Time-Domain Source Contribution Analysis Method for In-Room Pass-By Noise 2011-01-1609

This paper presents a new time-domain source contribution analysis method for in-room pass-by noise. The core of the method is a frequency-domain ASQ model (Airborne Source Quantification) representing each noise generating component (engine, exhaust, left and right tyres, etc.) by a number of acoustic sources. The ASQ model requires the measurement of local FRF's and acoustic noise transfer functions to identify the operational loads from nearby pressure indicator responses and propagate the loads to the various target microphones on the sides of the vehicle. Once a good ASQ model is obtained, FIR filters are constructed, allowing a time-domain synthesis of the various source contributions to each target microphone. The synthesized target response signals are finally recombined into a pass-by sound by taking into account the speed profile of the vehicle. This allows several useful analyses such as: i) analysis and ranking of the source contributions during a pass-by, ii) comparison of the summed path contributions with the measurement data, iii) in-depth time and frequency analyses, iv) auralization and sound quality evaluations. A large in-room test campaign was carried out to validate the proposed method. The tests were performed on a passenger car in a chassis dyno semianechoic room. Several operational tests were conducted including run-up, coast-down and constant speed experiments in different throttles and gears, tests on smooth and tarmac road profiles, measurements with the powertrain switched off and tests according to the ISO 362 standard (2007). A reduced ASQ model was utilized shortening the total measurement time. The test results were very satisfying, exposing physically realistic source contributions and a sound quality accurate synthesis up to 8 kHz.