A book I had read about studios, mentioned that:
1)there is a large space between the two glasses, contrary to how normal double glazed windows are constructed
2)that the glasses are NOT parallel to each other, but on a slight angle, to further diffuse the sound.

Personally, with no hard evidence other than my own ears, when we installed standard double glazed windows (aluminum frame, 200 cm Height, 130cm wide), we thought the world outside had died! Triple windows (at least here in Greece) are used more for their thermal insulation properties.

[This message has been edited by trident (edited 01-21-2007).]