Commercial vehicle NVH attributes primarily focus on interior noise for driver's comfort and exterior noise for environmental legislation. Major sources for both the interior and exterior noise are power train unit, exhaust and air intake system. This paper focuses on development of Air Intake System (AIS) for better interior and exterior NVH performance for medium and heavy commercial vehicles. For air intake system, structural radiations from its panels and nozzle noise are significant contributors on overall vehicle NVH.
Noise generation mechanism in air intake system occurs due to opening and closing of the valves and inlet air column oscillation by sharp pressure pulse from cylinder. Based on benchmarking, vehicle level targets have been arrived, and then cascaded to system and sub-system level targets. For air intake system, targets for nozzle noise at wide open throttle condition have been set for exterior NVH performance. These targets are further cascaded down to transmission loss (TL), snorkel breathing mode, isolation & dynamic stiffness attributed for improvement in interior/exterior noise and sound quality. The cascaded targets have been achieved by various design iterations through Test-Computer Aided Engineering (CAE) development approach.
Acoustic pressure pulsation measurements have been carried out to obtain acoustic load input for CAE analysis.