2 Years ago we had 2 'sash' type UPVC windows fitted to our upstairs front bedroom. Since then i have been concerned about the amount of noise i can hear through them. I can hear people speaking as they walk past my home and cars even gently driving past. So, today i took off the surrounding architrave that sticks to the wall and i think i know why. Gaps. Big ones. I understand that the contractors would have to measure to the narrowest point and that the actual hole itself is not level due to the age of the house, but should these gaps have been filled. My question to you experts is, what do i use. Expanding foam? Frame sealant? Plaster? The widest point is approx 20-25mm. Whichever method i use/you recommend, should this solve the problem.