بررسي خواص آكوستيكي لايه هاي بي بافت تهيه شده از الياف استبرق

چكيده انگليسي :

Inevestigation into Acoustic Properties of Nonwoven Layers Produced from Estabragh Fibers Sanaz Hassanzadeh s hassanzadeh@tx iut ac ir Date of Submission 18 09 2012 Department of Textile Engineering Isfahan University of Technology Isfahan 84156 83111 IranDegree M Sc Language FarsiDr Mohammad Zarrebini zarrebini@cc iut ac ir Dr Hossein Hasani h hasani@cc iut ac ir AbstractSound pollution has become an important issue that has faced world population This issue has been addressedby scientists of various disciplines Expansion and advancement of industries in different fields has necessitatedthe need to control noise in areas such as building and transportation Development of techniques for control ofnoise is a challenge that has to be faced by engineers and designers of various disciplines Various means usingdifferent structures that are used as sound absorbers are available The aim of this study is to introduce a novelfibrous structure composes of Estabragh fibers that posses unique property Estabragh is a natural hallow fiberwhich is grown widely in Iran The unique hallow structure of Estabragh makes the fiber the most suitablemeans for control of noise Production of fibrous carded layers due to the fact that Estabragh is a crimpless is animpossible task Thus in order to facilitate the production of nonwoven layers Estabragh blendes withpolypropylene fibers was used In this study five different blends of fibers were obtained containing 100 75 50 25 Estabragh and 100 of polypropylene fibers Nonwoven layers at three different weights usinga laboratory scale carding machine were produced The carded layers were needled on a laboratory scale needlepunching machine using five different punch densities In total 75 needled experimental samples were prepared The sound absorption property of the samples was evaluated at five different frequencies using Texsonic meter This apparatus measures the noise absorption coefficient NAC of the sample on impedance tube principle Among two different techniques that the impedance tube method employs movable microphone technique wasused in this research Results indicated that sound absorption coefficients of the samples depends upon variousparameters such as the percentage of the Estabragh fibers in the blend mass per unit area of the sample theamount of punch density exerted on the sample during needling operation and the frequency It was found thatsound absorbency increase with the increase in the proportion of Estabragh fibers in the blend This is due to thefact that voids in the sample are increased as Estabragh fiber content of the blend is increased Despite ofexcessive damage to fibers higher punch densities result in improvement of sound absorption by the samples More punch densities imparted to the nonwoven layers cause the fibers entangling more This phenomenonresult in decrease the pore size and increase the frictional resistance of layer simultaneously However it shouldbe noted that due to fineness of Estabragh fibers it is not possible to use excessive amount of punch densities The results also showed that sound absorption coefficient increases as mass per unit of sample is increased It isconcluded that the sample exhibited the best acoustic properties at frequency of 1000Hz A linear regression wasused in order to predict the noise absorption behavior of lightly needled Estabragh nonwoven layers Thecorrelation coefficient between predicted and observed NAC values is 0 758 indicating an acceptable capabilityof the regression model built Key wordsAcoustic Estabragh fibers NAC needling nonwoven punch density sound pollution

حسن زاده، ساناز

بررسي خواص آكوستيكي لايه هاي بي بافت تهيه شده از الياف استبرق

آلودگي صوتي , سوزن زني , ضريب جذب صوت