scholarly journals Acoustic Absorption Characteristics of Porous Asphalt Containing Coconut Shells

2019 ◽  
Vol 8 (3S3) ◽  
pp. 327-331
Keyword(s):  
Absorption Coefficient ◽  
Sound Absorption ◽  
Maximum Density ◽  
Acoustic Absorption ◽  
Impedance Tube ◽  
Porous Asphalt ◽  
Tube Test ◽  
Resistance To Oxidation ◽  
Coconut Shells ◽  
Absorption Characteristics

In this study, coconut shells were used as aggregate replacement in porous asphalt to observe its effect on sound absorption through Impedance Tube test. For coconut shells aggregate porous asphalt to be used in realistic situations it is essential to ensure its mix integrity, resistance to oxidation and raveling as well as its durability; therefore, the Cantabro Test, Binder drain-down test and Theoretical Maximum Density were also conducted in this study. The result showed that porous asphalt containing coconut shells exhibited significance improvement of sound absorption. The sound absorption coefficient of porous asphalt incorporating 10%, 30% and 50% of coconut shells approximately at the peak of the curve which is at the frequency of 850hz are 0.93, 0.96 and 0.93 while for conventional porous asphalt is 0.89. This study also found that porous asphalt containing 10 - 50% of coconut shells contributed a significance improvement in sound absorption compare than conventional porous asphalt at the frequency of 200 – 1600 Hz. However, only porous asphalt containing 10% of coconut shells satisfied all the parameters tested similar to the conventional porous asphalt.

Sound Absorption Characteristics of Porous Steel Manufactured by Lost Carbonate Sintering

2009 ◽  
Vol 1188 ◽  
Author(s):  
Miao Lu ◽  
Carl Hopkins ◽  
Yuyuan Zhao ◽  
Gary Seiffert
Keyword(s):  
Absorption Coefficient ◽  
Pore Size ◽  
Sound Absorption ◽  
Single Layer ◽  
Normal Incidence ◽  
Sound Absorption Coefficient ◽  
Absorption Coefficients ◽  
Impedance Tube ◽  
Absorption Characteristics

AbstractThis paper investigates the sound absorption characteristics of porous steel samples manufactured by Lost Carbonate Sintering. Measurements of the normal incidence sound absorption coefficient were made using an impedance tube for single-layer porous steel discs and assemblies comprising four layers of porous steel discs. The sound absorption coefficient was found not to vary significantly with pore size in the range of 250-1500 μm. In general, the absorption coefficient increases with increasing frequency and increasing thickness, and peaks at specific frequencies depending on the porosity. An increase in porosity tends to increase the frequency at which the sound absorption coefficient reaches this peak. An advantage was found in using an assembly of samples with gradient porosities of 75%-70%-65%-60% as it gave higher and more uniform sound absorption coefficients than an assembly with porosities of 75%.

Effect of Percentage Ratio of Hydroxylated Biomonomer with Synthetic Epoxy of Polymer Foam for Sound Absorption Study

2013 ◽  
Vol 465-466 ◽  
pp. 1034-1038 ◽  
Author(s):  
Noor Quratul Aine Adnan ◽  
Anika Zafiah M. Rus
Keyword(s):  
Absorption Coefficient ◽  
Vegetable Oil ◽  
Sound Absorption ◽  
Acoustic Property ◽  
The Other ◽  
Absorption Study ◽  
Polymer Foam ◽  
Impedance Tube ◽  
Tube Test ◽  
Percentage Ratio

Biopolymer foam was prepared based on vegetable oil and Polyol Flexible (Epoxy) with commercial Polymethane Polyphenyl Isocyanate (Modified Polymeric-MDI) with the different proportion ratio. This research is to study the acoustic property between different proportion ratio of biomonomer and epoxy. The acoustic property of biopolymer foam was examined by using an impedance tube test according to ASTM E-1050 of sound absorption coefficient (α). Based on the result obtained, mostly the values of α were consistent at the samples F. It was observed that, sample F gave the highest value of α that is 0.997 at of 3500Hz. Sample F from ratio 100:0 from epoxy to biomonomer and gave the best sound absorption than the other foam. So, different ratio give different α at different frequency (Hz).

