I recently finished my Extreme noise isolation project. After building in 140Kg of bitumen and noise isolation sandwich membrane, the results are quite impressive. The wind noise is so noticeable, however the cars aerodynamic did not changed, because anything else has been silenced effectively. I have not only the complete floor,doors,roof,hood,trunk covered in 3 layer (Vibration dampening,Foam,MLV membrane), but also the big surface of internal plastic covers,dashboard,fender liners and the inner side of front fenders was an ideal place to insert the self -adhesive composite membranes. Because i did not removed the dashboard, the easier solution was to apply covering to the reachable areas underneath. The most evil areas are the passengers foot compartments left side from firewall, and the rear right wheel covering inside where the rolling noise of the tyres comes in in spite of the 6mm bitumen+4mm foam+3mm MLV + 6mm(35db) MLV sandwich on the plastic carpet. I think deep sounds can not be isolated with foam, only with sandwich membrane effectively, which consist on some mm of heavy MLV and some foam. Water repellent rubber spray is also recommended to protect the sandwich membrane from condensation water, unless you live in desert area. Also recommended to use 3-4 different type/strength/weight/thickness of sandwich material and at least 2-3 different bitumen. I used Bitumen with loss factor 0.40 on the roof, a thicker 3mm 0.49 on the external walls and 0.66 on the floor. From sandwich membrane i used 6mm/28db in the doors+hood, 35db on the floor and 38db 9mm thick at the rear fenders of the cabin. Morover from 3mm/35db MLV and 4mm/30db sandwich used in the places where place was limited, and heat insulating was not a goal. The front floor was with double layer of sandwich membrane insulated 6mm/35db and 4mm 32decibel on the top of it so its together 36.8decibel.The passenger foot compartments left side towards the firewall remained the most noise infected area, probably due the exhaust pipe, where after using 2 layer of 35db sheet the noise still remained 68db from the original 75 measured befor the project. If someone finding interesting my article, please write what nois levels are you measured in your HDJ100 or what is the road noise in your LX470, before and after the noise insulation.
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