The design of vibration-damped equipment and engine mountings are the most effective engineering methods of controlling vibration exposure. The exposure limits are given as frequency-weighted acceleration that represents a single number measure of the vibration exposure level. The frequency-weighting is based on a scheme recommended in the international standard ISO 5349. The horizontal axis in Figure 2 represents vibration acceleration. RMS is a method of determining average for quantities that fluctuate with time about a central value.
Weighting accounts for variation in human sensitivity to vibration of different frequencies.
As frequency increases above this range the sensitivity decreases. The standard provides methods for calculating weighted RMS accelerations and equivalent acceleration values where the level of daily exposure varies with time. The standards and guidelines concerning whole-body vibration are designed to reduce vibration to a level where most workers can perform job tasks without discomfort. Exceeding these exposure limits makes it difficult for passengers to eat, read or write when travelling. For example, fatigue impairs performance in flying, driving and operating heavy vehicles.