Partial filling of a honeycomb structure by granular materials for vibration and noise reduction

In this paper, the damping effect of granular materials is explored to reduce the vibration and noise of mechanical structures. To this end, a honeycomb structure with high stiffness is used to contain a granular filling which presents the possiblity for the distribution of the granular material to be designed. As a particular application example, the oil pan bottom of a combustion engine is used to investigate the influence on the vibration behavior and the sound emission. The effect of the honeycomb structure along with the granular mass, distribution, and type on the vibration behaviour of the structure is investigated via laser scanning vibrometry. From this, an optimized filling is determined and then its noise suppression level validated on an engine test bench through measurements with an acoustic array.