The HF 5 HP T29 pump is a lot quieter at 775 RPM. The vibration is a bit more pronounced at this lower RPM but I don't think it's significant. It could be driven with a 3 HP motor at this speed. I'll keep it set up like this and try to do something with the IR Type 30 as an auxiliary pump before I get into any sustained blasting again. It's pretty quick to change it back if I need more air.
Factory w/plastic filter (1388 RPM): 86 dB
W/ intake silencers (1388 RPM): 81 dB
With 3" pulley+silencers (775 RPM): 75 dB