I moved in a new home 2 months back in the Netherlands. The house is directly next a main road traffic light and unfortunately you constantly hear motorbikes and cars speed along, ambulances, police. In addition to the already badly isolated house some genius installed windows on one side that cannot be opened. However there is this built in metal window gap that you can open and close with a screw driver for fresh air. But even closed, it does not seal all the way. So it let’s in incredibly much noise. I am trying to find a way to soundproof this and would be incredibly happy about suggestions. Replacing the window is unfortunately not an option.
Does someone have ideas what I could use to seal this gap? It’s about 80x20cm.