I'm Making acoustic panels to treat my home studio and plan to use mineral wool or fibreglass insulation to do so. Likely Owen's Corning 703 or something marketed as safe insulation like Bradford Sound Soundscreen or Roxul Safe n' Sound. Regardless of how safe salespeople market these fibrous materials I still want to seal in this material, which leads to the questions:
- What material can I wrap around the insulation in order to trap the fibrous particles in but still allow sound to pass?
- Is there some kind of measurement that I should be looking for such as stitching density?
I can't find any data about the size of the particles for fibreglass or mineral wool. One company uses a material called Micromesh but provides no data about it: 
Best Answer
You would do fine using simple burlap. Given the wavelengths of the signal that must pass through, cotton fibers will pose no problem. They are also considerably smaller than the coarse fibers found in commercial acoustic panels. In fact, any material used as speaker cover would work for your application. Incidentally, fiberglass is a very hard and acoustically very reflective material. You may do better with a panel of dense open cell, soft urethane-based foam; they may be found at a local craft store.