THE NISSAN LEAF IS QUIET. It’s so quiet, in fact, that it has to play a little tune to let you know it’s awake. I step inside a light-blue SL model outside its place of birth, Nissan’s Yokohama HQ, and push a button that illuminates the deep-blue LED dashboard, which alerts me that I have 84 miles’ worth of charge and cues a musical snippet reminiscent of “The Jetsons.” And after that, silence: the sound of the automotive future.