Sorry I can't provide a link for this, but years ago when I made panels for myself I remember running across a website where an acoustician addressed this topic. Basically he said that only two options were advisable, either burlap if one was on a budget or ideally, purchase cloth specifically designed for acoustic panels. Anything else was going to have substandard performance in some respect. One can purchase Guilford of Maine fabric from GIK Acoustics and other places. If you Google the topic you can investigate the subject to your hearts content.