End of the window saga, or almost; ideas?

[Garald]

As some of you know, I was a little unhappy with my library windows - yes, they were rated at 40-45dB (with 40dB being a more realistic measurement of sound reduction for typical street noise) but these are first-floor 2mx2m windows overlooking a sometimes busy two-way street.

 

So, I had a second set of windows installed at about 15cm from the existing windows - single-pane heavy safety glass (high-transparency of course). They are rated at 36-38dB, though again the frame takes some off that.

I had calculated the resonance frequency of the resulting system would be 340/(2*pi))*sqrt((1.22/0.15)*(1/45+1/35)) = about 32.5Hz.

 

The result was good but not extraordinary: I knew I'd always be able to hear a bass rumble, but I could still hear passing motorcycles. The problem did not seem to be coupling (both window-frames are attached to the masonry by tick-tacky) but rather (I conjectured) the edges of the frame.

 

So, I stuck some cork in it, and also applied some weatherstripping. Then I added more cork to the sides (2cm thickness), for absorption, making sure the cork planks would not or would barely touch (to avoid introducing coupling).

 

I'm pretty happy now. It's not perfect, but one can now hear motorcycles more clearly from the *other* side of the house (which faces a courtyard).

 

And now I've got my own mini-greenhouse! The basil plant is happy. We shall see how the bougainvilleas do.

 

Things I can still do:

- cover the bottom with cork (but then I would need to waterproof it, since I'm putting plants there; what is good for waterproofing cork?)

- put nicer-looking 1cm cork on top, leaving less or no spacing (you can see this in one of the pictures),

- weatherstrip the sides and bottoms (easy, but after the first two steps)

 

Do any of the measures here strike you as pointless or counterproductive? For instance - am I introducing coupling after all?