scholarly journals Textiles for Noise Control

2021 ◽  
Author(s):  
Mallika Datta ◽  
Srijan Das ◽  
Devarun Nath
Keyword(s):  
Heat Conduction ◽  
Energy Dissipation ◽  
Sound Absorption ◽  
High Frequency Range ◽  
Viscous Effects ◽  
Noise Absorption ◽  
Factors Influencing ◽  
Absorbing Material ◽  
Human Ear ◽  
Interconnected Pore

This chapter includes the mechanism of sound absorption and the classes of sound absorbing material to control the noise. The basic phenomena related to the reduction of sound by allowing it to soak in and dissipate also were introduced first, which, can be realised by viscous effects, heat conduction effects, and internal molecular energy interchanges. Porous absorbers are materials where sound propagates through an interconnected pore network resulting in sound energy dissipation. They are only effective at the mid-to-high frequency range, which is most sensitive to the human ear. The applications of different textile fibres and their various forms were identified later in the chapter. Finally, specific discussions are given to sound parameters, noise absorption coefficient, and its measurement technique. The chapter also deals with various factors influencing sound absorption.

Sound Absorption Characteristic of Pseudostochastic Diffusers

1995 ◽  
Vol 2 (2) ◽  
pp. 455-460
Author(s):  
Shengwo Sheng
Keyword(s):  
Energy Dissipation ◽  
Sound Absorption ◽  
Low Frequency ◽  
Nonlinear Effects ◽  
Absorption Characteristic ◽  
Absorption Phenomenon ◽  
High Absorption

Sound absorption phenomenon of pseudostochastic diffusers was investigated in this paper. The mechanism of high absorption at low frequency was explained from the point view of energy dissipation due to nonlinear effects.

Sound absorption of a finite flexible micro-perforated panel absorber back by a rigid air cavity filled with a fibrous porous material

2021 ◽  
Vol 263 (3) ◽  
pp. 3625-3632
Author(s):  
Ho Yong Kim ◽  
Yeon June Kang
Keyword(s):  
Energy Dissipation ◽  
Porous Material ◽  
Fibrous Material ◽  
Alternative Energy ◽  
Sound Absorption ◽  
Sound Pressure ◽  
Absorption Coefficients ◽  
Air Cavity ◽  
Acoustic Cavity ◽  
Absorption Performance

Back by a rigid cavity filled with a layer of porous layer, the sound absorption performance of a micro-perforated panel (MPP) can be enhanced in comparison with other resonance based sound absorbers. In this paper, a theoretical model of a finite flexible MPP back by a rigid air cavity filled with a fibrous porous material is developed to predict normal sound absorption coefficients. Displacements of MPP and sound pressure field in fibrous porous material and acoustic cavity are expressed using a series of modal functions, and the sound absorption coefficients of MPP system are obtained. Additionally, comparison of energy dissipation by MPP and fibrous material is performed to identify effects of a fibrous material on the sound absorption of a MPP. As expected, at anti-resonance frequency of an MPP, the fibrous material provide an alternative energy dissipation mechanism.

scholarly journals Hybrid acoustic metamaterial as super absorber for broadband low-frequency sound

2017 ◽  
Vol 7 (1) ◽  
Author(s):  
Yufan Tang ◽  
Shuwei Ren ◽  
Han Meng ◽  
Fengxian Xin ◽  
Lixi Huang ◽  
...  
Keyword(s):  
Energy Dissipation ◽  
Absorption Coefficient ◽  
Sound Absorption ◽  
Low Frequency ◽  
Functional Materials ◽  
Theoretical Method ◽  
Acoustic Metamaterials ◽  
Mechanical Stiffness ◽  
Acoustic Metamaterial ◽  
Frequency Sound

