Sound-attenuating ventilation

A sound-attenuating ventilation louver for location in an opening of a wall which separates a chamber containing a noise source from the external environment, said louver comprising a frame and a plurality of horizontally disposed profiled slats supported by said frame and so arranged that in the operative orientation of the louver in said opening, each slat slopes upwardly across its width away from said external environment whereby a first one of the two major surfaces of said slat faces upwardly towards said environment while the second one of said two major surfaces faces downwardly towards said chamber, each said slat being in the form of an aerodynamically-shaped blade the two major surfaces of which are connected by curved end sections of convex profile, each said slat comprising:

• a solid portion formed from sound-absorbent material and extending from an intermediate zone of the slat to the longitudinal edge thereof which in the operative orientation of the louver is nearest the said chamber containing the noise source, and
• a wall of rigid material defining a hollow portion extending from said intermediate zone to the longitudinal edge of said slat which in the operative orientation of the louver is nearest the said external environment, said hollow portion being sub-divided into a plurality of chambers each of which acts as a resonator and is in communication with the atmosphere through at least one hole defined in said wall.