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The present study aims to develop waste chicken feather and chopped glass fibre-based composites. Chicken feather (CF) is loaded in varied percentage of 5,10,15% by weight. Acoustic testing was performed on the fabricated composite samples to assess their sound absorption characteristics in accordance with ISO 10534-2:1998 standards for the frequency range of 63 Hz to 6300 Hz. Addition of chicken feather in the range from 5-15% by weight has significantly alters the transmission loss characteristics for moderate to higher frequency range. Adding 10%of CF by weight found to be optimal whereas loading CF tp 15% enhance the acoustic performance for higher frequency range. Obtained results, witness the dominance of feather-based composites could contribute greatly to sustainability approach and recommend theses composites to applications like automotive, aerospace industries.

The present study investigates the impact of sound transmission loss of vertical noise barriers for high-speed railways on insertion loss at various speed grades and heights. The findings reveal an initial increase in insertion loss followed by a plateau as sound transmission loss improves. A threshold value exists for weighted sound transmission loss, beyond which the insertion loss remains relatively constant. This threshold referred to as the minimum weighted sound transmission loss decreases with increasing train speeds and increases with higher noise barrier heights. The variation in insertion loss was calculated for noise barriers at heights of 2m and 3m under different sound transmission loss conditions, using measured sound source data corresponding to train speeds of 150km/h, 200km/h, 250km/h, 300km/h, and 350km/h. By polynomial fitting, at a train speed of 400 km/h, the minimum weighted sound transmission loss for 2m and 3m high noise barriers are determined to be 20dB and 21dB respectively.

In this paper, a novel auxetic structure with rotating squares with holes is investigated. The unit cell of the structure consists of four units in the shape of a square with cut corners and holes. Finally, the structure represents a kind of modified auxetic structure made of rotating squares with holes or sheets of material with regularly arranged diamond and square cuts. Effective and dynamic properties of these structures depend on geometrical properties of the structure. The structures are characterized by an effective Poisson’s ratio from negative to positive values (from about minus one to about plus one). Numerical analysis is made for different geometrical features of the unit cells. The simulations enabled the determination of the dynamic characteristic of the analyzed structures using vibration transmission loss, transmissibility, and mechanical impedance. Numerical calculations were conducted using the finite element method. In the analyzed cases of cellular auxetic structures, a linear elasticity model of the material is assumed. The dynamic characteristic of modified rotating square structures is strongly dependent not only on frequency. The dynamic behavior could also be enhanced by adjusting the geometric parameter of the structure. Auxetic and non-auxetic structures show different static and dynamic properties. The dynamic properties of the analyzed structures were examined in order to determine the frequency ranges of dynamic loads for which the values of mechanical impedance and transmissibility are appropriate.

Membrane-type acoustic metamaterials (MAMs) are the focus of the current research due to their lightweight, small size, and good low-frequency sound insulation performance. However, there exists difficulties for extensive application because of the narrow sound insulation band. In order to achieve broadband sound isolation under the premise of lightweight, a novel MAM with asymmetric rings is firstly proposed in this paper. The sound transmission loss (STL) of this MAM is calculated by an analytical method and is verified by the finite element model. The different properties of the membrane when it is loaded with one, two, or four mass blocks are analyzed. The comparison with the traditional MAM proves the superior performance of this novel MAM. Moreover, by discussing the influence of the eccentricity and distribution position of the masses on the results, the tunability of the sound insulation performance of this MAM is proven. Finally, the Isight platform is used to optimize the MAM to further improve the broadband sound insulation performance: the average STL of the MAM is improved by 15.7%, the bandwidth above 30 dB is improved by 11.5%, and the mass density is reduced by 30.01%.

The characteristics of sound transmission loss of V-type noise barriers for reduction of wind load under the influence of multiple parameters is numerically investigated in this work. The results show that sound-absorbing materials and the heights of ventilation channels are the most important factors affecting sound insulation property of V-type noise barriers. The increase of the airflow resistivity of sound-absorbing materials will increase sound transmission loss in the high frequency band of noise barriers. When the airflow resistivity is increased from 1000Pa*s/m 2 to 15000 Pa*s/m 2 , weighted sound transmission loss is increased by 7dB. The weighted sound transmission loss is inversely proportional to the height of ventilation channels. The height of ventilation channels is reduced from 51mm to 6mm, and the weighted sound transmission loss is increased by 5.7dB.

