https://www.vocalboothtogo.co.uk/p/vb2go-sonicvoid-2600-acoustic-blackout-curtain-soundproofing-2600g-m2-12mm-grommets-curtain-rod-rings-included/12811
VB2GO SonicVoid (double-layer) 2600 - Acoustic curtain (soundproofing) 2600g/m2, 12mm grommets,...
This is a double-layer version of the SonicVoid curtain 1300, so it is labeled 2600. The results of laboratory tests of the sound absorption of these curtains...
double layer