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Journal articles on the topic 'Sound Acoustical materials'
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1
Kumar, Sanjay, and Heow Pueh Lee. "Recent Advances in Acoustic Metamaterials for Simultaneous Sound Attenuation and Air Ventilation Performances." Crystals 10, no. 8 (August 7, 2020): 686. http://dx.doi.org/10.3390/cryst10080686.
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In the past two decades, acoustic metamaterials have garnered much attention owing to their unique functional characteristics, which are difficult to find in naturally available materials. The acoustic metamaterials have demonstrated excellent acoustical characteristics that paved a new pathway for researchers to develop effective solutions for a wide variety of multifunctional applications, such as low-frequency sound attenuation, sound wave manipulation, energy harvesting, acoustic focusing, acoustic cloaking, biomedical acoustics, and topological acoustics. This review provides an update on the acoustic metamaterials’ recent progress for simultaneous sound attenuation and air ventilation performances. Several variants of acoustic metamaterials, such as locally resonant structures, space-coiling, holey and labyrinthine metamaterials, and Fano resonant materials, are discussed briefly. Finally, the current challenges and future outlook in this emerging field are discussed as well.
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Panneton, Raymond, and Yacoubou Salissou. "Indirect acoustical characterization of sound absorbing materials." Journal of the Acoustical Society of America 126, no. 4 (2009): 2297. http://dx.doi.org/10.1121/1.3249416.
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Iannace, Gino. "The acoustic characterization of green materials." Building Acoustics 24, no. 2 (April 25, 2017): 101–13. http://dx.doi.org/10.1177/1351010x17704624.
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Natural materials are a valid alternative to traditional synthetic materials in the fields of acoustic treatments and energy saving. Natural fibres have been used to produce sound-absorbing panels. This article reports the acoustical characterization of the following natural fibres: straw, hay, plant litter and different sized wood chips. The acoustic measurements were carried out with an impedance tube. The acoustic absorption values were measured in a frequency range between 200 and 2000 Hz.
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Diharjo, Kuncoro, Ubaidillah, Wijang Wisnu Raharjo, Joko Pitoyo, and Mustaqim. "Underwater Acoustics Evaluation of Glass Fiber – Polyurethane Sandwich Composite." Applied Mechanics and Materials 660 (October 2014): 516–20. http://dx.doi.org/10.4028/www.scientific.net/amm.660.516.
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This article presents underwater acoustics evaluation of glass fiber – polyurethane sandwich composite which is useful for ship materials. The composite consists of two main functional laminations namely structural and acoustical lamination. The structural lamination is constructed from polyester and polyethylene fibers while the polyurethane is potential for acoustical lamination. The fabrication involves vacuum bagging and conventional hydraulic methods. The materials will be treated in both with and without immersion in sea water. The immersion process takes time about 72 hours. The properties of acoustics for each materials generally have high insertion loss (maximum found 25 dB), but some of them can reach low insertion loss (below 5 dB). The optimization of combination between structural and acoustic materials is promising to be investigated in near future to achieve the optimum properties of materials in terms of sound transparency.
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Xu, Xiaomei, and Ping Lin. "Parameter identification of sound absorption model of porous materials based on modified particle swarm optimization algorithm." PLOS ONE 16, no. 5 (May 4, 2021): e0250950. http://dx.doi.org/10.1371/journal.pone.0250950.
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Porous materials have been widely used in the field of noise control. The non-acoustical parameters involved in the sound absorption model have an important effect on the sound absorption performance of porous materials. How to identify these non-acoustical parameters efficiently and accurately is an active research area and many researchers have devoted contributions on it. In this study, a modified particle swarm optimization algorithm is adopted to identify the non-acoustical parameters of the jute fiber felt. Firstly, the sound absorption model used to predict the sound absorption coefficient of the porous materials is introduced. Secondly, the model of non-acoustical parameter identification of porous materials is established. Then the modified particle swarm optimization algorithm is introduced and the feasibility of the algorithm applied to the parameter identification of porous materials is investigated. Finally, based on the sound absorption coefficient measured by the impedance tube the modified particle swarm optimization algorithm is adopted to identify the non-acoustical parameters involved in the sound absorption model of the jute fiber felt, and the identification performance and the computational performance of the algorithm are discussed. Research results show that compared with other identification methods the modified particle swarm optimization algorithm has higher identification accuracy and is more suitable for the identification of non-acoustical parameters of the porous materials. The sound absorption coefficient curve predicted by the modified particle swarm optimization algorithm has good consistency with the experimental curve. In the aspect of computer running time, compared with the standard particle swarm optimization algorithm, the modified particle swarm optimization algorithm takes shorter running time. When the population size is larger, modified particle swarm optimization algorithm has more advantages in the running speed. In addition, this study demonstrates that the jute fiber felt is a good acoustical green fibrous material which has excellent sound absorbing performance in a wide frequency range and the peak value of its sound absorption coefficient can reach 0.8.
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Dlhý, Dušan, and Peter Tomašovič. "Effects of the Sound Insulation of the Outer Structure on the Price." Applied Mechanics and Materials 820 (January 2016): 472–77. http://dx.doi.org/10.4028/www.scientific.net/amm.820.472.
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Manufacturers indicate sound insulation of envelope structures of different materials. Acoustical properties of manufactured openings as windows and doors (plastic, wooden, metallic) are known. Following theoretic relations for calculation of consequential sound insulation of acoustic composite wall Rw, it is possible to work out options of walls and openings of various materials.
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Tang, Xiaoning, and Xiong Yan. "Airflow resistance of acoustical fibrous materials: Measurements, calculations and applications." Journal of Industrial Textiles 49, no. 8 (October 15, 2018): 981–1010. http://dx.doi.org/10.1177/1528083718805714.
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The acoustic performance of fibrous materials is mainly determined by its airflow resistance, and it is a parameter of the resistance that the airflow meets through the materials. This paper has summarized the recent advances on the measurements, calculations and applications of airflow resistance. Firstly, different methods for airflow resistance measurements are presented, mainly including the direct airflow method, alternating airflow method and acoustical method. We have summarized the development history, current status and industrial applications of these methods. Secondly, this paper has summarized the models of calculating airflow resistance. Most of these empirical models are based on the characteristic parameters of fibrous materials, for instance bulk density, fiber diameter, porosity and thickness. Thirdly, this review has gathered the applications of airflow resistance in sound absorption and noise control. It is a crucial parameter in the prediction of both normal incidence sound absorption and reverberation chamber sound absorption. In conclusion, this review has concluded with some perspectives for the measurements, calculations and applications of airflow resistance.
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Abbad, Ahmed, Kévin Jaboviste, Morvan Ouisse, and Nicolas Dauchez. "Acoustic performances of silicone foams for sound absorption." Journal of Cellular Plastics 54, no. 3 (September 21, 2017): 651–70. http://dx.doi.org/10.1177/0021955x17732305.
