I think they're supposed to generate some kind of sound at low speeds. Or at least the government wants them to. https://www.federalregister.gov/documents/2016

I think they're supposed to generate some kind of sound at low speeds. Or at least the government wants them to. https://www.federalregister.gov/documents/2016/12/14/2016-28804/federal-motor-vehicle-safety-standards-minimum-sound-requirements-for-hybrid-and-electric-vehicles https://www.federalregister.gov/documents/2016/12/14/2016-28...