The rectangular silencer is designed for damping noise in ventilation ducts. The silencer consists of a casing and internal baffles. The casing is made of a galvanized steel sheet duct with steel frames and profiles. Internal silencer baffles are profiled with a triangle-shaped metal sheet on one side to facilitate air flow. The baffles consist of a galvanized metal sheet and a mineral wool insert. Wool surface is coated with a special protective fabric.