I know that it’s common to feel like you’ve just heard the loudest sound in the world when leaving your local club after a metal band does its thing, or maybe compare that to the launch of Saturn V vehicle, but neither of those are even close. According to a fascinating article in the FiveThirtyEight, the loudest sound in world ever measured occurred on the morning of August 27th, 1883 when the volcanic island of Krakatoa blew itself to bits. It was reported that the sound was heard over 2,800 miles away, and there’s some evidence that the sound actually traversed the globe multiple times.
While a Saturn V has been measured at 204dB during launch, Krakatoa measured 174dB from 100 miles away, still loud enough to pop your eardrums!
What actually travelled around the world was the infrasonic sound waves (below our hearing range) from the blast. The way this was spotted was similar to the way nuclear tests are monitored and seismologists check for earthquakes – microbarometers and low-frequency microphones. In fact, a most recent case centered around the Chelyabinsk meteor that exploded over southern Russia on February 15th, 2013. The nearest monitoring station was 435 miles away, yet measured an infrasound level that was still 90dB.
So can infrasonic waves kill you? It turns out that the Air Force has done tests and found that humans exposed to an infrasonic level of 110dB experience changes in their blood pressure and respiratory rates to where they get dizzy and lose their balance. A 1965 test found that the test subjects began to feel their chests moving without their control at around 151dB, and at that point, their lungs were being artificially inflated and deflated.
While certainly not on the level of the full frequency range explosion of Krakatoa, yes, super low frequencies can be a killer as well. Just remember that a new active volcano has now emerged where Krakatoa once stood. Best to keep 3,000 miles away.