Simulation Best Practices in Vibro-Acoustics to improve NVH performance

Historically and up to some extent currently, product validation focusing on NVH heavily relies on physical testing in the later stages PDLC (Product Design Life Cycle) which extends the entire PDLC. NVH related changes are often radical and beget large scale redesign, Due to this, many-a-times design changes become expensive and time-consuming or simply not feasible. It is important to perform NVH investigation during the earlier stages of product validation cycle to minimize the redesign time and keep the PDLC efficient and economical. Industries like Automotive, Aero & Defense, High Tech, Industrial products generate differentiator based on NVH validation to win over customer perception battle. The automotive industry in particular cares a lot about customer comfort and well-being in terms of NVH. Whether it is related to passenger comfort, ride and handling, driver fatigue, structural worthiness, reliability & fatigue life requirements; they spare no validation. One interesting aspect is creating desired sound or design sound to alert driver, passenger & pedestrian while adhering to noise regulations. In electric vehicles, passengers are more sensitive about NVH performance. In a typical ICE vehicle, an internal combustion engine vibration and noise dominates over the other sources of noise. In electric vehicles, noise from transmission, electric motor, active sounds to alert driver/passenger/pedestrian, doors, normal squeaks, and rattle of vehicle structure, braking, cooling fans, road noise, wind, doors become more important for NVH performance. NVH design and simulation engineers oftentimes start right away with highly complex and computationally expensive simulations. It is important to realize. that the basic and inherent dynamic characteristics of a simulation model must be well correlated before one embarks on complex and highly expensive numerical simulations. The important variables of simulation models like overall mass, stiffness and damping matrices must be well correlated with physical testing using parameters like modal assurance criteria (MAC), coordinate modal assurance criteria (CoMAC), frequency response assurance criteria (FRAC) before running highly complex analysis. In this paper, a discussion will be done on what basic dynamic characteristics can be studied in early stages of the design that can facilitate easy correlation with physical test and lead to successful correlation of full detail NVH simulations in later stages. This also ensures a robust design to start with and hence leads to a very efficient and economical PDLC.