The Right Amount of Car Noise

Balancing Car Noise & Safety

The beep of a truck in reverse gear cuts through the bustle of city life to warn people to stay clear. Albeit an annoyance to some, it’s certainly an effective alert. As more and more electric cars take to the roads, warning sounds are soon to be regular features of our sonic landscape.

That’s because many cars, especially hybrid and electric cars, are quieter today than ever. Striking the right balance between safety and quality of life is a challenge. How do you make an eco-friendly auto that emits enough sound to protect (frequently distracted) pedestrians and motorists and yet still provides a satisfying experience for drivers, passengers and residents of unquiet urban areas?

It’s a global dilemma that has intensified since the introduction of hybrids 15 years ago. Today, new urgency comes from growing sales of electric (EV) and hybrid (HV) vehicles, a rising number of pedestrian and cyclist accidents, and an increase in the number of self-driving test cars on the road. Governments, automakers and suppliers around the globe are slowly but surely working towards solutions.

U.S. Mandates Warning Sounds

Concern about the issue led the U.S. Congress to pass the Pedestrian Safety Enhancement Act of 2010, which is to be implemented in 2019.

Proposed Department of Transportation standards require that new hybrid and electric cars create a sound that warns pedestrians of their presence when moving at or below 18 mph — the speed range proven most difficult for pedestrians and cyclists to hear these quiet cars. Electronically generated Artificial Vehicle Sounds (AVS) can range from intermittent beeps, chirps and chimes to continuous simulations of engine noise or tires crunching over gravel.

The National Highway Traffic Safety Administration (NHTSA) estimates that the new warning noises will prevent 2,800 pedestrian and cyclist injuries and 35 deaths annually from all electric and hybrid vehicles on the road. That’s good news, as the agency’s 2015 report showed a 9.5% rise in injuries and deaths resulting from these types of collisions — the highest jump in 20 years.

The U.S. joins Japan, the U.K. and others moving to add safety noise to EVs and HVs. New European Union (EU) rules requiring audio warning systems in all new electric cars went into effect in July.

Furthermore, many auto makers — including electric/hybrid leaders Honda, Toyota, Nissan and Chevy — already offer warning and performance sounds.

Drivers, Cities, Others Want Less Noise

While advocates for the blind and various safety groups applaud the new measures, some anti-noise advocates have expressed concerns. “AVS is unmitigated noise pollution,” declared Noise Off, a site dedicated to the reduction of car noise pollution, adding: “Drivers want to keep noise outside and the passenger compartment quiet.”

The Association of Global Automakers and the Alliance of Automobile Manufacturers support the warning rules, and asked NHTSA to find a car noise level that alerts pedestrians without being too loud for those inside and outside of the vehicle.

In Europe, legislators have taken notice. While mandating warning systems, the EU also enacted new standards to reduce new-car noise levels by four decibels over the next decade. It’s part of a larger effort to cut overall EU noise pollution 25% by 2026. All new cars, including EVs and HVs, must now display labels showing how many decibels of noise they produce.

The U.S. has not yet passed similar rules. But some global car brands are already working to evolve sound engineering to achieve quieter and safer performance.

Sweet Sounds

BMW’s new i8 plug-in hybrid sports car is a great example of how EV/HV driver experience and pedestrian protection can evolve in parallel lanes.

For example, the i8 features a resonator, made of glass-fiber reinforced DuPont™ Zytel® PLUS 95G35, tuned to reduce high-frequency air intake sounds and thus create a quieter experience for driver, passengers and passersby. As a 2016 model, it also includes EU safety and noise compliance plus a “city collision” warning and automatic braking feature for avoiding pedestrians.

Such efforts are helping keep the industry on a win-win track: hybrid and electric vehicles that will satisfy drivers, passengers, pedestrians, cyclists and noise-conscious city residents alike.