Sound Essay

1657 WordsJun 29, 20137 Pages
Sound Sound is a mechanical wave that is an oscillation of pressure transmitted through some medium (like air or water), composed of frequencies within the range of hearing Propagation of sound Sound is a sequence of waves of pressure that propagates through compressible media such as air or water. (Sound can propagate through solids but there are additional modes of propagation). Sound that is perceptible by humans has frequencies from about 20 Hz to 20,000 Hz. In air at standard temperature and pressure, the corresponding wavelengths of sound waves range from 17 m to 17 mm. During propagation, waves can be reflected, refracted, or attenuated by the medium.[2] The behaviour of sound propagation is generally affected by three things: • A relationship between density and pressure. This relationship, affected by temperature, determines the speed of sound within the medium. • The propagation is also affected by the motion of the medium itself. • The viscosity of the medium also affects the motion of sound waves. It determines the rate at which sound is attenuated. • When sound is moving through a medium that does not have constant physical properties, it may be refracted (either dispersed or focused).[2] Perception of sound [edit] The perception of sound in any organism is limited to a certain range of frequencies. For humans, hearing is normally limited to frequencies between about 20 Hz and 20,000 Hz (20 kHz), [3] although these limits are not definite. The upper limit generally decreases with age. Other species have a different range of hearing. For example, dogs can perceive vibrations higher than 20 kHz, but are deaf to anything below 40 Hz. As a signal perceived by one of the major senses, sound is used by many species for detecting danger, navigation, predation, and communication. Earth's atmosphere, water, and virtually any physical

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