Thanks I will just test a few out to try find them now am happy withThe quietest aquarium(s) with air pumps I've heard, have been ones with the air pumps kept separate from the tank they service. That is, really loooong air line hoses, with the actual air pump(s) sited in a different room! Yes, electric air pumps have gotten much quieter than the ones sold and used 'back in the day'. But unfortunately, those things still really are industrious humming and buzzing little boxes of constant activity and noise.
There isn't an electric air pump made today, that I can honestly say runs very quietly.