How are air compressor decibel ratings measured?
Air compressor decibel ratings almost never say how they were measured: of the sixteen compressors we checked, only one states a distance and none names a test standard.
This is the thing to know before comparing. Of the sixteen compressors we checked:
Only one states a distance.
Campbell Hausfeld's spec table lists the DC080500 at 68 dBA at 3 ft.
None names a test standard.
The rest give a bare number.
California Air Tools lists 56 to 70 dB, Makita 58 to 60 dB and DEWALT 60.3 dB(A), with no distance.
A reading taken close to a machine is higher than one taken farther away. That means Campbell Hausfeld's 68 dBA at 3 ft could sound no louder than a compressor listed at 60 dB. Use the figures to shortlist, not to split hairs.
Some brands publish no figure at all. We found none for Eagle, Ryobi, or Makita's and SENCO's other compressors. Harbor Freight's site blocked us, so we could not check its Fortress models.
How much air does a quiet compressor give up?
Quiet air compressors give up air delivery: in our list, the 56 to 59 dB machines deliver 0.7 to 1.20 CFM at 90 PSI, against 5.30 CFM for the 70 dB models.
Every quiet compressor makes the same trade. In our list, the lowest figures belong to the smallest machines:
- 56 to 59 dB: California Air Tools 1P1060S, Makita MAC100Q and Metabo HPT EC28M, delivering 0.7 to 1.20 CFM at 90 PSI.
- 60 dB class: California Air Tools 8010, Makita MAC210Q and Rolair JC10PLUS, at about 2 to 2.4 CFM. DEWALT's DXCMS20045US stands out at 5.0 CFM for 60.3 dB(A), but weighs 98 lbs.
- 70 dB: California Air Tools' 2.0 HP models, at 5.30 CFM.
Check the CFM at 90 PSI your tools need before you look at decibels. A brad nailer needs little. Our brad and finish nailer guide covers the air nailers such a compressor would feed, and the cordless ones that need no compressor at all.
Sanders, grinders and spray guns need much more, and a compressor that cannot keep up will run constantly.
If you are weighing an air impact wrench against a battery one, our impact wrench guide ranks the cordless and corded kind and leaves air wrenches out, because they are declared under different standards.
What makes a quiet air compressor quieter?
Quiet air compressor makers mostly credit a slower motor, such as California Air Tools' 1680 RPM motors and Makita's 1,750 RPM Quiet Series.
California Air Tools says its motors run at 1680 RPM, and its cabinet model at 1400 RPM. Makita says its Quiet Series runs at 1,750 RPM, and Rolair describes low speed, oil-free drives. Rolair's loudest model we saw, at 79 dBA, runs at 3400 RPM.
Maintenance matters too. California Air Tools says to keep the intake filters attached so the unit runs as quietly as possible. Rolair says its thin reed valves play a major role in quiet running.
How should you set up a quiet air compressor?
Set up a quiet compressor the way its manual says: give it space, keep it on its rubber feet, use more hose rather than an extension cord, and check before running it indoors.
Give it space. Makita says to keep the compressor at least 12 inches from a wall. California Air Tools asks for 2 feet of clear space around and above the 8010.
Keep it on its feet. Makita says the compressor should rest securely on its rubber feet. Rolair says to keep the rubber vibration pads in place, and that running without them voids the warranty.
Use more hose, not an extension cord. Makita, DEWALT and Campbell Hausfeld all say to use a longer air hose instead of an extension cord. California Air Tools allows a cord no more than 25 feet long and at least 14 gauge.
Check before you run it indoors. DEWALT's product page promotes indoor use, but its manual says not to operate the unit indoors or in any confined area. Follow the manual for your model.
Drain the tank
Makita and DEWALT say daily or after each use. California Air Tools says every 1 to 2 days on average.
Do you need hearing protection with a quiet compressor?
Yes, a 60 dB compressor is quiet for a compressor, not silent, and air tools add their own noise, so Makita, DEWALT and Campbell Hausfeld all tell you to protect your hearing.
The manuals agree. Makita says to wear hearing protection against exhaust noise and noise during operation. DEWALT says to always wear ear protection. Campbell Hausfeld says to use hearing protection when operating the unit.
OSHA says exposure over 85 decibels can damage your hearing. Its rule of thumb: if you need to raise your voice to speak to someone 3 feet away, the noise may be over 85 dBA.
Five mistakes trip up quiet compressor buyers, starting with buying the lowest number without checking how much air the machine delivers.
Buying the lowest number without checking the air
The quietest units deliver about 1 CFM.
They may not be measured the same way.
Running a small compressor flat out
California Air Tools suggests 1 HP units avoid running more than 30 to 45 minutes at a time.
Using a long, thin extension cord
California Air Tools warns it can overheat the motor.
Skipping hearing protection because the box says quiet
The makers still tell you to wear it.
