air compressor work: It Hath Risen

 After considerable trials and tribulations... 

(have I mentioned lately the love-hate relationship
I have with concrete anchors?  No?  I say, do I ever
have a love-hate relationship with concrete anchors!)

...the new compressor is on its 15" riser.  There are rubber vibration isolation pads between the riser base and the floor, and there will be another set between the compressor tank feet and the riser... as soon as they arive in the mail.

 Now here is a thing which bugs me: all the installation guides for any large air compressor show the rubber pads between the compressor's feet and the floor... but then they also have a big bolt or anchor tightened through the pad, firmly connecting - mechanically and acoustically - the compressor foot to the cement through the bolt, isolation pad be damned.

 So I've been experimenting with some additional rubber pads under washers under the bolt heads / anchor nuts.  We'll see.

 Now that the compressor is (presumably) installed, my efforts are focused on finishing the intake muffler.  The loudest and most penetrating sound the compressor makes is the pulses from the intake valves.  This is very low frequency, so it carries a long way and is more likely (than the other, higher-pitched noises) to be irritating in my wife's office on the other side of the building.  Thus, the elaborate intake muffler seen at right, which remains disassembled until a big pile of stainless steel pot scrubbers arrive, destined to become muffler stuffing.

  The stock muffler and intake filter is the black blivet at lower left, and is still necessary to filter the air, although it does very little to muffle the noise.  The black dingus at upper right is a modified lawnmower muffler.  The muffler at top right, the long large pipe stuffed with porous steel filler, the short piece of small pipe which extends inside the larger one at the bottom, and the original filter, all work together to trap virtually all of the intake rumble.

 However, early experiments reveal that a surprising amount of sound comes through the side of the compressor pump's cast iron case so, short of painting the entire thing with rubber (a terrible idea because of heat dissipation) there's not a damned thing I can do about that emission short of placing the entire thing within an acoustic enclosure... which is actually part of my long-range plans, assuming we don't move in the next year or two.

 A third source of sound which makes up the compressor's overall racket is generated when the freshly compressed air exits the one-way valve into the tank.  The most effective way to ameliorate that would be with a muffler inside the tank right where the air exits the valve, but that is fundamentally impossible.

 On the other hand, that high-pitched sound is exacerbated by the tendency of the tank to "ring", so it may be possible to reduce that sound with some mass-loaded vinyl slabs attached to the outside of the tank with adhesive.  To be evaluated, but probably a waste of time, IF the enclosure happens.