For decades, automakers have been on a quest to make cars quieter: an auto that purrs, and glides almost silently in traffic.
J. Emilio Flores for The New York Times
Kevin Walsh, an engineer, monitored waves from sounds that Fisker Automotive Inc. developed to use on their hybrid car.
They have finally succeeded. Plug-in hybrid and electric cars, it turns out, not only reduce air pollution, they cut noise pollution as well with their whisper-quiet motors. But that has created a different problem. They aren’t noisy enough.
So safety experts, worried that hybrids pose a threat if pedestrians, children and others can’t hear them approaching, want automakers to supply some digitally enhanced vroom. Indeed, just as cellphones have ring tones, “car tones” may not be far behind — an option for owners of electric vehicles to choose the sound their cars emit.
Working with Hollywood special-effects wizards, some hybrid auto companies have started tinkering in sound studios, rather than machine shops, to customize engine noises. The Fisker Karma, an $87,900 plug-in hybrid expected to go on sale next year, will emit a sound — pumped out of speakers in the bumpers — that the company founder, Henrik Fisker, describes as “a cross between a starship and a Formula One car.”
Nissan is also consulting with the film industry on sounds that could be emitted by its forthcoming Leaf battery-electric vehicle, while Toyota has been working with the National Highway Traffic Safety Administration, the National Federation of the Blind and the Society of Automotive Engineers on sounds for electric vehicles.
“One possibility is choosing your own noise,” said Nathalie Bauters, a spokeswoman forBMW’s Mini division, who added that such technology could be added to one of BMW’s electric vehicles in the future.
The notion that battery E.V.’s and plug-in hybrids might be too quiet has gained backing in Congress, among federal regulators and on the Internet. The Pedestrian Safety Enhancement Act of 2009, introduced early this year, would require a federal safety standard to protect pedestrians from ultra-quiet cars.
Karen Aldana, a spokeswoman for traffic safety agency, which is also working on the issue, said, “We’re looking at data on noise and E.V. safety, but manufacturers are starting to address it voluntarily.”
A Toyota spokesman, John Hanson, said: “I don’t know of any injuries related to this, but it is a concern. We are moving rapidly toward broader use of electrification in vehicles, and it’s a fact that these cars are very quiet and could pose a risk to unsighted people.”
A study published last year by the University of California, Riverside and financed by the National Federation of the Blind evaluated the effect of sounds emitted by hybrid and internal-combustion cars traveling at 5 miles per hour.
People listening in a lab could correctly detect a gas-powered car’s approach when it was 28 feet away, but could not hear the arrival of a hybrid operating in silent battery mode until it was only seven feet away.
Some electric-vehicle drivers have taken a low-tech approach to alerting pedestrians. When Paul Scott of Santa Monica, Calif., drives his 2002 Toyota RAV4 electric car, he often rolls down the windows along busy streets and turns up his radio so people know his virtually silent vehicle is there.
Mr. Scott, vice president of the advocacy group Plug In America, said he would prefer giving drivers control over whether the motor makes noise, unlike, say, the Fisker Karma, which will make its warning noise automatically.
“Quiet cars need to stay quiet — we worked so hard to make them that way,” he said. “It’s the driver’s responsibility not to hit somebody.”
Mr. Scott has already warmed up to the idea of a car ring tone.
“It should be a manually operated noisemaker, a button on the steering wheel triggering a recording of your choice,” he said. “It could play ‘In-a-Gadda-Da-Vida,’ or anything you like.”
