Re: How do scientist know certain animals make sound waves?

One form of animal communication is vocalization. Such animals not only are able to produce sound wave but also hear them. The range of sound frequencies that animal produce and hear may vary but both of them coincides. For example, normally human being's vocal apparatus is capable of producing sound frequencies ranging between about 1 kiloHertz (i.e one thousand cycles per second) to 5 kiloHertz and he is capable of hearing between 17 Hertz to 17 kiloHertz. Sound frequencies below human range of hearing (i.e less than 17 Hertz) are called INFRASOUND frequencies whereas those that are more than 17 kiloHertz are called ULTRASOUND frequencies. Human beings cannot hear both of them. Bats for example produce ULTRASOUND for their navigation in darkenss. They use their ears to "see" in darkness through a process called "ECHOLOCATION" (locating objects through echoes).[for interesting information on bats visit the website: http://www.batcon.org/] Thank God (rather Evolution!) we are not able to hear them! Scientists study about such sound production either by behavioural studies or by neurophysiological studies. There are special "bat detectors" and tape-recorders to record ultrasounds and to play them back. These ultrasound tape recorder operates at great speed while recording (72 inches per second) and during play back the tape speed is greatly reduced, this expands the sound wave length (reducing its frequency) and hence it is audible to us while play back. Reference: Fenton, M.B (1992) Bats. Published by Facts on File, NY ISBN 0-8160-2679-3