Preliminary Study on Bamboo as Sound Absorber

2014 ◽  
Vol 554 ◽  
pp. 76-80 ◽  
Author(s):  
Fazlin A. Khair ◽  
Azma Putra ◽  
Mohd Jailani Mohd Nor ◽  
Nurul Atiqah ◽  
M.Z. Selamat
Keyword(s):  
Absorption Coefficient ◽  
Sound Absorption ◽  
Hollow Structure ◽  
Chemical Substance ◽  
The Body ◽  
Natural Material ◽  
Sound Absorber ◽  
Tube Test ◽  
Average Absorption Coefficient ◽  
Preliminary Study

Synthetic acoustic materials are known for their poisonous chemical substance to the environment and also the particles which are harmful to human health. Research is now directed towards finding an alternative acoustic absorber made from natural materials. This paper presents the utilization of bamboo, a natural material having hollow structure to act as sound absorber. In an impedance tube test, the hollow path is arranged to face the sound incidence. The result reveals that bamboo having length of 2 cm has average absorption coefficient of 0.95 at frequency above 3 kHz. Performance at lower frequencies can be controlled by adding the air gap behind the system. Introduction of microholes along the body shows no significant effect to increase the sound absorption.

Sound Absorption Characteristics of a Single Micro-Perforated Panel Backed by a Natural Fiber Absorber Material

2020 ◽  
Vol 307 ◽  
pp. 291-296 ◽  
Author(s):  
Meifal Rusli ◽  
Fakhrur Rahman ◽  
Hendery Dahlan ◽  
Gusriwandi ◽  
Mulyadi Bur
Keyword(s):  
Absorption Coefficient ◽  
Sound Absorption ◽  
Natural Fiber ◽  
Natural Fibers ◽  
Absorption Characteristic ◽  
Coconut Fiber ◽  
Single Leaf ◽  
Absorber Material ◽  
Resonance Absorber ◽  
Absorption Characteristics

A micro-perforated panel (MPP) works as a Helmholtz-type resonance absorber formed by an air-gab cavity in order to minimize the reflected sound effectively at a selective resonance frequency. Furthermore, the use of natural fibers as sound absorbing materials recently has attracted more attention because it is completely biodegradable, environmental friendly and more economical. In this paper, the combination of MPP and natural fiber as sound absorptive material is investigated. The MPP is made of a transparent acrylic board with 1.5 mm thickness and backed by a coconut fiber panel. The effect of the fiber panel that inserted in the air-gab cavity to the sound absorption characteristic of a single leaf MPP is observed. Sound absorption coefficient is measured by transfer function method using two microphones-impedance tube. It is found that the sandwich model of MPP backed by a coconut fiber changes the sound absorption characteristics of MPP by shifting the maximum absorption coefficient into the lower frequency and making a wider band of frequency absorption. Moreover, the air-gab cavity between MPP and fiber panel give fewer contribution to construct the MPP frequency resonant than the natural fiber panel one.

The effect of the combination of multiple woven fabric and nonwoven on acoustic absorption

2019 ◽  
pp. 152808371985877 ◽  
Author(s):  
Pilar Segura-Alcaraz ◽  
Jorge Segura-Alcaraz ◽  
Ignacio Montava ◽  
Marilés Bonet-Aracil
Keyword(s):  
Absorption Coefficient ◽  
Sound Absorption ◽  
Woven Fabric ◽  
Sound Absorption Coefficient ◽  
Acoustic Absorption ◽  
Experimental Conditions ◽  
Resistive Layer ◽  
Textile Materials ◽  
Acoustic Absorption Coefficient ◽  
Fabric Structures

