In mechanics, vibration (from Latin vibrāre 'to shake') is oscillatory
motion about an equilibrium point. Vibration may be deterministic if the
oscillations can be characterised precisely (e.g. the periodic motion of a
pendulum), or random if the oscillations can only be analysed statistically
(e.g. the movement of a tire on a gravel road).
Vibration can be desirable: for example, the motion of a tuning fork, the reed
in a woodwind instrument or harmonica, a mobile phone, or the cone of a
loudspeaker. In many cases, however, vibration is undesirable, wasting energy
and creating unwanted sound. For example, the vibrational motions of engines,
electric motors, or any mechanical device in operation are typically unwanted.