scholarly journals Acoustic performances of silicone foams for sound absorption

2017 ◽  
Vol 54 (3) ◽  
pp. 651-670 ◽  
Author(s):  
Ahmed Abbad ◽  
Kévin Jaboviste ◽  
Morvan Ouisse ◽  
Nicolas Dauchez
Keyword(s):  
Thermal Characteristic ◽  
Low Frequency ◽  
Curing Temperature ◽  
Acoustic Properties ◽  
Absorption Properties ◽  
Acoustic Behaviour ◽  
Acoustical Properties ◽  
Ratio Of Components ◽  
Pore Cell ◽  
Elaboration Process

The aim of this study is to investigate the link between the elaboration process, the microstructure and the acoustic behaviour of silicone foams obtained using a two-component silicone. Different parameters such as the ratio of components, the addition of a thinning agent and the curing temperature are varied, with the objective of understanding the influence of each parameter in the foam’s acoustic absorption. The microstructure is analysed using scanning electron microscopy and acoustic properties are measured. Two non-acoustical properties of the porous material are also investigated, namely the porosity and the flow resistivity. Pore cell size and interconnected porosity have great impact on acoustical properties. Significant enhancements of the absorption properties could be obtained in the low-frequency band by increasing the rate of agent B through an increase in the amount of interconnected porous cells. An improvement in absorption is observed in the higher frequency range when a thinning agent is added to the mixture. Representative models of the foam for acoustic simulations are obtained allowing estimation of the tortuosity, viscous and thermal characteristic length from acoustic measurements. These models are able to simulate the acoustic behaviour of the silicone foams when embedded in sound packages.

Acoustic Properties of Auxetic Foams With MR Fluids

2003 ◽  
Author(s):  
F. Scarpa ◽  
W. A. Bullough ◽  
M. Ruzzene
Keyword(s):  
Low Frequency ◽  
Acoustic Properties ◽  
Acoustic Absorption ◽  
Frequency Bandwidth ◽  
Frequency Range ◽  
Absorption Properties ◽  
Open Cell ◽  
Mr Fluids ◽  
Acoustic Absorption Coefficient ◽  
Open Cell Foams

This paper presents an experimental investigation on the acoustic properties of novel concepts of auxetic (Negative Poisson’s ratio) open cell polyurethane gray foams. The acoustic absorption coefficients and real and imaginary part of the specific acoustic impedance for the considered foams are measured with an ASTM standard impedance tube using a transmissibility technique. The auxetic foams show a significant increase of the absorption properties in the low frequency range compared to equivalent conventional open cell foams. Their acoustic properties are identified using an empirical model to describe the main structural characteristic. In addition, measurements for auxetic foams seeded with a magnetorheological fluid are also presented. The results show the capability of the seeded foam of shifting the peak acoustic absorption coefficient within a given frequency bandwidth when concentrated magnetic fields are applied.

scholarly journals Acoustic Characterization of Some Steel Industry Waste Materials

2021 ◽  
Vol 11 (13) ◽  
pp. 5924
Author(s):  
Elisa Levi ◽  
Simona Sgarbi ◽  
Edoardo Alessio Piana
Keyword(s):  
Thermal Characteristic ◽  
Environmental Benefits ◽  
Acoustic Properties ◽  
Physical Parameters ◽  
Industry Waste ◽  
Acoustic Characterization ◽  
Minimization Procedure ◽  
The Difference ◽  
By Products

From a circular economy perspective, the acoustic characterization of steelwork by-products is a topic worth investigating, especially because little or no literature can be found on this subject. The possibility to reuse and add value to a large amount of this kind of waste material can lead to significant economic and environmental benefits. Once properly analyzed and optimized, these by-products can become a valuable alternative to conventional materials for noise control applications. The main acoustic properties of these materials can be investigated by means of a four-microphone impedance tube. Through an inverse technique, it is then possible to derive some non-acoustic properties of interest, useful to physically characterize the structure of the materials. The inverse method adopted in this paper is founded on the Johnson–Champoux–Allard model and uses a standard minimization procedure based on the difference between the sound absorption coefficients obtained experimentally and predicted by the Johnson–Champoux–Allard model. The results obtained are consistent with other literature data for similar materials. The knowledge of the physical parameters retrieved applying this technique (porosity, airflow resistivity, tortuosity, viscous and thermal characteristic length) is fundamental for the acoustic optimization of the porous materials in the case of future applications.

scholarly journals Study on the sound absorption behavior of multi-component polyester nonwovens: experimental and numerical methods

2018 ◽  
Vol 89 (16) ◽  
pp. 3342-3361 ◽  
Author(s):  
Tao Yang ◽  
Ferina Saati ◽  
Kirill V Horoshenkov ◽  
Xiaoman Xiong ◽  
Kai Yang ◽  
...  
Keyword(s):  
Numerical Methods ◽  
Absorption Coefficient ◽  
Empirical Model ◽  
Surface Impedance ◽  
Sound Absorption ◽  
Low Frequency ◽  
Accurate Method ◽  
Small Error ◽  
Sound Absorption Coefficient ◽  
Acoustical Properties

This study presents an investigation of the acoustical properties of multi-component polyester nonwovens with experimental and numerical methods. Fifteen types of nonwoven samples made with staple, hollow and bi-component polyester fibers were chosen to carry out this study. The AFD300 AcoustiFlow device was employed to measure airflow resistivity. Several models were grouped in theoretical and empirical model categories and used to predict the airflow resistivity. A simple empirical model based on fiber diameter and fabric bulk density was obtained through the power-fitting method. The difference between measured and predicted airflow resistivity was analyzed. The surface impedance and sound absorption coefficient were determined by using a 45 mm Materiacustica impedance tube. Some widely used impedance models were used to predict the acoustical properties. A comparison between measured and predicted values was carried out to determine the most accurate model for multi-component polyester nonwovens. The results show that one of the Tarnow model provides the closest prediction to the measured value, with an error of 12%. The proposed power-fitted empirical model exhibits a very small error of 6.8%. It is shown that the Delany–Bazley and Miki models can accurately predict surface impedance of multi-component polyester nonwovens, but the Komatsu model is less accurate, especially at the low-frequency range. The results indicate that the Miki model is the most accurate method to predict the sound absorption coefficient, with a mean error of 8.39%.

