## 5 Conclusions  
This study, based on the three-parameter approximation of the JCAL model, investigated the effects of fiber diameter variation and zeolite particle addition on the pore size distribution of porous materials and analyzed their influence on the acoustic performance of glass fiber porous materials. The following conclusions were drawn:  
Smaller pore sizes improve the low-frequency sound absorption performance of glass fiber porous materials. However, excessively small pores increase density and flow resistivity, resulting in significant sound wave reflection and negatively impacting acoustic performance. Thus, the sound absorption performance of fiber porous materials exhibits an optimal pore size range, with the best acoustic performance observed for pores between 60 and 80 \(\upmu\)m.  
Both density and fiber diameter influence pore size and, consequently, the acoustic performance of sound-absorbing materials. As the density of fiber porous materials increases, the median pore size decreases, leading to improved mid-to-low-frequency sound absorption performance. The best acoustic performance is achieved at a density of 120 kg/m\({}^{3}\). At the same density, smaller fiber diameters reduce pore size and enhance acoustic performance. For composite porous materials made of glass fibers and zeolite particles, zeolite replacement reduces acoustic performance at low density. Conversely, at higher densities, a small amount of zeolite improves acoustic performance by optimizing the pore structure. The best sound absorption performance is achieved at a density of 120 kg/m\({}^{3}\) with a zeolite replacement ratio of 10%, yielding a noise reduction coefficient (NRC) of 0.65. The comparison between experimental and simulated results using the JCAL three-parameter model shows a high degree of agreement for single-fiber porous materials. However, for composite materials, discrepancies arise due to their complex microstructural changes. Particularly in composite materials, the interfacial structures between layers and the interaction between fibers and particles introduce complexities in predicting acoustic impedance, leading to deviations between experimental and simulated data. The following supporting information can be downloaded at: [[https://www.mdpi.com/article/10.3390/app15063104/s1](https://www.mdpi.com/article/10.3390/app15063104/s1)]([https://www.mdpi.com/article/10.3390/app15063104/s1](https://www.mdpi.com/article/10.3390/app15063104/s1)), Figure S1: Sound absorption coefficient curves under different median pore size; Figure S2: Schematic Diagram of the Sound Absorption Testing Device; Figure S3: SEM image of potassium silicate attached fiber surface. Table S1: Averaged normalized mass percentages measured by EDS; Table S2: Median pore size of composite porous materials with different volumetric weight, Table S3: NRC of single fiber porous material under different volumetric weight, Table S4: NRC of fiber composite porous materials under different volumetric weight. H.S. : writing--original draft, visualization, software, investigation, data curation; J.X. : writing--review and editing; D.L. : conceptualization; Y.F. ([PERSON]): formal analysis; P.T. : writing--review and editing, resources, supervision, funding acquisition; Y.F. ([PERSON]):  
Figure 12: (**a**) Interlayer microstructure of composite materials; (**b**) Schematic illustration of the sound absorption mechanism of composite materials. writing--review and editing, supervision, resources, funding acquisition. All authors have read and agreed to the published version of the manuscript. This work was funded and supported by the National Natural Science Foundation of China (Grant No. 52108245) and the National Key R&D Program of China (Grant No. 2023 YFC3806301-03). Not applicable. The original contributions presented in this study are included in the article/Supplementary Materials. Further inquiries can be directed to the corresponding authors.