In the past years auto makers have spent high efforts to get improvement for interior quietness of the vehicles. Excluding Squeak&Rattle issues, vehicle interior quietness is likely to be a perception of combination of primarily noise sources composed by wind, road and engine noise. From these, Power train NVH that includes engine noise and his auxiliaries system (Transmission, AIS, Exhaust, Alternator, ect…) is one of the most relevant system to address interior quietness perception. However, recent trends show that power train NVH improvement is more than quiet engines; in fact, it requires refinement, which brings sound quality on the spot.
This paper presents a practical reading of Masking Perception Analysis Software (MPAS) [1], a methodology and toolset developed to address this need. The tools were developed by NVH Ford North America (FNA), and it has been introduced in Ford Brazil. The method consists on determine acceptable tones level from the components and systems which produce narrow band noise, such as power steering moan noise, transmission gears whine, engine chains and oil pump whine, alternator high pitch noise, and others that may produce significant annoying tones under vehicle driving conditions.