When one thinks of all the dangers threatening whales and dolphins, ocean noise is not one that comes to mind right away, but is one that is increasing every day. A study showed that ambient noise in the oceans rose 10 decibels between 1950 and 1975 – a 900% increase in 25 years! The “Silent World” that Jacques Cousteau described years ago is no longer silent.
Marine mammals depend on sound to communicate, navigate and to search for food in our oceans. When we increase the ambient noise in the oceans, we decrease their ability to survive.
Sources of Ocean Noise A modern-day supertanker cruising at 17 knots (about 20 mph) fills the lower frequencies with a steady sonic roar of about 200 decibels, the equivalent of a commercial jet at takeoff.
The offshore oil industry relies on the explosive power of airguns, discharging tens of thousands of blasts as loud as 250 decibels.
The Navy is developing a “low-frequency” active sonar system, designed to detect foreign submarines by bombarding the seas with sound, reportedly in the range of 235 decibels or higher. (See Navy Noise!)
The federal government is preparing to test a new pulsed power “acoustic harassment” technology that will intentionally bombard marine mammals with potentially deafening underwater noise and disorienting shock waves for the purpose of determining whether California sea lions can be prevented from eating the fish caught by party boats. This noise will be as loud as 230 decibels!
