Did you use Ultegra or DuraAce before? I didn't and some of the noises I hear from my Ultegra Di2 R8050 do seem a little odd from the quietness that was my 105 5800. I put if off as just different materials used for their construction. Particularly the cassette.
I don't think they are loud enough to be noticed by anyone but me, except for maybe when with others at times it might be real quiet, peaceful and smooth road.
Cleaning the cassette pretty much assures me I'm going to hear some tinny sounds on the next ride.