A few months ago, the media covered an effort by the U.S. Navy to activate a new underwater submarine detection system using active sonar at 230 decibels (dB). This is sonar that sends out signals that bounce off objects such as rocks and submarines--and whales. You saw an example of this sonar if you watched the movie Hunt for Red October. In the movie, an American submarine captain (Scott Glenn) sends a Morse code message to the captain (Sean Connery) of the Russian submarine Red October telling him to respond with one or two sonar "pings" for "yes" if he is defecting to the West, or "no"--I forget which by now.
Incidentally, in the same movie, "Jonesy," an American sonar operator with the echo-locating capability of a bat, uses passive sonar to listen for submarines, surface ships--and whales.
Jean-Michel Cousteau wrote that sonar was bad for whales in a May 13, 1998 article on line at ENN. He discusses the U.S. Navy's Low Frequency Active Sonar (LFAS) for identifying submarines in shallow waters where traditional sonar doesn't work. He cites Dr. Alexandros Frantzis from the University of Athens as saying there is a correlation between strandings of Cuvier's beaked whales and NATO testing of LFAS in the Mediterranean Sea.
At 230 dB, the new Navy sonar pulse would be louder than a jet engine, which produces 120 dB. You and I can suffer hearing loss at 150 dB. Normal conversation is about 65 dB; a kitchen blender--about 85 dB, lawn mower--about 95 dB; busy New York City intersection-more than 100 dB; a power saw--about 110 dB; and a firearm--150 dB. According to Arthur Baggeroer, an MIT ocean engineering professor quoted in an Associated Press (AP) story "The Ocean is a Loud Place These Days" by Paisley Dodds, oil rigs, he wrote, "can ring out about 180 decibels."
The Navy isn't the only noise maker. The Scripps Institution of Oceanography in La Jolla, Ca., has been interested in monitoring changes in the ocean's temperature by measuring how long it takes sonar bursts to travel 6,000 miles to a receiver. This measurement is called acoustic thermometry, in case you're interested, and it is supposedly useful for understanding global warming. The Scripps' sonar ping, which starts at 195 dB and is still 135 dB half a mile away, has been going on since 1995.
Scripps also says, according to David Cromwell in Science Tribune, that its acoustic experiments accompany a marine mammal research program that "is designed to provide information on hearing capabilities of marine mammals and sea turtles. . .."
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