In the last two decades, worldwide economic development has resulted in phenomenal growth of industrialization and urbanization and consequently numerous environmental issues such as noise pollution. Noise pollution has become a very threatening issue to urbanized societies. Public awareness in regard to noise pollution has forced governments to introduce mandatory legislation either to limit or eliminate noise pollution. Reduction in sound level or elimination of noise can be achieved using acoustic absorbers. Nonwoven textiles are considered to be one of the most effective and advantageous acoustic absorbers. Ease of formability, bulkiness, microstructural engineering ability, complex internal structure and relatively low production cost has made nonwoven textiles as a very viable material for use in acoustic engineering. In this study, the effect of in-plane fiber orientation, needling density and thermal calendering on needled nonwoven samples micro-structure and acoustic behavior were investigated. 3D images of micro structure of the samples were obtained using X-ray micro-computed tomography (?CT). The micro structure image of samples was analyzed using image analysis and the effect of production parameters on the internal structure of the samples was investigated. Using computational fluid dynamics (CFD) and by solving Navier-Stokes equations in the micro-structure od samples, the flow resistivity of the nonwoven samples was calculated. Miki model was used to predict sound absorption at different frequencies. A two microphone impedance tube was used to measure the sound absorption coefficient of the samples. Comparison of experimental and predicted results showed that for the same amount of porosity, samples with moderately aligned fiber orientation had the largest pore diameter (342 ?m) and the lowest flow resistivity. It was also found that samples with random in-plane fiber orientation in comparison to parallel oriented samples had the smallest pore diameter (196 ?m) and higher flow resistivity. It was found that increase in the fiber alignment along the flow direction due to decrease in resistance to flow leads to increase in permeability of the samples. Additionally, it was found that subject to constant pore diameter, in-plane orientation of fibers has no significant effect on the flow resistivity and permeability of the samples. Results also showed that 19 mm thickness samples with moderately aligned fiber orientation had a lower sound absorption coefficient in comparison to samples with random fiber orientation. It was established that sound absorption coefficient in samples with 31 mm thickness was not affected by in-plane fiber orientation at frequencies above 2200 Hz. Results showed that peak of absorption coefficient of the samples shifts from 4000 Hz to 2000 Hz when sample thickness increases from 19 mm to 31 mm. It was found that the absorption coefficient of the samples at frequencies below 3000 Hz decreases due to the decrease in sample thickness despite the increased resistance to flow due to the increased needling density. Results showed that at frequencies below 3000 Hz, the acoustic behavior of the samples is more affected by the thickness of the sample rather than by the flow resistivity. Results showed that increase in the punching density from 52 to 387 needles/cm 2 , causes the maximum sound absorption coefficient shifts from the frequency of 2000 Hz to the frequency of 5000 Hz. It was concluded that thermal calender finishing process adversly affects the sound absorption coefficient of the samples. Finally excellent compatibility was found to exist between the experimental data and the results of the proposed model. Key words: Nonwoven fabric, sound absorption, Miki model, computational flow dynamics, X-ray micro-computed tomography.