Vibration is a mechanical phenomenon whereby oscillations occur about an equilibrium point.
Vibration can be desirable or .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.
The studies of sound and vibration are closely related. Sound, or pressure waves, are generated by vibrating structures; these pressure waves can also induce the vibration of structures. Hence, attempts to reduce noise are often related to issues of vibration. Vibration is calculable by an accelerometer. This device measures acceleration, speed and width oscillation transmitted on the body.
Some example:
| Ship/ plane | 2 Hz |
| Tractor/bus/subway | 20 Hz |
| Pneumatic drill/ milling machine | 40 Hz |
Vibration are transmitted through skeleton in human body. Low frequency are more tolerated than high (considered intolerable).
Vibration perception change with the frequency, like acceleration:
| Description | Frequency 1-10 Hz
max. acceleration (mm/s2) |
Frequency 10-100 Hz
max. acceleration (mm/s2) |
| Quite Perceptible | 34 | 0,5 |
| Cleary Perceptible | 100 | 1,3 |
| Unpleasant | 550 | 6,8 |