GM already is equipping its new Chevrolet Volt extended-range electric car with a driver-activated warning system. The car will emit a short audible horn pulse about as loud as the ring of a telephone when the driver pulls back on the turn-signal switch.

"We want to make sure it is something friendly and not startling," says Volt's chief engineer, Andrew Farah. He says they already believed the sound had to be "clearly automotive" in nature. And the collaboration with the federation is aimed at seeing if something more is needed.

Other automakers aren't so sure. Tesla, which already has sold about 900 all-electric Roadsters, is reluctant to make noise.

"One of the top attributes that our customers bring up is that (the car) is so quiet," says spokeswoman Rachel Konrad. "The majority of the sound is not from the engine. It's tire noise and wind resistance."

As a result, she says, Tesla is monitoring research and regulations around the issue as it might affect its $109,000 two-seater, but probably won't add a noisemaker unless there is a "compelling reason."