Whales communicate through a diverse array of sounds. Their vocalizations range from complex songs to sharp clicks, serving various purposes in the vast underwater world.
The Decibel Scale and Underwater Sound
Sound intensity is measured using the decibel (dB) scale, a logarithmic unit. A 10 dB increase signifies a tenfold increase in sound pressure level. Underwater, sound travels much faster (approximately 1500 meters per second) than in air (about 340 meters per second), allowing it to propagate much farther.
Measuring underwater sound requires a different reference point than in air. Airborne sound uses a reference pressure of 20 micropascals (μPa), while underwater sound uses 1 μPa. This difference means underwater decibel levels are not directly comparable to airborne levels. For instance, 190 dB re 1 μPa underwater is roughly equivalent to 128 dB re 20 μPa in the air.
Loudest Whale Calls Explained
Blue whales produce some of the loudest sustained sounds, with calls reaching 188 to 189 dB re 1 μPa. These low-frequency vocalizations allow blue whales to communicate across vast distances. Fin whales also emit powerful, low-frequency sounds known as “20-Hz pulses,” which can reach up to 186 to 190 dB re 1 μPa.
Sperm whales generate extremely intense clicks, primarily for echolocation, as loud as 230 to 236 dB re 1 μPa. These clicks are short, focused bursts of sound, unlike the longer vocalizations of baleen whales. For perspective, a jet engine at takeoff typically produces airborne noise between 120 and 140 dB, and a loud rock concert can reach 90 to 129 dB in air.
Why Whales Make Loud Sounds
Whales rely on sound for essential functions in their underwater environment. A primary reason for their loud vocalizations is long-distance communication. Low-frequency sounds, such as those made by blue and fin whales, travel efficiently through water, allowing individuals to find mates, warn others of dangers, or coordinate group movements over vast distances.
Toothed whales, like sperm whales, use loud clicks for navigation and hunting via echolocation. They emit sound pulses and interpret echoes, creating a detailed acoustic map of their surroundings. This sonar-like ability helps them locate prey and navigate obstacles, especially in the deep, dark ocean where visibility is limited. Some researchers also suggest that the immense power of these clicks might help to disorient or stun prey, though this remains an area of ongoing study.
Human Impact on Whale Communication
Human activities introduce significant noise into the marine environment, which can interfere with whale communication. Sources of this human-generated underwater noise include shipping traffic, sonar systems used by navies, and seismic surveys conducted for oil and gas exploration. This increased noise creates a “smog” of sound that can have several detrimental effects on whales.
The primary impact is acoustic masking, where human noise drowns out or obscures the whales’ calls, making it difficult for them to hear each other. This interference can disrupt vital behaviors such as feeding, mating, and migration. Studies indicate that exposure to anthropogenic noise can also lead to behavioral changes, increased stress levels, and even temporary hearing loss in marine mammals.