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The aim of this study is to investigate the link between the elaboration process, the microstructure and the acoustic behaviour of silicone foams obtained using a two-component silicone. Different parameters such as the ratio of components, the addition of a thinning agent and the curing temperature are varied, with the objective of understanding the influence of each parameter in the foam’s acoustic absorption. The microstructure is analysed using scanning electron microscopy and acoustic properties are measured. Two non-acoustical properties of the porous material are also investigated, namely the porosity and the flow resistivity. Pore cell size and interconnected porosity have great impact on acoustical properties. Significant enhancements of the absorption properties could be obtained in the low-frequency band by increasing the rate of agent B through an increase in the amount of interconnected porous cells. An improvement in absorption is observed in the higher frequency range when a thinning agent is added to the mixture. Representative models of the foam for acoustic simulations are obtained allowing estimation of the tortuosity, viscous and thermal characteristic length from acoustic measurements. These models are able to simulate the acoustic behaviour of the silicone foams when embedded in sound packages.
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Shahani, Fereshteh, Parham Soltani, and Mohammad Zarrebini. "The Analysis of Acoustic Characteristics and Sound Absorption Coefficient of Needle Punched Nonwoven Fabrics." Journal of Engineered Fibers and Fabrics 9, no. 2 (June 2014): 155892501400900. http://dx.doi.org/10.1177/155892501400900210.
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Control of acoustical related phenomenon in environments, such as work place and residential homes, using various textile materials has gained paramount importance. Nonwoven fabrics in general are ideal acoustical insulator due to their high volume-to-mass ratio. This research examined acoustic characteristics of structured needle punched floor coverings in relation to fiber fineness, surface effect, punch density, areal density, and chemical bonding process. Sound absorption of the test samples was measured using the impedance tube method. Results indicate that fabrics produced from finer fibers absorb sound waves more efficiently. It was found that, samples with no surface effect enjoy the maximum sound absorption. This is followed by velour and cord surface effect samples. It was established that, higher levels of punch density and higher areal density caused the noise reduction coefficient (NRC) of the fabrics to be increased. It was also found that chemical finishing adversely affected the sound absorption property of the samples.
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Wang, Yan Song, Jian Peng Zhou, and Yan Feng Xing. "Development of a Standing Wave-Tube System for Acoustical Property Measurement of Sound Absorption Materials Used on Vehicles." Key Engineering Materials 474-476 (April 2011): 1146–50. http://dx.doi.org/10.4028/www.scientific.net/kem.474-476.1146.
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A standing wave-tube system for acoustical property measurement of vehicle-used sound absorption materials is developed in this paper. Theoretically, the standing wave ratio method and the two-cavity method with two-microphone configurations are combined and applied for calculating some acoustical parameters, such as sound absorption ratio, reflection coefficient, characteristic impedance, propagation constant, of a sample material. Based on the combined method, the standing wave-tube system including two microphones, an A/D board, a signal amplifier, a DSP computer and a set of software is carefully designed and performed. The verification results suggest that the newly designed system is accurate for acoustical property measurement of the materials used on vehicles. It can be directly used for selecting noise-control materials in vehicle acoustical designs.
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Egab, Laith, Xu Wang, and Mohammad Fard. "Acoustical characterisation of porous sound absorbing materials: a review." International Journal of Vehicle Noise and Vibration 10, no. 1/2 (2014): 129. http://dx.doi.org/10.1504/ijvnv.2014.059634.
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Dlhý, Dušan. "The Effect of Free Joints on Sound Insulation of Constructions." Advanced Materials Research 855 (December 2013): 233–36. http://dx.doi.org/10.4028/www.scientific.net/amr.855.233.
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Noise protection of a building ́s interior is one of the fundamental functions of building constructions. These constructions can be understood as internal partitions, ceilings or external wall-/roof claddings. However, walls often consist of basic building materials and openings; such windows and doors as well as the acoustical properties of such structures are determined by both parts (e.g., a windows and the wall structure). The acoustical quality of opening is in general affected not only by the particular structure, but also by the concept of the mounting. Acoustical requirements should be applied in all its parts, such as the construction of the window (door) frame, window (door) wing and the realization of the functional gap as well as by application of a sealant. On the base of experimental measurements in Acoustics Chambers of the Faculty of Civil Engineering of Slovak Technical University and mathematical analysis we have determined index of sound insulation of free joint.
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Abdul Latif, Hanif, Musli Nizam Yahya, Mohamed Najib Rafiq, Mathan Sambu, Mohd Imran Ghazali, and Mohamed Nasrul Mohamed Hatta. "A Preliminary Study on Acoustical Performance of Oil Palm Mesocarp Natural Fiber." Applied Mechanics and Materials 773-774 (July 2015): 247–52. http://dx.doi.org/10.4028/www.scientific.net/amm.773-774.247.
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As the population increases, the demand of a comfortable environmental such as sound pollution is getting higher. Sound pollutions also have become worsen and creating concerns for many peoples. Due to this problem, synthetic materials as acoustic absorbers still applied as commonly acoustical panels and this material may hazardous to human health and contribute significantly a pollution to the environments. However, researchers have interested in conducting their research on natural fiber to be an alternative sound absorber. This study investigated the potential of oil palm Mesocarp fiber for sound absorbing material. The Mesocarp fibers were mixed with polyurethane (PU) as binder with ratio of 70:30. The thickness was varied in 10mm, 20mm, 30mm, and 40mm. This study also investigated the air gap of 5mm and 10mm in the sound absorption performance. Impedance Tube Method was used to measure sound absorption coefficient (a). The measurement was done on accordance with ASTM E1050-98, which is the standard test method for impedance and absorption of acoustical materials using a tube. The results showed that the optimum value for Mesocarp fiber is 0.93. The optimum value obtained at 5000 Hz. The influence of air gap increases the sound absorption especially from 250 Hz to 4000 Hz. These results indicate that fiber from Mesocarp is promising to be used sound absorbing material.
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Kaselouris, Evaggelos, Chrysoula Alexandraki, Yannis Orphanos, Makis Bakarezos, Michael Tatarakis, Nektarios A. Papadogiannis, and Vasilis Dimitriou. "Acoustic analysis of impact sound on vibrating circular membranes." INTER-NOISE and NOISE-CON Congress and Conference Proceedings 263, no. 3 (August 1, 2021): 3378–85. http://dx.doi.org/10.3397/in-2021-2389.
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A finite element method (FEM) - boundary element method (BEM) model is developed to compute the sound generated by of a force acting on a circular membrane (drumhead). A vibro-acoustic analysis that combines modal FEM analysis, a FEM steady state dynamic analysis (SSD), considering harmonic loading and boundary element acoustics, is performed. The drumhead vibrates due to the force impact and the sound is emitted in the air. The vibration of structural response is initially computed, and the obtained results are set to be the boundary conditions of the acoustic analysis in the vibro-acoustic simulation. The radiated sound can be computed at any point of the solution domain. Various materials used by drumhead manufacturers are tested and a parametric analysis focusing on the mesh density of the models is presented. The impact sound and the acoustical characteristics of the simulated test cases are evaluated. The Rayleigh method is also applied to the acoustic simulations and is further compared to the BEM simulation results. The outcomes of this study may be further used as reverse engineering inputs, to machine learning models for the estimation of the physical and mechanical parameters of drumheads from audio signals.
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Lin, Wei, and Wei Hwa Chiang. "Acoustical Design Study on Application of Absorption Materials." Applied Mechanics and Materials 711 (December 2014): 546–49. http://dx.doi.org/10.4028/www.scientific.net/amm.711.546.
