Concept for Measuring Aeroacoustic Noise Transmission in Trains Derived from Experience Gained in Aircraft Testing

In high-speed trains aeroacoustic source excitation is one of the most important sources. While the exterior aeroacoustic noise can be measured in wind tunnels the transmission from aeroacoustic noise sources into the passenger cabin is a difficult task. The concept for measuring aeroacoustic noise transmission will show how to determine the source, the response of the body shell and the noise radiation into the cabin of an aircraft. It has already been used on a DLR flight-test campaign [1] and can be applied to high-speed trains, as well.

The aeroacoustic sources were obtained with a two-dimensional array of pressure transducers which allows distinguishing between aeroacoustic and hydrodynamic sources underneath the turbulent boundary layer (TBL). The excitation and transmission of vibro-acoustic energy were measured with accelerometers on the fuselage, the cabin and the aircraft structure while the sound reception inside the cabin was measured with microphones and an artificial head. The data from simultaneous measurements were used to analyse the transfer of the acoustic energy on the basis of correlation methods and to validate empirical and numerical source and transfer models. The measurement concept and results from the flight test will be presented, whereupon the potential for applying this concept to high-speed train measurements will be discussed.