Vehicle development is amidst three concurrent revolutions – electrification, autonomy and the shift in product design and engineering to more up-front simulation. Any one of those would be a challenge for engineers. And in all, attenuating and shaping NVH (noise, vibration, and harshness) is a key focus. NVH issues traditionally have been related to reliability and quality. With electric and connected vehicles, however, noise-and-vibration control plays an increasing role in enhancing the entire vehicle experience.
Much of the noise from an ICE powertrain is lower-frequency boom and rumble below 200 Hz, experts note. Electric motors and EV final-drive gearing noise is generally at higher (1000 Hz and above) frequencies. And there’s always the question of how much acoustic feedback is desirable. But development teams face a hurdle: Clear NVH indications often are available only when the first physical prototypes are available. This reduces the window for improvements that don’t significantly impact deadlines and costs.
“All the automakers are trying to do more up-front design, reduce the number of prototypes and shorten time to market,” noted Dave Bogema, director of NVH Solutions at VI-grade, a provider of software products, services and professional driving simulators for use in system-level simulation. “Engineers at many of our customers are having their physical prototypes taken away. That’s where NVH simulators, and virtual NVH prototypes that are easy to build, come into play.”
VI-grade’s tools create an interactive, full-spectrum driver-in-the-loop simulation of a specific vehicle’s NVH signature. They “bring sound and vibration data into the real world, so it can be experienced by real people,” Bogema, a 25-year NVH and simulation veteran, said. “We translate the rich data content from computer models, from CAE and CFD analyses, and from different test measurements, and integrate it into a simulation that engineers can hear and feel. During a vehicle sign-off, the chief engineer wants to drive and experience the vehicle – he or she doesn’t want to just be told why 3 dB is better.”
Holistic NVH engineering
The company’s recently introduced 2021.0 NVH Simulator incorporates new features and capabilities aimed at easier use. The standard application is a desktop workstation; Bogema said many customers use it “almost as a CAE tool,” that can be scaled up.
“We’ve got static simulators that resemble a vehicle buck; these give a very immersive environment to sit in, with a big screen. It also can be combined with VI-grade’s full-motion simulators, to integrate the NVH characteristics in with the vehicle dynamics,” he explained. The desktop and full-motion simulators feature full wheel-and-pedal “controls” to replicate the driver-to-vehicle interface, as the tool user builds up the model.
High-fidelity vehicle sound is played through headphones or speakers. Calibrated, accurate, independent multiple-degrees-of-freedom vibration is applied at all driver touchpoints, allowing the driver/engineer to experience the sound and vibration of a vehicle throughout all the dynamic aspects of driving – accelerating, changing gears and transitioning to different road surfaces.
Combined with inputs from ADAS technology and HMI, as well as different user interfaces, the latest VI-grade simulator offers “capability to provide a holistic experience for vehicle development engineers,” Bogema said. “Getting all those attributes together brings NVH engineers as close as possible to a real vehicle.”
The VI-grade tool includes an Exterior Sound Simulator that projects the NVH virtual prototype into a virtual environment, where engineers can understand how the vehicle will impact and be perceived by those outside the vehicle. EVs will increasingly be equipped with AVAS [acoustic vehicle alerting systems], generating warning sounds outside the vehicle.
“You want to make sure that it doesn’t adversely impact the interior of the vehicle. How much of that noise is getting into the cabin—and is it pleasant or unpleasant? The sound designers craft these sounds; in the studio they sound amazing. Then you put them on the vehicle and they sound different.”
According to Bogema, engineering responsibility for AVAS can be ambiguous, depending on the company. “Who owns it—NVH? Safety? We’ve seen a significant uptick in the need to evaluate these sounds for EVs. And the focus is not on AVAS only. All manner of interior sound cues are getting added to give the vehicle character, too.”
‘Multi-attribute’ simulation next
NVH simulation’s increasing capabilities are also in demand with subsystems and component developers, including tire designers, to elevate the performance of their products, according to Bogema. “In the past many of them [subsystems] have been developed in a vacuum, he said. Now they’re looking at those noises in the context of the rest of the vehicle’s noise. “That’s one of the powerful parts of the NVH Simulator technology – it lets you take the AC compressor noise, for example, and put it into context of what the vehicle occupants are actually hearing,” he explained.
Technical progress in NVH simulation is moving swiftly. “From the NVH side our focus is on continuing to make the tools easier to use, so engineers can be more efficient in making high-fidelity virtual prototypes, make decisions faster and accelerate product development,” Bogema noted. He said the next five years there will see greater focus on ‘multi-attribute’ simulation – sound, vibration, ride, handling, ADAS functionality, all simulated at once. “It’s going to come together,” Bogema predicted.
Alliance for active sound design
In late March 2021, VI-grade and BlackBerry QNX announced a partnership to enable real-time active sound design for the entire vehicle soundscape, by integrating VI-grade’s NVH Simulator with QNX’s Active Sound Design software. The partnership allows designers to work interactively with a complete NVH simulation of the target vehicle and to experience the sound design in a realistic way, the companies said.
The VI-grade NVH Simulator connects QNX ASD to other sound and real-time data sources in the vehicle, so that tests and modifications can be performed much earlier in the design process. This helps reduce the need for physical prototypes and saves development time and costs.
“With this combination of technology, sounds can be designed and tuned on a computer, in the context of all other vehicle sounds, over the entire operating envelope of the vehicle and evaluated with a free driving, driver-in-the-loop simulation, drastically reducing the need for prototype vehicle testing and tuning,” Bogema observed.Continue reading »