Studio double windows: truth and fiction

Hi all, on a quest to separate fact from fiction, could we list the advantages and disadvantages of angeling two panes of glass in a double window construction? I've read what I could find, here on the forum, in Mr. Gervais' book and in the BBC R&D documents. But I'm still a bit in the dark. Could we discuss a few statements I've gathered along the way and file them as either right or wrong? Statement 1: A double window consisting of 2 glass panes which run parallel to one another is a potential resonance cavity for wavelengths equal to a multiple of the distance between the two reflective, glass surfaces. Statement 2: Angeled glass panes have a potential to give rise to reflections of light which diminish see-through visibility. Statement 3: Using glass panes of different thickness is advisable. This is intended to avoid both panes having the same critical frequency at which they are prone to transmit sound energy. The thickness of one pane should not be equal to a multiple of the other. There you go , Sigert

Re Statement 1: True, but this is not nearly such a big deal as some have made it out to be. Absorbent material lining the interior around the perimeter of the window between the two panes can help minimize some effects of resonance. Also, using laminated glass helps considerably. (Learned that last one the hard way...) Re Statement 2: The light reflection issues are often exacerbated by using angled glass. There are lighting techniques that one can use to maximum the visibility through a double (parallel) window with a wide gap. A good architectural lighting expert will be able to advise you well in this regard. Re Statement 3: True. Different thicknesses of glass are always advisable. In general, angling window panes is not worth the effort. One justification you didn't mention is that angling should be done to change the direction of reflection coming off the glass. This simply doesn't work in practice because the window can never be angled enough to have the desired effect - even an angled window is "acoustically parallel" due to the large wavelengths relative to the size of the window, as well as the relatively short microphone-talent-window distances that are typically involved. Most importantly, the transmission loss of the window is dependent on the width of the air cavity. Angling the glass limits the depth of the air cavity along one edge of the window. The transmission loss will only be as good at this narrowest gap. Since the primary purpose is transmission loss, the air gap should always be maximized. Everything else is secondary. IMO, the only time to seriously consider angled glass is when the entire wall - or a majority percentage of a wall area - is going to consist of glass. Even then, it is often best to angle both panes equally to maintain parallelism, and thus maximize transmission loss.

Additional info: I tracked down this old SOS thread. The link I gave (my SOS handle is "Savant") is dead, but I've attached the file below. I resized it to hopefully meet the thread limits without those annoying scroll bars at the bottom. Let me know if that's not the case. Also, I think the only part that's hard to read is the window angle, which is 5° in both cases. All the best,

Well, I think that reply was about as detailed and thorough as I could've hoped. Thank you for taking the time to share it. One less question to ponder about. :lol: Cheers, Sigert

thanx lovecow