Choosing a quiet compressor requires consideration of the machine's internal compression mechanism, lubrication type, and power source. Another factor to keep in mind when choosing a quiet compressor is the overall size of the machine. Some compressor manufacturers offer machines with external paneling to prevent excessive noise generated from the internal motor. Additionally, you could purchase one of the specialized compressors that are deemed "silent" by their manufacturers, which have noise outputs of about 30 decibels.
Most experts agree that a rotary screw compressor is the quietest of all compression mechanisms available in the marketplace. This quiet compressor uses two large internal screws that are set parallel to one another; the screws' grooves mesh together as they turn simultaneously. Air entering the compressor is trapped within the moving grooves. As the mechanism rotates, a greater volume of air is compressed into the tank. An air tool attached to the compressor receives this compressed air and uses it to generate mechanical motion.
Compressors are available in oil and oil-free versions; however, a quiet compressor will be oiled compressor. The lubrication that the oil provides dampens the noise output from the compressor's motor. Oil-free compressors have more friction as the motor operates since their pre-lubricated internal coating does not provide as much noise reduction.
The power source is another factor you should consider when shopping for a quiet compressor. These machines are offered in electrical or gas-powered versions; many experts agree that electric compressors are much more quiet than gas. Although the motor still generates noise during basic operation, the electrical hum is not as distracting as the combustion processes within a gas compressor, which is similar to the sounds a car engine puts out.
In general, a larger compressor size will require a bigger motor that generates more noise. A quiet compressor will normally be a smaller model, such as a portable product. The small motor within the portable compressor cannot produce a lot of noise since the operating mechanisms, like the pistons moving within the cylinders, are much smaller and move in a more limited area compared to a bigger compressor.
Some manufacturers make and sell what they call a silent compressor. These compressors can be expensive since the physical construction of the tank and surrounding housings are thicker; this design feature muffles the noise produced by the machine. You should keep in mind that these compressors are not silent, but they do have a very low sound output.