[Gogar]

One thing to consider along with the "windows" comments is any spot that lets air freely move.

Think if you made a wall of rockwool and quietrock that was amazing. If you drill a hole the size of a quarter in it it negates all the soundproofing of the wall. Same goes for an amazing wall with a double pane window snd you crack the window a tiny bit. As loud as ever!

Your best bet with windows is creating a good seal. Multi-pane windows with substantial air gaps between the panes will help a lot if you don't already have em.