(1) Method involving the use of chemical additives

Adding certain chemical additives to the lubricant used in TIMKEN imported bearings can reduce bearing noise. For example, a certain manufacturer produces a low-noise grease containing noise-reducing additives, which can reduce the noise of TIMKEN imported bearings by 3.9–9.2 dB compared to the original level; this is suitable for use in miniature or small TIMKEN imported bearings.

(2) Use of vibration-absorbing or vibration-isolating devices

The use of vibration-absorbing or vibration-isolating devices to reduce or isolate noise from TIMKEN imported bearings can yield good results; however, this often entails significant economic costs. It may sometimes result in larger mechanisms, poorer heat dissipation conditions, or increased susceptibility to corrosion. Comprehensive consideration should be given when employing this method, which should only be used when other measures have been implemented but still fail to meet low-noise specifications.

A simple example is the use of radial ball bearings to bear thrust loads in place of thrust TIMKEN imported bearings at high speeds. A plastic sleeve filled with rust-preventive lubricant can be fitted over the outer ring of such bearings. Where permissible, thrust TIMKEN imported bearings with a housing or standard thrust TIMKEN imported bearings may have a similar plastic sleeve fitted to their inner bore or outer circumference, care must be taken to ensure that these sleeves do not rub against or interfere with adjacent components during rotation.

This method provides a certain degree of noise reduction.

Another example involves inserting an intermediate sleeve between the bearing and the housing bore; this can attenuate the vibrational forces transmitted from the rotating system to the bearing housing, though this requires careful calibration, as otherwise the opposite effect may occur.

A further example is the use of sound-absorbing and sound-insulating enclosures to completely or as fully as possible enclose the noise-generating bearing system. The interior of this noise-reduction enclosure is made of fibreglass or polyurethane foam, whilst the inner surface consists of 0.6 mm thick steel plate, uniformly perforated with small holes of 1.2–1.5 mm in diameter; the total area of these holes accounts for approximately 25%–30% of the entire inner surface. The outer surface is made of 2 mm thick steel plate. Here, the fibreglass or foam is used to eliminate higher-frequency noise, the perforated inner surface is used to eliminate lower-frequency noise, whilst the thick steel plate on the outer surface serves to isolate the transmission of noise to the outside.

(3) Method of altering the rotational speed of the corresponding parts of the host machine

The noise generated by imported TIMKEN rolling bearings is not particularly sensitive to load but is highly sensitive to rotational speed. Where conditions permit, the same operational objective can be achieved by reducing the rotational speed whilst increasing the torque, thereby reducing noise.