Thicker is always better, kinda like milkshakes
Here's a brief rundown on glass -
Tempered is safer than plate (sometimes called float plate) but not much different in sound quality, other than possibly a slighly different resonance for the same size due to hardness change - tempered glass breaks into little "pebbles" rather than long, sharp "shards", so there's little danger of cuts that have been known to result in bleeding to death. You cannot cut tempered glass, it has to be ordered to exact size. Period.
Float plate is just plain glass - not allowed in commercial establishments in some areas, and never near doors where the door could swing into it.
Laminated is also referred to as Safety Glass - this used to be used in cars for glass, til they found they could temper glass cheaper than laminating it - not sure, but I wouldn't be surprised if the higher priced luxury cars STILL used laminated for its improved sound isolation.
Glass in general weighs roughly 3 times what gypsum wallboard (sheet rock) weighs, so the minimum thickness you want in a studio wall in order to not compromise the performance, would be at least 1/3 the total wallboard thickness, unbalanced slightly to either side the same as you would do with the wallboard for best TL.
For laminated glass, this 1/3 rule of thumb should be enough - for home studios, if budget is tight and you end up using float plate, I'd recommend more like 40% of total wallboard thickness.
Examples: if the wallboard on one side of a frame is two layers of 1/2", the glass in that side should be 3/8" minimum. If the wallboard on the OTHER side of the wall, on the other frame, is two layers of 5/8, then minimum glass should be 1/2".
As with opaque walls, all the other physics of good isolation still apply - more mass, unbalanced slightly, wider gap between, only two panes, well sealed, all still apply.
Insulated glass can be either two separate panes separated by air and well sealed at the perimiter, or a single hollow glass "block", with the air space sealed by the fact that the window was "blown" at the factory as sort of a "flattened glass ball" - in either case, this constitutes two leaves from an acoustic standpoint, so should be avoided in almost all cases of serious isolation. Insulated glass is NOT the same as laminated, although it's possible (don't know) that some insulated glass IS laminated - if so, then each side of the air gap would have at least two separate panes glued together with some type of elastomeric sheet between them.
Laminated glass is sold as the finished thickness - two panes of 1/4" glass with a thin membrane of elastomeric material in between would be considered 1/2" laminated glass.
Finally - Laminated is the best (and most expensive) for sound control, giving anywhere from 6 to maybe 10 dB better performance than the others depending on frequency.
There's no point to using tempered laminated glass that I'm aware of, although it's possible. It would be even more expensive than laminated.
Thicker is almost always better, but see my 1/3 ratio comments above.
Wider air gap between panes is always better, especially at lower frequencies.
Splaying glass has more value for fighting glare in lighting than it does for acoustics, although if you have plenty of space between window panes it can minimise flutter echoes between them.
I think we just ran out of what little I know (or at least remember) about glass... Steve
Steve
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