My copy (on 5D2) sounds just like this one
Canon 40mm f2.8 STM Lens (HD) Review - DSLR FILM NOOB
EDIT: I'm sorry, time code didn't work, it is at 3m 45sec.
It is completely quiet if I turn the focusing ring reeeaaally slow, faster MF makes more noise.
That video only shows the AF sound though.
And mine is silent too when I MF slowly...
So I guess the MF noise is normal? If so then I don't know if I want to keep this lens...