Check the alternator bearings with a mechanics stethoscope ($15 at harbor freight), as the new belts and being tighter may have disturbed the bearings in there enough to make them rough.
Otherwise, I'm thinking U-Joints and or birfields. and wheel bearings.
You may have unrelated issues here and you can hear it now because you've eliminated other noise.
When you say accelerating, do you mean in gear or in neutral or park while sitting still?
It looks like there's a serious buildup of crud under that hood. Did you disturb a chunk and one of the...