In my experience amount of noise decibels (db) is similar for both compressors rotary vane and rocking piston.
Type of noise from a rocking piston is different compared to a rotary. There has been past discussion here about the noise level of both compressors. See this previous discussion
http://forums.pondboss.com/ubbthreads.php?ubb=showflat&Number=39389Many aeration compressors are manufactured by GAST Manufacturing. From their technical information the rotary vane operates at around 38 decibels (db) and their rocking piston operates at around 55 db (db's range 40-60+). Many 'places' that sell aeration products offer an insulated cabinet to help suppress compressor noise. For D-I-Y systems be sure to install a fan in the cabinet to keep the compressor cool.
