Yes, those are enterprise disks(meant for a server room) , you can buy other disks that are optimized for noise.

Due to the technology/application, the noise level is slightly increased.

Well, it doesn't do that for me.
NAS hard drives shouldn't click loudly either.
I would make a warranty case out of it.

If you have previously written very large amounts of data to it, this can happen. Many hard drives make clicking noises when they defragment. During this phase, the read/write arm moves continuously at very short intervals across the entire hard drive, as data is read, deleted and written again in groups at different locations.
In idle mode or under normal load, these clicking noises should probably not occur. The situation is difficult to assess on the basis of text.