Our house has had a lot of problems with the windows since we moved in. They are triple-glazed aluminum windows. It always amazes me how soundproof it is. For example, when I woke up this morning, I heard birds chirping. There's nothing wrong with that, but I'm surprised when the window is closed and there's no tree in front of it. Or I'm standing on the 1st floor at the window (closed) and I hear the neighbors in the next garden (a house with a terrace, so not that far away) talking (they're not screaming). Is this normal and am I just expecting too much?
Well, it depends on who the manufacturer is. One has a minimum standard of so-and-so, the other has so-and-so.
It's like comparing cars, "mine is faster," without knowing which car it is.
We have plastic windows with 3 panes with no additional soundproofing. You can hear large cars and mopeds, passing cars, maybe just. I can't hear any birds or voices.