Vibrations are motions, usually unintentional, which occur frequently in rotating as well as stationary machines and structures. Prolonged exposure to vibration at a level well in excess of the threshold of perception (20-1000 Hz) leads to physiological disorders, and in some cases to occupational diseases (for example, as a result of using pneumatic drilling equipment or power saws). The very low-frequency vibrations (under 2 Hz) produced by various forms of transport can cause distress in some people. The disturbances originate in the central nervous system and are due to stimulation of the labyrinth. The degree of disturbance may vary with circumstances and particularly the weather. Low-frequency vibration (1.5-16 Hz) produced by vehicles is transmitted through the body to all the internal organs. The effects of such vibration are cumulative and include postural reactions, neurological symptoms, behavioural changes and problems of concentration. In addition to their effect on the human body, vibrations may cause damage to buildings, and in particular to buildings of historic interest which were not constructed in anticipation of such effects.
In all sectors of modern industry, machinery, equipment and power-driven tools can be encountered which generate intense vibration that may be transmitted to the workers who operate them.