| 摘要 |
A sound absorbing tile (20) comprising cementitious material having a plurality of punched perforations (22,24) extending into the cementitious material. The cut edges of the perforations have a cut quality index of greater than 0.98. The cut quality index is defined as the ratio of pixels occupied by the perimeter of a digitized image of a perforation after a smoothing operation has been applied, to the number of pixels occupied by the perimeter of a digitized image of a perforation before a smoothing operation has been applied. The smoothing operation comprises four levels of binary erosion followed by binary dilation.
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