The inherent quietness of EVs, especially at lower speeds where tire noise is not as noticeable, has brought regulators to require they make noise so pedestrians can hear them for safety reasons. Here is what Audi is developing for their upcoming EV lineup.
https://www.slashgear.com/the-2021-audi-e-tron-gt-will-sound-unlike-any-electric-car-08641523/
https://www.slashgear.com/the-2021-audi-e-tron-gt-will-sound-unlike-any-electric-car-08641523/