WHOLE BODY VIBRATION ANALYSIS
Whole Body Vibration (WBV) testing is a type of vibration analysis geared towards estimating the effects on the operator. There are three categories of concern for the operator, health and comfort, perception, and motion sickness. The goal for any WBV test is to ensure that under normal operating conditions there is no significant or lasting effect of the vibration experienced by the operator.
A common application of WBV analysis is to evaluate vehicle vibration. Commercial drivers will spend several hours a day driving, exposed to road and engine vibration through the seat, floor and steering wheel. Excessive levels of vibration can cause fatigue and numbness in the back, feet, and hands. The ability to measure the vibration and estimate the effect of prolonged exposure to helps to reduce the possibility of injury.
Whole Body Vibration analysis is both application and position dependent. Motion sickness is caused by low frequency vibration with periods of 2 to 10 seconds (0.1 ? 0.5 Hz). Perception, and Health and Comfort measurements are evaluated from 0.5 ? 80 Hz. Depending on the application, up to three different body positions can be tested: seated, standing, and recumbent (laying). All of these variables play a role in the analysis of how long a person can safely operate under specific levels of vibration.
The amount of time someone is exposed to vibration is also critical to the analysis. In general, the vibration is very similar between a consumer vehicle and a commercial vehicle, the key difference is the average amount of time spent under those conditions. Consumer vehicles are generally used for shorter trips. An eight hour drive in a car would be considered a very long day. An eight hour shift for commercial drivers would be considered normal. This is why buses and semi-trucks usually have air suspension for the driver seat. The levels of vibration are similar, but the duration of exposure is much longer.
(For step-by-step instructions on how to conduct modal testing on the CoCo instruments, click here to download the CoCo Modal Data Acquisition Operation Manual.)
Whole Body Vibration Testing
Measurements for Whole Body Vibration testing require triaxial data in nearly all testing locations. For this example we will look at a basic WBV test to evaluate health risks. Analysis for health applications are concerned with seated persons and the vibration from 0.5 Hz to 80 Hz. Vibration in this bandwidth can cause disruptions to the functioning of the spinal column and associated nervous system, as well as potentially disrupting the digestive system.