the Sound of Silence

in a few years, the government will require electric cars and gasoline-electric hybrids to emit some type of noise at low speeds, when their battery-driven motors usually run silent. The promised rules—aimed at making the vehicles safer for vision-impaired pedestrians and others who rely on aural cues—have launched auto makers on a quest for the perfect sound.

The new electric cars are nearly silent, and that's a potential hazard for pedestrians who are blind or visually impaired. The Nissan Leaf has added sounds for when the car starts up and accelerates, or backs up. WSJ's Mike Ramsey reports.

Among those considered: noises reminiscent of jet engines, bells, birds, flying saucers and revved-up sports cars.

In developing their electric car, the Leaf, Nissan Motor Co. marketers initially saw the false-sound feature as a branding opportunity, a chance to create a distinctive sound, like a Jetsons jet pack, that would identify an approaching vehicle as a Leaf.

The near-silence of a battery-powered car is a point of pride for many hybrid drivers, an illustration of its ability to run at speeds of 40 mph or more without burning fossil fuel. The quiet ride has been a marketing point for auto makers, who spend millions on insulation and sound-damping technology to make cars quieter.