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This work presents an application of airborne source path contribution analysis with emphasis on prediction of wideband sounds inside a cabin from measurements made around a stand-alone engine. The heart of the method is a time domain source path receiver technique wherein the engine surface is modeled as a number of source points. Nearfield microphone measurements and transfer functions are used to quantify the source strengths at these points. This acoustic engine model is then used in combination with source-to-receiver transfer functions to calculate sound levels at other positions, such as at the driver's ear position. When combining all the data, the in-cabin engine sound can be synthesized even before the engine is physically installed into the vehicle. The method has been validated using a powertrain structure artificially excited by several shakers playing band-limited noise so as to produce a complicated vibration pattern on the surface.

An application involving noise source reconstruction on a full automotive powerplant including the engine, manifolds and the transmission is considered herein, to demonstrate the versatility of modern generalized acoustical holography. The complex source geometry necessitates measurements on non-conforming surfaces. The acoustic pressures were experimentally acquired at three different engine excitations. Accelerometers were mounted at select locations on the powerplant in order to study the accuracy of the reconstructed vibrations from acoustical holography. Through a series of synthetically generated holograms with added random noise, it is conclusively demonstrated that the error margins in the reconstructed vibrations on the powerplant are consistent with errors in reconstructed vibrations from numerically synthesized holograms of a similar Signal to Noise Ratio (SNR).