Sound Simulation and NVH Tuning of a Multi-Mode Engine

This paper describes the use of an interactive NVH simulator in simulating and designing the sound character of a vehicle with a multi-mode engine and active exhaust valve. When designing a vehicle for sound quality, it is not sufficient to merely record some discreet operating conditions and modify these in a traditional sound quality program. The ability to simulate the sound quality of the vehicle over the full operating envelope is a necessity. Additionally, the ability to break down the sound contributions from intake, exhaust and other key contributors to the driver's ear, and manipulate these independently is also essential. In the case described here, an additional factor makes it mandatory that an accurate vehicle sound simulation is performed. The state of the engine and exhaust contribution, and thus the sound of the vehicle, change based on several parameters - vehicle speed, load demand and gear. Not only is it important to ensure that the sound of the vehicle has the desired character over the full operating envelope of each powertrain state, it is also important to ensure that the transition points between states are appropriate and designed to produce optimum sound quality. This paper demonstrates the process and results of designing a multi-mode powertrain for sound quality using an NVH simulator.