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.

scholarly journals Experimental Study on the Sound Absorption Properties of Finger Millet Straw, Darbha, and Ripe Bulrush Fibers

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
K. M. Rakesh ◽  
Ramachandracharya Srinidhi ◽  
S. Gokulkumar ◽  
K. S. Nithin ◽  
S. Madhavarao ◽  
...  
Keyword(s):  
Absorption Coefficient ◽  
Sound Absorption ◽  
Finger Millet ◽  
Natural Fiber ◽  
Fiber Type ◽  
Natural Fibers ◽  
Noise Pollution ◽  
Sound Absorption Coefficient ◽  
Human Beings ◽  
Fiber Arrangement

Nowadays, emerging noise pollution by external factors causes harmful diseases in human beings. The development of a bio-based filler or panel will help to eliminate some unwanted noise in working places and living rooms. This work aimed to develop an ecowaste fiber (leftover after harvesting)-based sound absorber and analyze its capabilities for sound absorption. The ecowaste fibers are collected by the gleaning process, i.e., the process of collecting leftovers from fields. The sound absorption capabilities of three natural fibers extracted from Eleusine coracana (Finger millet) straw, Desmostachya bipinnata (Darbha), and Typha domingensis (Ripe bulrush) plants are investigated in this study, both individually and in hybrid combinations. The sound absorption property mainly depends on factors such as porosity, flow resistivity, thickness, density, and tortuosity. Fiber length and fiber type play a significant role when fibers are arranged individually or in hybrid combinations. The stacking effect on the sound absorption coefficient of hybridized fiber arrangement was experimentally analyzed. The sound absorption coefficient (α) was found to be lower in the range of 1000 Hz–2500 Hz for all the combinations. As a homogenous fiber arrangement, the darbha fiber exhibited the better NRC (noise reduction coefficient) of 0.86 for 50 mm thickness among three different fibers and as a hybrid composition, ripe bulrush and darbha fibers exhibited NRC of 0.90 which is more capable of absorbing sound in the critical frequency range of 500 to 2000 Hz. These types of natural fiber fillers are highly capable of better sound absorbing and used in the applications such as classrooms, sound recording rooms, and theatres.

scholarly journals Acoustic, Mechanical and Thermal Properties of Green Composites Reinforced with Natural Fibers Waste

Polymers ◽  
2020 ◽  
Vol 12 (3) ◽  
pp. 654 ◽  
Author(s):  
Tufail Hassan ◽  
Hafsa Jamshaid ◽  
Rajesh Mishra ◽  
Muhammad Qamar Khan ◽  
Michal Petru ◽  
...  
Keyword(s):  
Absorption Coefficient ◽  
Sound Absorption ◽  
Natural Fiber ◽  
Coefficient Of Thermal Expansion ◽  
The Other ◽  
Fiber Reinforced Composites ◽  
Sound Absorption Coefficient ◽  
Mechanical And Thermal Properties ◽  
Reinforced Composites ◽  
Fiber Reinforced

The use of acoustic panels is one of the most important methods for sound insulation in buildings. Moreover, it has become increasingly important to use green/natural origin materials in this area to reduce environmental impact. This study focuses on the investigation of acoustic, mechanical and thermal properties of natural fiber waste reinforced green epoxy composites. Three different types of fiber wastes were used, e.g., cotton, coconut and sugarcane with epoxy as the resin. Different fiber volume fractions, i.e., 10%, 15% and 20% for each fiber were used with a composite thickness of 3 mm. The sound absorption coefficient, impact strength, flexural strength, thermal conductivity, diffusivity, coefficient of thermal expansion and thermogravimetric properties of all samples were investigated. It has been found that by increasing the fiber content, the sound absorption coefficient also increases. The coconut fiber-based composites show a higher sound absorption coefficient than in the other fiber-reinforced composites. The impact and flexural strength of the cotton fiber-reinforced composite samples are higher than in other samples. The coefficient of thermal expansion of the cotton fiber-based composite is also higher than the other composites. Thermogravimetric analysis revealed that all the natural fiber-reinforced composites can sustain till 300 °C with a minor weight loss. The natural fiber-based composites can be used in building interiors, automotive body parts and household furniture. Such composite development is an ecofriendly approach to the acoustic world.

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.

