Hello,

Recently, traffic in my street got a lot more busy as it used to be. As it
really gets on my nerves, I want to insulate my house. I noticed most/if
not all of the noise comes through the main double glazed window.
It's a modern construction, no air leaks. After reading the internet, I
found out one of the best solutions is to make a 2nd glazing, inside the main
window. As this is the easiest to do in the existing setup, I want to know
what sound reduction I can expect from it. Let me sum it up:

situation now: main window 4/6/5 mm 1.4m x 2m, normal double glazed.
situation later: behind this, at about 4 cm distance, from the inside, a
2nd window, 8mm thick.

Most of my annoyances are in the low frequency spectrum. How many dB's
will this be reduced? And what is this insulation in real-life? (I'm not a sound
engineer). Any ways I can improve it any more?

thanks for any answers,
Remco