I apologize if this is a silly question but is that currently mandated or is this something that will likely be mandated when the EVs become dominant? My impression was that they are currently relatively silent but that might just because they are always in proximity to a combustion engine idling next to them.

Currently mandated - newer electric cars make this noise that I would put somewhere between "future theremin"[1] and "terrifying alien chorus."[2]

[1] https://www.youtube.com/watch?v=6Qe1wuDsXVk

[2] https://www.youtube.com/watch?v=SvX7NnlhiOE

Bonus: Kia's sounds like an ambient synth track: https://www.youtube.com/watch?v=NdZwVJPN0Ow

There are electric school buses in my area that emit the sound of the Montreal Metro when driving at low speeds:

https://m.youtube.com/watch?v=Hu_1JM_UiuA

This is because the manufacturer is based in Quebec.

it's worth testing indeed, that said these car sounds are under control, not impossible that in slow dense urban spot you can lower them