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Taipei Top Church Auditorium is a hall primarily intended for praise and worship. A three dimensional ray tracing computer simulation was used to provide sound energy distribution on the audience area of the hall, realistic design have been performed. The volume of the hall is 24600m3, which is occupied for 2200 people and equipped the hall with acoustical curtains by modifying its acoustical characteristics. Objective measurements of impulse response are reported, and background noise control and noise isolation are also be considered in the design phase. Reinforcement system is conducted to meet all the activity for the acoustical environments.
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Mohammed, Garoum, and Chaimaa Benayad. "Sound Absorption Measurements and Numerical Estimation of Non Acoustical Parameters of some Moroccan Raw Green Materials." Advanced Materials Research 1051 (October 2014): 95–101. http://dx.doi.org/10.4028/www.scientific.net/amr.1051.95.
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Knowledge of acoustical properties of granular and fibrous sustainable materials has been stimulated thanks to their rather easy handling and durability. In this work direct measurements of the normal incidence sound absorption coefficient of three non consolidated materials (esparto fibers, cork and perlite) have been carried out using the so-called transfer function method. These materials are plentiful in Morocco and they require low amounts of energy for processing, which makes them attractive as either thermal insulating or sound absorbing materials. Results show that the acoustical efficiency of studied materials is comparable to traditional materials. In addition, an inverse estimation of non acoustical parameters (flow resistivity, tortuosity and porosity) of these materials has been performed introducing a new predictability approach. This is based on Global Sensitivity Analysis combined with Global Numerical Optimization Techniques, regarding most usual mathematical models.
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Kusumaningtyas, Indraswari, and Subagio Subagio. "Indonesian Wood as Material for Acoustic Guitars and Violins." Wood Research Journal 3, no. 1 (August 27, 2017): 11–17. http://dx.doi.org/10.51850/wrj.2012.3.1.11-17.
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Traditionally, acoustic guitars and violins are made from European woods. Spruce is most preferred for the top plate (soundboard), whereas maple, sycamore and rosewood are often used for the back plate. However, these woods are not easily available in Indonesia. In this paper, we present a study on the suitability of a selection of Indonesian woods, namely acacia, mahogany, pine, sengon and sonokembang, as materials for acoustic guitars and violins. The most important acoustical properties for selecting materials for musical instruments, i.e. the speed of sound, the sound radiation coefficient and the damping factor, were investigated. Furthermore, the performance of pine and mahogany were tested by making them into a violin and a guitar. The vibration frequency spectrum and the damping factor of the top plate were measured. The results show that the acoustical characteristics of mahogany are very close to those of maple and still quite close to those of Indian rosewood, which makes it a very suitable local material for back plates. Pine has quite similar acoustical characteristics to spruce. Although its sound radiation coefficient is slightly lower, its aesthetic appeal and workability makes pine a suitable alternative for top plates. However, instruments with pine top plates exhibit different tonal colour compared to instruments with spruce top plates, due to some differences in the vibration frequency spectrum. Furthermore, the generally higher damping factors of pine and mahogany compared to those of the European woods should be taken into account, because they affect the sustain-time of the generated sound.
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Tang, Xiaoning, Xiansheng Zhang, Xingmin Zhuang, Huiping Zhang, and Xiong Yan. "Acoustical analysis of corduroy fabric for sound absorption: Experiments and simulations." Journal of Industrial Textiles 48, no. 1 (August 7, 2017): 201–20. http://dx.doi.org/10.1177/1528083717725912.
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Corduroy fabrics have been widely used in interior decoration currently. This work mainly investigated the acoustical properties of corduroy fabrics in relation to air permeability and airflow resistance. Five specimens with similar surface density and different wale width are used. The results indicated that corduroy fabrics with thicker wale width exhibited higher air permeability and lower airflow resistance. Furthermore, the increased width of wale is beneficial to improve the acoustic absorption of corduroy fabric. Two models based on air permeability and airflow resistance are taken to characterize the acoustical behavior. It has been indicated that Pieren model could well predict the acoustic absorption coefficient of corduroy fabric, and the difference of acoustic absorption is due to the varied air permeability and airflow resistance resulting from the different wale width.
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Sü Gül, Zühre Sü. "Acoustical Impact of Architectonics and Material Features in the Lifespan of Two Monumental Sacred Structures." Acoustics 1, no. 3 (July 16, 2019): 493–516. http://dx.doi.org/10.3390/acoustics1030028.
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Hagia Sophia and Süleymaniye Mosque, built in the 6th and 16th centuries, respectively, are the two major monuments of the İstanbul World Heritage Site. Within the context of this study, sound fields of these two sacred multi-domed monumental structures are analyzed with a focus on their architectonic and material attributes and applied alterations in basic restoration works. A comprehensive study is undertaken by a comparative analysis over acoustical field tests held in different years and over an extensive literature review on their material and architectural characteristics. Initially, the major features of Hagia Sophia and Süleymaniye Mosque are presented, and later, basic alterations in regard to function and materials are provided. The methodology includes the field tests carried both within the scope of this research as well as the published test results by other researchers. Acoustical simulations are utilized for comparison of unoccupied versus occupied conditions and also for discussion on original materials. The impact of historical plasters on the acoustics of domed spaces is highlighted. Common room acoustics parameters as of reverberation time and clarity are utilized in comparisons. The formation of multi-slope sound energy decay is discussed in light of different spiritual and acoustical needs expected from such monumental sacred spaces.
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Salter, Ethan, and Dylan Mills. "Biophilic Sound Masking Systems: Promoting Acoustical Comfort in Workspaces." INTER-NOISE and NOISE-CON Congress and Conference Proceedings 263, no. 5 (August 1, 2021): 1320–28. http://dx.doi.org/10.3397/in-2021-1813.
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Promoting speech privacy and acoustical comfort in office buildings has always been an important consideration for designers, owners, and occupants. Acoustical comfort has many degrees, including reduction of stress, enhancing focus, and reducing distractions. It can also create a more pleasurable and relaxing environment. Concurrently, the sustainable and green design movements have evolved the "language" of design and building to include a more holistic understanding of occupant comfort. This includes the materials and systems that occupants interface with and use. Additionally, interior environmental quality considerations, including noise, are incorporated into green building rating systems such as WELL, LEED, CHPS, and others. However, it is not merely about providing a slightly better or more efficient system, but also understanding on a deeper level the effects of a building's environment on people's health. One aspect of this is the concept of "biophilia," where designers look to natural systems and materials for inspiration. The interior acoustical environment is a significant part of that. Electronic sound masking systems have been used in office environments for decades, and their efficacy, when appropriately designed and installed, has been proven repeatedly. What has been changing in recent years is the concept of biophilic sound masking systems, which do not merely broadcast broadband noise (AKA pink noise or "white" noise) in a space. These systems can broadcast "natural" sounds such as running water, animals, wind, etc. that are not only pleasing and soothing, but also effective in sound masking. This paper will describe biophilia in general how it relates to the interior noise environment, and related design considerations. In addition, the paper includes a case study of an office building project that employed a sound masking system with biophilic capabilities.
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Autio, Hanna, Mathias Barbagallo, Carolina Ask, Delphine Bard Hagberg, Eva Lindqvist Sandgren, and Karin Strinnholm Lagergren. "Historically Based Room Acoustic Analysis and Auralization of a Church in the 1470s." Applied Sciences 11, no. 4 (February 10, 2021): 1586. http://dx.doi.org/10.3390/app11041586.
