Which animal produces the loudest sound?

The blue whale's call reaches around 188 decibels underwater, which is louder than a jet engine at close range, and at frequencies so low that much of it is below human hearing. Before the oceans filled with ship noise, those calls may have carried across entire ocean basins.

Comparing underwater and airborne decibels is not straightforward - the reference pressures differ, and a figure measured in water is not the same quantity as one measured in air - so any ranking that mixes them needs treating carefully. On a like-for-like basis the sperm whale's click is probably louder still, a focused burst used to stun or locate prey.

Among land animals the honours go to smaller things than you would expect. The howler monkey carries several kilometres. A pistol shrimp, a few centimetres long, snaps its claw fast enough to create a collapsing bubble that produces a crack of around 200 decibels and a flash of light, which is a lot of physics for an animal that size.