Fractal Model for Acoustic Absorbing of Porous Fibrous Metal Materials

Weihua Chen,Jiuhui Wu,Tianning Chen,Xiaopeng Wang,Suobin Li

doi:10.1155/2016/2890857

Weihua Chen, Jiuhui Wu + Show 3 more

Open Access

https://doi.org/10.1155/2016/2890857

Copy DOI

Abstract

To investigate the changing rules between sound absorbing performance and geometrical parameters of porous fibrous metal materials (PFMMs), this paper presents a fractal acoustic model by incorporating the static flow resistivity based on Biot-Allard model. Static flow resistivity is essential for an accurate assessment of the acoustic performance of the PFMM. However, it is quite difficult to evaluate the static flow resistivity from the microstructure of the PFMM because of a large number of disordered pores. In order to overcome this difficulty, we firstly established a static flow resistivity formula for the PFMM based on fractal theory. Secondly, a fractal acoustic model was derived on the basis of the static flow resistivity formula. The sound absorption coefficients calculated by the presented acoustic model were validated by the values of Biot-Allard model and experimental data. Finally, the variation of the surface acoustic impedance, the complex wave number, and the sound absorption coefficient with the fractal dimensions were discussed. The research results can reveal the relationship between sound absorption and geometrical parameters and provide a basis for improving the sound absorption capability of the PFMMs.

Highlights

Over the last two decades, the propagation characteristics of acoustic wave in porous fibrous metal materials (PFMMs) have attracted considerable attention because of their potential engineering applications [1,2,3]
The PFMM is a new type of multifunctional structural material and has demonstrated various novel physical properties, the sound absorption under extreme conditions such as high sound pressure level and high temperature
Allard and Champoux [12] found that the flow resistance of porous fibrous materials is closely related to the porous structure, but the accuracy of calculation for the static flow resistivity depends on the extent of approximation of the actual microstructures

Summary

Introduction

Over the last two decades, the propagation characteristics of acoustic wave in porous fibrous metal materials (PFMMs) have attracted considerable attention because of their potential engineering applications [1,2,3]. Cox and D’Antonio [8] studied the static flow resistivity of porous absorbers and summarized several empirical and semiempirical formulas for the parallel and perpendicular fibers, random fibrous arrangement, polyester fibers, and so forth. These empirical formulas can be used to evaluate the static flow resistivity. Kawasima [9] and Tarnow [10, 11] established the microstructure acoustic model and studied the sound propagation and the static flow resistivity of fibrous materials. For the Biot-Allard model, a layer of porous material is assumed to be a layer of equivalent fluid with the effective density ρ and bulk modulus K. In (1), the value of static flow resistivity is usually measured but the relationship between the static flow resistivity and geometrical parameters of the PFMM cannot be revealed.

Objectives

Results

Conclusion