Sound, a form of energy traveling in waves, is measured in decibels (dB). The decibel scale is logarithmic, meaning a small increase in dB represents a much larger increase in sound intensity. For example, a 10 dB increase signifies a sound ten times more intense. Animals produce a wide range of sounds, from nearly inaudible frequencies to those louder than human-made machines.
The World’s Loudest Animal
The sperm whale (Physeter macrocephalus) produces the loudest known animal sound. Its clicks, used for echolocation and communication, can reach 236 decibels underwater. For comparison, a jet engine at takeoff registers about 150 decibels. These powerful clicks allow sperm whales to navigate and hunt for prey in the deep ocean. Sound perception differs between air and water, so this sound would be less intense if heard in the air.
Other Remarkable Sound Producers
Beyond the sperm whale, other animals also create loud noises:
- Blue whales (Balaenoptera musculus) emit calls up to 188 decibels, communicating across vast oceanic distances.
- The tiny pistol shrimp (Alpheus bellulus) generates a cavitation bubble with a claw snap, producing sounds up to 210 decibels to stun prey.
- Male cicadas produce mating calls ranging from 80 to 120 decibels; some species, like the African cicada Brevisana brevis, reach 107 decibels.
- The lesser water boatman (Micronecta scholtzi), a small aquatic insect, produces sounds up to 99.2 decibels through stridulation, making it the loudest animal relative to its body size.
- The fish Danionella cerebrum, only 12 millimeters long, can produce sounds over 140 decibels using a drumming mechanism with its swim bladder.
- The kakapo, a flightless parrot, emits mating calls over 132 decibels, audible for several kilometers.
Mechanisms of Sound Production
Animals employ diverse biological and physical methods to generate loud sounds:
- Vocalization: A common method involving specialized structures like vocal cords or folds, seen in many mammals and birds. The larynx in terrestrial mammals vibrates vocal folds as air passes through. Aquatic mammals also use air-driven systems adapted for underwater sound production.
- Stridulation: Widespread among insects and some crustaceans, this involves rubbing two body parts together, such as cricket wings or cicada tymbals. Cicada tymbals are ribbed membranes that buckle rapidly, creating a series of clicks.
- Cavitation: Utilized by the pistol shrimp, this involves the rapid closure of a claw to create a high-speed water jet. This forms and then collapses a bubble, generating an intense shockwave and loud snap.
- Percussion: Some animals use percussion, like woodpeckers drumming on trees or palm cockatoos striking sticks against surfaces.
The Purpose of Loud Calls
Loud animal calls serve various evolutionary and ecological functions:
- Attracting mates: As seen with male cicadas, frogs, and kakapo, whose calls travel long distances to signal their presence.
- Territorial defense: Animals like gibbons and lions use loud vocalizations to mark and protect their territories from rivals.
- Warning predators or communicating danger: Rattlesnakes use their rattle to deter threats, and vervet monkeys have specific alarm calls for different predators.
- Communication within a social group: Over long distances, such as the infrasound calls of elephants or complex whale vocalizations.
- Navigation and hunting: Particularly in low-visibility environments, like echolocation employed by whales and bats to map surroundings and locate prey.