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A New Empirical Model for Predicting the Sound Absorption of Polyfelt Fibrous Materials for Acoustical Applications
Engineering and Construction
Pages 4 (1004 words)
A New Empirical Model for Predicting the Sound Absorption of Polyfelt Fibrous Materials for Acoustical Applications I. Introduction Accurate modeling of the acoustical properties of porous materials is of considerable interest to acoustic and noise engineers and material manufacturers.
Empirical models do not require detailed knowledge of the internal structure of the material nor are they derived from theoretical considerations. Delany and Bazley  showed that the values of the characteristic acoustic impedance and propagation coefficient for a range of fibrous materials, normalized as a function of frequency divided by flow resistivity could be presented as simple power law functions. Model for Impedance The model is based on numerous impedance tube measurements and is good for determining the bulk acoustic properties at frequencies higher than 250 Hz, but not at low frequencies [2,3]. The validity of this model for lower and higher frequencies was further extended by Bies and Hansen .Dunn and Davern  calculated new regression coefficients between characteristic acoustic impedance and propagation coefficient for low airflow resistivity values of polyurethane foams and multilayer absorbers. ...
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