There are three components that will affect how this affects the response in-room:
1) the area of absorption.
2) the distance off teh wall behind
3) The mass of the curtain material
1) probably has the largest direct effect; ideally a curtain for adjustable acoustic control is hung so that it is 1.2-1.5x the wall length when fully drawn, ie still slightly 'gathered' this is because:
2) affects the frequency above which useful absortion starts (where d = quarter wavelength; so 3" / 75mm off the wall has useful absortion at 1Khz and above - below , also, but much reduced). So the amount of 'gather' in (1) in effect decreases the 'Q'.
3) directly affects efficacy of the absorption; where the use of curtains to control acoustics is required I'd suggest 300grammes/m^2 is a good target. The ideal material is close-woven but permeable (ie you can breath through it) - it's frictional disspation that provides the useful sound absorption.
There are companies that will happily sell you 'acoustic control curtains' but you are payin for the label; they'll be designed on the outine above...
HTH!
edit: going much above 1.5x wall length gives you more absorption, but also less control overall, because the curtain when withdrawn will take up more wall space. Beware using too much curtain, killing the room above the midrange is easy and will sound very dead - and even odder if the bass spectrum up to 500Hz is not similarly addressed
Hi,
One whole side of my listening room consists of a patio door and two large windows. I curtain rail runs across down the entire side so it seems like a good idea to mount a thick sound absorbing curtain. Do specific products exist or is it just best to find the thickest conventional curtain that you can?
Regards,
Nick.
