CLTD Sound Proof Ducting is designed and optimized by CLET on the basis of original prototype. The Ducting consists of flat steel shell, metallic framework, composite acoustic material, metal punching plate and surrounding flange. The space between punching plate and external shell is filled with acoustic pillow. Thanks to advanced plating processing technique and design conception, the quantity of components being used has been greatly reduced and thus cutting the cost. The external casing is assembled through welding. Punching plate is connected to framework through rivet. If the ducting is deployed as an inlet passage, the whole connection shall be assembled through welding process in order to reduce the number of rivets that drops to hamper facility operation. The ducting is able to provide sound absorption, sound proofing and thermal insulation. The noise reduction for straight and elbow ducting is 10 dB and 20 dB respectively. As for those engineering instances that the required noise reduction is less than 20 dB, the ducting could be used as a replacement with traditional silencer. The ducting is functioned as flow direction and connection between facility and silencer, transition between facility inlet and outlet. In the working conditions without direct sunlight or rainfall, the shelf life of the ducting could be extended up to 20 years. The ducting parameters may vary due to specific project; nevertheless the main structure remains the same. The average noise reduction of the ducting is 40 dB, and could be even higher than 65 according to customer requirement specifications.