The underwater world is filled with powerful sounds, many from its largest inhabitants, the whales. Understanding whale vocalizations and the physics of underwater acoustics helps clarify any potential danger to humans.
The Nature of Whale Sounds
Whales communicate using a diverse array of sounds, ranging from low-frequency moans and rumbling growls to high-pitched whistles and rapid clicks. Baleen whales, such as blue whales and fin whales, typically produce low-frequency sounds, some as low as 10 to 40 Hertz (Hz), which are often below the human hearing threshold of 20 Hz. These low-frequency vocalizations can travel immense distances, sometimes thousands of kilometers, particularly within the deep sound channel of the ocean.
Toothed whales, like sperm whales and dolphins, generally produce higher-frequency sounds, including whistles and rapid clicks. These clicks are primarily used for echolocation, a biological sonar system that helps them navigate, locate prey, and perceive their environment. While blue whale calls can reach intensities of up to 188 decibels (dB), sperm whale clicks are considered the loudest animal sounds, potentially reaching 230 to 236 dB.
Sound Physics and Human Physiology
Sound behaves differently in water compared to air, traveling approximately four times faster and much farther due to water’s higher density and incompressibility. Acoustic measurements in water use a different reference pressure for decibels than those in air, meaning a decibel level in water does not directly equate to the same decibel level in air. For instance, a sound measured at 190 dB in water is roughly equivalent to 128 dB in air.
Exposure to high-intensity sound can have several physiological effects on the human body. Auditory damage, such as eardrum rupture, can occur at sound pressure levels around 150 dB in air. Barotrauma, a condition caused by pressure differences, can affect air-filled cavities like the ears, sinuses, and lungs, leading to pain or temporary hearing loss. While direct evidence from whale sounds is limited, some reports from divers suggest that very close proximity to powerful whale vocalizations might cause sensations of vibration or temporary paralysis in a limb, though these are rare and anecdotal.
Evaluating the Risk to Humans
Despite the power of whale sounds, it is improbable for them to be lethal to humans under normal circumstances. The intensity of sound diminishes rapidly with distance, meaning that by the time whale sounds reach human proximity, their energy has significantly decreased. Humans rarely encounter whales at close ranges where their sounds could cause severe harm.
Other underwater sounds, such as military sonar and seismic surveys, are more disruptive and potentially harmful to marine life, with source levels that can exceed 200 dB. While these human-generated sounds have been associated with mass strandings and physiological effects in marine mammals, lethal outcomes for humans from whale sounds are non-existent. Although a sperm whale’s echolocation clicks are loud, reaching over 230 dB at the source, they are short, highly directional, and primarily used for hunting, not as an attack mechanism. Therefore, while very close encounters might cause temporary discomfort, such as eardrum issues, the risk of a whale’s vocalizations causing death is negligible.