https://www.siliconvalley.com/2019/10/07/elon-musk-likes-coconuts-and-bleating-goats-for-teslas-safety-sounds/

One of the issues some people have with electric cars is how quiet the vehicles are. For example, if you’ve ever walked though a parking garage, you might have done a double take when you noticed a Tesla Model 3 on your tail that you had no idea was there. This is what happens when a car doesn’t have an internal combustion engine to rumble, roar and let you know it’s about to take you over.

Leave it to the federal government to step into the way of that oncoming car. Starting in September of next year, federal regulations will go into effect that will require new electric cars sold in the United States to emit artificial sounds when those vehicles are traveling below 18.6 miles per hour. The concept is simple: When the cars start to slow down, or come to a stop, they will make a noise, possibly similar to a standard car engine, that will make pedestrians aware of their presence, and create a safer overall vehicle and pedestrian situation.