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Worship space acoustics have been established as an important part of a nation’s cultural heritage and area of acoustic research, but more research is needed regarding the region of northern Europe. This paper describes the historical acoustics of an important abbey church in Sweden in the 1470s. A digital historical reconstruction is developed. Liturgical material specific to this location is recorded and auralized within the digital reconstruction, and a room acoustic analysis is performed. The analysis is guided by liturgical practices in the church and the monastic order connected to it. It is found that the historical sound field in the church is characterized by the existence of two distinct acoustical subspaces within it, each corresponding to a location dedicated to the daily services of the monastical congregations. The subspaces show significantly better acoustic conditions for liturgical activities compared to the nave, which is very reverberant under the conditions of daily services. Acoustic transmission from the two subspaces is limited, indicating that the monastic congregations were visually and acoustically separated from the visitors in the nave and each other.
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Gómez Escobar, Valentín, Guillermo Rey Gozalo, and Carlos J. Pérez. "Variability and Performance Study of the Sound Absorption of Used Cigarette Butts." Materials 12, no. 16 (August 14, 2019): 2584. http://dx.doi.org/10.3390/ma12162584.
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There has been increasing interest in new sustainable materials that can be used as construction materials. Among them, sound-absorbing materials have an important role in both acoustical room conditioning and in room insulation. As a proposal for recycling, one of the most common residues in the world, cigarette butts, is studied. Samples were prepared with used cigarette butts as acoustical absorbent materials. Several samples were prepared and grouped by similarity. Variability analyses of the samples prepared in each group were performed. Moreover, the analysis of some possible influences on absorption properties, such as the length of butts, presence of burnt regions, presence of wrapping paper, etc., were analyzed. The results show the potentiality of this residue to be used as an acoustical absorbent since the absorption coefficients found are greater than 0.8 for frequencies over 2000 Hz. The observed variability in the study group and samples can be considered low, as it was below 2% for the major part of frequencies. Influences on the absorption coefficient, for both the length and status of the butts, were statistically confirmed.
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Sü, Zühre, and Mehmet Çalışkan. "Acoustical Design and Noise Control in Metro Stations: Case Studies of the Ankara Metro System." Building Acoustics 14, no. 3 (September 2007): 203–21. http://dx.doi.org/10.1260/135101007781998910.
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The aim of this research is to demonstrate the importance of initial strategies in acoustical design of underground metro stations. The paper searches for practical design solutions by evaluating different materials for providing optimum acoustical conditions in such spaces. Acoustical designs of three metro stations on a new expansion line in Ankara including Sogutozu, Bilkent and ODTU metro stations are presented through computer simulation. Predictions of room acoustical parameters are presented for both platform and ticket office floors in terms of parameters like reverberation time (RT), speech transmission index (STI) and A-weighted sound level (SPL) distribution within spaces. Simulated reverberation times are evaluated in view of legislative requirements. The study confirms the importance of using sound absorbing materials on the ceiling and sidewalls together. The nonwoven material, used behind perforated metal suspended ceilings, has proved effective in reverberation control.
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Zhao, Caiyou, Ping Wang, Li Wang, and Dan Liu. "Reducing Railway Noise with Porous Sound-Absorbing Concrete Slabs." Advances in Materials Science and Engineering 2014 (2014): 1–11. http://dx.doi.org/10.1155/2014/206549.
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The effect of porous sound-absorbing concrete slabs on railway noise reduction is examined in this paper. First, the acoustical absorption coefficients of porous concrete materials with various aggregate types, gradations, fibre contents, and compaction indexes are measured in the laboratory. The laboratory results show that porous concrete that uses a composite of expanded perlite and slag as aggregate can not only obtain good acoustical absorption properties but also satisfy mechanical requirements. Also, the gradation of the combined aggregate has a significant effect on the acoustic absorption performance of the porous concrete, with an optimal aggregate gradation of 1~3 mm. Furthermore, the fibre content and compaction index affect both the strength and the acoustic absorption property of the porous concrete, with the optimum value of 0.3% and 1.6, respectively. Then, the findings from the laboratory studies are used to make porous sound-absorbing concrete slabs, which are applied in a test section. The measurements indicate that porous sound-absorbing concrete slabs can significantly reduce railway noise at different train speeds and that the amount of the noise reduction changes roughly linearly with speed when the train is traveling at less than 200 km/h. The maximum noise reduction is 4.05 dB at a speed of 200 km/h.
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Tsay, Huoy-Shyi, and Fung-Huei Yeh. "Design of acoustic foam wedge panels by finite element frequency domain acoustical analysis." Journal of Cellular Plastics 55, no. 3 (March 26, 2019): 283–95. http://dx.doi.org/10.1177/0021955x19837499.
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Acoustic foam wedge panels provide good sound absorption qualities in the mid and high frequency ranges. In this study, a finite element frequency domain acoustical analysis is used for analysis. Such a numerical method is more efficient than the earlier studies by saving the calculation time on the elements of the incident acoustic field. During the design of a wedge panel, the cross-sectional width and the area of one section of the wedge panel are kept the same throughout the study. By varying the wedge angle, the maximum sound absorption capability of the wedge foam can be found. It is concluded that in the interested frequency regions, 100–4000 and 2000–4000 Hz, the wedge foam with wedge angle of 31° has the excellent sound absorption capability.
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Farid, Mohammad, and Tri Heriyanto. "Correlation of Normal Incidence Sound Absorption Coefficient (NAC) and Random Incidence Sound Absorption Coefficient (RAC) of Polyester/Ramie Fibre Composite Materials." Advanced Materials Research 789 (September 2013): 269–73. http://dx.doi.org/10.4028/www.scientific.net/amr.789.269.
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The acoustical properties of polyester/ramie fibre composite materials that was applied as a sound absorbing material is discussed in this paper. The aim was to determine the correlation between Normal Incidence Sound Absorption Coefficient (NAC) and Random Incidence Sound Absorption Coefficient (RAC) of the fibre composites. The acoustic measurement with Impedance Tube Kit followed the ASTM 1986 E – 1050 – 98 standard. The portion of the ramie fibre was modified with fibre length varied from 0.25 cm, 1 cm to 1.5 cm but at a constant fibre diameter. A constant volume fraction of fibre 20 % was used.The Beevers method was applied to characterize the fibre’s diameter. Results indicated that the sound absorption performance of the composite fibre can reach as high as 99% at frequency of 1225 Hz at aspect ratio of 42. A correlation between NAC and RAC was presented based on a quantitative result.
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Bhat, Gajanan, and Magdi El Messiry. "Effect of microfiber layers on acoustical absorptive properties of nonwoven fabrics." Journal of Industrial Textiles 50, no. 3 (February 12, 2019): 312–32. http://dx.doi.org/10.1177/1528083719830146.
