Fractal approach seems to be a potentially useful tool to describe hierarchical systems and is suitable to link the structure and properties of fiber assembly. X-ray microtomography is used to detect the microstructure of acrylic and goose down fiber assembly. Furthermore, the pore area fractal dimension of fiber assembly is calculated, using 2D images of the cross-section. And the sound absorbing behavior of assembly is measured. Correlation between the fractal dimension of fiber assembly and its mass, porosity and the sound absorption property is also studied. The results indicate that the pore area fractal dimension is positive correlated with fiber mass, and negative with porosity. For acrylic staple fiber assembly, the maximum acoustic absorption coefficient grows linearly with increasing pore area fractal dimension, while for goose down fiber assembly, there is a critical dimension which makes the sound absorption coefficient maximum. And for both assemblies, the critical frequency moves towards lower frequency with increasing fractal dimensions.%分形学是描述无序系统结构特征的有效方法,可以将纤维集合体的结构与性能联系起来.使用X射线断层扫描法分别探测了腈纶短纤和鹅绒纤维集合体的结构,利用扫描得到的纤维集合体内部截面的二维图像,计算孔洞面积分形维数；同时测量了纤维集合体的吸声性能.研究了分形维数与纤维集合体的质量、孔隙率以及吸声性能的关系,结果表明,纤维集合体的分形维数与纤维的质量呈线性正相关,而与孔隙率呈负相关关系.对腈纶短纤集合体,最大吸声系数随着分形维数的增大而增大；对于鹅绒纤维集合体,存在一个临界维数,使最大吸声系数达到最大.两种纤维集合体的吸声临界频率都随着分形维数的增大而降低.
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