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 Acoustic Panels Made of Paper Sludge and Clay Composites

2021 ◽  
Vol 13 (2) ◽  
pp. 637
Author(s):  
Tomas Astrauskas ◽  
Tomas Januševičius ◽  
Raimondas Grubliauskas
Keyword(s):  
Absorption Coefficient ◽  
Sound Absorption ◽  
Composite Panel ◽  
Sound Absorption Coefficient ◽  
Core Material ◽  
Paper Sludge ◽  
Frequency Range ◽  
Absorption Properties ◽  
Air Gaps ◽  
The Core

Studies on recycled materials emerged during recent years. This paper investigates samples’ sound absorption properties for panels fabricated of a mixture of paper sludge (PS) and clay mixture. PS was the core material. The sound absorption was measured. We also consider the influence of an air gap between panels and rigid backing. Different air gaps (50, 100, 150, 200 mm) simulate existing acoustic panel systems. Finally, the PS and clay composite panel sound absorption coefficients are compared to those for a typical commercial absorptive ceiling panel. The average sound absorption coefficient of PS-clay composite panels (αavg. in the frequency range from 250 to 1600 Hz) was up to 0.55. The resulting average sound absorption coefficient of panels made of recycled (but unfinished) materials is even somewhat higher than for the finished commercial (finished) acoustic panel (αavg. = 0.51).

Sound Absorption Characteristics of Composite Panel Made from Coconut Coir and Oil Palm Empty Fruit Bunches Fibre with Polyester

2021 ◽  
Vol 18 (3) ◽  
pp. 9022-9028
Author(s):  
M. Rusli ◽  
R.S. Nanda ◽  
H. Dahlan ◽  
M. Bur ◽  
M. Okuma
Keyword(s):  
Absorption Coefficient ◽  
Oil Palm ◽  
Sound Absorption ◽  
Natural Fibre ◽  
Composite Panel ◽  
Frequency Range ◽  
Empty Fruit Bunches ◽  
Coir Fibre ◽  
Coconut Coir ◽  
Absorption Characteristics

The development of pure natural fibres as sound absorptive material remains overlooked due to their lack of mechanical and moist properties, low durability, and vulnerability to be damaged by the environment. Certain fibre treatments are needed to improve such disadvantages. This paper investigates sound absorption characteristics of coconut fibre (coir) and oil palm fibre made from empty fruit bunches (OPEFB) fibre bonded by polyester that can protect them from the ambient environment in order to increase their durability. Two types of fibre-polyester composites have been tested. The first is the fibre-polyester composite (FPC) type, which is totally coated with polyester as the composite matrix. Another type is the fibre-polyester bonded composite (FPBC), in which the polyester is brushed into slice by a slice of the fibre layer in order to coat and bond the fibre, although porous among the fibre remains possible. A two-channel impedance tube is used in the measurement within 200 Hz to 3000 Hz of the frequency range. It is found that FPBC type panel has almost similar sound absorption characteristics to its purely natural fibre as it is able to maintain the panel porosity. The coconut coir fibre panel and its composite have a maximum absorption coefficient of almost 100% within the frequency range 1500-2000 Hz, considerably better than the OPEFB fibre, with only about 80% of the absorption coefficient. If the FPC layer exists, the sound absorption is reduced, and the frequency peaks are also shifted. Additions of the FPC panel layer thickness produced lower sound absorptions and shifted the peaks to the lower frequency range. The FPBC panel type is viable to protect the fibre from the environment without changing its sound absorption characteristics.

scholarly journals Effect of Porous Materials Combination in Layers on Sound Absorption Characteristics

2015 ◽  
Vol 773-774 ◽  
pp. 210-215
Author(s):  
Muhd Hafeez Zainulabidin ◽  
M.H.M. Yusuff ◽  
Al Emran Ismail ◽  
M.Z. Kasron ◽  
A.S.M. Kassim
Keyword(s):  
Absorption Coefficient ◽  
Sound Absorption ◽  
Low Frequency ◽  
Sound Absorption Coefficient ◽  
Frequency Range ◽  
Sound Absorber ◽  
Number Of Layers ◽  
Combination Number ◽  
Impedance Tubes ◽  
Absorption Characteristics

This paper describes the investigation and analysis on two materials in which one material is a relatively good sound absorber at low frequency range and another is a relatively good sound absorber at high frequency range, combined together in layers to form a better sound absorber for a wider range of frequencies. The layer combinations of the materials are varied and the values of Sound Absorption Coefficient, α are measured experimentally by using impedance tubes with two microphones transfer function method according to ISO 10534-2 standard. The results obtained are compared in terms of the order of material and the number of layer combinations of materials for each sample. The orders of combinations and number of layers of combinations have significant influence on the sound absorption characteristics. The order of materials has reversed effect on Sound Absorption Coefficient, α as the number of layer combination is increased. Increase in the combination number will make the specimen performed relatively better at a wider frequency range.

