National Highway Traffic Safety Administration requiring hybrid vehicles to add extra noise. Image credit: Justin Sullivan/Getty Images

Hybrid car owners, so accustomed to the silence of their electric motors, may soon need to get ready to rumble.

The government is asking automakers to turn up the volume on all new hybrid and electric vehicles. They are sometimes so quiet, says the Department of Transportation, that pedestrians and cyclists don't notice them.

So the National Highway Traffic Safety Administration has proposed that manufacturers of hybrid and electric vehicles add extra noise to the cars in an effort to reduce accidents. The agency estimates that making these cars louder could prevent 2,800 pedestrian and bicycle accidents each year.

"This proposal will help keep everyone using our nation's streets and roadways safe, whether they are motorists, bicyclists or pedestrians, and especially the blind and visually impaired," said U.S. Transportation Secretary Ray LaHood.

This push comes after Congress passed the Pedestrian Safety Enhancement Act of 2010, which mandates that all cars make a certain amount of noise to alert passersby.

The added sounds would need to be detectable over background noise when these fuel-efficient cars are traveling less than 18 miles per hour. Once a hybrid or electric car speeds up, it makes enough noise to be noticed without the extra sound.

Wade Newton, a spokesman for the Alliance of Automobile Manufacturers, said these changes won't affect current hybrid or electric car owners; the changes will be phased in for new vehicles.

He added that different situations may call for louder signals.

"The sound you would need in Times Square would be quite different than one that would be appropriate on a rural road," Newton said.

Under the new proposal, each automaker would have a range of choices about the sounds it chooses for its vehicles, but those sounds would need to meet certain minimum requirements to be audible. Also, vehicles of the same make and model would need to make the same set of sounds.

"We understand the proposal allows for some flexibility," Newton said. "But it avoids a Pandora's box of sounds."