According to WD, this irritating noise is a ‘feature’ of their newer drives; there are quite a few threads on this kind of thing all over the place: e.g. Periodic Noise from Head Movement WD Black 4TB - #29 by MikeVeltri
Make sure to create a support ticket or return your drive so that WD know that it’s just plain stupid for an idle drive to be making this kind of noise so regularly.