Air compressors are noisy and in a home workshop, air compressors can be the loudest second only to some air tools. Air-less air compressors are typically the louder than the air-filled alternatives. However, the California Air Tools Ultra Quiet CAT-10020C (oil-less) is amazingly quiet compared to the DeWalt D55155 (oil-filled) that is being replaced. The CAT air compressor will make life around my small shop more comfortable. Measured at the same distance, the CAT-10020C was roughly 75 dBA while the DeWalt D55155 is 85 dBA. The CAT-10020C is 1/10 as loud as the DeWalt.