Busses are not going to be quiet. Around here we have pretty cool "Van Hool ExquiCity" trolley busses and they can glide gracefully at slow speeds, but when they are hurtling down patched up streets they are not much quieter than the traditional busses.
Most city buses spend most of their time going fairly slowly. The electric buses are absolutely a lot quieter, at least around here. Crucially, also, they don’t vibrate; I’ve never been on a diesel bus where vibration from the engine wasn’t at least somewhat noticeable.
On the older busses in the city I live in, the level of vibrations actually make me sooo motion sick, I have gotten off the bus and immediately evacuated my insides.
