Papers by Keyword: Sound Absorption

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Authors: Wei Guang Zheng, Ying Feng Lei, Qi Bai Huang, Chuan Bing Li
Abstract: This paper presents the concept of a compact hybrid sound absorber, based on a combined approach for sound absorption. A flexible micro-perforated panel (MPP) is used as the passive sound absorber for mid and high frequencies and a piezoelectric patch as the active control actuator for low frequency. The volume of this new absorber is highly reduced compare to conventional hybrid systems which employ porous layer as passive part and loudspeaker as active part. The vibration effect of the MPP in the hybrid system is also considered. Theoretical and experimental results show that the flexible MPP has the potential to dissipate more energy and can be utilized to improve absorption performance of the hybrid system by appropriately selecting its parameters.
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Authors: H.B. Zhu, P.M. Wang, C.S. Wang, G.T. Yan, Y.S. Cheng, L.M. Wu
Abstract: Both of noise and building energy efficiency are attached importance to in the world. A novel material is developed to control noise, save building energy and decorate for buildings. Porous absorber, cavity resonator resonance sound absorber, film resonance sound absorber, functional absorber and high sound absorber are utilized to improve the sound absorbability. Perlite, Ordinary Portland cement, silicon fume, re-dispersible emulsion powder or emulsion, air-entraining agent, superplasticizer, short fiber and mesh fabrics are used to prepare novel material. Organic silicone waterproof material is used to prevent it from destroying, assist for sound absorbability and decorate for surface. After designing wedge sound absorber by mould, forming cavity resonator resonance sound absorber by air-entraining agent, and controlling compression ratio, diameter of perlite grain and cement dosage, final performances of sound absorbability and heat preservation can meet requirements of ASTM C423-84A and GB/T 20473-2006 respectively.
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Authors: Hanif Abdul Latif, Musli Nizam Yahya, Mohamed Najib Rafiq, Mathan Sambu, Mohd Imran Ghazali, Mohamed Nasrul Mohamed Hatta
Abstract: 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.
247
Authors: Elwaleed Awad Khidir, Nik Abdullah Nik Mohamed, Mohd Jailani Mohd Nor, Mohd Faizal Mat Tahir, Rozli Zulkifli
Abstract: In this study sound absorption properties of a single layer date palm fiber has been investigated. Experimental measurements were carried out using impedance tube at the acoustic lab, Faculty of Engineering, Universiti Kebangsaan Malaysia. A constant thickness sample was considered in this study.The results show that the values of absorption coefficient are small at low frequencies, rising with increasing frequency but exhibiting a significant peak. The low density of the sample is reflected in the overall sound absorption performance of the date palm fiber. An improvement in the sound absorption in the lower frequency range was achieved by backing the sample with air gap of different thicknesses of 10 mm, 20 mm and 30 mm. The increase in the air gap thickness moved the peaks toward lower frequencies and improved the low frequencies absorption. However, that increase coincided with reduction of absorption in medium frequency range and reduction in the absorption peak. A linear relationship was found between sound absorption peaks and the air gap thickness. The performance of the date palm fiber can be improved by increasing the density of the sample, using different sample thicknesses and adding perforated plates to the date palm fiber panel.
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Authors: Elwaleed A. Khidir, N. Nikabdullah, M.J.M. Nor, M.F.Mat Tahir, M.Z. Nuawi
Abstract: Sound absorption of self-facing natural date palm fibershas been investigated.A single layer sample of the fibers was tested for its sound absorption properties. The sample was then faced with the originally date palm fiber netted structure. Experimental measurements were conducted on the impedance tube at the acoustic lab, Faculty of Engineering, UniversitiKebangsaan Malaysia, to determine the sound absorption coefficient.The single layer was also tested using an aluminum perforated plate, as facing, for comparison purposes.The results show a good improvement in the sound absorption for the self-facing panel for the whole frequency range. However, when using the aluminum perforated panel an improvement in the sound absorption was observed only above 2500 Hz. The effect of introducing air gap thickness was studied. The results show improvement for the sound absorption the low frequency.