Abstract A hybrid acoustic metamaterial is proposed as a new class of sound absorber, which exhibits superior broadband low-frequency sound absorption as well as excellent mechanical stiffness/strength. Based on the honeycomb-corrugation hybrid core (H-C hybrid core), we introduce perforations on both top facesheet and corrugation, forming perforated honeycomb-corrugation hybrid (PHCH) to gain super broadband low-frequency sound absorption. Applying the theory of micro-perforated panel (MPP), we establish a theoretical method to calculate the sound absorption coefficient of this new kind of metamaterial. Perfect sound absorption is found at just a few hundreds hertz with two-octave 0.5 absorption bandwidth. To verify this model, a finite element model is developed to calculate the absorption coefficient and analyze the viscous-thermal energy dissipation. It is found that viscous energy dissipation at perforation regions dominates the total energy consumed. This new kind of acoustic metamaterials show promising engineering applications, which can serve as multiple functional materials with extraordinary low-frequency sound absorption, excellent stiffness/strength and impact energy absorption.

Experimental Study on the Sound-Absorption Capability of Nonwoven Sound-Absorbing Material under Different Density Combination

2011 ◽  
Vol 332-334 ◽  
pp. 1304-1307
Author(s):  
Wen Su ◽  
Xiao Ming Qian ◽  
Xin Yu Li ◽  
Shu Sen Liu
Keyword(s):  
Experimental Study ◽  
Sound Absorption ◽  
Low Density ◽  
Surface Material ◽  
Nonwoven Materials ◽  
Absorbing Material

In this paper, the influence of different combination of different density of nonwoven materials on the sound-absorption capability is studied through the serial experiments. The results show that the structure with low density on the surface material and dense density in the middle of the material will have better capacity in absorbing sound.

scholarly journals A Preliminary Study on Acoustical Performance of Oil Palm Mesocarp Natural Fiber

2015 ◽  
Vol 773-774 ◽  
pp. 247-252 ◽  
Author(s):  
Hanif Abdul Latif ◽  
Musli Nizam Yahya ◽  
Mohamed Najib Rafiq ◽  
Mathan Sambu ◽  
Mohd Imran Ghazali ◽  
...  
Keyword(s):  
Oil Palm ◽  
Sound Absorption ◽  
Natural Fiber ◽  
Standard Test ◽  
Air Gap ◽  
Test Method ◽  
Synthetic Materials ◽  
Absorbing Material ◽  
Absorption Performance ◽  
Impedance Tube Method

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.

Modelling the Effect of Flexural Vibration on Sound Absorption of a Micro-Perforated Panel Using Wave Propagation Method

2013 ◽  
Vol 471 ◽  
pp. 255-260
Author(s):  
Azma Putra ◽  
Muhammad Sajidin Py ◽  
Norliana Salleh
Keyword(s):  
Wave Propagation ◽  
Sound Absorption ◽  
Flexural Vibration ◽  
Rigid Wall ◽  
Flexural Wave ◽  
Wave Propagation Method ◽  
Rigid Condition ◽  
Absorbing Material ◽  
Absorption Performance ◽  
Propagation Technique

Micro-perforated panel (MPP) is well known as the alternative green sound absorbing material replacing the synthetic porous absorber. Several works have been established which model the sound absorption performance of the MPP with various arrangements. However, most existing models are for MPP with rigid condition and rarely discuss the effect of vibration due to the impinging sound. In this paper, a simple approach using wave propagation technique is proposed to take into account the effect of flexural wave in the MPP on its sound absorption. The model begins with an MPP coupled with a solid panel separated by an air gap. The impedance of the back solid panel can then be adjusted to a very large value to simulate a rigid wall.

Measured Variation of High Frequency Sound Absorption in Porous Metals Subject to Changes in Temperature and Temperature Gradient

2013 ◽  
Author(s):  
Weihua Chen ◽  
Tianning Chen ◽  
Xiaopeng Wang ◽  
Zhiping Ying
Keyword(s):  
Temperature Gradient ◽  
High Frequency ◽  
Sound Absorption ◽  
Porous Metal ◽  
Temperature Gradients ◽  
High Frequency Range ◽  
Frequency Range ◽  
Porous Metals ◽  
Testing Module ◽  
Peak Value

