Frequency of Bat Sonar

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Bibliographic Entry Result
(w/surrounding text)
Standardized
Result
Ramsey, William L. Holt Physical Science. New York: Holt, 1986: 157. "10,000 Hz to 120,000 Hz" 10–120 kHz
"Sound." World Book Encyclopedia. Chicago: World Book, 1998: 600. "10,000 Hz to 120,000 Hz" 10–120 kHz
Wilson, Don E. Bats in Question: the Smithsonian Answer Book. Washington, DC: Smithsonian Institution Press, 1997: 15. "Beyond our hearing capacity anything over about 15 kHz" > 15 kHz
Giancoli, Douglas C. Physics: Principles with Applications. New Jersey: Prentice Hall, 1980: 309. "Bats can detect frequencies as high as 100,000 Hz" < 100 kHz
Davis, Wayne H. "Bat." Collier's Encyclopedia. New York: Macmillan, 1992: 698. "Echolocation sounds commonly range in frequency from 40,000 Hz to 100,000 Hz" 40–100 kHz

We as humans can hear many things. From the giant truck driving by to the writing of a pen. The few sounds we cannot hear are bat sounds. Their frequencies of producing sound is much higher than ours and so we can't hear it.

Frequency is how fast an object vibrates and sound vibrates in waves. The vibrations are measured in Hertz. So one Hertz (1 Hz) is equivalent to one vibration in a second. Humans can hear from 20 Hz to 20 kHz. Anything higher is called ultrasound or ultrasonic sound. The reason that bats use ultrasound is because it has such a high frequency and it has a low diffraction or it bends less. They use this sound to do a couple of things like to catch their prey and also just to get around. The method of doing such tasks is called echolocation. They make a sound and wait for it to bounce back to hear it. If they hear it come faster in a particular area than the rest of the sounds then they know that something is near. The frequencies of bats are different in many books found. In one source like the encyclopedia it says that the frequency is 120 kHz. While in another it says 100 kHz. The truth is it ranges because when the bat makes a sound it isn't of the same frequency all the time.

So, then the values the frequency ranges from are stated to be as low as 10 kHz to as high as 120 kHz.

Juan Cancel -- 1998

Bibliographic Entry Result
(w/surrounding text)
Standardized
Result
Cutnell, J.D. & Johnson, K.W. Physics. 3rd ed. New York: Wiley, 1995: 491. "… up to a frequency of 100 kHz. < 100 kHz
MacDonald, D. "Bats." The Encyclopedia of Mammals. New York, 1984: 792-794. "Humans can perceive sounds from 20 Hz to 20,000 Hz while bats' sensitivity ranges from less than 100 Hz to 200,000 Hz (normally written as 200 kHz)." 0.1200 kHz
Whitaker, J.O. National Audubon Society Field Guide to North American Mammals. New York, 1996: 312. "While flying the bat emits through its' mouth or nose a continuous series of supersonic [sic] sounds (some 30-60 squeaks per second) ranging in frequency or pitch from below 20 kHz up to about 100 kHz." 20100 kHz
Long, M.R. & Savage, J.G. Mammal Evolution. New York: Harper, 1976: 108. "Most bats use frequencies in the range 20-80 kHz, only a few bats use frequencies less than 20 kHz which is the upper limit of human hearing." 2080 kHz
http://www.kom.auc.dk/
[lost in cyberspace -- ed.]
"The actual cry is very short (1 ms), but consist of a sweep over 50 kHz." > 50 kHz

Bats are in the family Mammalia and in the order Chiroptera [literally, hand-wing]. They are night-flying mammals with forelimbs modified into wings. Ages before scientists developed sonar, bats were using sound waves for communication and navigation. At one time, people had thought that only bats possessed this ability, but later investigations have shown that a number of animals also use such means including some fish. Insect-eating bats are one of the animals with the best sonar.

In 1793, Lazzaro Spallanzani of Italy discovered that bats were not affected if their eyes were blindfolded but were disoriented if they could not hear. It was suggested by an English physiologist in 1920 that bats navigate, locate, and captured their prey by hearing. With the invention of the microphones sensitive to high frequencies in the 1930s, Donald Griffin discovered that bats produce ultrasonic sounds (sounds of higher frequency than those audible to humans). He taped one or both of their ears shut and found that the bats could no longer navigate. Experiments conducted with hundreds of wires crisscrossing an enclosure were used to demonstrate the sonic guidance of bats. It is now known that bats emit ultrasonic sounds ranging from 20 to 100 kHz. The sounds are emitted through the bats' mouth or nostrils and are aided by a complex flap-structure to provide directivity. The echo that returns from such emissions enable the bats to pick out tiny flying insects from some distance. The bats can also determine the size, location, density and movement of an object.

Audrey Chan -- 1998

Bibliographic Entry Result
(w/surrounding text)
Standardized
Result
Ramsey, Gabriel, McGuirk, Phillips, Watenpaugh. Holt Physical Science. New York: Holt, Rinehart and Winston Publishers, 1986. "Frequency Heard 1.1kHz-120kHz"

"Frequency Produced 10kHz-120kHz"
1.1120 kHz
(hearing)

10120 kHz
(speaking)
"Sound"The New Encyclopaedia Britannica. 15th edition. Chicago: Encyclopaedia Britannica, 1998. "Low 1 kHz … High 150 kHz" 1150 kHz
Thomas H. Kunz and Paul A. Racey. Bat Biology and Conservation. Wasington and London: Smithsonian Institution Press, 1998. "The search signals of bats hunting for insects in uncluttered space are overlap-sensitive QCF signals or barrow band (<.5 octave) and low (<30kHz) to medium (~30-60kHz) terminal frequency." 3060 kHz
"Bats"Encyclopaedia Britannica. USA. Encyclopaedia Britannica, 1969. "For example, the common little brown bat of the United States usually emits pulses which begin at about 100,000 cycles per second (c.p.s.) and drop to 40,000 c.p.s. by the end of a pulse of sound that last only about 2 milliseconds" 40100 kHz
Bat Detector. Society For Amateur Scientists, 15 October 2000. "Some bat species can hear up to 160kHz" 160 kHz
[see table below] 1150 kHz

 

Frequency Range of Hearing for Humans and Selected Animals

  animal                        frequency   (hertz)
                                    low       high
  Humans                             20      20,000
  Cats                              100      32,000
  Dogs                               40      46,000
  Horses                             31      40,000
  Elephants                          16      12,000
  Cattle                             16      40,000
  Bats                            1,000     150,000
  Grasshoppers and locusts          100      50,000
  Rodents                         1,000     100,000
  Whales and dolphins                70     150,000
  Seals and sea lions               200      55,000

Reference: Encyc. Britannica.

Sonar is a system in which objects are detected by sound waves. These waves are very high in frequency and are called ultrasonic. Ultrasound waves have frequencies above 20 kHz. Few animals can hear ultrasonic waves. Some of the animals that can hear them are dogs, cats, porpoises, rodents, whales, dolphins, seals, sea lions and bats.

Bats rely heavily on ultrasonic waves for echolocation. They use echolocation to navigate while flying and to track down prey. Bats will also sneak up on some of its prey by using echolocation. Bats usually live in dark areas or in caves. To help navigate they rely on sonar. They send out ultrasonic waves with very high frequencies. When the waves return to them that are able to map out the location they are in. A bat's sonar is so advanced that it allows then to fly in complete darkness, swoop down and snatch insects without warning and hover right above water level to get a drink.

Ricky Wells -- 2002


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