Separation of Engine and Tyre Noise using Operational Measurement Only

Increased focus on exterior noise from vehicles creates a demand for faster and better tools to understand the underlying noise sources in order to reduce noise levels. Since noise sources act simultaneously and overlap in frequency content during vehicle operation the problem of isolating sources and finding their noise contribution becomes a challenging task. Typical analysis techniques take their beginning in transfer path modelling requiring source models for noise components and airborne transfer functions between source points and microphones in the near-field. Additional far-field microphones are needed for noise evaluation. The methodology requires both an operational measurement for which the analysis is done and also a whole series of speaker measurements with a controlled sound source. In this paper, a pure operational method for separating the noise contributions from tyres and engine component will be discussed. Blind separation is introduced to solve the problem of unmixing the data measured by the nearfield microphones to have clean reference signals representing each noise source. A controlled setup using a vehicle on an indoor chassis dynamometer together with an engine noise simulator is used to demonstrate the source separation performance and the accuracy of the contribution analysis.