Acoustic protection structure e.g. cover sheet, for wall of motor vehicle, has separation units provided for spacing average frequency absorption porous layer from wall and creating air layer between absorption porous layer and wall

摘要

The structure (1) has a high frequency absorption porous layer (3) whose resistance to passage of air ranges between 300 and 800 Newton seconds per cubic meter. An average frequency absorption porous layer (4) is arranged against the layer (3), where resistance to passage of air of the layer (4) ranges between 500 and 2500 Newton seconds per cubic meter. Separation units (5) are provided for spacing the layer (4) from a wall (2) and creating an air layer (6) between the layer (4) and the wall.