Vibration in bearings generally does not generate noise itself. The "bearing noise" we usually perceive is actually the sound effect of vibrations generated directly or indirectly by the bearing in relation to its surrounding structure. This is why noise problems are often considered vibration problems affecting the entire bearing application.
(1) Excitation due to changes in the number of loaded rolling elements: When a radial load is applied to a bearing, the number of rolling elements carrying the load will change slightly during operation, causing a shift in the load direction. The resulting vibration is unavoidable but can be mitigated by axial preloading, applied to all rolling elements (not applicable to cylindrical roller bearings).
(2) Localized damage: Due to operational or installation errors, small portions of the bearing raceways and rolling elements may be damaged. During operation, rolling over the damaged bearing components will generate specific vibration frequencies. Vibration frequency analysis can identify damaged bearing components. This principle has been applied in condition monitoring equipment to detect bearing damage. To calculate bearing frequencies, please refer to the calculation program "Bearing Frequency". 
(3) Precision of related components: In the case of a tight fit between the bearing ring and the bearing housing or drive shaft, the bearing ring may deform due to its fit with the shape of adjacent components. If deformation occurs, vibration may occur during operation.
(4) Contaminants: If operating in a polluted environment, impurities may enter the bearing and be crushed by the rolling elements. The degree of vibration generated depends on the number, size, and composition of the crushed impurity particles. Although it may not produce a typical frequency pattern, an annoying noise can be heard.