What should a nine-thousand-pound electric vehicle sound like?

The electrification of mobility presents humanity with a rare opportunity to reimagine the way cities might sound. Electric motorcycles, cars, trucks, and vans are legally mandated to replace all internal-combustion-engine (I.C.E.) vehicles in New York, L.A., and other cities by mid-century—a shift that will profoundly alter the acoustic texture of urban life. The internal-combustion engine, in addition to being the single largest source of CO2 emissions, is the leading cause of global noise pollution, which studies have shown to have a similarly corrosive effect on human health. When moving at higher speeds, electric vehicles, or E.V.s, produce roughly the same wind and road noise that I.C.E. vehicles do, but at lower speeds they operate in near-silence: electricity flows from the battery to the motor, which spins with a barely audible hum. Therein lie the promise and the peril of E.V.s for city dwellers.