Loudest animal sound

The loudest sounds made by an animal are unidirectional clicks produced by sperm whales (Physeter macrocephalus), which they use for echolocation while hunting for prey in the low-light ocean depths. These clicks can be as powerful as 236 decibels (dB); in air, to the human ear, that's equivalent to around 10 times the loudness of a thunderclap. Sperm whales are able to hear each other's vocalizations several tens of kilometres away.

The loudness of animal sounds is notoriously difficult to measure and compare. Even when comparing sounds using the same measurement method, factors such as proximity and whether the sound is travelling through air or water affect the outcome (e.g., there is a difference of some 61.5 dB between a sound passing through air or water). The study that recorded sperm whale clicks reaching up to 236 dB were measured in relation to a reference pressure of one micropascal (1 μPa).

The study was a collaboration between the University of Aarhus, University of Copenhagen and Computer Sciences, Corporation Scandinavia (all Denmark), led by Bertel Møhl of the Department of Zoophysiology at the Institute of Biological Sciences, University of Aarhus, Denmark. It was published in the Journal of the Acoustical Society of America in August 2003.

Sperm whales have been recorded producing a range of different sounds for different situations, including usual clicks, creaks, slow clicks and "codas" (patterns of clicks). Interestingly, sperm whale clans have also been found to have distinct "dialects" based on the codas that are used to socialize. Within these regional variations, codas have also been shown to differ between individuals, which suggests that each animal could have its own identifying "voice".