Science and Technology in 2005 and approved for publication. Following the publication of this report, a UK forum was created, which the charity are part of, to discuss sound in the marine environment further.
Underwater noise UK report

Beaked whale strandings relating to seismic surveys

There have also been many instances in recent years where cetacean strandings, particularly beaked whales, have occurred in areas where seismic surveys were being conducted by companies looking for oil or gas. Arrays of airguns using blasts of compressed air create impulses that hit the ocean floor which are then picked up by hydrophones; giving a reading of what’s beneath the ocean floor. As an example, noise from a single seismic survey can flood a region of almost 300,000 sq/km.
Click here for an example of the blasts which cetaceans experience

Click below for a list of strandings that relate to such activities, and a report from one incident that the Marine Connection investigated in the Azores.
Strandings list and investigative report