The remarkable properties of natural lignocellulosic fibers such as biodegradability, light weight, low density, low cost and non-toxicity as well as being an alternative to sound absorbers made of synthetic fibers have attracted many researchers in the field of acoustics. The purpose of the present study was to compare the estimated sound absorption coefficient of composite samples made of natural coconut fibers by using empirical models and comparing them with the results of experimental data. The normal sound absorption coefficients of the samples were measured with an impedance tube. The samples were fabricated in three different thicknesses (25, 35 and 45 mm) with air gaps behind them and had a constant density of 200 kg/m³. Next, calculations were made to estimate the absorption coefficients of the samples by coding in MATLAB and using the differential equation algorithm along with Delany–Bazley, Miki and Johnson–Champoux–Allard models. Based on the results, the sound absorption coefficients of the samples increased significantly with increasing frequency. Additionally, increasing the thickness of materials at constant densities increases the absorption of sound, especially at lower frequencies (< 1000 Hz). Comparison of the experimental data and estimations of the models showed that by increasing thickness, the predicted acoustic absorption coefficients for the samples become closer to the data from the experimental tests. At frequencies < 1000 Hz, increasing the air gap at the back of the sample to 3 cm would elevate the values of sound absorption coefficient. The samples made of coir fibers would effectively dissipate the energy of sound waves. It is noted that increasing the absorption of the sound in such materials is related to the longer depreciation process of thermal and viscous transfer between the air and the absorbing materials in the composite.

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天然椰壳纤维的吸声特性及预测

天然木质纤维素纤维的卓越性能，例如可生物降解性，重量轻，密度低，成本低，无毒以及作为合成纤维制成的吸声材料的替代品，已吸引了声学领域的许多研究人员。本研究的目的是通过使用经验模型比较天然椰子纤维制成的复合样品的估计吸声系数，并将其与实验数据的结果进行比较。用阻抗管测量样品的正常吸声系数。样品以三种不同的厚度（25、35和45 mm）制造，后面有气隙，并具有200 kg / m ³的恒定密度。。接下来，通过在MATLAB中进行编码，并使用微分方程算法以及Delany–Bazley，Miki和Johnson–Champoux-Allard模型，进行计算以估计样品的吸收系数。根据结果​​，样品的吸声系数随频率增加而显着增加。此外，以恒定的密度增加材料的厚度会增加声音的吸收，尤其是在较低的频率（<1000 Hz）下。实验数据和模型估计值的比较表明，通过增加厚度，样品的预测吸声系数变得更接近实验测试的数据。在频率<1000 Hz时，将样品背面的气隙增加到3 cm将提高吸声系数的值。由椰壳纤维制成的样品将有效地消散声波的能量。应当指出，在这种材料中增加声音的吸收与空气和复合材料中的吸收材料之间的热和粘性传递的更长的折旧过程有关。