[scott216]

I'd like to get a good compressor that's "relatively" quite. I've heard screw compressors are the quietest, but they are really for a high volume operation, not a one-man shop. The construction site type of oil-less compressors are pretty loud and this is what I have now, so I guess I'd like something that is not oil-less. My machine tools don't need much air, so it's mostly used for blowing chips and cleaning things. Any suggestions?

[sajurcaju]

Getting rid of the oil-less compressor will be a good step in the right direction. What I did to quiet my conventional compressor was to run it slower. The head is a two stage sized for a 5HP motor; I have a 3HP motor on it, spinning 3/5 as fast. This is a significantly quieter, but it still makes some noise.

By far the best thing is to make a dog house for your compressor outside. Just remember to check the oil regularly, and clean the mud wasp nests out of the air intakes.

Steve

[aarggh]

You should have the equivalent brand of this model we have in OZ:

https://sydneytools.com.au/chicago-h...air-compressor

They're very popular with dentists over here as they are about the quietest on the market. Little more expensive, but very nice quality.

cheers, Ian

[123CNC]

I've heard of the lower RPM, 1750 instead of 3600 or so, on larger compressors 7.5 Hp or more, to reduce noise on a piston compressor. The lower speed, lower harmonics, rather than lower hp is what helps.

You may also want to look at scroll compressors, these are pretty darn quiet. Capacity and reliability can be increased with multiple low hp units, e.g. four 5 hp units for up to a 20 hp supply.

You may also consider multiple refrigeration unit compressors with a larger reserve tank.

You can also just try to improve the intake and exhaust with longer piping and or additional silencing or muffling baffles. As well, enclose the entire unit with proper air intake and exhaust. Some report great success with actual egg cartons stapled to inside of wood enclosure, or using egg crate bedding foam.

Another enclosure approach is to essentially build a box in a box in a box that directs the sound through the walls or baffles from end to end to exit.

[sajurcaju]

Sorry, I didn't mean to imply the HP reduction was causal. That's the motor I had at the time, and how I stumbled into a quieter unit.

[dharmic]

How about enclose your current noisemaker in a timber, foam lined box with appropriate mazes for ventilation so it can stay cool but quiet?

[InMesh]

My trusty old V twin has done 35 years now with just bearings on the motor and oil changes ,Not quiet no but I would insulate as stated by 123 cnc and also put the compressor out side and bring the intakes in to a warmer area to slow the damp air down.

[dharmic]

Sorry, 123CNC, missed your post where you already suggested the enclosure.

Not so much with shop compressors but with SCUBA compressors (which tend to be 2-3 stage and pump to 3500 PSI instead of 150 and NOISY at it) I've seen amazing things done with very simple MDF enclosures lined with a couple of different types of foam (eg HD foam on the board with a sponge foam layer on top of that). From 110+ dB SPLs where it's hurting your ears to be in the same room for more than a few seconds down to something where you can hold a normal conversation in the same room.

The real tricks are identifying the peak frequencies and designing the enclosure such that it does not resonate at those frequencies, and to be very careful about how sound diffracts and reflects when it comes to any openings for ventilation, and cable/power routing. Some pretty simple iPhone / Android apps out there now to do a sound frequency analysis and the maths isn't insane if you're prepared to do a bit of research.

[scott216]

I'd like to start with as quite an air compressor as I can, then if necessary, I'll put an enclosure around it. Putting it outside isn't an option for me.

[mkd]

sounds like you want a nice little 5hp kaeser rotary screw.
i think they have about the quietest rating of what i researched, but there is prolly less than 8 decibel difference from one brand to the other.

i ended up with a kinda large 15 hp IR TAS this week. loving it compared to the unbelievably loud and weak two stage piston.

[scott216]

The Kaesers look nice. 3 HP would probably be more then enough for me. They look expensive. I asked them for a quote.
An 8 db difference in sound level is quite a lot. The "perceived" sound level doubles every 10 db (actual power doubles every 3 db). So a 70 db compressor will sound twice as loud as a 60 db.

[mkd]

my partner got a 10hp kaeser for $6300 few years ago, just for reference.
(no dryer)

[Brian FRF]

Bought a "belt driven" compressor only from Surplus Center. Made a mounting plate for it and the old motor from a oilless compressor. Put a v-groove pulley on the motor, connect with a belt, done. Runs on 110v, the compressor was about 100, had the old tank. I get a lot of comments on how quiet my compressor setup is. Id guess Im underdriving the head by a little bit, maybe running it only 75%. System has to have a bit of hardline from compressor head to blow off valve, then to tank. Otherwise the motor tries to crank over the compressor when there is 90psi against the head. It needs that little bit of volume to fill up while the motor gets up to speed.

[scott216]

sounds like you want a nice little 5hp kaeser rotary screw.
i think they have about the quietest rating of what i researched, but there is prolly less than 8 decibel difference from one brand to the other.

i ended up with a kinda large 15 hp IR TAS this week. loving it compared to the unbelievably loud and weak two stage piston.

I spoke with a Kaiser distributor, he said the screw compressors are designed to run warmed-up so they need to be running a lot, not just a few minutes here and there. I had heard this, but it was good to get confirmation.

[LeeWay]

None of them make any noise until they cycle on. Getting a larger volume compressor with faster cycle times will reduce the noise. Then sequestering it in it's own out building will lessen the noise even further as mentioned.

[eterpay]

California Air Tools makes quiet compressors. I have a tiny one and its under 60 decibels. I think they make ones up to 20 gallons in size.