Influence of Thermodynamic Nonequilibrium on the Acoustic Properties of Gases

2005 ◽  
Vol 4 (3) ◽  
pp. 373-383 ◽  
Author(s):  
Nonna E. Molevich ◽  
Anatoly I. Klimov ◽  
Vladimir G. Makaryan
Keyword(s):  
Acoustic Properties ◽  
Theoretical Studies ◽  
Dispersion Coefficients ◽  
Acoustical Properties ◽  
Nonequilibrium Gas ◽  
Gas Plasma ◽  
Experimental And Theoretical Studies

This paper is a brief review of results of experimental and theoretical studies in the field of acoustics of nonequilibrium gas-plasma media. New acoustical properties of nonequilibrium media caused by the change in sign of the second viscosity and the dispersion coefficients are considered. Such media are acoustically active. Conditions are discussed for generating new nonlinear acoustical structures.

Facile synthesis and enhanced microwave absorption properties of anthracite-based carbon/Ni3Fe/NiO ternary composites

2020 ◽  
Vol 44 (33) ◽  
pp. 13962-13970
Author(s):  
Hengdong Ren ◽  
Jialin Ma ◽  
Jun Zhou ◽  
Xiangfeng Shu ◽  
Zhenying Liu ◽  
...  
Keyword(s):  
Microwave Absorption ◽  
Microwave Radiation ◽  
Low Frequency ◽  
Microwave Absorber ◽  
Facile Synthesis ◽  
Absorption Properties ◽  
Microwave Absorption Properties ◽  
Radiation Method ◽  
Microwave Radiation Method

A low-frequency microwave absorber was synthesized by using a microwave radiation method.

scholarly journals Water Absorption Properties of Geopolymer Foam after Being Impregnated with Hydrophobic Agents

Materials ◽  
2019 ◽  
Vol 12 (24) ◽  
pp. 4162
Author(s):  
Hiep Le Chi ◽  
Pavlína Hájková ◽  
Su Le Van ◽  
Petr Louda ◽  
Lukáš Voleský
Keyword(s):  
Compressive Strength ◽  
Water Absorption ◽  
Positive Impact ◽  
High Sensitivity ◽  
Acoustic Properties ◽  
Total Water ◽  
Absorption Properties ◽  
Major Barrier ◽  
Water Absorption Coefficient ◽  
Hydrophobic Agent

Geopolymer foam is classified as a lightweight material with high porous in its matrix which has great offer for applications requiring fire-resistant, thermal, and acoustic properties. However, the high sensitivity to humid environments can be a major barrier of geopolymer foam that limits the variety of applications of this material. Based on this drawback, two types of hydrophobic agent (Lukosil M130 and Lukofob ELX) were used as an impregnator to treat the surface of geopolymer foam samples. This paper presented the results of water absorption properties of the untreated and treated geopolymer foam composites. The obtained properties were flexural strength, compressive strength, density, total water absorption, the rate of water absorption, and water absorption coefficient. The results showed that the samples after being impregnated with hydrophobic agents improved significantly their waterproof property especially using Lukosil M130. Moreover, the samples treated with Lukosil M130 had positive impact on their mechanical strength.

A Preliminary Study on the Sound Absorption of Self-Facing Date Palm Fibers

2014 ◽  
Vol 565 ◽  
pp. 25-30 ◽  
Author(s):  
Elwaleed A. Khidir ◽  
N. Nikabdullah ◽  
M.J.M. Nor ◽  
M.F.Mat Tahir ◽  
M.Z. Nuawi
Keyword(s):  
Sound Absorption ◽  
Date Palm ◽  
Perforated Plate ◽  
Low Frequency ◽  
Single Layer ◽  
Absorption Properties ◽  
Date Palm Fibers ◽  
Layer Sample ◽  
Good Improvement ◽  
Preliminary Study

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.

EXPERIMENTAL STUDY OF ENERGY ABSORPTION PROPERTIES OF GRANULAR MATERIALS UNDER LOW FREQUENCY VIBRATIONS

2004 ◽  
Vol 18 (17n19) ◽  
pp. 2708-2712
Author(s):  
MAO-BIN HU ◽  
XIANG-ZHAO KONG ◽  
QING-SONG WU ◽  
ZHEN-GANG ZHU
Keyword(s):  
Experimental Study ◽  
Granular Materials ◽  
Energy Absorption ◽  
Vibration Frequency ◽  
Absorption Rate ◽  
Low Frequency ◽  
Vibration Energy ◽  
Torsion Pendulum ◽  
Absorption Properties ◽  
Low Frequency Vibration

The low frequency vibration energy absorption properties of granular materials have been investigated on an Invert Torsion Pendulum (ITP). The energy absorption rate of granular material changes nonlinearly with amplitude under low frequency vibration. The frequency of ITP system increases a little with granular materials in the holding cup. The vibration frequency of ITP system does not change with time.

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.

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