scholarly journals Vibration Damping and Acoustic Behavior of PU-Filled Non-Stochastic Aluminum Cellular Solids

Metals ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 725
Author(s):  
Vitor Hugo Carneiro ◽  
Hélder Puga ◽  
José Meireles
Keyword(s):  
Absorption Coefficient ◽  
Sound Absorption ◽  
Transmission Loss ◽  
Polyurethane Foams ◽  
Vibration Damping ◽  
Acoustic Properties ◽  
Sound Absorption Coefficient ◽  
Cellular Solids ◽  
Infiltration Process ◽  
Wide Range

Aluminum-based cellular solids are promising lightweight structural materials considering their high specific strength and vibration damping, being potential candidates for future railway vehicles with enhanced riding comfort and low fuel consumption. The filling of these lattices with polymer-based (i.e., polyurethane) foams may further improve the overall vibration/noise-damping without significantly increasing their density. This study explores the dynamic (i.e., frequency response) and acoustic properties of unfilled and polyurethane-filled aluminum cellular solids to characterize their behavior and explore their benefits in terms of vibration and noise-damping. It is shown that polyurethane filling can increase the vibration damping and transmission loss, especially if the infiltration process uses flexible foams. Considering sound reflection, however, it is shown that polyurethane filled samples (0.27–0.30 at 300 Hz) tend to display lower values of sound absorption coefficient relatively to unfilled samples (0.75 at 600 Hz), is this attributed to a reduction in overall porosity, tortuosity and flow resistivity. Foam-filled samples (43–44 dB at 700–1200 Hz) were shown to be more suitable to reduce sound transmission rather than reflection than unfilled samples (21 dB at 700 Hz). It was shown that the morphology of these cellular solids might be optimized depending on the desired application: (i) unfilled aluminum cellular solids are appropriate to mitigate internal noises due to their high sound absorption coefficient; and (ii) PU filled cellular solids are appropriate to prevent exterior noises and vibration damping due to their high transmission loss in a wide range of frequencies and vibration damping.

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.

scholarly journals Acoustic Properties of 316L Stainless Steel Hollow Sphere Composites Fabricated by Pressure Casting

Metals ◽  
2020 ◽  
Vol 10 (8) ◽  
pp. 1047
Author(s):  
Chunhe Wang ◽  
Fengchun Jiang ◽  
Shuaiqi Shao ◽  
Tianmiao Yu ◽  
Chunhuan Guo
Keyword(s):  
Absorption Coefficient ◽  
Hollow Sphere ◽  
Sound Absorption ◽  
Random Distribution ◽  
Transmission Loss ◽  
Acoustic Properties ◽  
Sound Absorption Coefficient ◽  
Pressure Casting ◽  
Sound Transmission Loss ◽  
At Resonance

In this study, we prepared metal hollow sphere composites (MHSCs) using metal hollow spheres (MHSs) by pressure casting under vacuum conditions, and investigated the acoustic properties. The density of the MHSCs was measured using the mass to volume ratio, the microstructure of the MHSCs was observed using a scanning electron microscope, and the acoustic properties of the MHSCs were tested using an impedance tube. The measured MHSCs showed that the densities of the MHSCs with the random distribution of MHSs with diameter ~3.28 mm (1.74 g/cm3 to 1.77 g/cm3) (MHSC-3.28) were nearly equal to that of the MHSCs with the random distribution of MHSs with diameter ~5.76 mm (1.74 g/cm3 to 1.76 g/cm3) (MHSC-5.76), and lower than that of the MHSCs with the layered structure of MHSs with diameter ~3.28 mm (1.93 g/cm3 to 1.97 g/cm3) (MHSC-LS). Microstructural observations confirmed that the interface region between the MHSs and matrix demonstrated a simple physical combination pattern with pores. The acoustic properties of the MHSCs showed that the sound absorption coefficient of MHSC-LS was lower than that of MHSC-3.28 and higher than that of MHSC-5.76 at off-resonance. The sound absorption coefficient peak value of MHSC-3.28 was higher than that of MHSC-LS, and lower than that of MHSC-5.76 at resonance. The sound transmission loss of MHSC-3.28 was lower than that of MHSC-5.76, which shows the rules are independent from the resonance. The sound transmission loss of MHSC-LS was higher than that of MHSC-5.76 at resonance, but lower than that of MHSC-3.28 at off-resonance. In addition, we discuss the propagation mechanism of the sound waves in the MHSC, which is mainly determined by the distribution of the MHSs in the MHSC.

