An oscillatory motion of a mechanical system, including the human body. The natural modes of vibration of an object are its RESONANT frequencies.
Compare: SOUND. See: CYCLE, FREQUENCY, OSCILLATION, SIMPLE HARMONIC MOTION, STANDING WAVES, VOWEL. See also: SYMPATHETIC VIBRATION.
A SOUND WAVE of extremely low frequency is called INFRASONIC vibration. It cannot be heard in the conventional sense, but is rather felt as a vibration. The major effect of such sound is its ability to cause vibration in any mechanical object or structure, particularly one which is poorly DAMPed or which has a large surface area in contact with the vibration.
Vibration is easily confused with sound because it often creates other sounds, such as rattling window panes. Also, it may include low frequency components which are in fact heard as sound, but which may also induce vibration in the cavities of the body. Infrasonic sounds may also be analysed with a VIBRATION ANALYSER. See INFRASONIC for further discussion.