Hybrids like the new 2012 Toyota Prius can save you from filling up and at slow speeds are almost silent, until someone steps in its way. It's a low hum that sounds more star-wars then engine-like.
"It's called the vehicle proximity notification system," explains David Maus, of David Maus Toyota in Sanford.
New Toyota hybrids now make the sound when going under 15 miles an hour. That's when the motor is off and running only on electric power. It lets pedestrians know there's a car coming.
"You can hear it from a good ways away, and most the time people aren't going to be standing in front of a moving vehicle anyway, so once you hear that little sonar, it kind of says get out of the way," Maus says.
A 2009 study by the National Highway Traffic Safety Administration found that at slow speeds, like at a stop light or parking lot, hybrid cars are two times more likely to be involved pedestrian accidents then cars with gas engines.
A new federal law now says all hybrid and electric vehicles have to include some type of noise-making technology within five years.
"They've got a few years to do it, but this is something they can almost do overnight with the electronics and a lot of the manufactures have," says automotive writer Steven Cole Smith.
He says some cars, like the Toyota, have already done it, but he says even cars with traditional gas engines will eventually have to make noises too. More and more car makers are introducing partial hybrids and cars that turn off at a stop, then start the engine when you lift your foot from the brake, which could be just as dangerous.
"It kind of comes back to putting playing cards in our bicycle spokes back in the old days," Cole Smith says. "I don't think it matters what kind of sound it makes, but it has to make some type of sound when it's just sitting."
The only problem: car manufactures haven't decided on one universal sound.