Experimental contribution analysis of external noise components to interior noise of an automobileExperimental contribution analysis of external noise components to interior noise of an automobile

The contribution analysis of various automobile noise sources to the interior noise is important, enabling to design an automobile with a low interior noise level. However, it is difficult to experimentally analyze the contribution of physically meaningful noise sources to the interior noise using the state-of-the-art contribution analysis method, for example, based on the transmissibility matrix method and the singular value decomposition (SVD), since the source strengths decomposed by using the SVD procedure are difficult to be associated with physical sources. Here, it is proposed to decompose an interior noise auto-spectrum into multiple auto-spectra, each represents the contribution of a physically meaningful noise source to the interior noise, by using the LDL decomposition. Through an experiment with the three speakers driven by three independent, filtered random noise signals, it was shown that the measured noise spectrum could be successfully decomposed into three contributions, each associated with noise radiated from only one speaker. Then, an automobile instrumented with 64 exterior and 4 interior microphones was tested on a highway at the speeds of 65 miles per hour (mph) and 80 mph. The contribution results obtained by processing the measured microphone signals indicated the highest contributions of the aeroacoustic sources on the windows and the hood to the interior noise.