Textile materials can be used as acoustic materials. In this study, the acoustic absorption coefficient of multilayer fabrics with 60 ends/cm and 15, 30, 45, and 60 picks/cm is measured when the fabric is added as a resistive layer on top of a polyester nonwoven, in order to study the influence of the fabric spatial structure in the acoustic absorption of the assembly. Five different fabric structures are used. Design of experiments and data analysis tools are used to describe the influence of two manufacturing factors on the sound absorption coefficient of the ensemble. These factors are the fabric weft count (picks/cm) and the thickness of the nonwoven (mm). The experimental conditions under which the maximum sound absorption coefficient is achieved are found. The influence of each factor and a mathematical model are obtained. Results of statistical and optimization analysis show that for the same fabric density, sound absorption coefficient increases as the number of layers decreases.

scholarly journals Elucidating the Sound Absorption Characteristics of Foxtail Millet (Setariaitalica) Husk

Materials ◽  
2020 ◽  
Vol 13 (22) ◽  
pp. 5126
Author(s):  
Dhayalini Balasubramanian ◽  
Senthil Rajendran ◽  
Bhuvanesh Srinivasan ◽  
Nirmalakumari Angamuthu
Keyword(s):  
Absorption Coefficient ◽  
Sound Absorption ◽  
Foxtail Millet ◽  
Air Gap ◽  
Composite Panel ◽  
Sound Absorption Coefficient ◽  
Mass Content ◽  
Frequency Range ◽  
Backing Material ◽  
Absorption Characteristics

The current study deals with the analysis of sound absorption characteristics of foxtail millet husk powder. Noise is one the most persistent pollutants which has to be dealt seriously. Foxtail millet is a small seeded cereal cultivated across the world and its husk is less explored for its utilization in polymer composites. The husk is the outer protective covering of the seed, rich in silica and lingo-cellulose content making it suitable for sound insulation. The acoustic characterization is done for treated foxtail millet husk powder and polypropylene composite panels. The physical parameters like fiber mass content, density, and thickness of the composite panel were varied and their influence over sound absorption was mapped. The influence of porosity, airflow resistance, and tortuosity was also studied. The experimental result shows that 30-mm thick foxtail millet husk powder composite panel with 40% fiber mass content, 320 kg/m3 density showed promising sound absorption for sound frequency range above 1000 Hz. We achieved noise reduction coefficient (NRC) value of 0.54. In view to improve the performance of the panel in low-frequency range, we studied the efficiency of incorporating air gap and rigid backing material to the designed panel. We used foxtail millet husk powder panel of density 850 kg/m3 as rigid backing material with varying air gap thickness. Thus the composite of 320 kg/m3 density, 30-mm thick when provided with 35-mm air gap and backing material improved the composite’s performance in sound frequency range 250 Hz to 1000 Hz. The overall sound absorption performance was improved and the NRC value and average sound absorption coefficient (SAC) were increased to 0.7 and 0.63 respectively comparable with the commercial acoustic panels made out of the synthetic fibers. We have calculated the sound absorption coefficient values using Delany and Bezlay model (D&B model) and Johnson–Champoux–Allard model (JCA model) and compared them with the measured sound absorption values.

scholarly journals The Effects of Various Additive Components on the Sound Absorption Performances of Polyurethane Foams

2015 ◽  
Vol 2015 ◽  
pp. 1-9 ◽  
Author(s):  
Shuming Chen ◽  
Yang Jiang ◽  
Jing Chen ◽  
Dengfeng Wang
Keyword(s):  
Absorption Coefficient ◽  
Sound Absorption ◽  
Transmission Loss ◽  
Polyurethane Foams ◽  
Acoustic Properties ◽  
Acoustic Absorption ◽  
Absorption Properties ◽  
Maximum Enhancement ◽  
Flexible Polyurethane ◽  
Pu Foams

Flexible polyurethane (PU) foams comprising various additive components were synthesized to improve their acoustic performances. The purpose of this study was to investigate the effects of various additive components of the PU foams on the resultant sound absorption, which was characterized by the impedance tube technique to obtain the incident sound absorption coefficient and transmission loss. The maximum enhancement in the acoustic properties of the foams was obtained by adding fluorine-dichloroethane (141b) and triethanolamine. The results showed that the acoustic absorption properties of the PU foams were improved by adding 141b and triethanolamine and depended on the amount of the water, 141b, and triethanolamine.

