Thanks ARC. I used 1/2 " untempered glass. Rick Fitzpatrick recommended I use two, but I tried one and it works great. No transmissions whatsoever through the single pane. Because I used a hollow core door, I get some sound transmission through it. But I will upgrade to a solid core later on, I just could not afford to special order one right now due to all the other upgrades I had to make. But with a solid core, I know beyond a shodow of a doubt it would eliminate all of the sound from the control room (simply because so little leaks through now)