Paradigm Shift in NVH

A new wave of vehicle technologies is changing the way Brüel & Kjaer attacks noise, vibration and harshness.

June 1, 2019

Lindsay Brooke

B&K’s NVH Simulator, shown with Gary Newton at the wheel, can link CAE outputs to the previous generation vehicle’s benchmark data—and play ‘what if’ scenarios to optimize the platform going forward.

When you’re in the business of NVH solutions, you get to know noise and vibration up close and personal. And for these experts, it can be difficult to sequester the ‘N and V’ throughout their own day. Ask Dr. Gabriella Cerrato, manager of global sound and vibration engineering services at Brüel & Kjaer.

“I can’t be in a hotel room and not be aware of things like the refrigerator compressor, the ice maker, or the air conditioning,” she noted. “Although I’m not a geek about it—I don’t immediately ponder the sources and potential noise paths of the hotel HVAC, for example — it sometimes drives me nuts.”

That’s likely not surprising to industry engineers wrestling with sound and vibration challenges in a world that’s increasingly attuned to the effects of noise pollution on one hand, while thrilling to the growl of a Corvette on wide-open throttle—or the serenity of an electric luxury sedan on the highway.

“Fundamentally, our approach to NVH is to create a quality sound and feel for the driver,” Dr. Cerrato explained, while meeting the acoustic and harmonic challenges that come with vehicle lightweighting, electrified propulsion and automated driving. Brüel & Kjaer (known simply as ‘B&K’ among industry engineers) is even addressing the subject of adding electronic ‘sound enhancement’ to EVs.

“We have an area in ‘sound design’ where we are helping several OEMs design the best sound for the interior or exterior of their EVs. No one knows what that sound should be – what an electric Ford or an electric Ferrari should sound like,” she explained. “To me, it’s a push-button gadget. It’s a very geographic thing, I think.”

On a higher frequency

Dr. Gabriella Cerrato says B&K is learning to adapt its processes and technology to the challenges of automated vehicles.

Dr. Cerrato’s route to the Denmark-based company [bksv.com] started with her Ph.D in fluid dynamics and led into the acoustics realm and co-ownership of an NVH consulting firm. She recently sat down with Automotive Engineering to talk about how NVH analysis and technologies are evolving to meet future technology and market trends. The emerging EV and self-driving frontiers generated much discussion.

“I don’t consider EVs to be as much of a paradigm shift as autonomous driving. EVs still have motors and generate gear whine and high frequency noise at 6000 Hertz and above,” she said. “You just need to set targets and work with the motor and gear manufacturers. We’ve done several projects with a number of CAE companies and take their outputs and plug it into our simulator model. We’re launching a series of seminars with them.”

EVs don’t fundamentally change the NVH approach, to create a good sound and feel for the driver, she opined, because “they have the same ‘receiver’ — a human driver.”

Driverless AVs, however, are the true paradigm shift for B&K and others in the NVH field because they don’t have a clear receiver.

“It’s a passive experience; you may want to have a meeting or make a phone call or watch a movie; it’s all about maximizing the user experience,” said Dr. Cerrato. “The issues are about infotainment, comfort, and speech intelligibility. It’s a challenge for us; we must adapt. Sound quality and how it engages us with the vehicle, has become irrelevant to a certain extent.”

She compares the NVH challenges with AVs to the acoustic challenges in building architecture — except with AVs, ‘the building’ is moving. B&K’s next major opportunity is to further develop the tools and processes for addressing NVH in the user experience, she said.

The industry’s growing focus on AVs also is causing a shift at the OEMs in terms of their NVH engineering staffs. According to Dr. Cerrato, many NVH specialists—whose focus had been in abating road noise, powertrain NVH, suspension harshness — are moving into different areas and are now focused on user experience.

High-fidelity inputs

B&K’s expanding product portfolio is notably heavy with software-based toolsets aimed at identifying root-cause NVH sources and their pathways. It also features a series of NVH simulation tools, developed within the context of vehicle development and design.

For vehicle development teams, the Brüel & Kjaer NVH simulators have proved to be popular tools for establishing NVH goals early in vehicle development, before the design and hardware are finalized. Most automakers and some Tier 1s own one, according to Dr. Cerrato.

The tool’s software is commonly paired with a steering wheel and pedals to allow drivers to experience the sound and vibration data. High-fidelity vehicle sound is played through headphones or speakers, allowing the ‘driver’ to experience the vehicle sound quality throughout the dynamic aspects of driving such as accelerating and traversing different surfaces. Such realistic immersion helps in selecting appropriate sounds, comparing alternative designs and, B&K claims, increasing confidence in evaluating concepts or physical prototype updates.

“We take a production vehicle and sort of ‘break it down’ into the various noise and vibration sources and paths, and how they transfer to the driver,” she explained. “Then we put it back together in the lab so you can actually shift gears and hear the sounds. That is so important in developing the new vehicle, particularly when we want to use the existing powertrain — which is very typical in the industry. With a new body you have different isolation from the outside, different noise paths.”

Added Gary Newton, B&K’s director, Automotive Americas, as he demonstrated an NVH simulator to AE: “We can link the CAE outputs to the previous generation vehicle’s benchmark data. We can generate what that vehicle should sound like, is going to sound like, then play the ‘what if’ scenarios to optimize that platform with accurate design and engineering decisions going forward.”

Newton admitted that a lot of subjectivity exists in the traditional vehicle sign-off process. Typically, all the ‘ears’ involved don’t come into play until four or five prototype iterations down the road.

“Here’s what often happens,” he said. “The development team sits in a room, as I have, where you have 2-D graphs on the board and everybody is arguing over some breach in the target that may or may not be an issue – and they’re arguing about investing engineering resources over the next three months for a fix. That’s what the simulator was designed to avoid,” he said.