we are using two pieces of acrylic glass
First off, do NOT use ACRYLIC. Use REAL glass as it has more mass than acrylic, is more rigid, and it's cheaper. However, IMO, angling is the least of your worries.
Here's the real deal. Unless your wall has the depth to make angling effective, there is no reason to do it. Pro studios usually have a double wall with a depth that allows for angling at an effective angle. 12degrees is considered the minimum to have an effect on reflections, and size has a lot to do with it too. But a standard wall depth(4.5") is too shallow to angle the pane at an effective angle. In fact, if you do angle it, you are actually making the TL of the assembly worse.
For a standard residential 2 leaf wall, with 1 layer of drywall per leaf, the Transmission Loss(TL) is so minimal, it doesn't make any sense to angle the glass, as you lower the TL of the window assembly as you angle it, due to closing up the airgap. And frankly, here is the real issue.
Due to the "weak link" syndrome, a window assembly with a TL LESS than the wall makes no sense, as it now becomes a weak link in the whole wall assembly. And if you OVERBUILD it, then the wall becomes the weak link, not to mention flanking paths that may negate the entire partition in the first place. Things like HVAC ducts, wooden floor membranes common to both rooms, or even concrete floors that are common to both rooms can be structural flanking paths that transmit impact sounds fairly easy.
So, the issue of angling a piece of glass becomes almost nill compared to the real issues here. To properly isolate one space from another is not an easy task, especially for drums which can easily create 110db sounds. So, even if the rest of the rooms assemblies are up to snuff, flanking wise, simple residential walls will not isolate one space from the other by any measure. Even speech can transmit easily. Therefore, a window assembly, that equals the TL of the surrounding assembly, will also transmit sounds very easily. Which makes angling a moot point.
Now, If you had a double two leaf wall, with each leaf a minimum of two layers of 5/8", and an 18" airgap, THEN you might consider angling one pane. But mind you, to equal the TL of such an assembly, it would take one pane of 1/2" glass, and another of 3/4" glass, which is not cheap, nor easy to install correctly.
In your case, IF this is a standard wall, and all flanking issues addressed, just to equal the TL of said wall would take one sheet of 1/4" glass and another 3/8". And it STILL would transmit just as easily as the wall. Especially with drums. Isolating 100db sounds at close proximity is a lesson in physics and TL construction. And to be ABSOLUTELY frank...in terms of residential after the fact construction..is in all fairness...IMPOSSIBLE. Period. So I wouldn't worry about the angle issue. After all, the wall around the window is flat..which will specular reflect regardless if you angle the window. In fact, in small rooms such as this, the reflections have so little distance to travel, one small square footage at an angle, actually has very little effect on the over all room response.
Personally, I would spend some of your budget treating the ceiling above the drums. This will do more good than angling the glass ever would.
btw, my disclaimer is in full force here....ie...I ain't no expert...but common sense is my defense.
fitZ
