Vibration generation in a bearing
In general a rolling bearing does not generate noise by itself. What is perceived as "bearing noise" is in fact the audible effect of the vibrations generated directly or indirectly by the bearing on the surrounding structure. This is the reason why most of the time noise problems can be considered as vibration problems involving the complete bearing application.
Excitation due to varying numbers of loaded rolling elementsWhen a radial load is applied to a bearing, the number of rolling elements carrying the load varies slightly during operation, i.e. 2-3-2-3.... This generates a displacement in the direction of the load. The resulting vibration cannot be avoided, but can be reduced by applying an axial preload to load all the rolling elements (not possible with cylindrical roller bearings).
Accuracy of associated componentsIn cases where there is a tight fit between the bearing ring and the housing or the shaft, the bearing ring may take the shape the adjacent component. If form deviations are present, these may cause vibrations during operation. It is therefore important to machine the shaft and housing seat to the required tolerances, see section Dimensional, form and running accuracy of bearing seats and abutments.
Local damageDue to mishandling or incorrect mounting, small sections on the raceways and rolling elements can be damaged. During operation, overrolling a damaged bearing component generates a specific vibration frequency. Frequency analysis of the vibrations can identify which bearing component suffered damage. This principle is used in SKF Condition Monitoring equipment to detect bearing damage.
To calculate SKF bearing frequencies, see the Bearing frequencies calculation.