Whale Song & Social Sounds - An Overview |
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Humpback whales are well known for their songs Only a few hundred years ago the bays and inlets of the world were alive with the slow, restful breathing of whales and the songs whales make to communicate. The word "song" is used in particular to describe the pattern of regular and predictable sounds made by some species of whales (notably the humpback) in a way that is reminiscent of human singing. The mechanisms used to produce sound vary from one family of cetaceans to another. Marine mammals, such as whales, dolphins, and porpoises, are much more dependent on sound for communication and sensation than land mammals are, as other senses are of limited effectiveness in water. Sight is limited for marine mammals because of the way water absorbs light. Smell is also limited, as molecules diffuse more slowly in water than air, which makes smelling less effective. In addition, the speed of sound in water is roughly four times that in the atmosphere at sea level. Because sea-mammals are so dependent on hearing to communicate and feed, environmentalists and cetologists are concerned that they are being harmed by the increased ambient noise in the world's oceans caused by ships and marine seismic surveys. Bermuda has a small place in history when local Frank Watlington made some of the first recordings of humpback whales. Mr Watlington was an electronics specialist responsible for recording and identifying underwater sounds using hydrophones. In the 1950s and 1960s local Mr Frank Watlington was stationed at the U.S Government's Naval Underwater Systems Centre sonar listening base here in Bermuda. His job was to monitor underwater sounds for the tell-tale signs of Soviet submarines. Each spring unidentified sounds were recorded by the sonar devices, much to everyone's bafflement. It was Frank Watlington who solved the mystery, identifying the sounds as humpbacks and recording the songs. His recordings, some from as early as 1952, drew the attention of scientists including Dr Roger Payne and set in motion a series of studies of humpbacks and how they communicate. The recordings of Frank Watlington and Dr Roger Payne were included as a freebie in National Geographic and millions of readers were treated to 'Songs of the Humpback Whale', the 1979 sound sheet that made millions of readers put down their magazines and listen.
Production of soundHumans produce sound by expelling air through the larynx. The vocal cords within the larynx open and close as necessary to separate the stream of air into discrete pockets of air. These pockets are shaped by the throat, tongue, and lips into the desired sound. Cetacean sound production differs markedly from this mechanism. The precise mechanism differs in the two major sub-families of cetaceans: the Odontoceti (toothed whales-including dolphins) and the Mystceti (baleen whales-including the largest whales, such as the Blue and Humpback Whales). <<Back to topics
Toothed whale sound productionToothed whales do not make the long, low-frequency sounds known as the whale song. Instead they produce rapid bursts of high-frequency clicks and whistles. Single clicks are generally used for echolocation whereas collections of clicks and whistles are used for communication. Though a large pod of dolphins will make a veritable cacophony of different noises, very little is known about the meaning of the sound. Frankell (1998) quotes one researcher characterizing listening to such a school as like listening to a group of children at a playground. The multiple sounds themselves are produced by passing air through a structure in the head rather like the human nasal passage called the phonic lips. As the air passes through this narrow passage, the phonic lip membranes are sucked together, causing the surrounding tissue to vibrate. These vibrations can, as with the vibrations in the human larynx, be consciously controlled with great sensitivity. The vibrations pass through the tissue of the head to the melon, which shapes and directs the sound into a beam of sound for echolocation. Every toothed whale except the sperm whale has two sets of phonic lips and is thus capable of making two sounds independently. Once the air has passed the phonic lips it enters the vestibular sac. From there the air may be recycled back into the lower part of the nasal complex, ready to be used for sound creation again, or passed out through the blowhole. The French name for phonic lips-museau de singe-translates to "monkey lips," which the phonic lip structure is supposed to resemble. New cranial analysis using computed axial and single photon emission computed tomography scans in 2004 showed that, at least in the case of bottlenose dolphins, air may be supplied to the nasal complex from the lungs by the palatopharyngeal sphincter, enabling the sound creation process to continue for as long as the dolphin is able to hold their breath (Houser et al., 2004). <<Back to topics Baleen whale sound productionBaleen whales do not have phonic lip structure. Instead they have a larynx that appears to play a role in sound production, but it lacks vocal chords and scientists remain uncertain as to the exact mechanism. The process, however, cannot be completely analogous to humans because whales do not have to exhale in order to produce sound. It is likely that they recycle air around the body for this purpose. Cranial sinuses may also be used to create the sounds, but again researchers are currently unclear how. <<Back to topics
Purpose of whale-created sounds
The song of the Humpback Whale
Other whale sounds
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