Porous metal, as a new acoustic material, bears the general metal properties, such as good conductivity, ductibility, heat transfer and high specific stiffness and intensity, and meanwhile exhibits good performance in sound absorption. Thus, it enjoys a growing popularity in industrial and civilian sound-absorbing applications where non-metallic materials are impracticable. Therefore it is of great significance to explore the sound-absorption properties of porous metals. The existing studies mainly focus on the low frequency range and are under uniform temperature assumption. In this paper, an experimental setup was built up to investigate the sound absorption of porous metals subject to temperature gradients, and much concern was paid to that of high frequency range. The setup is composed of five modules: I. heating module; II. cooling module; III. temperature controlling & testing module; IV. spectrum analyzer and V. impedance tube testing module. Based on this setup, the sound absorption of a hard-backed porous metal in a high-frequency range (2000–4000Hz)and under different temperature gradients (+2°C/mm, +4°C/mm and +6°C/mm) are measured, and results show that: 1) The sound absorption of porous metal is significantly influenced by temperature gradients; 2) The peak of sound absorption curve moves to a higher frequency range as the temperature gradient increases in the frequency range 2000∼4000Hz but the peak value decreases slightly; 3) The peak value of sound absorption curve enlarges as the temperature gradient increases but the frequency of peak value is fixed.

scholarly journals Sustainable Rigid Polyurethane Foam from Wasted Palm Oil and Water Hyacinth Fiber Composite—A Green Sound-Absorbing Material

Polymers ◽  
2022 ◽  
Vol 14 (1) ◽  
pp. 201
Author(s):  
Nathapong Sukhawipat ◽  
Laksana Saengdee ◽  
Pamela Pasetto ◽  
Jatupol Junthip ◽  
Ekkachai Martwong
Keyword(s):  
Polyurethane Foam ◽  
Palm Oil ◽  
Water Hyacinth ◽  
Sound Absorption ◽  
Fiber Composite ◽  
Mesh Size ◽  
Alternative Material ◽  
Absorbing Material ◽  
Used Palm Oil ◽  
Water Hyacinth Fiber

A novel rigid sound-absorbing material made from used palm oil-based polyurethane foam (PUF) and water hyacinth fiber (WHF) composite was developed in this research. The NCO index was set at 100, while the WHF content was set at 1%wt with mesh sizes ranging from 80 to 20. The mechanical properties, the morphology, the flammability, and the sound absorption coefficient (SAC) of the PUF composite were all investigated. When the WHF size was reduced from 80 to 20, the compression strength of the PUF increased from 0.33 to 0.47 N/mm2. Furthermore, the use of small fiber size resulted in a smaller pore size of the PUF composite and improved the sound absorption and flammability. A feasible sound-absorbing material was a PUF composite with a WHF mesh size of 80 and an SAC value of 0.92. As a result, PUF derived from both water hyacinth and used palm oil could be a promising green alternative material for sound-absorbing applications.

scholarly journals Influence of Sound-Absorbing Material Placement on Room Acoustical Parameters

Acoustics ◽  
2019 ◽  
Vol 1 (3) ◽  
pp. 644-660 ◽  
Author(s):  
Jose Cucharero ◽  
Tuomas Hänninen ◽  
Tapio Lokki
Keyword(s):  
Speech Intelligibility ◽  
Sound Absorption ◽  
Sound Field ◽  
Acoustical Parameters ◽  
Open Plan ◽  
Absorbing Material ◽  
The Impact

The reverberation of a room is often controlled by installing sound absorption panels to the ceiling and on the walls. The reduced reverberation is particularly important in classrooms to maximize the speech intelligibility and in open-plan offices to make spaces more pleasant. In this study, the impact of the placement of the absorption material in a room was measured in a reverberation room and in a mockup classroom. The results show that absorption material is less efficient if it is mounted to the corners or on the edges between the walls and ceiling, if the sound field is more or less diffuse. If the room modes dominate the sound field, the most efficient location for the sound-absorbing material was found at one of the surfaces causing the modes. The results help acoustical consultants to place the absorption material in optimal locations and, generally, minimize the amount of material and save costs.

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