A New Empirical Model for Predicting the Sound Absorption of Polyfelt Article

A New data-based simulation for Predicting the Sound Absorption of Polyfelt Fibrous Materials for Acoustical Applications - Article ExampleEmpirical models do non require detailed knowledge of the internal structure of the material nor are they derived from hypothetic considerations. Delany and Bazley 1 showed that the set of the distinctive acoustic impedance and propagation coefficient for a range of fibrous materials, normalized as a function of frequence divided by flow resistivity could be presented as bare(a) power law functions. Model for Impedance The model is based on numerous impedance tube measurements and is good for determining the wad acoustic properties at frequencies higher than 250 Hz, but not at low frequencies 2,3. The validity of this model for take down and higher frequencies was further extended by Bies and Hansen 4.Dunn and Davern 5 calculated new regression coefficients between characteristic acoustic impedance and propagation coefficient for low ai rflow resistivity values of polyurethane foams and multilayer absorbers. To that effect, engineers can obtain the preoccupation coefficient of sound at normal incidence by using the equation below ZR = P0 * C0 (1 + C1 ((P0f)/r)-c2) The final exam model which comes as a derivative of the first model is Zt = (ZR + iZl)coth(a + iB) * l Zt = ZIR + iZIl Qunli 6 later extended this work to queer a wider range of flow resistivity values by considering permeable plastic open-cell foams.Miki 7, 8 generalized the experimental models developed by Delany and Bazley for the characteristics acoustic impedance and propagation coefficient of porous materials with respect to the porousness, tortuosity, and the pore shape constituent ratio. Moreover, he showed that the real part of surface impedance computed by the Delanys model converges to negative values at low frequencies. Therefore, he modified the model to give it real positive values thus far in wider frequency ranges. Other empirical m odels include those of Allard and Champoux 9. These models are based on the assumption that the thermic effects are dependent on frequency. The models work well for low frequencies. The Voronina model 10 is another simple model that is based on the porosity of a material. This model uses the average pore diameter, frequency and porosity of the material for defining the acoustical characteristics of the material. Voronina 11 further extended the empirical model developed for porous materials with strict frame and high porosity, and compared it with that of Attenboroughs theory. A significant agreement was found between their empirical model and Attenboroughs theoretical model. Recently, Gardner et al. 12 implemented a specific empirical model using neural networks for polyurethane foams with easily metric airflow resistivity. The algorithm embedded in the neural networks substitutes the usual power-law relations. The phenomenological models are based on the necessity physics of ac oustic propagation in a porous medium such as their worldwide features and how these can be captured in a model 13. Biot 14 established the theoretical explanation of saturated porous materials as similar homogeneous materials. His model is believed to be the most accurate and detailed description public treasury now. Among the significant refinement made to Biot theory, Johnson et al. 15 gave an interpolation formula for Dynamic tortuosity of the medium based on limiting behavior at zero and infinite frequency. The dynamic tortuosity employed by Johnson et al. is equivalent to the structure factor introduced by Zwikker and Kosten 16 and therefore