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There are several types of sound absorptive materials, such as natural and synthetic fibers, acoustic mineral wool, acoustic polyester panels, acoustic foam, cotton batts, that reduce the acoustic energy of a sound wave as the wave passes through. In this work, the use of nonwoven materials made of cotton, polyester, and polypropylene fibers for the development of sound absorptive nonwoven materials has been investigated. Samples of different materials (cotton, cotton/polyester blend, polyester fibers needle punched, and polypropylene melt blown nonwoven) and multilayer structures were tested on the designed impedance tube. Acoustic absorption properties of the fiber assemblies were studied in the frequency region of 100–1500 Hz. The values of sound absorption coefficient for different samples indicated that polypropylene microfiber melt blown nonwoven sample displayed a good sound absorption behavior in the entire frequency range. The use of multilayer samples improves the sound absorption coefficient with the condition that one of the layers is a thin melt blown nonwoven layer. The formation of nonwoven absorbent material consisted of hybrid layers, significantly reduces the resultant average sound absorption coefficient, especially when the upper layer is made from finer fibers of melt blown nonwoven of low air permeability value, and in this case the improvement reaches 50%. The use of melt blown layers of fine fibers values of noise reduction coefficient may reach 0.8. The multilayer nonwoven sound absorber design should take into consideration specific noise reduction coefficient values, not the absolute ones, particularly when the weight of the absorber is playing a decisive role.
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Bismor, Dariusz. "Optimal and Adaptive Virtual Unidirectional Sound Source in Active Noise Control." Advances in Acoustics and Vibration 2008 (June 22, 2008): 1–12. http://dx.doi.org/10.1155/2008/647318.
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One of the problems concerned with active noise control is the existence of acoustical feedback between the control value (“active” loudspeaker output) and the reference signal. Various experiments show that such feedback can seriously decrease effects of attenuation or even make the whole ANC system unstable. This paper presents a detailed analysis of one of possible approaches allowing to deal with acoustical feedback, namely, virtual unidirectional sound source. With this method, two loudspeakers are used together with control algorithm assuring that the combined behaviour of the pair makes virtual propagation of sound only in one direction. Two different designs are presented for the application of active noise control in an acoustic duct: analytical (leading to fixed controller) and adaptive. The algorithm effectiveness in simulations and real experiments for both solutions is showed, discussed, and compared.
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Tascan, Mevlut, and Edward A. Vaughn. "Effects of Fiber Denier, Fiber Cross-Sectional Shape and Fabric Density on Acoustical Behavior of Vertically Lapped Nonwoven Fabrics." Journal of Engineered Fibers and Fabrics 3, no. 2 (June 2008): 155892500800300. http://dx.doi.org/10.1177/155892500800300206.
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Acoustical insulation and absorption properties of nonwoven fabrics depend on fiber geometry and fiber arrangement within the fabric structure. The different structures of the fibers result in different total surface areas of nonwoven fabrics. Nonwoven fabrics such as vertically lapped fabrics are ideal materials for use as acoustical insulation products, because they have high total surface. Vertically lapped nonwoven technology consists of carding, perpendicular layering of the carded webs, and through-air bonding using synthetic binder fibers. The surface area of the fabric is directly related to the denier and cross-sectional shape of the fibers in the fabric. Smaller deniers yield more fibers per unit weight of the material, higher total fiber surface area, and greater possibilities for a sound wave to interact with the fibers in the fabric structure. The research in the literature uses two methods for measuring acoustical properties of fabric materials: the impedance tube and reverberation room method. Small test samples are in the impedance tube method and sound absorption coefficient is determined at each frequency. Large reverberation rooms and large test samples are used for the reverberation room method. A direct comparative acoustical properties measurement device that was designed and fabricated at Clemson University School of Materials Science & Engineering was used to measure acoustical insulation in this research. This paper provides a description of the measurement devices and acoustical measurement data for vertically lapped nonwoven fabrics made from three different polyester fiber shape and two denier levels.
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Liuzzi, Stefania, Chiara Rubino, Pietro Stefanizzi, and Francesco Martellotta. "Performance Characterization of Broad Band Sustainable Sound Absorbers Made of Almond Skins." Materials 13, no. 23 (December 1, 2020): 5474. http://dx.doi.org/10.3390/ma13235474.
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In order to limit the environmental impact caused by the use of non-renewable resources, a growing research interest is currently being shown in the reuse of agricultural by-products as new raw materials for green building panels. Moreover, the European directives impose the goal of sustainability supporting the investigation of passive solutions for the reduction of energy consumption. Thus, the promotion of innovative building materials for the enhancement of acoustic and thermal insulation of the buildings is an important issue. The aim of the present research was to evaluate the physical, acoustical, and thermal performances of building panels produced by almond skin residues, derived from the industrial processing of almonds. In this paper different mix designs were investigated using polyvinyl acetate glue and gum Arabic solution as binders. Air-flow resistivity σ and normal incidence sound absorption coefficient α were measured by means of a standing wave tube. Thermal conductivity λ, thermal diffusivity α, volumetric heat capacity ρc were measured using a transient plane source device. Finally, water vapor permeability δp was experimentally determined using the dry cup method. Furthermore, a physical characterization of the specimens in terms of bulk density ρb and porosity η allowed to study the correlation existing between the binder and the aggregates and the consequent acoustical and hygrothermal behavior occurring on the different mix designs. The achieved results suggested the investigated materials comparable to the main products currently existing on the market.
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Theocharis, Christoforos, Ernst Kainmüller, Josef Lechleitner, Ulrich Pont, and Ardeshir Mahdavi. "Improving the Impact Sound Insulation of an Existing and Refurbished Wooden Beam Floor Construction." Applied Mechanics and Materials 861 (December 2016): 527–36. http://dx.doi.org/10.4028/www.scientific.net/amm.861.527.
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A common source of dissatisfaction in buildings pertains to acoustical issues. Specifically, in existing buildings, exposure to impact noise represents a frequent problem. In Central Europe generally, and in Vienna (Austria) specifically, there is a significant number of existing buildings with floor constructions involving wooden beams as structural elements. Given the steady rise in inhabitants' expectations regarding buildings' acoustical quality, such existing floor constructions do not sufficiently provide the sufficient impact noise insulation. In many instances, the replacement of these floor constructions with concrete slabs is not an option, given a number of structural, financial, and legal (conservation related) obstacles and constraints. The present contribution thus explores the acoustical improvement potential of floor constructions with wooden beams by using modern materials and techniques. Toward this end, a typical 19th century building in Vienna downtown was selected. Multiple improvement options were realized. These involved the deployment of a honey-comb acoustic system, installation of stiffeners bolted to the original wooden beams, as well as an additional structurally decoupled ceiling layer. The impact sound was measured at different stages of retrofit and compared with the performance of the original construction.
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Sari, Nasmi Herlina, I. N. G. Wardana, Yudy Surya Irawan, and Eko Siswanto. "Corn Husk Fiber-Polyester Composites as Sound Absorber: Nonacoustical and Acoustical Properties." Advances in Acoustics and Vibration 2017 (February 19, 2017): 1–7. http://dx.doi.org/10.1155/2017/4319389.
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This study investigates the acoustical and nonacoustical properties of composites using corn husk fiber (CHF) and unsaturated polyester as the sound-absorbing materials. The influence of the volume fraction of CHF on acoustic performance was experimentally investigated. In addition, the nonacoustical properties, such as air-flow resistivity, porosity, and mechanical properties of composites have been analyzed. The results show that the sound absorptions at low frequencies are determined by the number of lumens in fiber, particularly the absorption coefficient, which increases the amount of fiber. For high-frequency sound, the absorption coefficient is determined by the arrangement of fibers in the composite. An absorption coefficient is close to zero when the fibers are arranged in a conventional pattern; however, when they are arranged in a random pattern, a high absorption coefficient can be obtained. The bond interface between the fiber and resin enhances its mechanical properties, which increases the longevity of the composite panel.
