Low noise is subjective to each person as I have not heard any fan @1800 RPM that can not be heard from six feet away in a quiet room. Now imagine six of them… NOISY
I have two systems in one room, one running three Noctua's @ 900 RPM and one running three GentleTyphoon's @ 800 RPM and all I hear is a DDC pump in one of the systems. Any higher fan speeds than that I can hear them as they get too loud for my taste.