Low frequency noise control is difficult due to the large wavelength. Acoustic metamaterials (AMs) bring a new sight for low frequency noise control because they can control low frequency wave with subwavelength structures. Since plate type structures are widely used in engineering, the plate type AM structures with different types of resonators are studied by both experiments and numeric simulations. The measured sound transmission loss (STL) curves of the samples show that there are several peak points appearing in the low frequency range. It is found from the numerical simulations that sound wave cannot transmit the plate at these points. The certain locally resonant modes of the resonators lead to good sound insulation properties of the plate type structures. By combing different types of resonators together, enhancement of STL in wide frequency ranges can be achieved. The results in this paper provide good guidance for noise control in engineering applications.

Multicore fiber is regarded as the most efficient way to realize SDM networks. Fabrication of low-loss and low-crosstalk multi-core fiber is the key to achieving high-capacity communication systems. This paper designed and fabricated low transmission loss seven-core single-mode fiber with a standard 125μm cladding diameter based on modified chemical vapor deposition. The preform of MCF is fabricated using drilling method. The seven-core fiber has achieved a low transmission loss of 0.19~0.28dB/km throughout the 1250-1600nm wavelength range. The transmission loss is below 0.19dB/km at 1550nm wavelength. The crosstalk is below -54dB/100km from 1200nm to 1600nm wavelength by utilizing a trench-assisted structure. At 1550nm wavelength, the bending loss (BL) is lower than 0.45dB/m with a bending radius of 5 mm, and the BL is 0.05dB/m with a bending radius of 15 mm. The fabricated multi-core fiber can be used for long-haul transmission and space division multiplexing communication systems.

To examine the acousto-structural behavior of a sandwich cylindrical shell benefiting from hexagonal honeycomb structures in its core and functionally graded porous (FGP) layers on its outer and inner surfaces, a comprehensive study based on an analytical model which also considers the effect of an external flow is conducted. A homogenous orthotropic model is used for the honeycomb core while its corresponding material features are found from the modified Gibson’s equation. The distribution pattern of FGP parts is either even or logarithmic-uneven, and a special rule-of-mixture relation governs their properties. Based on the first-order shear deformation theory (FSDT), Hamilton’s principle is exploited to derive the final coupled vibro-acoustic equations, which are then solved analytically to allow us to calculate the amount of sound transmission loss (STL) through the whole structure. This acoustic property is further investigated in the frequency domain by changing a set of parameters, i.e., Mach number, wave approach angle, structure’s radius, volume fraction, index of functionally graded material (FGM), and different honeycomb properties. Overall, good agreement is observed between the result of the present study and previous findings.

This paper examines effective and environmentally friendly materials intended for noise insulation and soundproofing applications, starting with materials that have gained significant attention within last years. Foam-formed materials based on cellulose fibers have emerged as a promising solution. The aim of this study was to obtain a set of foam-formed, porous, lightweight materials based on cellulose fibers from a resinous slurry pulp source, and to investigate the impact of surfactant percentage of the foam mixtures on their noise insulation characterisitcs. The basic foam-forming technique was used for sample assembly, with three percentages of sodium dodecyl sulphate (as anionic surfactant) related to fiber weight, and a standardised sound transmission loss tube procedure was used to evaluate noise insulation performance. Results were obtained as observations of internal structural configurations and material characteristics, and as measurements of sound absorption/reflection, sound transmission loss, and surface acoustic impedance. Based on the findings within this study, the conclusions highlight the strong potential of these cellulosic foams to replace widely used synthetic materials, at least into the area of practical noise insulation applications.

Due to the influence of mass law, traditional lightweight sandwich structures have struggled to surpass solid structures in sound insulation performance. To this end, we propose an acoustic metamaterial structure with a sandwich configuration based on the re-entrant negative Poisson’s ratio (NPR) structure and systematically investigate its sound transmission loss (STL) performance under incident plane wave conditions. We used the acoustic impedance tube method to experimentally study the sound insulation performance of the re-entrant NPR sandwich structure under free boundary conditions, and then established an acoustic analysis simulation model based on COMSOL Multiphysics software, which verified that the results obtained by the experiment and the numerical simulation were in good agreement. The results show that the sandwich structure exhibits excellent sound transmission loss performance in the studied frequency range (250–4000 Hz), and the overall sound insulation performance exceeds the curve of the mass theorem, basically achieving more than 20 dB when the sandwich thickness is 2 cm. Finally, we conduct parametric studies to establish a correlation between the geometric design of NPR sandwich structures and their sound transmission loss performance. The research shows that the changes of the length of the ribs, the distance from the ribs to the center of the unit, and the length of the upper wall and the lower wall have a significant impact on the sound insulation performance of the re-entrant NPR sandwich structure, while the change of the wall thickness basically will not affect the sound insulation performance of the sandwich structure. This research can provide practical ideas for the engineering application of noise suppression designs of lightweight structures.