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Kusno, Asniawaty, Kimihiro Sakagami, Takeshi Okuzono, Masahiro Toyoda, Toru Otsuru, Rosady Mulyadi, and Kusno Kamil. "A Pilot Study on the Sound Absorption Characteristics of Chicken Feathers as an Alternative Sustainable Acoustical Material." Sustainability 11, no. 5 (March 11, 2019): 1476. http://dx.doi.org/10.3390/su11051476.
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This communication reports the results of a pilot study on the sound absorption characteristics of chicken feathers (CFs). Recently, demands for natural and sustainable materials have been extensively studied for acoustical purposes. CF has long been left wasted, however, they can be used for sound-absorbing purposes to improve acoustical environments as a sustainable and green acoustical material. In order to clarify their feasibility, samples of CF absorbers of various densities and thicknesses were prepared, and their sound absorption coefficients were measured by the standard impedance tube method. The measured results were also compared with those of conventional glass wools of the same densities and thicknesses. The results show that CFs have potentially good sound-absorption performance, which is similar to typical fibrous materials: increasing with frequency. Results of direct comparison with glass wool demonstrate that the absorption coefficients of CFs are comparable and, at some frequencies, somewhat higher than conventional glass wools in some cases. Additionally, the first step for searching a prediction method for the sound absorption performance of CFs, their flow resistivity was measured and a Delany–Bazley–Miki model was examined. However, the resultant flow resistivity was unexpectedly low, and the model gave only a much lower value than that measured. The reason for the discrepancies is the subject of a future study.
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Sari, Nasmi Herlina, I. N. G. Wardana, Yudy Surya Irawan, and Eko Siswanto. "Physical and Acoustical Properties of Corn Husk Fiber Panels." Advances in Acoustics and Vibration 2016 (December 15, 2016): 1–8. http://dx.doi.org/10.1155/2016/5971814.
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This research focuses on the development of a sustainable acoustic material comprising natural fibers of corn husk that were alkali modified by 1%, 2%, 5%, and 8% NaOH. The morphology and the acoustical, physical, and mechanical properties of the resulting fibers were experimentally investigated. Five different types of sample were produced in panel form, the acoustical properties of which were studied using a two-microphone impedance tube test. The porosity, tortuosity, and airflow resistivity of each panel were investigated, tensile tests were conducted, and the morphological aspects were evaluated via scanning electron microscopy. The sound absorption and tensile properties of the treated panels were better than those of raw fiber panels; the treated panels were of high airflow resistivity and had low porosity. Scanning electron micrographs of the surfaces of the corn husk fibers revealed that the different sound absorption properties of these panels were due to roughness and the lumen structures.
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Sharma, S. K., S. R. Shukla, and A. K. Sethy. "Acoustical behaviour of natural fibres-based composite boards as sound-absorbing materials." Journal of the Indian Academy of Wood Science 17, no. 1 (April 6, 2020): 66–72. http://dx.doi.org/10.1007/s13196-020-00255-z.
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Horst Andrade, Fernanda, Rodrigo Scoczynski Ribeiro, and Manuel Teixeira Braz César. "Analysis of the acoustical environment of classrooms in three brazilian public schools through measurements and 3d simulation." INTER-NOISE and NOISE-CON Congress and Conference Proceedings 263, no. 6 (August 1, 2021): 91–99. http://dx.doi.org/10.3397/in-2021-1132.
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The present study analyses the outdoor and indoor sound pressure levels (SPL) and the reverberation time (RT) measured in three Brazilian public classrooms. For the SPL, a sound level analyzer (class II) was used, and for the RT it was used a smartphone for the measurements. The sound sources were the impulses of bursting balloons and the data was processed in a MatLab toolbox (ITA-Toolbox). The classrooms were also simulated in an open source modeling software (I-SIMPA), using ray-tracing principles. Based on the results of the simulations, supported by the low-cost measurements, it was observed that the classroom didn't reach the national standards for classroom acoustics. Some improvements were designed with sustainable materials in order to reach the lower limits of the standards using the same room acoustics software. It was observed that the low-cost measurements helped on the diagnosis of classroom's acoustic issues which was also verified in the 3D simulation. This procedure showed itself as a cheap solution for classroom acoustic designs.
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Kolar, Miriam A., Doyuen Ko, and Sungyoung Kim. "Preserving Human Perspectives in Cultural Heritage Acoustics: Distance Cues and Proxemics in Aural Heritage Fieldwork." Acoustics 3, no. 1 (March 3, 2021): 156–76. http://dx.doi.org/10.3390/acoustics3010012.
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We examine the praxis implications of our working definition of aural heritage: spatial acoustics as physically experienced by humans in cultural contexts; aligned with the aims of anthropological archaeology (the study of human life from materials). Here we report on human-centered acoustical data collection strategies from our project “Digital Preservation and Access to Aural Heritage via a Scalable, Extensible Method,” supported by the National Endowment for the Humanities (NEH) in the USA. The documentation and accurate translation of human sensory perspectives is fundamental to the ecological validity of cultural heritage fieldwork and the preservation of heritage acoustics. Auditory distance cues, which enable and constrain sonic communication, relate to proxemics, contextualized understandings of distance relationships that are fundamental to human social interactions. We propose that source–receiver locations in aural heritage measurements should be selected to represent a comprehensive range of proxemics according to site-contextualized spatial-use scenarios, and we identify and compare acoustical metrics for auditory distance cues from acoustical fieldwork we conducted using this strategy in three contrasting case-study heritage sites. This conceptual shift from architectural acoustical sampling to aural heritage sampling prioritizes culturally and physically plausible human auditory/sound-sensing perspectives and relates them to spatial proxemics as scaled architecturally.
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Sambu, Mathan, Musli Nizam Yahya, Hanif Abdul Latif, Mohamed Nasrul Mohamed Hatta, and Mohd Imran bin Ghazali. "The Acoustical Characteristics Analysis on Different Type of Natural Fibres." Applied Mechanics and Materials 773-774 (July 2015): 242–46. http://dx.doi.org/10.4028/www.scientific.net/amm.773-774.242.
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Natural fibres are fibre that can be directly obtained from an animal, mineral, or vegetable sources. Recently natural materials are becoming a good alternative for synthetic material as they provide good health to a greener environment. This aim of this study to investigate and compared the acoustic characteristics of three natural fibres; Kenaf fibre(Hibiscus Cannabinus), Ijuk fibre(Arenga Pinnata), and Coconut coir fibre, where each material is qualified for acoustical absorption. During the processing stage, each fibre is reinforced with 60:40 ratio of pure latex separately. The fibres are then compressed after the pure latex treatment into circular samples, of 28 mm and 100 mm diameters respectively. The thickness of each sample is fixed at 50mm. The acoustical performances were evaluated by using an impedance tube instrument. This study also investigates the effect of air gap of 10mm and 50mm in the sound absorption performance. The results show that, all the three fibres have reached an optimum level of sound absorption value of more than 0.7. The frequency peak value of Kenaf is obtained in a range of 700 Hz – 800 Hz, while for coconut coir is at 1000 Hz – 1075 Hz frequency range. Only Ijuk has obtained the highest frequency range of 3200 Hz – 3400 Hz. The results demonstrate that these three fibres are a promising light and environment-friendly sound absorption material as they are ready to replace the common synthetic fibre.
