Blue whales, the largest animals on Earth, possess an acoustic capability that matches their immense size. They produce the loudest and most far-reaching vocalizations in the animal kingdom. Their sounds travel through the ocean, creating an underwater acoustic landscape largely inaudible to humans. The ability of the blue whale to vocalize so powerfully allows it to navigate and communicate across entire ocean basins.
Pinpointing the Blue Whale’s Loudest Calls
The calls of a blue whale can reach an extraordinary volume, estimated to be in the range of 155 to 188 decibels (dB). These measurements represent the Sound Pressure Level (SPL) taken at the source of the sound, standardized at a reference distance of one meter. The specific metric used is decibels referenced to one micropascal at one meter (dB re 1 µPa at 1m), which is the standard for underwater acoustics.
These vocalizations are long, low-frequency moans and pulses, not high-pitched shrieks. The fundamental frequency of these calls is typically infrasonic, falling between 8 and 25 Hertz (Hz), which is below the average range of human hearing. The most distinct and loudest calls are categorized as A and B calls, which are long-duration and high-intensity tones that often occur in repeated sequences, forming what is known as a song.
How Sound Travels Vast Distances Underwater
The raw decibel number of a blue whale call is misleading when compared directly to sounds heard in air, due to a fundamental difference in measurement standards. Acoustic scientists use a different reference pressure for decibels in water than in air. The underwater reference point is one micropascal (1 µPa), while the standard for air is 20 micropascals (20 µPa), tied to the threshold of human hearing.
This difference in reference pressure accounts for approximately 26 decibels of disparity between the two systems. Consequently, a sound measured as 188 dB in water would translate to a significantly lower number if measured using the airborne standard. Beyond the reference point, sound naturally travels much faster and farther in water because the liquid medium is denser than air.
The immense distance these low-frequency sounds cover is further amplified by the Deep Sound Channel, or SOFAR (Sound Fixing and Ranging) channel. This is a deep ocean layer where sound waves are trapped between layers of water with different temperature and pressure characteristics. Within this channel, low-frequency sounds experience minimal energy loss, allowing them to travel for thousands of miles. The blue whale’s vocalizations are adapted to exploit this natural acoustic highway, allowing their calls to span entire ocean basins.
Why Blue Whales Need Such Powerful Calls
The primary purpose of these powerful vocalizations is long-distance communication in a habitat where visual cues are useless. Blue whales are generally solitary animals, and their calls are designed to connect individuals across the ocean. The loudest, most structured calls, particularly the A and B call sequences, are believed to function primarily in reproduction.
These songs are predominantly produced by males, suggesting they are used to advertise their presence to potential mates across hundreds of miles. The calls also play a role in navigation and maintaining social bonds, helping whales locate each other and identify migration routes. By listening to the echoes of their calls bouncing off distant geological features, the whales essentially create an acoustic map of their environment.
Other, less intense vocalizations, like the downswept D calls, are associated with social interactions that occur over shorter distances, often while the whales are feeding. The ability to communicate over large distances is essential for managing the movements of the largest animal on Earth, which must cover immense distances to feed and breed.
Contextualizing Extreme Ocean Loudness
To put a blue whale’s 188-decibel sound into perspective, it is often compared to some of the loudest terrestrial noises. For instance, a jet engine at takeoff is typically measured in the range of 125 to 155 decibels in air. This comparison suggests the blue whale is significantly louder than a jet, earning it the title of the loudest animal on Earth.
However, this high number does not mean a person next to a calling whale would be instantly deafened, largely due to the difference in decibel reference points. Because the underwater scale uses a more sensitive reference pressure, the sound is not as “loud” as the number suggests to human ears. Furthermore, the whale’s calls are low-frequency, meaning the sound energy is not felt in the same way as high-frequency terrestrial noise.
A person swimming near a blue whale would certainly hear an extremely loud sound. The high decibel number reflects the sound’s immense power at its source, measured in a dense medium and standardized with a sensitive reference pressure. The whale’s volume is a solution to the challenge of communicating over hundreds or even thousands of miles of open ocean.