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%.

scholarly journals Sound absorbing and insulating properties of natural fiber hybrid composites using sugarcane bagasse and bamboo charcoal

2021 ◽  
Vol 16 ◽  
pp. 155892502110448
Author(s):  
Santhanam Sakthivel ◽  
Selvaraj Senthil Kumar ◽  
Eshetu Solomon ◽  
Gedamnesh Getahun ◽  
Yohaness Admassu ◽  
...  
Keyword(s):  
Composite Materials ◽  
Physical Properties ◽  
Sugarcane Bagasse ◽  
Sound Absorption ◽  
Natural Fiber ◽  
Natural Fibers ◽  
Acoustic Properties ◽  
Sound Insulation ◽  
Bamboo Charcoal ◽  
Green Composite

This research paper reports a study on thermal and sound insulation samples developed from sugarcane bagasse and bamboo charcoal for automotive industry applications. The sugarcane bagasse and bamboo charcoal fiber is a potential source of raw material that can be considered for thermal and sound insulation applications. Natural fibers are commonly used in diverse applications and one of the most important applications is sound absorption. Natural fiber hybrid composite currently is in greater demand in industries because of their advantages such as low cost, biodegradability, acceptable physical properties, and so on. Eco-friendly sound-absorbing composite materials have been developed using bamboo charcoal and sugarcane bagasse fibers. From these fibers five types of natural fiber green composite were developed using the compression bonding technique. The natural composite noise control performance contributes to its wider adoption as sound absorbers. The sound absorption coefficient was measured according to ASTM E 1050 by the Impedance tube method. The physical properties of natural fiber composites such as thickness, density, porosity, air permeability, and thermal conductivity were analyzed for all samples in accordance with ASTM Standard. The result exposed that natural fiber green composite were absorbing the sound resistance of more than 70% and the natural fibers composites provide the best acoustic absorption properties, these composite materials have adequate moisture resistance at high humidity conditions without affecting the insulation and acoustic properties.

Sound Absorption Characteristic of Glass and Plastic Bottles: Considerations of Their Dependences on Material Properties

2018 ◽  
Author(s):  
Teruo Iwase ◽  
Satoshi Sugie ◽  
Hiroyasu Kurono ◽  
Masayuki Abe ◽  
Yasuaki Okada ◽  
...  
Keyword(s):  
Absorption Coefficient ◽  
Resonance Frequency ◽  
Sound Absorption ◽  
Helmholtz Resonator ◽  
Green Building ◽  
Sound Absorption Coefficient ◽  
Absorption Characteristic ◽  
Impedance Change ◽  
Perforated Plates ◽  
Section Area

Great number of bottles made by glass, plastic and metal are used to store beverages, liquid ingredients as water, milk, vinegar and also liqueur. Empty bottles after usage are collected for recycling use and resources. Many of them have narrow open mouth and look like typical shape in kinds of Helmholtz resonator. Authors thought that their reuse for functional building parts with sound absorption would be very valuable from points of view of green building and environmental policies, and authors then measured each resonance frequency and sound absorption coefficient of representative, including light-soft-plastic, bottles, with net capacity from 7 to 2000 ml, by setting on the edge of sound tube with diameter of 100 mm. Sound resonances with sound absorption coefficient of 0.3–1.0 at frequencies from 100 to 1000 Hz clearly depending on the capacity could be confirmed. It was also found that measured result was well matched to the numerical calculation based on acoustic impedance change at each section area gradually changed in bottle. It is thought that combination use of recycled bottles with independent resonance frequency is more effective than use of new uniform perforated plates for wide space where we need additional sound absorption in certain frequency range.

Comparative Study of Sound Absorption Coefficients of Coir/Kenaf/Sugarcane Bagasse Fiber Reinforced Epoxy Composites

2017 ◽  
Vol 730 ◽  
pp. 48-53 ◽  
Author(s):  
Elammaran Jayamani ◽  
Soon Kok Heng ◽  
Muhammad Khusairy bin Bakri ◽  
Sinin Hamdan
Keyword(s):  
Absorption Coefficient ◽  
Sugarcane Bagasse ◽  
Sound Absorption ◽  
Transfer Functions ◽  
Natural Fibers ◽  
Epoxy Composites ◽  
Sound Absorption Coefficient ◽  
Coconut Coir ◽  
Impedance Tube Method ◽  
Bagasse Fiber

This research focuses on the sound absorption coefficient of three different natural fibers reinforced epoxy composites. The natural fibers used are coconut coir, kenaf, and sugarcane bagasse. All of these fibers were mixed with epoxy resin and hardener with a ratio of 4:1. The mixtures were then poured into a circular mold and compressed by using compression molding technique. It was left for curing for 24 hours at standard room temperature. The results were obtained using the two-microphone transfer functions impedance tube method according to ASTM E1050-12. It is found that as the fiber loading increased, the sound absorption coefficient of the composites increased. 20wt% Coconut coir epoxy composites and 20wt% kenaf fiber epoxy composites have the highest sound absorption coefficient with almost similar sound absorption of 0.078 at 5000Hz. While, 20wt% sugarcane bagasse epoxy composites have sound absorption of 0.075 at 5000Hz.

