Approach Combined Numerical and Experimental Analysis for Motorcycle Engine Radiation Noise

In recent motorcycles, radiation noise from engine surface dominates high percentage since enough measures have been taken for other noise sources such as intake, exhaust and drive train noise. Since most motorcycle engines consist with transmissions, the radiation noise is caused not only from combustion pressure but also from the gear meshing. Therefore radiation noise accounts for higher frequency than the other noise sources like intake and exhaust. At present, in order to reduce the radiation noise, we have to take countermeasures on actual engines since CAE is difficult to apply because of the characteristic of many high frequency components. In this study, technical build-up was made to enable the estimation of the engine radiation noise. Build-up was made of the modeling know-how of FE models capable of analyzing high frequency. We determined excitation force to the bearing housings in consideration of combustion force and gear meshing force based on the experimental data. Thus, we achieved noise prediction accuracy up to 3 kHz.