Sound is essentially vibration in air, so the topic is familiar to us. From a noise control perspective, it's critical to understand how it is generated and propagated.
Vibration in structures, the ground and from machinery may effect humans and it's usually with that in mind that it causes concern.
Ground borne vibration from construction, transportation etc may cause cosmetic or structural damage to buildings or causes disturbance to occupants of the buildings. It may also cause re-radiated noise in buildings.
Occupational vibration may cause damage or task impairment to people at work, typically from hand-arm vibration (power tools etc) or whole-body (vehicles, platforms etc) vibration.
The most commonly used standard for environmental vibration assessment is BS 6472-1:2008 Guide to evaluation of human exposure to vibration in buildings. Vibration sources other than blasting. Most often it is used to assess railway vibration.
It sets out an unusual parameter known as the vibration dose value (VDV) or estimated vibration dose value (eVDV). Separate Day and Night-time periods apply.
Occupational exposure to vibration can be divided into
- Hand-arm vibration (HAV) comes from the use of hand-held power tools and is the cause of significant ill health (painful and disabling disorders of the blood vessels, nerves and joints).
- Whole-body vibration (WBV) is transmitted through the seat or feet of employees who drive mobile machines, or other work vehicles, over rough and uneven surfaces as a main part of their job. Large shocks and jolts may cause health risks including back-pain.
National health & safety legislation enacts the the European Directive Physical Agents directive. This sets out maximum vibration exposure limits and action levels for both hand-arm and whole-body vibration. Exposing unprotected workers to levels above the maximum limit is deemed to be unacceptable; whereas levels in excess of the action levels triggers various duties for both employers and employees.