EVs operate in near-silence, so cabin noise comes under greater scrutiny

  • At this week’s AutoTech: Detroit 2022, panelists tackle a nagging question: How is electrification changing the NVH playing field?
  • German company VI-grade has developed NVH simulators that allow vehicle developers to experiment with noise levels through virtual prototypes.
  • Camera-based systems to replace side mirrors (like on the Buick Wildcat concept above) could reduce wind noise inside the cabin.

    Electric vehicles pose a series of new challenges for automotive designers and engineers, well beyond the need to extract every ounce of energy from a large battery hidden under the floor.

    Without an internal combustion engine creating a four-stroke soundtrack of spinning belts, pumping pistons, exhaust tones and (often) forced induction, there’s not much aural experience for occupants. of the vehicle. In the age of electric vehicles, it comes down to wind noise, road noise and all the tunes playing on the stereo.

    This new dynamic is sure to make drivers and passengers much more aware of every sound in the cockpit, which is sure to be reflected in customer satisfaction surveys. Every hum, squeak and rattle is much more noticeable than noise, vibration and harshness.

    “The masking noise goes down dramatically when you go from an ICE to an electric car,” said Brent Dreher, NVH and sustainability manager at Faraday Future, during a panel discussion at the AutoTech: Detroit 2022 conference. of this week organized by WardsAuto and Informa.

    At Faraday Future, one of Dreher’s jobs is to “cascade” vehicle targets for noise levels to component suppliers. The California automaker recently said it had 401 pre-orders for its ultra-luxury FF 91 electric vehicle, a car that, if produced, must be as quiet inside as a bank vault.

    As electric vehicle buyers become more demanding, Dreher says he won’t be surprised if the industry adopts new noise level requirements for windows, seats, mirrors and other moving parts that could create an annoying rattle in the cabin.

    “Suddenly that seat adjustment motor that you didn’t hear before is now making a loud noise,” says Dreher. “Another example is the air conditioning compressor. It used to be an accessory on the engine – you’d never really hear it. But now the AC compressor is a separate unit mounted somewhere on the car with its own electric motor. You definitely don’t want to hear that click going on and off.

    Anti-noise foam inside the Pirelli tire.

    Pirelli

    Dreher says Faraday Future has experimented extensively with Pirelli’s noise-canceling tires, which incorporate a thick layer of polyurethane foam bonded to the inside of the tire along the tread. “And that makes a very noticeable difference in subjective road noise for vehicle passengers,” he says.

    Fans can be particularly problematic, not only blowing hot or cold air into the cabin, but also housed in cooled seats, where the fan can be extremely loud on a hot day. Without a combustion engine drowning out the sound of a fan, automakers might consider using modern fans to break the silence. “Maybe you don’t want it to be super quiet,” Dreher says. “Maybe you want it (blowing fans) as a little masking noise and the customer will never notice.”

    Automotive supplier Auria is positioning itself as a one-stop shop for foam and insulation materials to block and absorb interior noise, especially in electric vehicles. “If you roll down the window, you don’t want to hear that creak,” says panelist Jian Pan, Auria’s senior engineering manager. “If you move your seat, you don’t want to hear the engine moan.”

    road test with vigrade noise simulator
    Road tests with level VI noise simulator.

    grade VI

    Germany-based company VI-grade has developed a comprehensive suite of NVH simulators that allows vehicle designers and engineers to experiment with noise levels through virtual prototypes, even before a physical model has been built. Jeff Hodgkins, the company’s senior NVH applications engineer who has worked for Toyota for more than 15 years in this field, points out that side mirrors are troublesome because they protrude from the body and create aerodynamic turbulence.

    “It creates a lot of wind noise, and it’s just at the driver’s ear,” Hodgkins says on the panel. “I’ve seen some really cool designs now with vehicles that have all these cameras built in,” instead of mirrors. “This will significantly reduce a lot of the main sources of wind noise right there at the B-pillar.”

    Of course, prototype vehicles have been developed without mirrors for over 20 years, and yet production remains elusive, in part because images gathered by outward-facing cameras must be projected somewhere for the driver to see. see them. How many screens can a driver safely see while driving two tons of metal?

    How about laminated glass, which now extends from the windshields to the side windows? While it shields some noise in the front of the cabin, laminated glass makes it more likely you’ll hear more wind noise in the rear of the vehicle, especially in a pickup truck with an all-electric powertrain.

    “You need spatial balance. We fought against that all the time at Toyota,” Hodgkins says, referring to the noise becoming more noticeable if special acoustic glass was used on the vehicle. “Sometimes we would choose to get rid of that acoustic glass just to try and keep that front-to-back (sonic balance).”

    It is possible for car manufacturers to integrate specific sounds into electric vehicles. According to Hodgkins, a growing number of audio engineering companies are developing soundbanks which are then presented to automakers for specific vehicle programs. Automakers can closely analyze different sounds to see which ones best match a vehicle’s brand character.

    “And then they’ll have jury studies – they’ll bring in outside customers, people inside the company, people to sit and listen to these sounds and basically ask, ‘Which one do you prefer, which kind of feelings do you get from that?’ says Hodgkins. “The interesting thing is that customer A and customer B can have different perceptions, so do you really want to prevent the customer from buying this car because of a decision you had to make on this his ?”

    unbridled mode can create synthetic v8 exhaust note in ford mustang mach e
    Unbridled mode can create a synthetic V8 exhaust note in the Ford Mustang Mach-E.

    Tom Murphy

    Perhaps electric vehicles, like the Ford Mustang Mach-E with its button-activated V8 sound projector, will offer a range of sounds that drivers can select, depending on their mood.

    Panel moderator Rose Ryntz would like to see a time when car dealerships have headsets or sealed booths where customers can experience what one electric vehicle looks like over another.

    “I think that could definitely be a selling point — providing a little more a la carte for shoppers,” Hodgkins says. “You are going to get this vehicle and this is what it looks like.”

    As you drive the latest electric vehicles, how does that feel? Are they quiet in a good way, or not so much? Please comment below.

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