Growling, howling, whistles, and wind

Sept. 10, 2019
A vehicle’s ‘sound’ story starts at production, and carries on into your bay.

Shh. Our vehicles are becoming quieter … and drivers want to keep it that way.

Emerging electric and autonomous systems are leading the charge (as well as presenting unique challenges) when it comes to new noise, vibration, harshness (NVH) standards in new-to-market mobiles. The idea is to make them quiet and keep them quiet for the duration of a vehicle’s lifetime.

SAE International recently covered the topic of NVH at the design level in their June issue of Automotive Engineering. Here I learned NVH detection is not just an aftermarket crusade; it really begins early-on in vehicle development and starts with design.

Getting vehicles to an ideal noise level is no easy feat. Engineers are tasked with creating a quality sound and feel for drivers, which might include keeping the thrill of an engine growl to some extent while also tamping down nonessential sounds.

To achieve the desired level of noise, automotive engineers strip a vehicle down to its most basic components. They employ semi-anechoic and anechoic chambers to help understand OEMs’ systems and improve performance in NVH. These ‘quiet chambers’ dampen sounds and help identify NVH band-aids present on vehicles’ structures. The engineers may further research and use solutions to minimize NVH in today’s vehicles, such as integrating what the company Material Sciences Corp. (MSC) calls Quiet Aluminum and Quiet Steel, both of which are expanding from use in body components to other applications, including powertrain pans to replace castings and composites.

“The autonomous vehicle sector is creating a … new environment of noise and vibration solutions,” says Bruel & Kjaer Automotive - Americas Director, Gary Newton. “As OEMs continue their vehicle-lightweighting crusade, vibration will increasingly have an impact on vehicle design and materials selection.”

Acura now uses high-performance structural adhesives and sound-absorbing acoustic spray foam in 12 body cavities, which Automotive Engineering reports is a 15 percent increase (by surface area) in sound deadening material. Other sound ‘helps’ in use are triple door seals and acoustic-laminated glass.

Software-based toolsets and simulation tools for vehicle development and design come into play, too. Software may be paired with a steering wheel and pedals so drivers can experience sound and vibration data.

This month in Tool Briefing, contributing editor Barry Hoyland talks about NVH from the aftermarket perspective, specifically diagnosing NVH issues that present themselves in the repair bay (pg. 38). For shops, these types of NVH problems can be time-consuming to diagnose, and can have a myriad of causes, including worn system components or wind passing over or through the vehicle. While today's diagnostic procedures and tools can help to isolate and locate noise, it’s also essential to simply test and re-test these vehicles on the road, sometimes with another technician in the passenger seat.

Vehicles are becoming smarter, lighter, and quieter. This doesn’t mean you won’t still be working to isolate and fix the symphony of sounds that are driving your customers nuts well into the foreseeable future. 

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