"TALLAHASSEE - Marine conservation group Save Our Shores! Florida released a report today about a new danger to ocean animals living off Florida's coasts.The push to open Florida's coasts to offshore oil drilling brings to light many more issues than just the damage to Florida's white sand beaches and tourism industry. One of the most disturbing of these issues is the destructive scale of ocean floor mapping that is necessary before drillers "break ground" on new projects. The science behind ocean floor mapping is frightening.
To map the ocean floor, the oil and gas industry typically relies on airguns, which fire sonic blasts of up to 260 decibels (db). These airguns are towed behind boats in long arrays, firing shots of compressed air into the water approximately every ten seconds. The intense pulses that they produce travel down through the water column, penetrate the seafloor, and rebound to the surface where they can be analyzed.
These blasts have been called the most intrusive form of man-made undersea noise short of naval warfare, and with good reason.
A 260 db sound is very intense. As a comparison, damage to human hearing starts at 85 db. A police siren from thirty meters is about 100 db. Decibels are logarithmic, meaning every 10 db increase translates into roughly ten times more intensity, and sounds approximately twice as loud to the human ear, which also perceives sound logarithmically. That means the 260 db airgun blast translates to ten quadrillion times more intensity than a police siren at thirty meters, and would sound to humans about 16,384 times as loud.
The threshold at which humans die from sound alone is 160 db."
To read full story: http://www.examiner.com/x-29137-Tallahassee-Environmental-News-Examiner~y2010m1d14-Sonic-death-blasting-the-cceans-in-pursuit-of-oil?cid=exrss-Tallahassee-Environmental-News-Examiner