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Chiu, Min-Chie. "Numerical assessment of two-chamber mufflers hybridized with multiple parallel perforated plug tubes using simulated annealing method." Journal of Low Frequency Noise, Vibration and Active Control 36, no. 1 (March 2017): 3–26. http://dx.doi.org/10.1177/0263092317693477.
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Enormous effort has been applied to research on mufflers hybridized with a single perforated plug tube; nonetheless, mufflers conjugated with multiple parallel perforated plug tubes that disperse venting fluid and reduce secondary noise have been overlooked. To this end, an analysis of the sound transmission loss of two-chamber mufflers with multiple parallel perforated plug tubes that are optimally designed to perform within a limited space will be presented. Here, using a decoupled numerical method, a four-pole system matrix for evaluating acoustic performance (sound transmission loss) is derived. During the optimization process, a simulated annealing method, which is a robust scheme utilized to search for the global optimum by imitating a physical annealing process, is used. Prior to dealing with a broadband noise, the sound transmission loss’s maximization relative to a one-tone noise (200 Hz) is produced to check the simulated annealing method’s reliability. The mathematical model is also confirmed for accuracy. To understand the acoustical effects brought about by the various tubes (perforated tubes, internally extended non-perforated tubes, and non-perforated tubes), mufflers with internally extended non-perforated tubes and non-perforated tubes have been evaluated. The optimization of three kinds of two-chamber mufflers hybridized with one, two, and four perforated plug tubes have also been compared. The results are revealing: the acoustical performance of mufflers conjugated with more perforated plug tubes decreases as a result of the decrement of the acoustical function for acoustical elements (II) and (III). Accordingly, in order to design a better muffler, an advanced presetting of the maximum (allowable) flowing velocity is necessary before an appropriate number of perforated plug tubes can be chosen for the optimization process.
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Park, Se-Hwi, Min Lee, Pureun-Narae Seo, Eun-Chang Kang, and Chun-Won Kang. "Acoustical properties of wood fiberboards prepared with different densities and resin contents." BioResources 15, no. 3 (May 20, 2020): 5291–304. http://dx.doi.org/10.15376/biores.15.3.5291-5304.
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The demand for noise control in residential environments is steadily increasing, but the currently available noise-reducing materials used in walls and floors are unsustainable and expensive. As an alternative, wood-fiber could be a good resource to manufacture eco-friendly acoustic materials. In this study, fiberboards were prepared by mixing wood-fibers (Pinus densiflora) with melamine-urea-formaldehyde resin adhesive, obtaining specimens with different final densities and resin contents. The acoustic, physical, and morphological properties of the fiberboards were investigated. The sound absorption was greatly influenced by the density of the fiberboard: lower densities showed higher sound absorption performances. Furthermore, the low-frequency absorption coefficient was higher for lower resin contents. The materials met all the criteria required by the Korean standards for fiberboards. As the density increased, the dimensional stability and the bending strength increased; in contrast, the physical properties were not affected by the resin content. Microscopy observations confirmed that specimens with different densities and resin contents had different porosities; the porosity was assumed to be the main property that governs the noise-reducing ability. Due to their eco-friendliness and inexpensiveness, these fiberboards offer themselves as efficient and effective alternative sound-absorbing materials.
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Braccesi, Claudio, and Andrea Bracciali. "Least squares estimation of main properties of sound absorbing materials through acoustical measurements." Applied Acoustics 54, no. 1 (May 1998): 59–70. http://dx.doi.org/10.1016/s0003-682x(97)00044-3.
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Stapulionienė, Rūta, Saulius Vaitkus, and Sigitas Vėjelis. "Development and Research of Thermal-Acoustical Insulating Materials Based on Natural Fibres and Polylactide Binder." Materials Science Forum 908 (October 2017): 123–28. http://dx.doi.org/10.4028/www.scientific.net/msf.908.123.
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Recently natural fibres are becoming more and more popular and their significance to the industry is increasing as well. In the last two decades, natural fibres are more widely used in the production of thermal–acoustical insulating materials. It was brought to attention that these fibrous materials have good thermal and acoustical properties in comparison to glass fibres. Also, the product, made from natural fibres, can be recycled for several times, and eventually, easily utilized, when it becomes non- recyclable. Therefore, in order to implement such innovative solutions in environmental and building sectors e.g. to install energetically effective thermal–acoustical insulation materials in building industry, scientific research is required. The object of this research is to produce fibrous composites made from natural fibres (hemp fibres and sheep wool waste) and binder of polylactide fibres, which are made from plant products – corn – by biotechnological method. In current research thermal conductivity and sound absorption coefficient of fibrous composites were determined. The microstructure of fibrous composites were investigated as well. The paper describes the manufacturing possibilities with regard to thermal–acoustical insulating materials based on hemp fibres and sheep wool waste from easily renewable material resources provided by the agriculture.
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Wang, Rujia, and Shaoyi Bei. "Optimization of Fixed Microphone Array in High Speed Train Noises Identification Based on Far-Field Acoustic Holography." Advances in Acoustics and Vibration 2017 (February 1, 2017): 1–11. http://dx.doi.org/10.1155/2017/1894918.
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Acoustical holography has been widely applied for noise sources location and sound field measurement. Performance of the microphones array directly determines the sound source recognition method. Therefore, research is very important to the performance of the microphone array, its array of applications, selection, and how to design instructive. In this paper, based on acoustic holography moving sound source identification theory, the optimization method is applied in design of the microphone array, we select the main side lobe ratio and the main lobe area as the optimization objective function and then put the optimization method use in the sound source identification based on holography, and finally we designed this paper to optimize microphone array and compare the original array of equally spaced array with optimization results; by analyzing the optimization results and objectives, we get that the array can be achieved which is optimized not only to reduce the microphone but also to change objective function results, while improving the far-field acoustic holography resolving effect. Validation experiments have showed that the optimization method is suitable for high speed trains sound source identification microphone array optimization.
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Zhang, Yong Yan, Jiu Hui Wu, Song Hua Cao, Pei Cao, and Zi Ting Zhao. "New acoustical technology of sound absorption based on reverse horn." Modern Physics Letters B 30, no. 34 (December 8, 2016): 1650403. http://dx.doi.org/10.1142/s0217984916504030.
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In this paper, a novel reverse horn’s sound-absorption mechanism and acoustic energy focusing mechanism for low-frequency broadband are presented. Due to the alternation of the reverse horn’s thickness, the amplitude of the acoustic pressure propagated in the structure changes, which results in growing energy focused in the edge and in the reverse horn’s tip when the characteristic length is equal to or less than a wavelength and the incident wave is compressed. There are two kinds of methods adopted to realize energy dissipation. On the one hand, sound-absorbing materials are added in incident direction in order to overcome the badness of the reverse horn’s absorption in high frequency and improve the overall high-frequency and low-frequency sound-absorption coefficients; on the other hand, adding mass and film in its tip could result in mechanical energy converting into heat energy due to the coupled vibration of mass and the film. Thus, the reverse horn with film in the tip could realize better sound absorption for low-frequency broadband. These excellent properties could have potential applications in the one-dimensional absorption wedge and for the control of acoustic wave.
