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jsburger wrote: ↑Sat Aug 14, 2021 5:36 pm Piston air compressors are much quieter than diaphragm compressors. Years ago I had a 20 gallon vertical Craftsman compressor. It absolutely screamed. I replaced it with a 4 cylinder 30 gallon Quincy. The Quincy is much quieter than the Craftsman was.

That is clearly an indirect drive compressor, and if it slows down the RPMs at the crankshaft for the pistons it can reduce sound a great deal. It may not produce much more air than a direct drive single cylinder compressor but driving a single cylinder at 3450RPM creates much more noise. The picture also shows individual mufflers on the intake ports where most of the noise is generated.