Utilization of Treated Red Meranti Wood Dust as Polymer Foam Composite for Acoustic Study

2013 ◽  
Vol 594-595 ◽  
pp. 760-764 ◽  
Author(s):  
Shafizah Sa'adon ◽  
Anika Zafiah M. Rus
Keyword(s):  
Absorption Coefficient ◽  
Sound Absorption ◽  
Sound Absorption Coefficient ◽  
Wood Dust ◽  
Polymer Foam ◽  
Tube Test ◽  
Acoustic Study ◽  
Foam Composite ◽  
Absorbing Materials ◽  
Scanning Electron

A Red Meranti Wood Dust (RMD) act as a filler for polymer foam composite has been investigated and proved to have ability to absorb sound. In this study, treatment of wood dust with and without acid hydrolysis named as WDB and WDA respectively was use as filler. This study was developed to compare the ability of sound absorption based on treated filler and particle size of wood dust. By choosing the size of 355 μm, three different percentage has been selected which is 10%, 15% and 20% for both conditions. These samples has been tested by using Impedance Tube test according to ASTM E-1050 for sound absorption coefficient, α measurement and Scanning Electron Microscopy (SEM) for determine the porosity for each samples. 10% loaded of WDB as filler gives highest sound absorption coefficient of 0.999 at 4015.63 Hz. Meanwhile for 20% loaded of WDA gives 0.997 at 3228.13 Hz. When comparing the sound absorption coefficient for both sounds absorbing materials, WDB-polymer foam composite RMD showed higher value of sound absorption coefficient, α at higher frequency as compared to WDA-polymer foam composite.

scholarly journals Effect of Thickness and Perforation Size on the Acoustic Absorption Performance of a Micro-Perforated Panel

2021 ◽  
Vol 335 ◽  
pp. 03016
Author(s):  
Yi-San Wong ◽  
Vignesh Sekar ◽  
Se Yong Eh Noum ◽  
Sivakumar Sivanesan
Keyword(s):  
Absorption Coefficient ◽  
Urban Areas ◽  
Sound Absorption ◽  
Rapid Development ◽  
Noise Pollution ◽  
Sound Absorption Coefficient ◽  
Sound Insulation ◽  
Acoustic Absorption ◽  
Psychological Disturbance ◽  
Absorption Performance

In current times, noise pollution is especially apparent in urban areas due to rapid development in transportation, industrialization, and urbanization. The worsening noise pollution is detrimental to human health and behaviour as it can contribute to disorders and psychological disturbance. Thus, noise regulation is crucial and must be addressed with immediate effect. Micro-perforated panels (MPP) can be a potential solution to mitigate noise on a commercial scale. Researchers have addressed the mechanics behind the enhancement of acoustic absorption through micro-perforation and some suggestions have been made, such as the effect of structural variation on sound absorption performance. Hence, this research aims at optimizing the sound absorption performance of an MPP by determining the connection between thickness and perforation size with sound absorption coefficient. Three cases were considered: (i) varying perforation size, (ii) varying thickness, and (iii) varying perforation size and thickness simultaneously. Based on the Maa prediction model, the sound absorption performance for all three cases have been simulated through the MATLAB software. Results show that the increase in both thickness and perforation size together increases the peak value of sound absorption coefficient (SAC). It also shifts the peak towards the higher frequency region and narrows the bandwidth. The findings of this study indicate the potential of thick MPPs as commercial sound absorbers by adjusting the size of perforations. Thicker and sturdier MPPs with optimal acoustic resistance and reactance can act as reliable sound absorbers for sound insulation purposes.

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