Absorption panel it is not. Whatever you hear thru the curtain held in front of you will reflect from the glass. Curtains should help at high frequencies but you might think of some fiberglass absorption panels. I'm putting twelve 2'x4'x2" high density fiberglass (Johns Manville 817) panels on the wall behind sofa I'm sitting on (first reflection point) knowing, that they work only from approx 200Hz up. I wish I could use 4" panels but it looks worse on the wall (WAF).
http://www.jm.com/insulation/performance_materials/products/ci9_800series_spin-glas.pdf
Look at 812 1" panels. Their absorption coefficient shows good damping from 1kHz up. Thickness of the curtains in comparison to 1" thick panels suggests that curtains will help only at tweeter frequencies.
http://www.jm.com/insulation/performance_materials/products/ci9_800series_spin-glas.pdf
Look at 812 1" panels. Their absorption coefficient shows good damping from 1kHz up. Thickness of the curtains in comparison to 1" thick panels suggests that curtains will help only at tweeter frequencies.