The Tip of the NVH Iceberg
Standard practice among automotive OEMs is to subjectively rank NVH performance indicators on a 10-point scale, then verify these via hardware testing, to create objective, measurable, targets. This traditional approach works well, but requires physical prototypes before targets can be signed-off by program management. But deciding targets is really only the tip of the NVH iceberg, it’s how to deliver them that’s nine-tenths of the work. If targets could be set early in a program, then work on delivering them could begin earlier when there is the opportunity to influence strategic vehicle decisions, potentially leaving a much simpler NVH task before launch.
With the introduction of sophisticated aural simulation techniques, known for some time but only recently viable due to increased computing power, it is now possible to have decision makers sign-off NVH targets, based on synthesised sounds, in the early stages of the development process. For example, an on-road simulator allows management, without special training, to evaluate the sound of virtual vehicles, and even benchmark competitive vehicles, under real driving conditions. They can, therefore, decide on NVH targets with confidence without prototype hardware, thus giving the NVH teams the opportunity to concentrate on delivering targets in parallel to other development, rather than waiting for physical prototypes to become available and scrambling at the 11th hour to tailor the sound.
One of the main tools available for developing targets, and subsequently engineering components and sub-systems to deliver them, is the PULSE NVH Simulator. This accurately reproduces the noise and vibration of a vehicle in a realistic, interactive driving environment and is used to style and engineer the sound of vehicles to meet brand and customer expectations. Using the simulator, assessors interactively evaluate NVH data by gauging the sounds and vibrations of a selected car as they “drive” through a virtual scenario. The stimuli are determined by user inputs to the controls, and changes in engine rpm, vehicle speed, road surface, and so on. The simulator can be set up in a room, where assessors sit at a typical vehicle driver interface – steering wheel, pedals, gear shift lever/paddles, or fitted into a real vehicle for driving under real conditions – the simulator providing supplementary aural information, via headphones, to the sound and vibration already present in the vehicle. A range of jury evaluation and engineering interfaces are available to allow assessors and engineers to interact with the NVH data in real-time.
With the PULSE NVH Vehicle Simulator, everyone can make the right judgements about sound and vibration by experiencing physical stimuli, just like when driving a real vehicle. Decision makers can confidently decide, does this sound right, will the customer notice, and is it worth the cost? NVH engineers can modify individual source or component contributions in real-time, under any driving condition, for real or virtual vehicles, and they can assess sound (and vibration) in an interactive driving environment – the only way to get correct perception. More importantly, NVH engineers gain a leap in efficiency of data interpretation, because the complete driving envelope can be evaluated and understood in minutes, rather than the weeks needed to prepare and use graphs, thus giving them more time to be ingenious and deliver NVH solutions on time.
Nissan Technical Centre Europe
The On-road Vehicle NVH Simulator was developed for a project with Nissan Technical Centre Europe and enables the sounds of virtual vehicles to be evaluated while driving on an actual road and on a variety of surfaces. Recently the “On-road” and “Desktop” simulators were used at the concept stage to deliver an exciting sound to enhance and compliment a new B-segment vehicle.
At a recent company sound event, the sound was universally accepted as natural and resulted in senior project management agreeing that the concept proposal sound was the right sound for the vehicle and that they would consider any request for investment or technology to help deliver the sound.