If you go for WD red plus 12TB drives, they are helium filled and less noisy even than the 8TB air versions.
I have one and it is silent when not tracking, but all hard drives have some seeking noise. Mostly because it is irregular so human ears pick it up more than white fan or spinning noise.
Best idea for absolute noise reduction in the same room is getting a good closed case, reinforcing with some foam panels with a direct air path that you can direct through a cupboard cutout for example.
What you are looking for is high capacity SSDs in this situation, but that is pricey.