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Application of Acoustical Method to Characterize Nonwoven Material
Tao Yang,Xiaoman Xiong,Yuanfeng Wang,Rajesh Mishra,Michal Petrů,Jiří Militký 한국섬유공학회 2021 Fibers and polymers Vol.22 No.3
Some structural parameters, such as tortuosity, viscous and thermal characteristic lengths, are difficult to obtainthrough direct measurements. Existing indirect methods, i.e. acoustical method, make it possible to estimate theseparameters. This paper presents an application of acoustical inversion methods for estimating structural parameters ofpolyester nonwoven materials. A four-microphone impedance tube was used to measure sound reflection and transmissioncoefficients. The inversion methods used in this research are least square and Bayesian approaches. The least square methodwas achieved via Nelder-Mead algorithm. The Bayesian inversion process was conducted with Metropolis-Hastingsalgorithm and maximum a posteriori. Inversed parameters from two methods as well as front and back sides of nonwovenfabric were compared. Moreover, inversed porosity and airflow resistivity were compared with measured values. The resultsshow that the least square and Bayesian methods has a good agreement. Estimated parameters from Bayesian method wereselected for further analysis. A sizable differences on thermal characteristic length were found by comparing the values fromtwo sides, while the differences are relatively small for other parameters. It is also found that the inversed porosity, tortuosityare reasonable. The results suggest that the acoustical inversion methods can be used to accurately characterize polyesterfibrous materials.
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