Turn it down a bit; I can't swim.
Thursday, 18 July 2002
By Correspondent
The US Navy have approved the use of a sonar that generates 230dB of signal underwater! How loud is that? Well, in air the readings generally look like:
Jet Engine taking off ? 140 dB
Chainsaw ? 120 dB
Lawn Mower ? 100 dB
Alarm Clock ? 80 dB
Normal Speech ? 60 dB
Whisper ? 40 dB
In water you have to minus about 63dB so 230dB under water would be about 167dB
From what I remember about decibels each additional 10dB makes a sound 10 times louder than what it is!
If my calculations are right that makes this sonar over a hundred times louder than a jet engine taking off, and that is sound travelling underwater.
So whats the big deal?
Well the device kills nearby whales (nearby being within several miles), whose eardrums rupture.
When they were testing this baby 16 whales and a spotted dolphin on Bahamian shores over 36 hours.
X-ray studies showed bleeding around the inner ears, along with trauma to the auditory system and parts of the brain and throat sensitive to intense pressures. In one animal, the ligament that holds an eardrum-like membrane taut had ruptured, evidence of having been exposed to a powerful physical force. Other studies found that all but one of the animals had been healthy (the dolphin was diseased, and its demise has not been linked to the Navy), and the report ruled out other causes of injury, such as physical strikes by ships or underwater seismic events.
Gosh, you wouldn't want to be using your ears to navigate with all that hubbub going on! Earplugs anyone?
