What is Vibration?
'''Vibration''' means quickly moving back and forth (or up and down) about a point of [[equilibrium]].<ref>Tongue, Benson 2001. ''Principles of vibration''. Oxford University Press. {{ISBN|0-195-142462}}</ref> The vibration may be periodic (having a pattern) or [[random]]. Something that is vibrating may shake at the same time. If it vibrates in a regular way, it may produce a [[music]]al [[note (music)|note]] because it can make the [[air]] vibrate. This vibration will send [[sound]] [[wave (physics)|waves]] to the [[ear]] and to the [[brain]]. In [[structural engineering]] including [[earthquake engineering]], vibrations may be bad. They may cause the structure to [[failure|fail]]. Vehicles and their passengers or cargo may also suffer damage from vibrations. The time it takes a vibrating object to go back and forth completely is the period. The number of back-and-forth movements in one second is its frequency, measured in [[Hertz]] (Hz). The farthest possible distance from the equilibrium point is the [[amplitude]]. == Types of vibration == '''Free vibration''' occurs when vibration is set off with a push and allowed to vibrate freely. Examples of this type of vibration are pulling a child back on a swing and then letting go or hitting a tuning fork and letting it ring. The mechanical system will then vibrate at a '[[Natural frequency]]' and gradually wind down. '''Forced vibration''' is when an alternating force or motion is applied to a mechanical system. Examples of this type of vibration include *a shaking washing machine due to an imbalance. *transportation vibration (caused by a combination of truck engine, springs, road). *vibration of a building during an [[earthquake]]. In forced vibration the frequency of the vibration is the frequency of the force or motion applied. The size of the effect depends on the actual mechanical system. ==Related pages== *[[Acoustics]] *[[Oscillation]] *[[Wave (physics)]] *[[Vibration isolation]] *[[Vibration control]] *[[Vibrato]] ==References== {{commons ca