Noise of a bicycle planetary gear system

Planetary gear systems are very compact and efficiently transmit large amounts of power. Their advantages have resulted in the recent use of such systems on bicycles. However, since planetary gear systems are also complicated mechanisms with many elements, noise and vibration have been found to hamper their use. Therefore, it is desired that noise from bicycle planetary gear systems be reduced. Experiments to measure noise produced by a planetary gear system installed on a bicycle are undertaken. It is revealed that noise levels increase as gear mesh frequency increases and that the main frequency component of the sound is the natural frequency of the casing surrounding the planetary gear system. Recommendations for reducing noise are to reduce the number of gear teeth and improve the casing of the system.