Aparently 180 dB causes eardrum rupture and intense pain and thus is extremely deadly.
For comparison’s sake, Krakatoa volcano’s eruption was measured at around 183dB.
In: Biology
Water and air have very different densities, so dB means a different thing underwater and in air. On top of that, dB underwater is measured differently – the reference point is 20 times quieter in water, which corresponds to dB levels that are 26 dB higher. Putting those effects together, [subtract 63 dB](https://fas.org/man/dod-101/sys/ship/acoustics.htm)*. Now you’re at 137 dB which is very loud, but not eardrum rupture loud. In other words, 200 dB underwater is the same acoustic energy per area as 137 dB in air.
Now if you’re outside in the air, sound has to travel from the water out in the air, which adds yet more inefficiency, due to the acoustic impedance mismatch between water and air. You’re going to lose about another 30 dB there, if you’re outside the water. Now you’re at 107 dB, which is like a stereo turned all the way up.
Further, sperm whales communicate by *clicking*. The actual sound lasts about 100 microseconds, or 0.0001 seconds. That’s very different from a sustained loud sound. For example, a popping balloon can go as high as 168 dB, but the actual balloon pop is an [extremely brief sound](https://www.youtube.com/watch?v=MyP7i1B_QNk) (what we normally think of as the sound of a balloon popping is actually all the echoing from the initial sound).
* Edit: I think 61.7 dB is closer to the real figure, but there’s some extra rounding error when the linked article splits it into two components and rounds to the nearest dB.
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