Windows - Line of sight, not just sound
So you have built your air tight studio with a zillion layers to your walls, and all the right materials: Now cut big gaping holes in them for windows! That is the cruel joke of building an isolation room. But they are necessary (although I have seen a couple of interesting designs using closed circuit cameras that are interesting). First let's talk materials:
- Plexiglass - scratches too easily, you want to be able to see inside after a couple of years....
- Float glass - can be up to 1 inch in thickness - readily available and can be cut on site at most local glass places but not as effective in isolation as other types
- Heat Strengthen or Tempered glass - often found in sliding doors for it's durability, but cannot be cut once it is made - better isolation than float glass
- Laminate Glass - Made with an inner plastic layer (the laminate) between two pieces of glass which significantly reduces sound transmission - lab test have shown this to be the best glass for sound isolation
Before this article turns into a book, I will get to the point. A typical studio will use two of these pieces of glass, suspended each in their own frames, without touch one another. Creating an air tight frame is important. The more density and stiffness to the glass, the more it will be like an extension of the wall and create good isolation. In my study, angling one piece of glass may help reduce the sound transmission between having parallel pieces on one hand, but may actually increase sound transmission by decreasing the air spring between the pieces of glass. Before going out and having glass cut, which can get quite expensive, consider these options:
1. Sliding doors between the studios: If they are made with tempered glass and you double the doors up, this might double as an entrance as well a line of sight - better than cutting an extra whole in your airtight room since you will need a door anyway
2. Double pre-framed exterior windows. I was trying to finish my studio within a reasonable budget and so I found six foot long exterior house windows that were being recycled. They used laminate glass have seemed to do the trick. See the picture below. We framed each window into each wall and used black material between them to keep the dust out and give it a nice finish. You'll want to make sure the inside windows are very clean before installing them! A friend told me about a studio that had a fly sitting dead between the panes of glass..