My noise reduction set up is getting old and needs to be replaced but was pretty effective since built in 1984.
I built an enclosure with about 12" of clearance around the perimeter and above the cylinders. The enclosure is on the outside of the garage, on the north side where it is the coolest and shaded. It is basically just a box with a removable front for easy access. The box was framed with 2X3s stud walls that were staggered on 2X4 bottom plates. It was then insulated with hard foam freezer panel sheets. The staggered studs keep sound/vibration transfer to a minimum. The removable front is built the same. My garage is climate controlled and I have a fan that pipes air from the garage into the enclosure automatically while the compressor is running. The intake filters are an upgrade to the type that were original and were an improvement. It is a 5HP cast iron unit with an 80 gal tank, that was the smallest one built by London (sold under various names) at the time They built very large industrial compressors at the time. Other than general maintenance I have only replaced the automatic pressure switch and the tank drain a few times. I'm back to a manually operated drain on the tank. The compressor is still bolted to the 2X6 skids it was shipped on that sets on a 1/2" rubber mat. I use a flexible rubber hose from the compressor through the wall to my cooling tower mounted on the garage wall.
I am planning on building another to replace it. I have houses built on either side of me now that weren't there when first installed. Got to keep the peace.