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A Review of Sustainable Materials for Acoustic Applications
Abstract and Figures
Acoustical sustainable materials, either natural or made from recycled materials, are quite often a valid alternative to traditional synthetic materials. The production of these materials generally has a lower environmental impact than conventional ones, though a proper analysis of their sustainability, through Life Cycle Assessment procedures, has to be carried out.Airborne sound insulation of natural materials such as flax or of recycled cellulose fibres is similar to the one of rock or glass wool. Many natural materials (bamboo, kenaf, coco fibres) show good sound absorbing performances; cork or recycled rubber layers can be very effective for impact sound insulation. These materials also show good thermal insulation properties, are often light and they are not harmful for human health. Furthermore, many of these materials are currently available on the market at competitive prices.There is however a need to complete their characterization, both from an experimental and a theoretical point of view, and especially to propose a standard and unique procedure to evaluate their sustainability.The paper presents an updated survey on the acoustical properties of sustainable materials, both natural and from recycled materials, including mixed and composite materials and systems such as green roofs and green walls, and is completed by a wide selection of recent related bibliography.
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... The review shows that natural materials have better environmental aspects and efficiency than conventional materials. Natural organic materials such as wood, charcoal, coconut shells, peat, natural bitumen and asphalt, hemp, kenaf, and sheep's wool are moving toward a completely sustainable energy strategy [23]- [25]. Demibras showed in his research that lowcost and environmentally sustainable charcoal raw materials produced from biomass sources from wood, woody agricultural products, the biogenic fraction of municipal waste, nut shells, etc. [26]. ...
Wood charcoal is a sustainable, renewable, and environmentally friendly material with the use that the acoustic device can produce. Charcoal made of wood waste materials allows for improving indoor acoustical quality. Therefore, this objective of the article is to investigate the sound scattering coefficients of QRD with the perforation ratio of oak wood charcoal elements. Sound scattering coefficient calculated with the measurement of the reverberation time in the reverberation chamber. The calculation results of the scattering coefficient show the growth of scattering in the frequencies - the highest value reached 0.88 (diffuser N7 with charcoal). The effectiveness of diffusers to diffuse sound waves increases as the number of wells grows. The diffuser with 80 % charcoal elements showed a higher scattering coefficient compared to the diffuser without charcoal elements.
... This type of material can be classified into four main categories (Asdrubali 2012). ...
In this paper, an experimental procedure is aborted in order to fight against noise and reduce noise pollution through the synthesis of an ecological material with acoustic potential made from industrial waste. In fact, phosphate sludge is a sound absorber and it is really possible to exploit the tons of this material discarded in the wilderness without any recovery and without any beneficial contribution. To improve its ability as sound absorber an experimental characterization of the material and measurement of absorption coefficient is conducted. The Kundt tube was used to determine the absorption coefficient of the samples Several samples were prepared with different physical and geometric properties such as: the thickness of the samples, the percentage of paper, and the percentage of surfactant. The measured absorption curves were analyzed in order to study the influence of physical and geometric parameters on the measured absorption coefficient.
... Few studies have conducted comparative LCA studies for applications in the building or construction industry [3,23,24,29]. Some studies have shown that replacing conventional plasterboards with composites significantly reduces environmental impacts [23,24]. ...
As one of the most pollution-generating industries in the world, the textile industry generates large volumes of waste at the end of its manufacturing process. This waste is frequently dumped in open areas or is openly burned, contributing to GHG emissions. In recent years, emphasis has been placed on developing new materials from textile waste to promote a circular textile economy. The construction industry is one application for these novel materials. The construction industry consumes a lot of resources and energy. As a result, recycled and upcycled building materials are gaining popularity in the construction industry. The research team developed a new composite material for non-structural applications using polyester textile waste and thermoplastic packaging waste. This study aimed to conduct a Life Cycle Assessment (LCA) to determine the sustainability of this new material as a substitute for partitioning wall materials available in the market. The goal of the LCA study was to compare the Global Warming Potential (including biogenic CO2) of the production phase of the composite material against the gypsum partitioning board. The scope of the study focused on the Sri Lankan context. The functional unit for this study was considered as 1 m2 of each type of material. The modeling was carried out using GaBi LCA modeling software (V8.7.1.3). The LCI inputs for the production phase of the composite were based on literature data, the GaBi database (V8.7.1.3), and the Ecoinvent 3.8 database. According to the analysis, the production of 1 m2 of the new composite board as an alternative material saves GHG 8.4617 kg CO2 eq compared to virgin gypsum boards. These findings suggest that using waste resources to create new construction materials aids the sustainability efforts of both industries. The findings are also useful in making decisions on using waste-based composites in specific applications.KeywordsGHGGlobal Warming PotentialLCAWall partitioning materialTextile wasteThermoplastic composite
A concentração urbana apresenta desafios à sustentabilidade: a poluição sonora por ruídos e ambiental por resíduos. Neste artigo demonstra-se uma metodologia experimental do desenvolvimento de uma nova composição porosa a partir de resíduos de poliuretano e núcleo de chapas de gesso reciclados de 9,5 mm. O objetivo foi caracterizar a estrutura celular da porosidade e desempenho de absorção acústica diante dos coeficientes acústicos em diferentes frequências. As características celulares porosas são essenciais para o desempenho acústico. Os resultados revelaram três materiais com células de poros abertos pequenos (61,27%) com diâmetro de 1 a 3,99 m (57,35%), poros médios e grandes entre 4 a 9 m de diâmetro (42,65%) composta por maior parte de poliuretano rígido (83,33%) com porosidade de 43,12% sendo oxigênio (60,24%), cálcio (19,75%) e enxofre de cálcio (18,06%). Os coeficientes de absorção sonora são relevantes em todas as frequências crescendo sucessivamente, destacando-se em altas frequências sendo: 1000 hz – 0,59; 1250 hz – 0,64, 1600 hz – 0,69; 2000 hz – 0,74, 2500 hz – 0,76. Assim, o novo material reciclado sustentável poroso é indicado para aplicações acústicas para altas frequências como núcleos para a construção civil e setores industriais para reduzir ruídos e vibração. Contribui-se como alternativa para a gestão dos resíduos nas cidades.
