SMYRNA, TN - In response to criticism that noise-free electric cars pose a safety risk to pedestrians -- particularly blind pedestrians -- Nissan has given its LEAF electric car a soft whine that fluctuates in intensity with the vehicle's speed, the Washington Post reported. 

When moving in reverse, the LEAF emits a clanging sound. 

Nissan chose to add those sounds after exploring about a hundred other options, including chimes and motor-like noise. The automaker worked closely with advocates for the blind, a Hollywood sound design company, and acoustic psychologists to come up with the audible alerts. The artificial noises come into play when the car is operating at lower speeds. 

The sounds are emitted through a speaker in the engine compartment. Though a switch inside the LEAF can turn the sounds off temporarily, the sound system automatically resets to "on" when the car is started again.