A low noise/vibration rating is achieved by paying particular attention to the surface finish of the raceways and balls, the roundness of the rings and balls and correct cage design.
To help reduce noise levels even further, low noise greases are available and the choice is now greater as improved manufacturing techniques mean these greases are more finely filtered and contain fewer, smaller solid particles. These particles generate noise when they pass between the balls and raceway.
External factors such as surrounding vibration can affect bearing noise. Another problem, particularly with smaller and thin-section bearings, is ring distortion caused by poor shaft or housing roundness. Dirt or dust contamination will also increase noise and vibration levels. Poor fitting practice or incorrect handling is sometimes to blame, causing shock loads which, in turn, create scratches or dents in the raceway.