Waging a War on Noise
Cultivate an optimal passenger experience by virtually testing and optimizing acoustic EV performanceWednesday, July 14, 2021
By Massimiliano Calloni
Electric vehicles gain popularity, and problems
New electric vehicle (EV) manufacturers, as well as traditional automakers, are rapidly updating their entire fleets, as EVs continue gaining popularity with consumers - drivers seem excited to make the shift towards saying ‘farewell’ to traditional combustion engines. But as public interest in EVs rises, so do grievances, specifically related to interior noise – noise coming from the road and tires, other vehicles, Acoustic Vehicle Alerting Systems (AVAS), wind, or other new sources that seep into the vehicle’s cabin. Regardless of what engine a vehicle has in it, drivers expect the most comfortable driving experience possible when purchasing a new vehicle, including a quiet interior, but probably most especially when buying something as high-tech like an electric car.
Naturally, this poses a new set of problems for EV manufacturers, not to mention that late-stage intervention can cost exorbitant amounts of money for each vehicle variant. Let’s zoom in on a few.
EVs bring the…noise?
The most obvious difference between a traditional vehicle and an electric vehicle is the propulsion system – one uses a traditional combustion engine and the other runs on electric motors. Although traditional combustion engines and powertrains create their own set of noise issues, replacing this with an electric propulsion system poses an entirely new set of challenges for EV manufacturers. With ancillary air exhaust and intake systems absent, things like tire and wind noise are more dominant. On top of that, electric motors and ancillary systems such as pumps, HVAC, battery cooling systems and compressors can add undesirable, tonal and highly annoying noise contributions.
Another classic pain point with EVs is limited range. And what’s the best way to increase the range? By building a lighter vehicle. Except that when a vehicle becomes lighter and stiffer, it is usually noisier as the mass and damping counteracting noise is reduced. The design exercise becomes an iterative process: remove weight, evaluate the increase in noise, selectively add treatments, mass and damping to correct the problem. This turns into quite an optimization challenge for automakers...
Let’s shift our focus back to the passengers for a moment. Today, a typical feature you’d expect in almost any new vehicle – especially a high-end, luxury electric vehicle – is speech recognition. Speech recognition systems were created to keep drivers focused on the road instead of constantly being distracted by the handheld devices our eyes are typically glued to. These systems can do anything from asking Siri® to read you an incoming text or calling home. But when noise interferes with the driver using the system, this negates the benefit of having the system altogether as the driver may revert to picking up the phone – and lead to a very frustrated and distracted driver. Manufacturers’ highest priority is driver safety, which is bolstered by an effective speech recognition system.
In keeping with the theme of safety, we can’t forget about the safety of vulnerable road users (VRU) including pedestrians and cyclists. By now, most of us have heard about incidents of people being seriously injured or even killed because they could not hear an electric vehicle approaching. This quickly led to the Acoustic Vehicle Alerting Systems (AVAS). This system, which is a requirement for EV manufacturers in several countries as of 2019, is designed to emit vehicle warning sounds and alert VRUs to the presence of electric vehicles at low speeds. And while nobody would argue against having this vital feature, OEMs still need to ensure that, while minimum noise level standards are met externally, it doesn’t create yet another acoustic disturbance for passengers inside of the cabin.
How to combat the noise
Solving each one of these challenges is a complex task, due to the interoperability and interconnection of the required engineering disciplines. Yet, getting new technologies to market first and establishing trust in their performance prior to market launch and throughout the lifecycle, OEMs must figure out all these outcomes equally and commit early with confidence. This is adding complexity on top of complexity. Engineers can only efficiently manage the growing complexity if they can virtually assess the full picture of the final vehicle in real life. The ability to experiment virtually with real data and real physics at the same time gives engineers just the extra degree of freedom they need to meet noise targets right the first time: Virtual Prototyping brings the freedom to displace physical tests and prototypes by virtually replicating product development, testing and manufacturing with simulations.
A virtual prototype, in this case, our virtual new vehicle, is based on multi-domain simulation models, captures ESI’s unique experience in material physics and is equipped with acoustic simulation capabilities for both interior and exterior noise analysis. Acoustic engineers from leading automakers like Bentley rely on Virtual Prototypes to digitally predict noise paths and sources specific to electric vehicles and demonstrate the acoustic performance upfront in the development cycle:
- Quantify and rank the most important noise paths contributing to interior acoustic performance
- Determine aero-acoustic contributions to interior noise arising from the vehicle’s body
- Design and optimize sound insulation packages that meet brand noise targets on a cost-effective basis for weight, cost and noise reduction
- Mitigate tonal noise using electric motor acoustic encapsulation
- Assess structural and acoustic contributions from tires for both interior and exterior noise
ESI partners with industry leaders in leveraging advanced digital technologies to achieve their bold sustainability goals. Take Bentley for example. They started pivoting away from single-point numerical simulation to 100% Virtual Prototyping. Simon Noble, Acoustic Engineer at Bentley Motors shares this:
“By using Virtual Prototyping, Bentley succeeded in what we set out to do – optimize every component of the Flying Spur in the virtual world first before creating physical parts. At the same time, we reduced physical prototypes, creating the quietest in-cabin experience for our customers. Virtual Prototyping means building fewer prototypes and reducing our testing mileage. It also helps influence the design and engineering of the car at an early stage and affords significant benefits in the extensive testing phase."
Find out more about how to design, engineer, manufacture, assemble and test a new vehicle concept fully virtually – reducing scrap and emissions, and introducing more agile and safe operations with a strong focus on the well-being of humans. Watch our ON DEMAND webinar Optimal Acoustic Experience & Safety with EV Engineering.
Vibro-Acoustic Product Marketing Manager
Massimiliano Calloni is the Vibro-Acoustic Product Marketing Manager for ESI Group. Dott. Ing. Massimiliano Calloni has a M.Sc. in Aerospace Engineering, which he obtained from Politecnico di Milano, Italy. Massimiliano has more than 20 years’ experience in Noise & Vibration and worked at AgustaWestland Helicopters for six years as a consultant for both test and simulation. He continues to hone his skills in business development at ESI Group in the role of VA Product Marketing Manager. He support activities in Europe and Asia with emphasis on Italy, India, China, Korea and Japan.
Tags: Sustainable mobility, Vibro Acoustics, Electric Vehicles, Optimization