I've got six WD Reds and can't hear them at all. I put them in a Fractal Design R5 silent case. :) It's a home NAS but I figure I can shut it down to replace

I've got six WD Reds and can't hear them at all. I put them in a Fractal Design R5 silent case. :) It's a home NAS but I figure I can shut it down to replace a drive. No need for drive bays, neat as they are.