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Exterior Noise Measurements on a Rover 220 GSi

The acceptable exterior noise level from passenger cars is constantly decreasing through national and international regulations. Most recently, the acceptable level within the European Union has been lowered to 74 dB(A). To fulfill these demands, still more advanced measuring techniques have to be used in the development process and for troubleshooting. In this example, traditional measuring techniques suggested that the main noise source was the exhaust orifice. Detailed analysis of the sound field using Spatial Transformation of Sound Fields showed that the engine air intake system was dominant. As a result the overall sound pressure level was reduced by minor adjustments to the intake system as opposed to major modifications to the exhaust system.