Sound as safety is absolutely not an issue. Sitting in a car, with the windows up, it is impossible to hear any other vehicle unless the exhaust system is missing.
Especially this time of year when windows are rolled up, AC blasting, radio on. I’ve see people roll through an intersection with a fire truck coming because they had a green light and didn’t hear the sirens.
So, even an electric vehicle with a fire truck siren running constantly, wouldn’t make enough noise to protect itself from inattentive drivers.