The silence of hybrid cars isn't always golden, some researchers and safety groups say the vehicles can pose risks for unsuspecting pedestrians and the blind who use sound cues to travel safely.

With government reports suggesting that silence is a safety hazard in hybrid and electric cars, American lawmakers want the vehicles to be more noisy.

Congress is adding sound performance requirements for hybrids and electric cars to an auto safety bill being considered after the massive Toyota recalls.

That's because researchers and safety groups say quiet hybrid vehicles at low speeds pose risks for unsuspecting pedestrians and the blind, who use sound cues.

Advocates for the blind have sought the addition of artificial noises in hybrids for several years.

In fact, a report by the U.S. National Highway Traffic Safety Administration last year said hybrid vehicles are twice as likely to be involved in pedestrian crashes at low speeds compared with cars that have conventional engines.

Lawmakers could consider the changes this summer.

Car companies most likely would then have to have the artificial sounds ready to go three years after that.