sound insulation
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Materials ◽  
2022 ◽  
Vol 15 (2) ◽  
pp. 490
Author(s):  
Shande Li ◽  
Di Xu ◽  
Xiaoxun Wu ◽  
Renjie Jiang ◽  
Geman Shi ◽  
...  

The existing sandwich structure of the aircraft cabin demonstrates a good sound insulation effect in medium and high frequency bands, but poor in the low frequency band. Therefore, we propose an infinite new lightweight broadband noise control structure and study its sound transmission loss (STL). The structure is an orthogonally rib-stiffened honeycomb double sandwich structure with periodic arrays of shunted piezoelectric patches, and demonstrates lighter mass and better strength than the existing sandwich structure. The structure is equivalent according to Hoff’s equal stiffness theory and the effective medium (EM) method. Using the virtual work principle for a periodic element, two infinite sets of coupled equations are obtained. They are solved by truncating them in a finite range until the solution converges. The correctness and validity of the model are verified by using simulation results and theoretical predictions. Eventually, a further study is performed on the factors influencing the STL. All the results demonstrate that the STL in low-frequency can be improved by the structure, and the sound insulation bandwidth is significantly broadened by adding shunted piezoelectric patches. The structure can provide a new idea for the design of broadband sound insulation.


2022 ◽  
Vol 905 ◽  
pp. 246-253
Author(s):  
Hong Wei Tian ◽  
Hai Feng Chang ◽  
Hong Jun Ye

The sandwich structure with foldcore is a new type of structural material with light weight, high specific strength, high specific rigidity and multi-functional potential, which is connected with each other in core space, this kind of three dimensional structures can be formed by folding based on two dimensional materials. The main research achievements and characteristics of sandwich structure with foldcore in recent years are summarized and analyzed according to the lightweight and multi-functional requirements of aircraft structure in this paper. The configuration optimization scheme and fabrication process of the sandwich structure with foldcore are described. Moreover, the research status of multi-function of the sandwich structure with foldcore are summarized, including sound insulation, thermal protection, stealth performance of the structure, etc.


2022 ◽  
Vol 185 ◽  
pp. 108399
Author(s):  
Mikko Kylliäinen ◽  
Lauri Talus ◽  
Jesse Lietzén ◽  
Pekka Latvanne ◽  
Ville Kovalainen

Polymers ◽  
2021 ◽  
Vol 14 (1) ◽  
pp. 163
Author(s):  
Enikő Mester ◽  
Dániel Pecsmány ◽  
Károly Jálics ◽  
Ádám Filep ◽  
Miklós Varga ◽  
...  

Polyurethane flexible foams are widely used for a variety of applications to improve comfort and durability. Their long-term frequent use inevitably leads to the generation of waste that needs to be treated. The recycling and reuse of polyurethane waste are essential to achieve an environmentally friendly economy. The present study investigates the potential to reuse and repurpose flexible polyurethane foam from automotive seat cushion waste materials. Flexible foams were prepared with different hardnesses using isocyanate–polyol ratios between 0.8 and 1.2 NCO-index. Dry heat aging tests were performed to mimic the long-term usage of the materials. The decrease in compressive strength was compared with the change in acoustic damping properties before and after the aging tests using an acoustic tube, and the change in foam cell structures was also analyzed by micro-CT. On the basis of the results obtained, although the foam systems are no longer suitable to be used as seat cushions due to aging, they can still be used as sound insulation materials within a given frequency range, as their sound absorption capacity is suitable for such purpose.


2021 ◽  
Vol 14 (1) ◽  
pp. 103
Author(s):  
Silviu Nastac ◽  
Petronela Nechita ◽  
Carmen Debeleac ◽  
Cristian Simionescu ◽  
Mihai Seciureanu

Lignocelluloses residues from the post-harvest crop are receiving great scientific attention nowadays. Generally, the composite materials based on lignocelluloses waste present low density and weight, and better insulation properties compared with those petroleum-based. This study presents the results of experimental investigations regarding soundproofing capabilities for a composite material based on expanded perlite (EP) and natural polymers matrix (starch) reinforced with rapeseed stalks waste. The preparation of light-weight samples of composites was performed at room temperature through a mechanical mixing process of EP with starch polymers and rapeseed residues until optimum moisture content composition was obtained. Rapeseed stalks long fibers were avoided through the preliminary dry grinding procedure, and the composite was air-dried at room temperature for 48 h. Four samples of composites with different ratio of EP and rapeseed waste were considered. The evaluation of sample sound insulation characteristics was performed using the transfer-matrix method based on a four-microphone acoustic impedance tube. The paper concludes that the proposed composite provides comparative sound insulation capabilities to actual materials, with few particular aspects presented within the paper. Thus, these new materials are promising as a viable alternative to the actual large-scale utilization solutions in soundproofing applications.


Author(s):  
Д. В. Монич ◽  
И. В. Матвеева ◽  
П. А. Гребнев ◽  
Д. С. Кузьмин

Состояние проблемы. Звукоизоляция легких перегородок значительно зависит от места их установки в здании. Необходимы исследования структуры звукового поля в несоразмерных помещениях и анализ его влияния на звукоизоляцию легких ограждений. Результаты. Проведены натурные и лабораторные экспериментальные исследования звукоизоляции каркасно-обшивной перегородки, установленной в коридоре. Для случая соразмерного помещения получена хорошая сходимость результатов. Теоретически исследована структура звукового поля при зеркальном отражении звука (с использованием метода прослеживания лучей). Выполнены расчеты с получением распределений долей осевых, касательных и косых лучей в помещениях, расчеты уровней интенсивности звуковых волн, падающих на боковые стены и потолок коридора. Учитывалось положение источника шума относительно перегородки и других ограждений. Выводы. Пропорции помещений влияют на звукоизоляцию легких ограждений. В диапазоне ниже граничной частоты диффузности несоразмерного помещения с источником шума структура звукового поля неоднородная, звуковые лучи падают на ограждение неравномерно с различных направлений. Это приводит к уменьшению совпадений мод колебаний в воздухе и в ограждающей конструкции, частотная характеристика звукоизоляции ограждения имеет пикообразный вид. Statement of the problem. Sound insulation of lightweight partitions depends significantly on the place of installation in the building. It is necessary to study the structure of the sound field in disproportionate rooms and analyze its effect on the sound insulation of light enclosures. Results. Natural and laboratory experimental studies of the sound insulation of the frame partitions installed in the corridor were carried out. For the case of a commensurate room, good convergence of the results was obtained. The structure of the sound field with mirror reflection of sound has been theoretically investigated using the method of tracing of sound rays. Calculations were performed to obtain the distributions of the proportions of axial sound rays, tangential sound rays, oblique sound rays in the premises, and the calculations of the intensity levels of sound waves incident on the lightweight partition and other enclosures of the corridor. The position of the noise source relative to the lightweight partition and other enclosures of the corridor was taken into account. Conclusions. The proportions of the rooms affect the sound insulation of lightweight enclosures. The structure of the sound field of a disproportionate room with a noise source is non-uniform in the range below the boundary frequency of diffuse sound field. Sound rays fall on the lightweight partition unevenly from different directions. This leads to a decrease in the coincidence of wave modes in the air and wave modes in the lightweight partition. The frequency characteristic of the sound insulation of the lightweight partition has a peak-like appearance.


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