Method for the analysis of sound sources in rotating systems

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Rotating machinery parts are often significant causes of noise. Accordingly, many efforts to control noise focus on noise control measures on these parts. The experimental analysis of sound generation in rotating systems often falls back to an analysis in the non-rotating system. For example, instead of a whole fan just one blade of a fan is analyzed in a wind tunnel. The conclusions from such examination cannot always be transfered to the conditions that can be found in rotating system. In some cases (for example an electric motor) such procedure is inherently impossible. Thus, the project aims at a considerable contribution to the analysis and the improved understanding of the sound generation in rotating systems. This should be accomplished by developing a new experimental method allowing detailed and reliable measurements of location, kind and strength of sound generation at rotors. Basis of the method is a measurement using a fixed, non-rotating microphone array. Using appropriate signal processing, the array is virtually rotated with the source and using various sound source and sound propagation models the properties of the rotating sound sources are estimated by a calculation method. Essential to the project is the examination of which models and methods yield reliable results. To this end various models and methods are implemented and analyzed using a Monte-Carlo-approach and various sets of synthesized test data sets. Additionally, the practical application is tested using two laboratory experiments. The importance of the project aims results from the possibility to test hypotheses, model predictions or numerical calculations of sound generation in rotating systems with much greater detail as it is possible today. This enables more focus noise control measures at the source.