I got bubble whooshing at power on for a week or so (slowest bleed yet, but I am used to CSP 750, that DDC5 moves TONS of water comparatively).
That has settled out.
I think I accidentally put my DDC5 in a really good location behind my drives, on the lowest deck, mounted on velcro, and pump up to the CPU. My cross flow 120mm on lowest setting (these
Maddog Whisper fan) but put into this (
Antec LED Fan) surround to get an LED whipser combo.
Even at 1200 rpm or so, they are louder than any part of the watercooling loop IMO.