O uso da madeira de plantios florestais como material construtivo mostra-se uma alternativa mais sustentável no meio da construção civil, seu uso em painéis pré-fabricados faz-se interessante como solução de vedação leve para edificações mais econômicas e otimizadas. Mas, há de se considerar a necessidade de isolamento termoacústico nesses painéis, e aqui se insere a proposta do artigo, que visa preencher a lacuna de pesquisas sobre materiais isolantes ecológicos. A partir de investigação nas literaturas técnico-científicas e no mercado, nacional e internacional, foi constatado que existem muitos materiais naturais ou reciclados com propriedades adequadas para o emprego como materiais isolantes na construção civil, e inclusive alguns desses já são comercializados no exterior com preços competitivos. No Brasil, esse mercado ainda é incipiente, entretanto percebe-se o potencial no uso de resíduos agrícolas como isolantes, tendo em vista a alta produção do país.
In this paper, a time-conserving fragility curve formulation methodology for extreme events is discussed. Uncertainty is a parameter that has a significant effect on the probabilistic estimations of infrastructure failures. Structural damages to civil infrastructure range from minor defects to collapse relative to serviceability or restoration measures. In this paper, earthquake-induced landslides are used as a sample case study, to study empirical methods of fragility curve formulation. Method of maximum likelihood and best-fit regression methods are applied to an extreme event, and fragility curves are derived. Monte Carlo stimulation is applied to analyse the behaviour of uncertainty parameter concerning standard sections of highway and railway embankments. Finally, the coefficient of determination was calculated to illustrate the correlation between developed curves and data points. The proposed method suggests an optimum method to quantify the failure probability from an available data sample or a real incident-based data sample, which is computationally very effective. Improvement in vulnerability estimations provides high maintenance and efficient restoration schemes for transportation networks which are prone to extreme events such as landslides.KeywordsFragility curvesEarthquake-induced landslidesMaximum likelihoodMonte Carlo
Residential apartment buildings are widely implemented in Sri Lanka due to rapid urbanization and land scarcity. The confined spaces and controlled ventilation in such apartments could result in adverse health effects, including Sick Building Syndrome (SBS). Because of the usage of chemical products such as incense sticks in such compact spaces for religious activities in South Asia, SBS can occur. This study is one of the first field studies to establish a connotation between the indoor air quality of apartment buildings in Colombo, Sri Lanka, with various chemicals, including incense products and SBS. Measurements were taken from multiple locations in 50 apartments of various indoor environment parameters. Significant Total Volatile Organic Compound (TVOC) concentrations (up to 4.500 ppm) were associated with the use of chemicals, particularly cube-type incense products. Higher CO2 concentrations were associated with migraine and headaches. The relationship between chemical and incense products with higher levels of TVOC and SBS symptoms calls for urgent attention of the key urban planning stakeholders in Sri Lanka to improve ventilation and avoid using such products indoors.KeywordsSick Building SyndromeIndoor air pollutionIncense productsUrban high risersTVOC concentration
The study developed and designed polyvinyl acetate (PVAc) foams using advanced freeze-drying technology, which exhibited good heat-insulating ability, flame retardancy, and mechanical properties. Different combinations of bleach kraft pulp, water-soluble chitosan, and zinc borate were used to reinforce the foams. The foams exhibited desirable compression and flexural properties, with compression strength and compression modulus ranging from 0.01 MPa to 0.08 MPa and 0.05 MPa to 0.29 MPa, respectively, while flexural strength and flexural modulus ranged from 0.12 MPa to 5.37 MPa and 9.86 MPa to 260,85 MPa, respectively. The use of zinc borate as a reinforcement resulted in improved thermal properties and reduced mass loss at 600°C by 20.69%. Thermal conductivity tests indicated that the foams had low thermal conductivity values ranging from 0.037 W/mK to 0.074 W/mK. The foams with zinc borate (60 g/L) and high molecular weight water-soluble chitosan (70 g/L) reinforcement exhibited high limiting oxygen index (LOI) of 28.72%. Overall, the results suggest that the PVAc foams could serve as a promising sustainable alternative in thermal insulation and construction fields.
