Bearing Noise Research Articles

Varying compliance vibrations of rolling bearings

The most fundamental cause of noise and unsteady running of rolling bearings is the so-called varying compliance vibrations. These are parametrically excited vibrations that occur irrespective of the quality and accuracy of the bearing. Varying compliance of the bearing assembly can give rise to both radial and axial displacements of a shaft supported by rolling bearings. In this study, however, attention is focused on radial vibrations of radially loaded bearings having a positive radial clearance. Previous studies of this phenomena are quasi-static in approach—the inclusion of inertia forces reveals characteristics not previously recognized. Examples of theoretical solutions obtained through digital simulation are presented and comparisons with experimentally obtained results are made.

ころがり軸受の騒音とその対策(<小特集>騒音)

ころがり軸受の騒音とその対策(<小特集>騒音)

The Effect of a Biphase Lubricant on Induction Motor Bearing Noise and Stability

A specially constructed single-phase induction motor was used to study the effect of a biphase (liquid-solid) lubricant on the stability of and noise from its bearings. It is shown that the stability of a full-film bearing was improved when a biphase lubricant was used. The biphase lubricant was an SAE 20 oil with from 5% to 20% (by volume) to l-μ fluorinated ethylene propylene (FEP) particles in suspension. A small reduction in bearing noise was observed. This was associated with the corresponding stabilizing effect of the FEP-loaded lubricant.

Establishment of Objective Criteria Reflecting Subjective Response to Roller Bearing Noise

In recent years, the question of noise generated by rolling element bearings has been given considerable attention. That a certain irreducible “minimum” noise will be created by a properly functioning bearing has been pointed out in earlier work. Acceptable roller-bearing noise levels above this minimum are regarded, in this paper, as being of necessity set by subjective standards. The paper addresses itself first to the validity or consistency of certain subjective evaluations of bearing noise made by a group of observers in representative circumstances. Next, the question is examined of what quantitative objective measurements are to be made in order accurately to reflect the character of the subjective evaluations. Finally, correlations between objective and subjective data are shown to be good. A representative method is thus defined for providing objective criteria that reflect subjective appraisal in this type of problem.

A Method of Axial Testing for Roller Bearing Noise Qualities

A number of investigators have studied the vibration of rolling element bearings by taking samples of bearing race vibratory velocity, acceleration, or displacement at one point on the race the bearing being run in a somewhat isolated enviroment. While such methods have lead to considerable progress in the evaluation and amelioration of bearing-generated noise, there has been a constant trend toward improvement of the methods. One promising step in this process is reported here. The present paper discusses the replacement of accelerometer radial testing by accelerometer axial testing, the new connecting link between bearing and accelerometer being a metallic exponential horn. The horn technique avoids problems of accelerometer strain sensitivity and dependence of results upon accelerometer angular orientation with respect to specific bearing anomalies.

Noise of Ball Bearing in Electric Motor

There are many performances of electric motors equipped with rolling bearings, and one of the most important performances is running noise. Especially, for a small three phase a-c induction motor, quiet running is demanded. However, the component noises in the motor noise are not well known and the influences of ball bearing on the motor noise are not made clear. Therefore, to abate the motor noise, we must study it. So, in the first place, the noise of a small three phase a-c induction motor was divided into several component noises, and ones influenced by ball bearings were found out ; next, the influences of ball bearings were examined, lastly the causes of the influences were made clear in the present paper. As a result of the above studies, we could establish the most suitable treatment of ball bearings theoretically, and further obtain new knowledges on fitted ball bearing noise.

Noise of Ball Bearing : 2nd Report, Case of Fitted Ball Bearing

Noise of ball bearing can be divided into two cases ; one is the case of a simple ball bearing, the other is the case of a fitted one. The noise of the latter case has not been researched systematically. The author measured the noise of three kinds of the fitted ball bearings, analyzed the peak frequency in the frequency spectrums, and obtained the results as follows : (1) The noise of a fitted ball bearing has the frequencies above 1 kc/sec. The frequencies of the noise do not change at many shaft speeds, but the sound pressure level increases with the shaft speed. (2) The principal noises of a fitted ball bearing are due to the vibrations on the race rings, and the other noises are due to the vibrations on the cage. (3) The fitted ball bearing noise and the simple one are identical in essence.

Noise of Ball Bearing : 4th Report, Clearance and Fitting Effects on Fitted Ball Bearing Noise

It is considered by experiences that a noise of fitted ball bearing is affected by many factors, especially the radial clearance and the race fitting. The author measured the noise of fitted ball bearing with known radial clearance and at several race fitting conditions under the radial load, analyzed the peak values of the frequency spectrums, and obtained the results as follows : -(1) the frequencies and the total sound pressure level of the noise decrease with the radial clearance. (2) The total sound pressure level of the noise is determined by the summation of some radial contact forces between the races and the balls and the size of the loaded zone. (3) The frequencies of the noise increase with the interference of the outer ring. But, the total sound pressure level increases with the interference of the outer ring in the case of small radial clearance, while it decreases in the case of large radial clearance.

Noise of Ball Bearing : 2nd Report, Clearance Effect on Simple Ball Bearing Noise

It is well known by experience that a noise of simple ball bearing is affected by the clearance. However, there has been no research work which described clearance effect on simple ball bearing noise and its causes. The author measured the noise of simple ball bearing with known radial clearance, analyzed about the peak values of the frequency spectrums, and obtained the results as follows : - (1) The noise of a simple ball bearing is affected by the amount of radial clearance, loading direction and the amount of load etc. (2) The frequencies and the total sound pressure level of the noise are increased by decreasing radial clearance. (3) Principal frequencies of the noise correspond to the bending natural frequencies of the outer ring with load. (4) The total sound pressure level of the noise is determined by the sound pressure level of a peak in the case of axial load, but the sound pressure levels of all peaks in the case of radial load.

Ball Bearing Noise and Vibration

Bearing noise was investigated in the case of a fractional horsepower motor using microphone, analyzer and noise meter. The resulting noise spectrum showed prominent notes which could all be attributed to the motor. The bearing noise was found to be essentially unpitched. A different type of analysis was used which made possible a correlation of the noise with the bearing vibration. The problem revolves itself into unpitched vibration transmitted through the machine and radiated as noise. The characteristics are determined mainly by the machine size and rigidity although the source of ball bearing noise is the vibration of the bearing and can be reduced by making the bearings smoother running or isolating the vibration.