Could you fit secondary glazing?
Wast_coast, was that a question to me?
Anyhow if it not fits, you just replace the frame right?
East_coast, so you mean that for noise reduction the special gas between the windows is not needed?
Could triple-glass be useful for noise reduction too?
Oh that's an interesting comparison you published by the way, that actually layering an extra level of glass over your existing glass, would be the most effective thing to do (-20db).
Do you know if this number is correct?? Also do you know if there is any even more powerful noice cancellation technology out there?