Honestly the power supply fan is more annoying (higher, winier pitch) than the actual ASIC fans themselves.
Under or over clocking is done in the firmware OS — I’m running Braiins.
I think for sound dampening Owens Corning 703 fiberglass acoustic insulation works wonders. I use it for audio baffles in a stereo setup and it’s the real deal. That egg crate foam can’t touch this stuff.