More than just silence - acoustic product optimization

The customer requirements for a modern driver's workplace in agricultural machinery are not only defined by compulsory limit values. Comfort is in demand! In this context, the Krone Company aims for the acoustic optimization of the cabin of their new self-propelled high-performance mower/conditioner BIG M II in cooperation with external research and development partners (IBAF, LMF). Starting point for the approach of optimization is the analysis of the existing system. With combined measurements of sound pressure, sound intensity and accelerations, an acoustic picture of the cabin can be obtained and interpreted with regard to the frequencies and amplitudes emitted by each component or assembly group. The dominating frequencies can be associated with particular sound sources and can be reduced or, if possible, eliminated by appropriate - mostly constructive - modifications. In current research activities at Ruhr-University Bochum a vibro-acoustic simulation technology is being developed which, in future, can already be applied during the development process of machines. The general procedure is shown for a cabin's floor assembly group. The determined excitations (multi-body simulation, measurements) are combined with the results of a modal analysis to make up a transient analysis. The structural FEM-model is transferred to a vibratory system with quantifiable frequencies and amplitudes. Extending the model by the acoustic environment finally allows e.g. the calculation of the spectrum of sound pressure acting on the driver's ear.