Evaluation and comparison the properties of acoustic boards made of date palm fiber

BioResources ◽  
2021 ◽  
Vol 16 (4) ◽  
pp. 7702-7715
Author(s):  
Mehdi Alishiri ◽  
Amir Hooman Hemmasi ◽  
Habibollah Khademi Eslam ◽  
Sedigheh Basirjafari ◽  
Mohammad Talaeipour
Keyword(s):  
Absorption Coefficient ◽  
Sodium Silicate ◽  
Sound Absorption ◽  
Date Palm ◽  
Agricultural Waste ◽  
Natural Fibers ◽  
Control Sample ◽  
Sound Absorption Coefficient ◽  
Synthetic Fibers ◽  
Particle Length

Applying acoustic panels made of natural fibers, due to their high biodegradable characteristics, light weight, low density, cheap price and non-toxicity, are proper alternatives to acoustic absorbers made of synthetic fibers. Considering their stance and vast applicability in industry, the possibility of producing them of natural palm fibers with sodium silicate adhesive of 10 and 20% in two 16 and 32 mm thicknesses, 350 and 450 kg/m3 densities, 50 and 100 mm particles length (strands), as variable factors in 16 types of matched panels with 3 repetitions is proposed in this article. The palm-trunk discs constituted the control sample. The effect of variables on sound absorption coefficient was assessed. The effect of variable thickness and adhesive percentage on all frequencies was significant and the effect of density variable on all frequencies except 250 and 2000 Hz was also significant. The effect of particle length was significant except at the 500 Hz frequency. The effects of all variables on porosity were significant. The results of this study suggest that by applying date palm-trunk (an agricultural waste) combined with sodium silicate adhesive, industrial environment-friendly panels can be produced with proper sound absorption coefficient in the field of acoustics. This 32-mm-thick panel was composed of 80% date palm-trunk particles of 50 mm length, 450 kg/m3 density, and 20% sodium silicate adhesive.

The effect of physical parameters on sound absorption properties of natural fiber mixed nonwoven composites

2012 ◽  
Vol 82 (20) ◽  
pp. 2043-2053 ◽  
Author(s):  
Merve Küçük ◽  
Yasemin Korkmaz
Keyword(s):  
Absorption Coefficient ◽  
High Frequency ◽  
Sound Absorption ◽  
Natural Fiber ◽  
Unit Area ◽  
Air Permeability ◽  
Physical Parameters ◽  
Fiber Types ◽  
Absorption Properties ◽  
Nonwoven Fabrics

In this study, the effects of physical parameters on sound absorption properties of nonwoven fabrics were investigated. Eight different nonwoven composites including different fiber types mixed with different ratios were tested. Along with sound absorption properties, thickness, weight per area, and air permeability parameters of the samples were measured. The increase in thickness and the decrease in air permeability results in an increase in sound absorption properties of the material. The samples including 70% cotton and 30% polyester resulted in the best sound absorption coefficient in the mid-to-high frequency ranges. The increase in the amount of fiber per unit area resulted in an increase in sound absorption of the material. Addition of acrylic and polypropylene into a cotton and polyester fiber mixture increased the sound absorption properties of the composite in the low and mid-frequency ranges also.

The Experimental Investigation on Water Absorption Characteristics of Natural Fiber Composites

2014 ◽  
Vol 984-985 ◽  
pp. 248-252
Author(s):  
S. Vijayakumar ◽  
S. Manikandan ◽  
L. Karunamoorthy
Keyword(s):  
Water Absorption ◽  
Rice Straw ◽  
Natural Fiber ◽  
Natural Fibers ◽  
Alkaline Treatment ◽  
Time Intervals ◽  
Synthetic Fibers ◽  
Reinforced Composite ◽  
Major Variation ◽  
Absorption Characteristics

Natural fibers are used for replacing synthetic fibers as reinforcement in various matrices. This paper is presents the fabrication and water absorption characteristics of various natural fibers reinforced composite fabricated by hand layering technique. The water absorbing capacity, diffusion and permeability of various natural fibers like rice straw, Kenaf, Coconut Spathe, Coconut Guinit reinforced composite with different dipping time intervals were analyzed. Morphological analysis was carried out on fabricated and soaked samples using scanning electron microscope. From the experimental work it is observed that coconut guinits and rice straw shows comparatively very low water absorbing capacity. Alkaline treatment of fibers doesnot have any major variation in water absorbing capacity.

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