A: 

If the bearing is in a good state of continuous rotation, it will emit a low whining or buzzing sound. If there is a sharp hiss, squeak and other irregular sounds, it often indicates that the bearing is in a poor continuous rotation condition. The sharp squeaking noise may be caused by improper lubrication. Inappropriate bearing clearance can also cause metallic noise.

The dents on the bearing outer ring track will cause vibration and cause a smooth and crisp sound.

If there is intermittent noise, it means that the rolling parts may be damaged. This sound occurs when the damaged surface is rolled over, and if there are contaminants in the bearing, it will often cause a hissing sound. Severe bearing damage will produce irregular and loud noises.

If it is caused by knocking scars during installation, noise will also be generated, and this noise will vary with the speed of the bearing.