Dramatic articles certainly get a point across. The unfortunate truth however, is that many claims are totally unfounded. In response to this article (www.huffingtonpost.com/mobilew…) I contacted a Bioacoustics professor at Georgia Tech to go over the "facts" stated in it. Please not, if you are someone who has posted or quoted this sort of information, THIS IS NOT TO ATTACK YOU, I just hope to spread corrected information. Below is the copied e-mail:
Interesting" article -- I'm in a workshop this week sponsored by Bureau of Ocean Energy Management (U.S. Dept. of the Interior) and will be on a panel with NRDC lawyer, Michael Jasny, and Dalhousie University researcher, Lindy Weilgart, on Wednesday. Since Navy reps will be there and the workshop is about mitigation of ocean noise and its biological impacts, I find it interesting that this article was published just prior to this workshop, which starts on Monday. This has happened before so I do not think it is a mere coincidence.
The article is full of misconceptions and exaggerations. Here are just some of them:
1. Sound from sonar transducers consists of frequency and amplitude modulated harmonic signals. It is not like a rocket blast or explosion or a shriek. Mid-frequency sonar signals are similar to chirps (similar to orca chirps) and low-freqeuncy sonar signals are like bursts from a fog horn -- I have some of these recordings and can play them for you, just remind me so that I have time to dig them out of my archives before our next meeting.
2. Sonar sounds are not shock waves -- a shock wave is a transient that would have a pressure peak higher than the ambient pressure. Ambient pressure increases with depth, so they are extremely hard to produce underwater without an explosive device.
3. Acoustic "source levels" underwater are theoretically estimated for a distance of 1 meter from the source. The theoretically estimated "source level" of a mid-frequency sonar transducer is 235 dB re 1 uPa at 1 m. This transducer consists of an array of mini sound projectors mounted on the hull of a ship and the 1-m location is actually inside the "transducer dome" which is the protective rubber-like material covering the array. So it is impossible to produce 235-decibel pressure waves in water. "Received levels" of sound depend on both the source and the surrounding environment (e.g., compare a referee's whistle outside on a football field with the same referee's whistle inside a gym at a volleyball or basketball game).
4. There are absolutely no data to support the claim of 200 dB causing lung rupture and 210 dB causing brain hemmorhage, and sound at sonar frequencies cannot "bore" through your head because the spatial wavelengths are on the order of the length of a human body. Only ultrasound (having much shorter wavelengths) can "bore" through tissue and it is used to do just that in many medical applications. To put things in perspective, the "source level" of many biomedical ultrasound transducers is on the order of 200-210 dB, and peak source levels of transducers used in lithotripsy to break up kidney stones are much higher (the lithotripter wave is a very short pulse with a high pressure peak; it is a shockwave). Also it takes a peak "received level" (not a "source level') of about 220 dB re 1 uPa to rupture a fish swim bladder, which is much more fragile than mammal lung tissue.
5. There is absolutely no data or evidence to support "millions" of dying dolphins and whales from sonar. Thousands of marine mammals strand all over the world every year and the number of strandings in the vicinity of sonar activities is miniscule compared to the total.
6. Ken Balcomb is not a scientist. He is retired from the Navy and was married to Diane Claridge -- the scientist in the Bahamas who has studied beaked whales there for many years. After they divorced Ken moved to Washington state. He is not recognized as an expert on orcas in the scientific community (which has many experts in this area). He did not document the beaked whale mass stranding that occurred in the Bahamas in March 2000 -- that is attributed to Diane. This was the "choke point" navy exercise that we discussed last Saturday and the navy has not repeated this type of exercise since then.
7. The March 2000 stranding event was due to mid-frequency sonar (2000-7000 Hz), not low frequency sonar (< 500 Hz).
8. Results of all research to investigate the "bends" hypothesis do not support this theory
9. Darlene Ketten, the scientist at Woods Hole and Harvard Medical School who has done all the necropsies on whale ears from stranded animals associated with military sonar, has never found any evidence of tissue in the ears being damaged, so the statement by Balcomb is just false. You can find reports of all the stranding events listed in this article (except the ones in the Canary Islands and Greece) at the NOAA Fisheries (National Marine Fisheries Service) website. These reports include the results of the necropsies.
10. Most people don't realize that the NRDC is an organization of lawyers, not scientists, whose mission is to file lawsuits in effort to protect the environment. They solicit and hire scientists and enviroinmentalists to support their viewpoints, which are not always based on scientific evidence.
11. The Cold War is over; however, "terrorists" do have submarines and they are the relatively small diesel-powered ones that are very difficult to detect.