Living (green) walls are used increasingly on building facades and environmental noise barriers. These systems combine good visual aesthetic qualities with high acoustic absorption that help to control the level of environmental noise. This work studies the acoustical and related nonacoustical properties of soil substrate that is used in green noise control elements as a function of moisture content. It is shown that the moisture added to soil either naturally or artificially has a dominant effect on its acoustic absorption coefficient. The difference in the absorption coefficient between moderately dry and heavily wetted soil specimens can be 5-10 folds. It is shown that the influence of moisture is reduced considerably when a soil specimen is blended with a hydrophilic granulates that retain a large proportion of water and keep the pores in the soil relatively dry. In this case, the acoustic absorption of soil substrate is similar to that expected from a good quality, man-made fibrous absorber. This effect predicted accurately using an acoustic model based on four measurable non-acoustic properties: flow resistivity, porosity, tortuosity and pore size distribution.
Acoustical performance and mechanical properties of different types of resilient underlayer, used in floating floors, are investigated on the basis of apparent dynamic stiffness measurement, compressibility and compressive creep and of laboratory measurement of the reduction of transmitted impact noise. Determining and quantifying resilient underlayers properties with time, on the basis of evaluation of thickness under load and behaviour under compression, is the aim of this study. The measurement and analysis methodologies of the macroscopical mechanical behaviour, although in first approximation, allow useful knowledge of acoustical performances of resilient materials used under floating floors.
The expert opinions of an international working group commissioned to assess the carcinogenic risks to humans from man-made mineral fibres are presented. It is concluded that ceramic fibres, glass wool, rock wool and slag wool may be carcinogenic to humans. However, glass filaments cannot be so classified.
Porous materials are widely used as sound absorbing materials in noise control engineering. In view of the growing interest in sustainable construction a new field involves the creation of the acoustic absorbents using recycled material based on industrial residues or derived from plants. Some authors already have models of prediction for this type of eco-materials. In this work, materials made from natural fibres (vegetative materials) or materials made from recycled materials are investigated as sound absorbers. The sound absorption coefficient and air flow resistivity of these materials have been evaluated and the potential applications in building acoustics and/or in noise barriers are proposed.
A research is initiated in Universiti Kebangsaan Malaysia to model the acoustic absorption of coir fiber. This natural porous material may be obtained in two types; natural fiber without any additives and the industrial type that is treated with binder. Biot-Allard model is implemented for acoustic modelling of fiber. Experimental validation supports the outcomes of the modelling technique. Results show that fresh coir fiber has an average absorption coefficient of 0.8 at f <1360 Hz and 20 mm thickness. Increasing the thickness has improved the sound absorption in lower frequencies, having the same average at f <940 Hz and 30 mm thickness. Biot-Allard model should be compensated for the industrial prepared fiber considering the binder additive. This form generally shows poor acoustical absorption in low frequencies. Inevitably, fiber has to be mixed with additives in commercial use to enhance its characteristics such as stiffness, unti-fungus and flammability. Hence other approaches such as adding air gap or perforated plate should be used to improve the acoustical properties of industrial treated coir fiber.
Green roofs have entire roof tops covered with vegetation as opposed to shingles, bitumen, cement or gravel in conventional roofs. During the previous four years, the number of extensive green roofs (which are characterized by a relatively shallow depth of the growing medium) in the United States has grown at the rate of about 50% each year. Even then the total coverage area for green roofs in the US remains insignificant as compared with Germany, where green roofs have grown steadily over the past 25 years. The future of green roofs in the US depends not only on right incentives, which are more or less non-existent at this time, but also on the establishment of national performance standards, research facilities and test methods. The need for test standards and performance criteria is especially urgent for synthetic materials such as waterproofing membranes, root barrier layers, geocomposites and geotextiles, where many competing products can quickly flood the market, making it almost impossible to distinguish between what works and what does not. Given the right conditions, it is not unlikely that the size of green roof market in the US could far exceed that in Germany in eight years, and perhaps sooner.
This paper focuses on the acoustical properties of mixes of hemp particles. A physical analysis of the experimental data revealed that acoustical dissipation in this material is governed by inter-particle pores in the tested frequency range. The evolution of the acoustical parameters of mixes of hemp particles is studied as a function of density and it was found that these parameters are strongly affected by the parallelepipedal shape of the particles. The relationships existing between these acoustical parameters and basic parameters of the material, such as the apparent density of the mix, the particle apparent density, the characteristic dimension of the particles and their shape factor are investigated. It is shown first that these basic parameters can be directly used to model the acoustical properties of the mixes, then that acoustical data can be very useful to characterize the shape and microstructure of these hemp aggregates.