Imaging of automotive engine components noise from non-synchronous sequential measurements

The quantification of automotive engine components noise is significant for high-efficiency engine system development, which meets great challenges for engine bay on-site measurement. A major challenge is that the sizes of engine components are small which radiate high frequency noise (beyond 5000Hz); the classic Near-field acoustical holography (NAH) has great difficulties to work at this scenario. For the sake of improving the spatial resolution of imaging, sequential measurements are investigated, which is a solution to achieve large array and/or high microphone density by moving sequentially a small prototype array to scan the object of interest. In comparison to a large array and/or high microphone density array that can acquire simultaneously all the information of the spectral matrix, non-synchronous sequential measurements can only acquire a block diagonal spectral matrix, while the cross-spectra between the sequential measurements remain unknown due to the missing phase relationships between consecutive positions; a propagation based Fast Iterative Shrinkage Thresholding Algorithm (FISTA) is proposed in this paper to achieve the non-synchronous sequential measurements, and the proposed approach is applied for the purpose of engine components noise quantification in engine bay on-site measurement, which is validated with specimen of industry in laboratory.