## 1 Introduction  
With the continuous development of industrialization and urbanization, the surge in traffic volume, frequent construction activities, operation of industrial equipment, and the rise in recreational activities has significantly increased noise generation [1,2]. Noise pollution has become a focal issue across multiple fields and disciplines. Researchers from various domains, including materials science [3, 4, 5], environmental engineering [6; 7; 8; 9], architectural design [10; 11], and urban planning [12; 13; 14], are actively exploring more effective noise absorption and reduction materials. Among various sound-absorbing materials, fiber-based porous materials are widely used in noise reduction due to their elongated morphology, which provides a high specific surface area and an open, continuous pore structure. However, these materials typically exhibit less effective sound absorption at mid-to-low frequencies compared to high frequencies, which limits their application scope. To address this limitation, significant efforts have been devoted to the design and fabrication of porous sound-absorbing materials, including modifications to fiber surface roughness [15], gradient pore structures [16; 17; 18], folded structures [19], and fiber cross-sectional shapes [20]. In recent years, porous composite materials [21; 22; 23] have garnered widespread attention due to their excellent physical properties, non-flammability, and acoustic performance. Fibro-granular composites are a new category of porous composite materials that are composed of granular material embedded in a fibrous matrix. These materials are typically lightweight, highly porous, and cost-effective. By leveraging the complementary sound absorption properties of different components and optimizing their overall acoustic performance through diverse structural and material combinations, fiber-granular composites demonstrate superior acoustic properties compared to single-component fiber or particle-based porous materials. However, the underlying mechanisms of fiber-particle composites in acoustics are limited in research. In order to delve into the propagation characteristics of sound waves in different media and to better predict the acoustic performance of materials, numerous scholars have established sound absorption models. To date, research on fiber-based porous materials has primarily focused on D-B type empirical models [24; 25; 26; 27] and Johnson-Champoux-Allard (JCA) type semi-phenomenological models [28; 29; 30; 31; 32], analyzing parameters such as porosity, flow resistivity, viscous characteristic length, thermal characteristic length, and tortuosity. Generally, models with a larger number of parameters are better equipped to accurately describe the dissipation of acoustic energy within porous media, thus enabling more precise predictions of their sound absorption coefficients. However, the inclusion of more parameters increases the complexity of the models. Some of these parameters are extremely challenging to measure directly and are often inferred from fitted data, which poses certain challenges for studying the microstructure of porous media. In recent years, [PERSON] et al. [33] demonstrated through theoretical and experimental studies that the acoustic impedance of porous media with a pore size distribution approximating a log-normal distribution can be predicted using only three parameters: porosity, median pore size, and the standard deviation of the pore size. This significantly simplifies the process of predicting the acoustic characteristics of porous media. Considering complexity and prediction accuracy, the three-parameter model is one of the most ideal models for sound absorption performance prediction, and it is widely used in the prediction of the sound absorption performance of foam [34; 35] and particle [36; 37] porous materials. However, the application of the three-parameter model in fiber and its composite porous sound absorption materials is limited.