Thesis

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Power-based analysis of airborne sound transmission

Authors Mittmannsgruber, R.
Year 2017
Thesis Type Master's thesis
Topic Audio Signal Processing
Abstract Sound emission of combustion engines and interior sound transmission are essential parts of vehicle development. As sound transmission can be divided into airborne and structure-borne parts, only airborne sound transmission is examined in this study. The main objective is the quantitive estimation of air pressure at the drivers position based on sound power of the engine and interior transfer functions. To achieve this, it is necessary to measure the sound power of an encased engine and to determine the transfer functions to the passenger compartment. The sound power of an engine is usually measured on an engine test bed. The measurement of the engine in the engine bay can reduce the overall effort, but it is restricted to near field measurement. The described measuring situation is examined by using an engine model. In a first step the near field computation and the far field computation of the sound power is compared. Furthermore the influence of an enclosure around the engine on the sound power computation is analysed. The necessary resolution of the measuring grid and the influence of certain reductions of the measuring grid on the computation of sound power is tested. A parameter study verifies the resulting data of the measuring system and it's properties. Based on the determined sound power the application of Statistical-Energy-Analysis (SEA) and Non-negativ-Matrix-Factorization (NMF) leads to the identification of the sound transmission to the passenger compartment and subsequently to the estimated sound pressure.
Supervisors Höldrich, R., Pomberger, H.