In general, rolling bearings themselves do not produce noise. Usually felt “bearing noise” is in fact the bearing directly or indirectly with the surrounding structure of the vibration of the sound effect. This is why many times the noise problem can be regarded as involving the vibration problem of the whole bearing application.

(1) Excitation caused by the change in the number of loaded rolling bodies: When a radial load is loaded on a bearing, the number of rolling bodies carrying the load will change slightly in operation, which causes the load direction deviation. The resulting vibration is unavoidable, but can be alleviated by axial preloading on all rolling bodies (not applicable to cylindrical roller bearings)

(2) Local damage: Due to operation or installation errors, a small part of bearing raceway and rolling body may be damaged. Rolling over damaged bearing parts during operation produces a specific vibration frequency. Vibration frequency analysis can identify damaged bearing components. This principle has been applied in condition monitoring equipment to detect bearing damage. To calculate the bearing frequency, refer to the calculation program “bearing frequency”.

(3) Accuracy of related components: in the case of close matching between the bearing ring and the bearing seat or the drive shaft, the bearing ring may be deformed by matching with the shape of adjacent components. If deformation occurs, vibration may occur during operation.

(4) Pollutants: if it runs in a polluted environment, impurities may enter the bearing and be rolled by the rolling body. The amount of vibration generated depends on the number, size and composition of the crushed impurity particles. Although it does not produce a typical frequency pattern, a disturbing noise can be heard.

Rolling bearings produce noise for more complex reasons, one is the bearing inner and outer ring mating surface wear. As a result of this wear, the bearing and the shell, the bearing and the shaft of the relationship, resulting in axis deviation from the correct position, in the shaft at high speed when the movement of abnormal sound. When the bearing fatigue, its surface metal spalling, will also increase the radial clearance of the bearing to produce abnormal sound. In addition, insufficient bearing lubrication, the formation of dry friction, and bearing crushing will produce abnormal sound. Bearing wear loose, cage loose damage, will also produce abnormal sound.

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