Abstract
Within a research project at the Fraunhofer Institute for Machine Tools and Forming Technology IWU, vibration description methods were applied using the example of an air conditioning (AC) unit from a railway vehicle. The AC unit consists of several components, where usually the compressors and fans contribute most to the radiated sound power resp. to the transmitted structure-borne sound into the vehicle. In a first step, forces and accelerations under steady state conditions have been measured on each of the six mounting points of the air conditioning unit. Afterwards, all of the dominant vibration sources of the unit were individually investigated concerning their contributions relating to the overall level at the mounting points. Finally, knowing the impedances of the mounting points between sources and unit enables detailed analysis of the system itself. Moreover, it also indicates "weak points" which have to be avoided according to an improved vibrational behavior of the complete air conditioning unit.