The Physics
An encyclopedia of scientific essays

Frequency of Dolphin Sonar

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Bibliographic Entry Result
(w/surrounding text)
Nicol, Colin. The Biology of Animals. London: Pitman, 1970: 407. "… from bottlenose dolphin pitch from 7,000 c/s–5,000 c/s. Frequencies are in sonic range from 1 kc/s–120 kc/s" 1–120 kHz
Grolier Multimedia Encyclopedia. Release 6. USA: Software Toolworks, 1993. "… frequency between 1 and 120 kc/s." 1–120 kHz
Stenuit, Robert. The Dolphin: Cousin to Man. New York: Sterling, 1969: 48-49. "… up to frequencies 10 times higher than a man can hear. 100 cycles/sec to 150,000 cycles/sec." 0.1–150 kHz
Norris, Kenneth. Whales, Dolphins and Porpoises. Los Angeles: University of California, 1966: 503-504 "… harmonics region of frequency was from 1 kc/s to 164 kc/s" 1–164 kHz
Montagu, Ashley. The Dolphin in History. Los Angeles: University of California, 1963: 43. "… frequencies from 8 kc/s to at least 200 kilocycles." 8–200 kHz
Howlett, Rory. "Flipper's Secret." New Scientist. 2088 (28 June 1997), 34-39. "… frequency range between 20,000 and 120,000 cycles per second" 20–120 kHz

Most marine dolphins have a large repertoire of sounds. These include pulsed sounds of two general types: those used for echolocation (SONAR) and those emitted in emotional states. Dolphins also emit pure tone sounds called whistles and chirps. Each individual has its own unique whistle that serves to distinguish who and where the whistle is coming from. The loudness and the duration of the whistle are also important.

People are constantly relying on the scientists and the writers of published references and textbooks as well as topic specific books for the "accepted values"of many things. It is quite ironic to find so many variations and inconsistencies among these values.

The low end ranges from 100 Hz to 8,000 Hz with three sources agreeing on a value of 1,000 Hz. The higher end of the range was more varying listing upper frequencies of 120,000 (two sources), 150,000, 164,000 and 200,000 Hz. One should seek the standard deviation of the machinery used before stating which is wrong and which is correct. The machine deals with large quantities and therefore what sounds like a big difference can be considered by scientists to be minimal.

Many reasons can be listed as to why these facts differ. As the advancements in science and machinery took place, the tools used to measure the frequencies may have changed in their sensitivity and accuracy. One also must take into consideration that all the scientists might not have been using the same type of dolphin. Variations in the location of the measurements, the size of the dolphin, the time of year, the gender, and the age of the dolphin are all variables that may have affected the results.

Rebecca Erber -- 1996

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