First of all, it's not clear that lack of noise from EVs had any impact on the fatality stats posted in the article, is it?
But more to the point. Electric motors under load have their own wonderful growling-whining sound. My suggestions is, don't mess with it. If anything, just amplify the sound some, at low speeds, if pedestrian safety is a real concern. And it would be best to allow each manufacturer to tune the sound of their own products, same as they do with ICE exhaust systems.
I think that the most practical in terms of being easy to distinguish would be some sort of pulsing tone where the pulse rate increases in frequency as car speed increases. Also important, I think, would be a smooth transition to where the sound turns off. I also agree that some sort of standardization is needed with perhaps some options as to the tone frequencies chosen
It is blind people who pushed for these minimum sound requirements. I am a blind engineer, and know that this problem has been under discussion for more than 10 years. In Montgomery County, Maryland, pedestrian safety campaigns recommend that pedestrians "make eye contact" with drivers. Good luck getting me to do that. Sound from an "idling" car is just as important as from one in motion. As much as possible, we need to be able to hear vehicles which may collide with us as we cross streets. I think manufacturers are going to be sensible about the sounds they select; a lot of groundwork has already been laid.
Perhaps we need some specific standards for this noise...otherwise everyone will play a different tune like in cellphone rings...specifying the dB levels in not sufficient...people need to know it is car coming!
If we are going down this road, then the new regulations need to apply to all vehicles, regardless of how it is powered (gas,EV,pedal power).
Personally I think it is just a knee jerk reaction to new technology. People need to be aware of their surroundings and take responsibility for themselves. If you are clueless enough to walk in front of a moving car because it is not loud enough, Darwin will see you to the exit door soon enough for a cause unrelated to EVs.