Three days for the old cat to get used to the new cat? How about three years! Even then, in the middle of the night the howling and the carrying on is considerable.
There's nothing like the sound of kitties at 3 a.m. trying to run 90 miles an hour on hardwood floors.
actually when my kitties want attention at 3 AM they run across the piano keys!
Now imagine a window right above your headboard and a bird landing on the windowsill at 5:30.