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Authors: Amelia Trematerra, Ilaria Lombardi
Abstract: Green materials can be considered as a valid alternative to traditional synthetic materials. The cork is a green material, in fact it is a sustainable material. Cork can be used to improve the acoustics inside buildings. The systems used consist of cork sheets mounted at a distance onto a rigid wall, with the thickness of the sheet being 1.5 mm. The distances from the rigid wall considered are equal to 5 cm, 10 cm and 15 cm. The absorption coefficient of the sample was measured in the frequency range from 100 Hz to 2000 Hz with an impedance tube.
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Authors: Nik Normunira Mat Hassan, Anika Zafiah M. Rus, S. Nurulsaidatulsyida, Siti Rahmah Mohid
Abstract: Green polymer foam was prepared by the reaction of green monomer based on vegetable oil with commercial Polymethane Polyphenyl Isocyanate (Modified Polymeric-MDI) and distilled water (H2O). The morphological study of green polymer foam was examined by Scanning Electron Microscope (SEM) and acoustic property by means of H2O composition ratio equivalent to weight of polyol. It was found that the cell size of green polymer foam has significantly increment as well as H2O loading increased. Increasing of H2O more than 50% equivalent to weight of polyol shows nonuniform pore distribution, large average pore size and smallest number of pore. Furthermore, the cell size of neat green polymer foam gives 400μm up to 1833.3μm with high loading of H2O. In addition, the cell size of green polymer foam influences by the increasing amount of H2O loading and enhanced the sound absorption property at low frequency level.
281
Authors: Muhammad Khusairy bin Bakri, Elammaran Jayamani, Soon Kok Heng, Sinin Hamdan, Akshay Kakar
Abstract: This research focuses on the simulation of sound absorption coefficient of banana fiber and experimentation of sound absorption coefficient of banana fiber epoxy composites. For simulation, ‘Mechel’ empirical model was used to manipulate the flow resistivity and ‘Delany and Bazley’ empirical model was used to develop the prediction of sound absorption coefficient at frequency ranges from 500 Hz to 6000 Hz. For experimentation, two-microphone transfer function impedance tube model was used to analyze the sound absorption coefficient at frequency ranges from 500 Hz to 6000 Hz. Based on simulation, it is predicted and analyzed that the sound absorption coefficient of banana fiber found to be as high as 0.97 for the effects on the material thickness of banana fiber and 0.64 for the effects on the fiber diameter size and flow resistivity of banana fiber in the frequency ranges from 500 Hz to 6000 Hz. According to experimental results, it is observed and analyzed that the sound absorption coefficient of banana epoxy composites found to be as high as 0.11 for untreated banana epoxy composites and 0.12 for treated banana epoxy composites in the frequency ranges from 500 Hz to 6000 Hz.
9
Authors: Lei Li Li, Sheng Jun Liu, Han Xu
Abstract: With the rapid development of economy in China, there has been a growth in motor vehicles, deteriorating the traffic pollution of roads year by year. The gas pollution, which mainly comes from complete and incomplete combustion of the fuel, includes CO, SO2, NOx, CO2, and VOC. Al, Ca, Fe and Mg and other non-enriched elements in the atmospheric particle originates from the road dust carried by the motor vehicle at the traffic junctions; the noise pollution emerges from the engine and tire friction. The primary methods applied worldwide covers MOBILE, OSPM and MVMS. For the noise pollution, FHWA and RLS90 are used. The roadside landscaping can absorb emissions, accumulate the heavy metal and reduce the dust and noise, which is an effective way to beautify the environment and prevent the pollution.
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Authors: Elwaleed Awad Khidir, Mojahed Osman Mohammed Ali, Mohammed Mustafa Ali, Mohd Faizal Bin Mat Tahir, Rozli Zulkifli
Abstract: This paper presents a study on the sound absorption properties of a single layer date palm fiber based on the flow resistivity. Experimental measurements were carried out to estimate the flow resistivity value using differential pressure tube. The average diameter of the fibers is 0.462 mm. A date palm fiber sample of 25mm thickness is used in this research. The flow resistivity of the date palm fiber sample was found to be 4.26 kPa.s/m2. The flow resistivity was used to calculate the sound absorption coefficient using Delany and Bazley model. The simulation showed that the values of absorption coefficient are small at low frequencies and rising with increasing frequency. To check the effect of flow resistivity on the sound absorption coefficient Delany and Bazley model was simulated for three different flow resistivity values. The simulation results showed that the sound absorption coefficient increases with the increase of the flow resistivity.
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