Prediction and assessment of re-radiated sound

Currently various methods are applied for predicting, measuring and assessing re-radiated sound linked to structural vibrations. They range from simple engineering approaches to the application of numerical methods with high detailing. The level of uncertainties in the prediction of the emissions depends on the characteristics of the excitation and on the transmission from the sources to the sound field inside of structures. Apart from the delimitation of the excitation and transmission, the quality of prediction depends on the required resolution with respect to frequency and space. The limitations of typical predictions are discussed. At existing sources, e.g. railway-lines, the excitation is usually described at the basis of measurements. For new sources and structures the prediction of structural vibrations in a first step typically starts with rough assessments. With increasing knowledge about the structural characteristics - obtained during the planning and construction process - The prediction can be delimited with higher precision. Measurements and predictions of re-radiated sound have to cope with the spectral characteristics of the signals and the resulting spatial distribution. Due to superposed direct sound, techniques are applied to measure re-radiated sound indirectly via vibrations. For the assessment differing guidelines in Germany, Austria, and Switzerland exist. The paper refers to work, carried out for the design of the guideline VDI 2038 [1].