The vibration of the ball bearing is caused by the contact excitation of the contact pair, so factors that affect the contact characteristics of the contact pair, such as load, speed and lubrication, will affect the vibration characteristics of the bearing.
The noise of the ball bearing is the result of the transmission of bearing vibration in the air by the human auditory system. The sound pressure level of vibration and noise of some domestic low-noise deep groove ball bearings is comparable to that of foreign low-noise bearings, but the sound pressure level of foreign bearing samples is uniform and the consistency is good, while the domestic bearing samples have large dispersion and poor consistency; Foreign samples have a low proportion of abnormal sound.
The abnormal sound of ball bearings is a new problem and an old one. It is a new problem because it is a problem exposed in the process of bearing quality from low vibration value to quiet development in recent years, and the continuous improvement of bearing quality. It is an old problem because there is no higher requirement for the sound quality of the bearing in the early stage of the pursuit of low vibration, but the abnormal sound of the bearing exists objectively. Once the vibration value of the bearing is stably reduced to a certain level, the abnormal sound The sound came out.
The early bearing vibration measuring instrument in our country can only detect the effective value of vibration as a parameter. Among the qualified products, users still think that some bearings have abnormal noise. This is because there is no close correlation between the measured vibration RMS and abnormal sound. The effective value of bearing vibration is the average level of vibration, and it cannot effectively judge whether there is abnormal sound in the bearing, but the peak limit specified in the technical requirements for the peak vibration acceleration level can effectively classify the vibration (noise) level of the bearing. The abnormal sound test of the bearing can play a certain normative role, so it has good rationality and practicability.
For the vast majority of bearings with low noise, large vibration value and abnormal sound, their vibration peaks are arranged in order from low to high: low-noise bearings, bearings with abnormal noise, and bearings with large vibration values. . This shows that the peak vibration acceleration level of the bearing with abnormal sound is between the low noise and the bearing with large vibration value. Therefore, the misjudgment rate of using the effective value of vibration to evaluate the abnormal sound of the bearing is relatively high.
There are currently two ways to detect abnormal sounds. One is an acoustic-based noise detection method, and the other is a vibration-based detection method. The noise detection method is to use a high-quality microphone to extract the bearing sound pressure signal at a certain distance and direction in an anechoic environment where the basic noise is less than 20db, and extract the abnormal sound components through a certain analysis method, which is the direct result of the abnormal sound. Measurement methods.
Vibration detection method is an indirect detection method of abnormal sound, which can be divided into qualitative detection method and quantitative parameter detection method. Among them, qualitative detection method is divided into monitoring abnormal sound method and observing vibration waveform method. The quantitative parameter detection method refers to the use of the measured parameter values ​​related to the abnormal sound in the vibration signal of the measured bearing, such as the peak value of the vibration and the crest factor to evaluate the abnormal sound of the bearing. 
There are many measuring instruments for measuring abnormal sound of bearings. Bearing measuring instruments can measure the effective value of bearing vibration, and can also measure the peak value, peak factor and pulse balance of bearing abnormal sound parameters.