Abstract
Improved levels of powertrain refinement in vehicles have led to an increased occurrence of ancillary noise vibration and harshness (NVH) quality problems and issues. These problems arise from alternators, power-assisted steering, air conditioning, and hydraulic pumps, for example. To address them, the Motor Industry Research Association (MIRA) has developed a hybrid rig and synchronous sampling system, which has been applied successfully to the NVH development of ancillary systems and their in-vehicle installation. The system provides a controlled repeatable in-vehicle environment for ancillary testing, with precise-angle domain analysis. It enables accurate, incisive indices to be developed for the objective noise parameters that correlate with subjective ratings for ancillary noise. By providing such accurate measurement of noise quality, this practical experimental technique can be used to identify the key paths and sources directly influencing noise quality parameters, thus ensuring an optimised solution. MIRA's electrically driven unit can drive ancillary systems under load in the vehicle, independent of the engine. The paper includes charts of typical frequency responses, harmonics, and noise variations in vehicle engines. For the covering abstract see ITRD E107095.
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