scholarly journals Development of Impedance Tube to Measure Sound Absorption Coefficient

2019 ◽  
Vol 8 (6) ◽  
pp. 3218-3222
Keyword(s):  
Absorption Coefficient ◽  
Sound Absorption ◽  
Transmission Loss ◽  
Acoustic Property ◽  
Small Sample ◽  
Textile Material ◽  
Acoustic Properties ◽  
Sound Absorption Coefficient ◽  
Impedance Tube ◽  
Significant Difference

An acoustic property of textile material can be measured using an impedance tube, is the most popular technique to measure normal sound absorption and transmission loss. This method consuming less time and a very small sample is required to assess the acoustic properties of the materials. Unfortunately, the cost of the impedance tube and software used for measurement is very high. This paper gives information about how to develop a cost-effective impedance tube suitable for researchers. The design, development, and fabrication of the impedance tube suitable for different frequencies with technical details are present here. Information related to some software which can be used to measure sound absorption coefficient also provided. To validate the testing results obtained from custom-build impedance tube, same samples were tested on commercially available impedance tube at PSG College, Coimbatore. It was observed that both the instruments provide almost same results, no statistically significant difference found in results. Base on the results design of customized impedance tube recommends to student and researcher interested in measuring acoustic properties of textile material

scholarly journals Vibration damping and acoustic characteristics of sisal fibre–reinforced polypropylene composite

2018 ◽  
Vol 50 (1) ◽  
pp. 13-21 ◽  
Author(s):  
Yashwant S Munde ◽  
Ravindra B Ingle ◽  
I Siva
Keyword(s):  
Absorption Coefficient ◽  
Natural Frequency ◽  
Sound Absorption ◽  
Transmission Loss ◽  
Experimental Results ◽  
Acoustic Properties ◽  
Sound Absorption Coefficient ◽  
Polypropylene Composite ◽  
Acoustic Characteristics ◽  
Sisal Fibre

Natural fibre composites attract industries because of their low density, low cost and the specific mechanical properties they possess in comparison to synthetic fibres. In this work, the randomly oriented sisal fibre–reinforced polypropylene composites are fabricated using extrusion–injection moulding technique. The aim of this study is to experimentally investigate the effect of fibre weight fraction (0%–30% in step of 10%) on vibrational damping and acoustic characteristics. The impulse hammer excitation technique is used to evaluate the free vibrational characteristics, namely, natural frequency and damping. An impedance tube is used in evaluating the acoustic properties, namely, sound absorption coefficient and transmission loss. Experimental results reveal that increase in fibre loading significantly alter the vibrational and acoustic response of the polypropylene composite. Modal analysis shows that incorporation of sisal fibres by 30 wt.% to polypropylene made the natural frequency superior when compared with other compositions. However, damping becomes worse with higher fibre content. In case of acoustic properties, incorporation of fibres at higher fraction enhances the sound absorption coefficient and transmission loss. Experimental results drive the research in development of such new materials system towards the application of vibration and sound diminutions.

