A louver defining an air passage between an outside and an inside comprising: a bottom plate and a top plate defining a height of the louver, and a first side plate and a second side plate defining a width of the louver; a plurality of vertical blades extending between the bottom plate and the top plate and having a profile in cross section, the profile including: one or more rain ingress prevention features (465; 470; 475; 480), configured to avoid rain or other precipitation to pass from the outside to the inside; an outer blade portion arranged closer to the outside and an inner blade portion arranged closer to the inside defining a concave blade side and a convex blade side ; the outer blade portion comprising an outer wall at the convex blade side and an outer retention flange at least partially included in the concave blade side that delimit at least in part an outer receptacle configured to receive acoustic absorber material ; the inner blade portion comprising an inner wall at the concave blade side and an inner retention flange at least partially included in the convex blade side that delimit at least in part an inner receptacle configured to receive acoustic absorber material ; and wherein the louver comprises acoustic absorber material in the inner and outer receptacles . a bottom plate and a top plate defining a height of the louver, and a first side plate and a second side plate defining a width of the louver; a plurality of vertical blades extending between the bottom plate and the top plate and having a profile in cross section, the profile including: one or more rain ingress prevention features (465; 470; 475; 480), configured to avoid rain or other precipitation to pass from the outside to the inside; an outer blade portion arranged closer to the outside and an inner blade portion arranged closer to the inside defining a concave blade side and a convex blade side ; the outer blade portion comprising an outer wall at the convex blade side and an outer retention flange at least partially included in the concave blade side that delimit at least in part an outer receptacle configured to receive acoustic absorber material ; the inner blade portion comprising an inner wall at the concave blade side and an inner retention flange at least partially included in the convex blade side that delimit at least in part an inner receptacle configured to receive acoustic absorber material ; and one or more rain ingress prevention features (465; 470; 475; 480), configured to avoid rain or other precipitation to pass from the outside to the inside; an outer blade portion arranged closer to the outside and an inner blade portion arranged closer to the inside defining a concave blade side and a convex blade side ; the outer blade portion comprising an outer wall at the convex blade side and an outer retention flange at least partially included in the concave blade side that delimit at least in part an outer receptacle configured to receive acoustic absorber material ; the inner blade portion comprising an inner wall at the concave blade side and an inner retention flange at least partially included in the convex blade side that delimit at least in part an inner receptacle configured to receive acoustic absorber material ; and wherein the louver comprises acoustic absorber material in the inner and outer receptacles . <EOS>