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Residents of the Red Hook neighborhood of Brooklyn euphemistically refer to the ever-rushing traffic on the Brooklyn-Queens Expressway on the sunken roadway below their streets as “the river." Traffic noise is ever-present in our cities—so much so that city dwellers often don't acknowledge it for what it is: a form of pollution. Electric vehicles (EVs) may change that. However, they present another problem: deadly silence.
According to research commissioned by The Guide Dogs for the Blind Association (Guide Dogs) in the UK, electric vehicles are 40% more likely to hit pedestrians. That's because, according to additional research from the University of California at Riverside, pedestrians can't hear an EV's approach until it's just a second from hitting them. That's especially true in the context of other noise around them.
Add visual impairment or headphones to the mix, and cities may have a recipe for disaster as electric cars stay on course to replace internal combustion (ICE) cars eventually. Already, Guide Dogs has seen a 54% uptick in pedestrian injuries by quiet vehicles.
Regulators around the world have responded by mandating that EVs produce warning sounds. The rules for the EU, for example, require new EVs to include so-called acoustic vehicle alerting systems starting in 2020.
All of which presents both opportunity and risk for EV makers and cities. Now that electric vehicles can usher in a quieter automotive age, how will we strike a balance between noise pollution and safety?
There's no question about the negative impact of road-traffic noise on city life, says Dr. Erica Walker, founder of the Community Noise Lab at Boston University. “There's an extensive literature showing negative relationships between road traffic noise and noise and health, including increased risks of myocardial infarction and hypertension."
That literature, for the most part, takes in ICE traffic, with engines idling, revving, and even intentionally enhanced engine sounds. At first blush, it might seem that far quieter EV motor sounds improve the situation. But since too-quiet engines create hazards of their own, EV makers are adding their own sounds to the mix. Could they end up simply replacing one noise problem for another?
It's a concern for at least one sound expert. “It is hard to think of any sort of warning signal—even ones we might think of as relatively pleasant—that would not become annoying very quickly given the number of vehicles and their frequency," says Berklee College of Music associate professor DJ Hatfield. “I just pray that it isn't a warning beep or a high-pitched hum."
Fortunately, it's in the best interest of EV companies to make their warning tones as appealing as possible, according to Danni Venne, senior producer and director of innovation at New York-based Man Made Music. That's because, she says, sound is a branding opportunity.
That was how Nissan presented the challenge to Venne's team when it hired the company to create approach sounds for new EVs. “The thing that really turned me on to the project," Venne says, “was thinking about if I was going to buy a Nissan, and it pulls up in front of me, the moment I see it, the moment I hear it — those first impressions are going to tell me so much about that car."
Venne says she and her team never seriously considered the notion that their sounds might create noise pollution. In contrast to low-register ICE sounds, the higher-pitched sounds created for EVs will instead fade quickly beyond the vehicle, Venne says. The driver won't even hear the sounds behind closed windows.
Nissan gave Man Made Music a three-second “canvas" on which to create what Venne terms a miniature sound painting. The resulting sound, called Canto, took about four months to get just right, including thorough testing with pedestrians.
Venne says she looks forward to future opportunities to create sounds for electric vehicles. “I want to score an automobile that is really well-crafted and deserves that personality and that soul." As EVs become increasingly common, it seems likely that she'll get that chance again.
In the meantime, Dr. Walker wants regulators and automakers to consider the impact of EV sounds throughout a city, not just in the neighborhoods where early adopters of EVs can afford them. “My concern is privilege and access. A lot of people with a lot of resources are able to get things quiet," she says. “So it would have to be an equitable distribution of quiet engine technology for it to be meaningful."