"The acoustic correction inside classrooms located in historical buildings using absorbent panels is difficult for aesthetic . reasons. Furthermore, architectural restrictions are often imposed to preserve the historical heritage. The acoustic . measurements inside the classrooms show high reverberation time values, which imply an adverse environment for speech . reception. In this paper the reverberation time in classrooms located in historical buildings was reduced by installing . removable sound absorbent panels. The panels were made with “green material”. The absorbent material was obtained by . crushing giant reeds of sweet water, a plant which grows quickly in wetlands. The crushed material was then put in jute . sachets, installed in the wooden frames and covered with different colours jute cloth for aesthetics. Acoustic measurements . were made in the classrooms with smooth plaster walls, without students. A virtual model of the classroom was drawn with . 3D CAD. The surface area covered with green material absorbent panels was evaluated by the software Odeon. After the . installation of the absorbent panels, comparisons between the virtual classroom acoustic properties and the real classroom . acoustic properties were made to validate the effect of the green absorption panels."