A study of exhaust noise in a motor vehicle using statistical energy analysis

This work uses statistical energy analysis (SEA) to study noise transmissio n through a commercial motor vehicle and in order to do this various sound and vibration power inputs associated with flanking transmission via the ex haust and engine noise are calculated. A modern commercial motor vehicle th at has an exhaust noise sensitivity problem is studied in this work. The ai m of this work is to demonstrate the application of SEA and to study the ef fects on noise transmission when the exhaust is incorrectly fitted (misalig ned). Airborne and structural paths for sound and vibration transmission to a veh icle saloon are considered. Also, the SEA framework is used to identify the relative importance of each structural and airborne power input in relatio n to the sound power that is transmitted to the vehicle saloon. It is shown that the importance of each sound power input varies with frequency. At lo w frequencies. sound transmission through the vehicle structure is most imp ortant. At high frequencies, airborne flanking noise transmission to the fl oor is important. In this case, exhaust vibration transmission is most impo rtant at frequencies between 250 Hz and 1 kHz when the engine is running at 5700 r/min, and the SEA model predicts the change in performance associate d with exhaust misalignment.