Broadening of the Sound Absorption Bandwidth of the Perforated Panel Using a Membrane-Type Resonator

2018 ◽  
Vol 140 (3) ◽  
Author(s):  
Xuezhi Zhu ◽  
Zhaobo Chen ◽  
Yinghou Jiao ◽  
Yanpeng Wang
Keyword(s):  
Absorption Coefficient ◽  
Sound Absorption ◽  
Degrees Of Freedom ◽  
Low Frequency ◽  
Absorption Capacity ◽  
Sound Absorption Coefficient ◽  
Sound Waves ◽  
Frequency Range ◽  
Absorption Bandwidth ◽  
Membrane Type

In order to broaden the sound absorption bandwidth of a perforated panel in the low frequency range, a lightweight membrane-type resonator is installed in the back cavity of the perforated panel to combine into a compound sound absorber (CSA). Because of the great flexibility, the membrane-type resonator can be vibrated easily by the incident sound waves passing through the holes of the perforated panel. In the low frequency range, the membrane-type resonator and the perforated panel constitute a two degrees-of-freedom (DOF)-resonant type sound absorption system, which generates two sound absorption peaks. By tuning the parameters of the membrane type resonator, a wide frequency band having a large sound absorption coefficient can be obtained. In this paper, the sound absorption coefficient of CSA is derived analytically by combining the vibration equation of the membrane-type resonator with the acoustic impedance equation of the perforated panel. The influences of the parameters of the membrane-type resonator on the sound absorption performance of the CSA are numerically analyzed. Finally, the wide band sound absorption capacity of the CSA is validated by the experimental test.

scholarly journals Sound Absorption Performance of Sugar Palm Trunk Fibers

2019 ◽  
Vol 130 ◽  
pp. 01003
Author(s):  
Anditya Endar Prabowo ◽  
Kuncoro Diharjo ◽  
Ubaidillah ◽  
Iwan Prasetiyo
Keyword(s):  
Absorption Coefficient ◽  
Bulk Density ◽  
Sound Absorption ◽  
Random Noise ◽  
Air Gap ◽  
Sound Absorption Coefficient ◽  
Low Frequencies ◽  
Central Java ◽  
Absorption Performance ◽  
Small Medium Enterprises

The purpose of this research is to investigate the effect of bulk density, thickness, and air gap to sound absorption performance on absorber based sugar palm trunk fibers. The fibers were obtained from solid waste on Small-Medium Enterprises of sago flour processing in Klaten, Central Java, Indonesia. The absorber specimens were formed from the fibers using a simple press molding in an oven at 150 °C. According to ISO 10534-2, the absorber samples were tested using two microphones impedance tube with random noise source to get the curve of the sound absorption coefficient. The result shows that the absorption performance can be improved by increasing bulk density and increasing of sample thickness. Especially at low frequencies, improvement of the sound absorption coefficient can be achieved (NAC > 0.8) by applying the air gap behind the sample. The best performance of absorber based sugar palm trunk fiber can be achieved for (1 000 to 6 000) Hz range frequency.

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 Synthesis and Evaluation of Polyurethane Foam Composites for Enhanced Sound Absorption at Low Frequency

2019 ◽  
Vol 8 (3) ◽  
pp. 6815-6818
Keyword(s):  
Absorption Coefficient ◽  
Polyurethane Foam ◽  
Sound Absorption ◽  
Low Frequency ◽  
Weight Fraction ◽  
Crumb Rubber ◽  
Polyurethane Foams ◽  
Sound Absorption Coefficient ◽  
Filler Materials ◽  
Frequency Range

Polyurethane foams are extensively used as sound absorbing materials in various automobile parts. However, the sound absorption capability of polyurethane foam ispoorin low frequency range. The advancement of technologies to develop newerpolymer composites, provide scope to develop composite polyurethane foam with better sound absorption coefficient in low frequency range. Composite foams are made with two different filler materials as crumb rubber and coconut fiber, in varying weight fraction of up to 2.0%. Density, Sound absorption coefficient, and Noise reduction, measurements were done on all polyurethane foams. The effect offiller additionsto polyurethane foams ondensity and sound absorption coefficient at low frequency are discussed.The 1.4 % crumb rubber polyurethane foam offers the best combination of low density, improved sound absorption coefficient value and noise absorption at low frequency.

scholarly journals Acoustic Properties of Composite Synthesized from Activated Zeolite and Fibre

2018 ◽  
Author(s):  
Hidjan Hidjan ◽  
Sutanto Sutanto ◽  
Nanang Rohadi
Keyword(s):  
Absorption Coefficient ◽  
Sound Absorption ◽  
Acoustic Properties ◽  
Sound Absorption Coefficient ◽  
Frequency Range ◽  
Porous Crystal ◽  
High Flexibility ◽  
And Shifts ◽  
Frequency Area ◽  
Banana Stem

The unique porous crystal structure of zeolite offers various important utilizations, it is one of the considerations in selecting zeolite at this study as component of composite for restraining noise. It so happens, previous experiments show that banana stem has porous structure, fibrous, high flexibility and can be applied as material for many various products including as component of acoustic material. The combination of both is alleged that it has capability in absorbing noise. This paper presents an investigation on the composite that it was synthesized of Activated Zeolite and Banana Stem Fibre in various weight for determining its sound absorption coefficient alpha (a). Activating natural zeolite was conducted by using 6M HCl in order for enlarging zeolite pores. The sound absorption coefficient was measured in the frequency range between 125 Hz up to 6000 Hz. The results show that the different weight of banana stem fibre as component of the synthesized composite affects the value of alpha and shifts the frequency area.

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