Air Flow's Acoustical Louvers provide insulated blades and varying louver depths provide sound attenuation to lower infiltrating or escaping noise, as well as protect against weather penetration. Airfoil blades are available for applications involving high velocity airflow. The sound ratings are based on sound transmission standards. ASTM E90-90 and ASTM E413-87. Acoustical louvers are available with visible and concealed vertical mullions and range in frame depths from 6 to 12-inches.