（1） raceways sound.
   
Raceway sound NTN Bearing rotation when the rolling element rolling in the raceway and inspire a smooth and continuous noise, to draw attention only when its sound pressure level or tone greatly when. In fact, the raceway sound inspired by the sound energy is limited, as in normal circumstances, the quality of the bearing raceway sound is 25 ~ 27dB.
 
This noise to withstand the radial load single row deep groove ball bearings of the most typical, it has the following characteristics: a noise, vibration is random; b vibration frequency at 1kHz or more; c.
 
Regardless of how changes in speed, the noise frequency almost the same sound pressure level with the speed increased with the increase; d when the radial clearance increases, the sound pressure level of a sharp increase; (e) NTN bearing rigidity increases, the lower the total sound pressure level, even if the speed l high, the total sound pressure level is also small extra cost; f lubricant viscosity, the higher the lower the sound pressure level, but for grease lubrication, viscosity, soap fiber shape and size can affect the noise value.
   
The raceway sound source is the subject of the inherent vibration of the ring after the load. Due to the elasticity of the ring and rolling element contacts constitute a nonlinear vibration system. Lubrication or processing accuracy is not high will be excited about this flexibility characteristics inherent vibration, transfer into the noise into the air. Well known that even the highest levels of contemporary manufacturing technology processing bearing parts, the work surface there will always be varying degrees of small geometric errors, so that tiny fluctuations in the raceway and the rolling body to stimulate the natural vibration of the vibration system. Although it is inevitable, however, can be taken to the surface of high-precision machining parts, the correct selection of NTN bearings and precision NTN bearings so NVH.
   
(2)Rolling sound of the falling body
   
The noise under normal circumstances, mostly at low speeds and withstand large radial load bearing. Of NTN bearings operating under radial load, the load area with non-load bearing area, bearing has a certain radial clearance, non-load the rolling body and the inner raceway contact, but the centrifugal force may For this reason, at low speeds, when centrifugal force is less than when the weight of the rolling body, scroll through the experience of falling and inner raceway or cage collision and stimulate the inherent vibration and noise of the NTN Bearing outer contact, and has the following characteristics: a. easy to produce grease lubrication, oil lubrication is not easy to produce.
 
Easier to generate when using poor quality grease. b winter often occur. only radial load, radial clearance larger easy to produce. d will produce a specific range of the speed range of different size bearings are also different. e may be continuous sound may be intermittent sound. f. the forced vibration is often to stimulate the outer ring of the second, third bending natural vibration and thus the issue of the noise. Through the use of pre-loading method can effectively reduce the noise, reduce the installed capacity of NTN Bearing radial clearance in selection of a good lubricant also has improved, some foreign companies with a light rolling element such as a ceramic roller or hollow roller technology measures to prevent the generation of this noise.
   
(3) the tip of song
   
It is quite intense screams of sliding friction between the metal bearing temperature is not high, without much impact on bearing life and grease life, does not affect the rotation, but not sweet sound disturbing, especially large radial load short cylindrical roller bearings often this noise, which is characterized by: (a) bearing radial gap large, easy to produce. b usually appears in the grease lubrication, oil lubrication is more rare. as NTN Bearing size increases and decreases, often with a certain speed range. d. winter often. e. its appearance is irregular, and unpredictable, and fill in the amount of fat and performance, installation and operation conditions. This noise can be used to reduce the NTN Bearing radial clearance and shallow outer ring raceway structure to prevent.




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