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Núñez, Gabriel, Rodolfo Venegas, Tomasz G. Zielinski, and François-Xavier Bécot. "Sound absorption of polydisperse heterogeneous porous composites." INTER-NOISE and NOISE-CON Congress and Conference Proceedings 263, no. 4 (August 1, 2021): 2730–39. http://dx.doi.org/10.3397/in-2021-2217.
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Sound absorption of polydisperse heterogeneous porous composites is investigated in this paper. The wave equation in polydisperse heterogeneous porous composites is upscaled by using the two-scale method of homogenisation, which allows the material to be modeled as an equivalent fluid with atypical effective parameters. This upscaled model is numerically validated and demonstrates that the dissipation of sound in polydisperse heterogeneous porous composites is due to visco-thermal dissipation in the composite constituents and multiple pressure diffusion in the polydisperse heterogeneous inclusions. Analytical and semi-analytical models are developed for the acoustical effective parameters of polydisperse heterogeneous porous composites with canonical geometry (e.g. porous matrix with cylindrical and spherical inclusions) and with complex geometries. Furthermore, by comparing the sound absorption coefficient of a hard-backed composite layer with that of layers made from the composite constituents alone, it is demonstrated that embedding polydisperse heterogeneous inclusions in a porous matrix can provide a practical way for significantly increasing low frequency sound absorption. The results of this work are expected to serve as a model for the rational design of novel acoustic materials with enhanced sound absorption properties.
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Liu, Xue Ting, Li Li, Xiong Yan, and Hui Ping Zhang. "Sound-Absorbing Properties of Kapok Fiber Nonwoven Composite at Low-Frequency." Advanced Materials Research 821-822 (September 2013): 329–32. http://dx.doi.org/10.4028/www.scientific.net/amr.821-822.329.
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More and more concern for environmental problems has led public to use natural and environmentally benign sound-absorbing materials. In this study, the sound-absorbing nonwoven composites based on kapok fiber and hollow polyester fiber were developed and sound absorption properties of kapok fiber nonwoven composites were investigated in the low frequency region of 100-500 Hz using the impedance tube method. The poor sound-absorbing at low-frequency is one of the difficult problems that urgently need to be solved in fibrous sound-absorbing materials. The effects of physical parameters, including bulk density and thickness, and depth of back cavity on sound absorption properties of composites were studied. Increasing of the bulk density, thickness and depth of back cavity is contribute to improve sound absorption properties of composites at low frequency. The comparisons of kapok fiber with polypropylene (PP) fiber and hollow polyester fiber indicated that as a natural fiber, kapok fiber had a superior acoustical properties at low frequency.
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Mężyk, Jordan, Artur Flach, and Andrzej Zbrowski. "Control System of a Manipulation Mechanism for Acoustical Measurement in Anechoic Chamber." Solid State Phenomena 198 (March 2013): 467–72. http://dx.doi.org/10.4028/www.scientific.net/ssp.198.467.
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The article considers the previously presented manipulating mechanism for positioning of a microphone during acoustical measurements in anechoic chamber. Usually the aims of acoustical measurements in anechoic chamber are: estimation of Sound Power Level of the noise source, measurement of directional characteristics of an electroacoustical transducer, measurement of the sound diffusion characteristic of a given structure and a measurement of Sound Pressure Level on a given measurement grid. The specific of that kind of measurements brings up the need of measurement microphone positioning in many points of the measurement space accordingly to relevant standards. In most cases during the tests it is necessary to position the microphone in certain points on the hemisphere. In such cases utilizing of typical microphone stands impedes the measurement and extends the time needed for the tests. The presented manipulation system for a measurement microphone allows positioning the microphone on the hemisphere around the tested object as required by the standards on the Sound Power Level measurement. Its construction is a simple, rigid form aiming at little effect on the acoustic field inside the chamber whereas the control system and the software are targeted at the maximal flexibility that allows not only standard testing but also scientific research in freely selected scenarios. Since its initial introduction the system has been extended by an additional axis that is used for rotating the microphone, which allows its positioning on the line that is coincident with the centre of rotation of the turntable. Such an extension eliminates the problem of use of the corrections of the directional characteristics of the microphone when measuring the sound signal. The microphone can be positioned directly towards the source of the sound. The article briefly reviews the mechanical construction of the positioning mechanism and focuses on the structure of the control section of the drive system constructed in the manipulator. The method for cooperation of actuators and the control system is presented. Also the description is given for the internal structure of the multi-level control circuits built in the applied drives. Finally the structure of the control application is presented.
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Giannella, Venanzio, Claudio Colangeli, Jacques Cuenca, Roberto Citarella, and Mattia Barbarino. "Experimental/Numerical Acoustic Assessment of Aircraft Seat Headrests Based on Electrospun Mats." Applied Sciences 11, no. 14 (July 11, 2021): 6400. http://dx.doi.org/10.3390/app11146400.
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The work proposes a methodology for the assessment of the performances of Passive Noise Control (PNC) for passenger aircraft headrests with the aim of enhancing acoustic comfort. Two PNC improvements of headrests were designed to reduce the Sound Pressure Level (SPL) at the passengers’ ears in an aircraft cabin during flight; the first was based on the optimization of the headrest shape, whereas the second consisted of partially or fully covering the headrest surface with a new highly sound-absorbing nanofibrous textile. An experimental validation campaign was conducted in a semi-anechoic chamber. A dummy headrest was assembled in different configurations of shape and materials to assess the acoustic performances associated to each set up. In parallel, simulations based on the Boundary Element Method (BEM) were performed for each configuration and an acceptable correlation between experimental and numerical results was obtained. Based on these findings, general guidelines were proposed for the acoustical design of advanced headrests.
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Kino, Naoki, and Takayasu Ueno. "Evaluation of acoustical and non-acoustical properties of sound absorbing materials made of polyester fibres of various cross-sectional shapes." Applied Acoustics 69, no. 7 (July 2008): 575–82. http://dx.doi.org/10.1016/j.apacoust.2007.02.003.
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Patinha, Sérgio, Fernando Cunha, Raul Fangueiro, Sohel Rana, and Fernando Prego. "Acoustical Behavior of Hybrid Composite Sandwich Panels." Key Engineering Materials 634 (December 2014): 455–64. http://dx.doi.org/10.4028/www.scientific.net/kem.634.455.
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This paper deals with the characterization of acoustic insulation behaviour of hybridsandwich composite panels for application in modular house construction. These sandwich panelsare a sustainable, light-weight and durable solution, since are based on natural fibers structureimpregnated with a thermosetting polymer. In this way, three different types of hybrid compositepanels containing polyurethane core and laminated composite skins were produced and analyzed,varying the composition of laminates. The composite laminates of the prototypes were producedusing a vacuum infusion technique and were composed of glass and jute fibers, impregnated with apolyester resin. The solutions developed were compared with a standard, composed of plasterboardshaving different thicknesses and used for thermal and acoustic insulation. Acoustic insulationcharacterization was performed on specimens with 220x220 mm size in a sound proof acousticchamber. The tested sandwich panels showed promising results; however, their overall performancewas lower as compared to the performance of standard solutions used for comparison. Nevertheless,the specific acoustic insulation performance, i.e. sound reduction per unit mass of material for thedeveloped sandwich panels was significantly higher as compared to the standard materials,indicating better suitability of this innovative solution for light-weight construction and modularhousing.