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It’s ironic that after years of working to make cars quieter, automakers are now heading in the opposite direction.

The reason for this about-face is the coming wave of electric cars. Virtually silent at low speeds, EVs pose a safety hazard for pedestrians, especially the blind, who rely on an audible indication of a car’s approach.

Today, EVs are few and far between, but affordable mass-market, battery-powered vehicles, like Chevrolet’s Bolt and Tesla’s Model 3, are entering the market. Assuming these models catch on with consumers, the lack of conventional engine noise will become an even more pertinent issue.

This question has been on automakers’ agendas for some years. Prompted by government authorities, car companies around the world have been figuring out the best way to create effective sound signatures for EVs. Late last year the National Highway Traffic Safety Authority published rules on the subject that go into effect by September 2019.

Artificial external sound systems have been included on certain hybrid vehicles for some time. And similar systems are being fitted to EVs like the Chevy Bolt. Typically these systems feature a weather-protected loudspeaker mounted behind the front fascia. At speeds up to approximately 20 miles per hour, the speaker creates a sound, described by a GM technology spokesman as “a whirring or humming sound, like a fan running at low speed.”

That sound is at a fixed pitch and volume and can be heard as soon as the vehicle is turned on. So even when the car is parked, pedestrians will be alerted that it may be about to move. “It sounds pleasant, it is not intrusive,” adds GM.

The sound cut-off point of 20 mph has been selected because it has been determined that by that speed other vehicle sounds, such as tire and wind noise, are sufficient to provide an audible alert.

GM says the whirring sound is the only one available. “We are working with other automakers to standardize the sound so it’s consistent across all cars,” says GM.

This may come as a disappointment to future EV drivers who could imagine being able to pick from a selection of optional external sound tracks; a hum one day, a Ferrari the next. Other automakers have been experimenting with artificial sounds for their forthcoming electric cars. Audi engineers have more conventional — even sporty — engine-like sounds in the works for their e-tron models.

However, it is probable that individually modifiable sounds will not be permitted.

“NHTSA didn’t single out a sound, nor did they rule one out,” says Wade Newton, of the Alliance of Automobile Manufacturers, a U.S. trade group. “The challenge for automakers is to get one that consumers accept. We think it’s important that the sound be consistent so that people learn to recognize it and are not confused by a variety of sounds.”

Much of the impetus for EV sound has been driven by concern for the safety of blind people, who naturally rely on vehicle noise when crossing a road.

“We have been working with the National Federation of the Blind for years,” adds Newton. “We learned that the blind use the sounds of cars for a lot of things. It tells them where streets are. If they hear a lot of cars idling in the same place, it indicates there is a traffic light, or if they hear cars stopping and then moving slowly, it tells them there is a drive-through nearby.”

Studies have shown that many accidents involving blind and sighted pedestrians, as well as bicyclists, occur in parking areas where vehicles are reversing. The use of external sound systems in EVs and hybrids should curb this problem.

So whether it’s in a parking lot or on the street, it’s time for us all to prepare for a new era of automotive sound.

John McCormick is a columnist for Autos Consumer and can be reached at jmccor@aol.com.

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