One of the reasons that it appears noisier than the house window-mounted AC is the fact that the structure it is nounted to is like a speaker box in that it resonates more easily than the window surround and wall in the case of the house window-mounted unit. On the other hand it is great white noise when in a CG with "less than quiet" neighbours.
We had a hybrid with non-ducted AC and that was quite noisy, but boy did it ever drown out the people who had no respect for "quiet hours". If you hear them above that then it is long past the time to call the rangers.