| 主权项 |
1. An acoustic panel comprising
a first cellular layer with cells having a first axis, a second cellular layer with cells having a second axis, and a perforated septum layer separating the first layer and the second layer, wherein the cells of both layers have an end distal to the septum layer and an end that meets the septum layer, the maximum diameter of the cells of the first layer is less than the maximum diameter of the cells of the second layer, and the septum layer is at least 0.5 mm thick, but no more than 1.5 mm thick, the septum layer has an open area of at least 5% and no more than 20%, and the perforations in the septum layer are provided as holes having a diameter of at least 1 mm and no more than 5 mm. |
