Hybrid cars, as well as their electric brethren, make so little noise on the road that the National Highway Traffic and Safety Administration is considering putting together guidelines for automobile manufactures that would require these vehicles to maintain a minimum noise level. So the next time you hear a hybrid car buzzing down the road, there’s a very strong possibility that the sounds coming from beneath the hood are completely simulated.

According to Chris Matyszczyk over at his CNET blog, hybrid and electric cars that are traveling at 35mph are 37 percent more likely to crush pedestrians and 66 percent more likely to cream bicyclists than those automobiles that require old-fashioned gasoline for fuel. The reason, of course, is that these vehicles make very little, if any, noise, giving individuals little warning when one is quickly barreling down upon them.

As a result of these accidents, the National Highway Traffic and Safety Administration has decided to impose a few regulations regarding the minimum amount of noise that a car can make. Although it may seem more than a little silly to some, the idea makes perfect sense, particularly in congested areas where pedestrians and cyclists rely on these sounds to make decisions while navigating the busy streets.

Currently, the 2012 Toyota Prius has a built-in noisemaker, as does Audi’s 2012 R8 eTron sports car, which comes equipped with sound effects crafted by a professional musician. By 2017, all hybrid and electric cars will be required to have some sort of simulated sounds in order to overpower the silence these automobiles generate.

For a few examples of quiet cars equipped with sound effects, take a look at the videos embedded below. To be honest, it’s kind of fascinating.