Exploration and optimization on the usage of micro-perforated panels as trim panels in commercial aircrafts

2020 ◽  
Vol 68 (1) ◽  
pp. 87-100
Author(s):  
L.I. Chenxi ◽  
H.U. Ying ◽  
H.E. Liyan
Keyword(s):  
Absorption Coefficient ◽  
Sound Absorption ◽  
Transmission Loss ◽  
Sound Absorption Coefficient ◽  
Aviation Industry ◽  
Sound Insulation ◽  
Aircraft Cabins ◽  
Aircraft Cabin ◽  
Specific Frequency ◽  
Trim Panel

Micro-perforated panels (MPPs), as an alternative to porous materials for sound absorption, have been commonly used in electronic industries and aircraft engines but are barely used in aircraft cabins. The effect of MPPs on the sound insulation and absorption properties of aircraft cabin panels has been investigated in this article. Theoretical modeling has been conducted on an aircraft cabin panel structure with a trim panel replaced by an MPP trim panel, using the transfer matrix method and the classic MPP theory. It is indicated by the theoretical results that, although the sound transmission loss (STL) of the cabin panel with an MPP trim panel is lower than that with an un-perforated panel, the MPP trim panel can significantly enhance the sound absorption coefficient of the entire cabin panel structure. Based on the well-developed MPP theory, the sound absorption coefficient of an aircraft cabin panel with an MPP trim panel can be improved by optimizing the MPP's parameters at a specific frequency. Taking an engine frequency 273 Hz as an example, the optimization can increase the sound absorption coefficient to 1 by using the doublelayered MPPs. When the thermal acoustic insulation blanket is considered, although the STL of the proposed structure with double-layered MPP trim panels in a diffuse field is lower than those without MPP trim panels, the sound absorption in the cabin is significantly enhanced due to the double-layer MPP trim panel at the specific engine frequency and across all frequencies. The STL of the structure with double-layered MPP trim panels and TAIB can be higher than 40 dB from 880 Hz in a diffuse field, which implies its effectiveness as sound insulation structure in aviation industry. MPP trim panels provide a new idea for the design of aircraft cabin panels and areworthy of further research

Studies of the Influence of Graphite on the Physical Mechanical and Thermal Properties of Polyurethane Foams for Construction Applications

2021 ◽  
Vol 887 ◽  
pp. 399-405
Author(s):  
L.N. Shafigullin ◽  
N.V. Romanova ◽  
G.R. Shafigullina
Keyword(s):  
Thermal Conductivity ◽  
Thermal Properties ◽  
Absorption Coefficient ◽  
Sound Absorption ◽  
Polyurethane Foams ◽  
Onset Temperature ◽  
Sound Absorption Coefficient ◽  
Expandable Graphite ◽  
Mechanical And Thermal Properties ◽  
Pu Foam

The paper shows the applicability of expandable graphite METOPAC EG 350-50 (80) in a rigid PU foam system as a substance that reduces the flammability (flame retardant) and improves the usability. The studies of the physical mechanical and thermal properties of PU foam with a higher graphite content revealed a higher normal sound absorption coefficient; insignificant influence on the thermal conductivity; a higher decomposition onset temperature; more difficult ignition. PU foam sample with a ratio of 15 graphite weight fractions to 100 polyol weight fractions has the highest physical mechanical and thermal properties, and, as compared to the starting PU foam, it features an increase in normal sound absorption coefficient by an average of 3 times; a decrease in the thermal conductivity by 8 %; an increase in the decomposition onset temperature by 6.7 °С. Therefore, the modification of PU foam with expandable graphite makes it possible not only to develop hardly combustible polyurethanes but also to improve its physical mechanical and thermal properties.

Acoustic Benefits of Ecofriendly Spent Tea Leaves Filled Porous Material

2017 ◽  
Vol 739 ◽  
pp. 125-134
Author(s):  
Kylie Wong ◽  
Qumrul Ahsan ◽  
Azma Putra ◽  
Sivarao Subramonian ◽  
Noraiham Mohamad ◽  
...  
Keyword(s):  
Absorption Coefficient ◽  
High Resistance ◽  
Sound Absorption ◽  
Transmission Loss ◽  
Acoustic Property ◽  
Tea Plant ◽  
Sound Absorption Coefficient ◽  
Acoustic Performance ◽  
Absorbing Material ◽  
Tea Leaf

This paper demonstrates the feasibility of spent tea leaf (STL) fiber as an eco-friendly sound absorbing material. STL fiber is a by-product which was extracted from tea plant. STL are rich in polyphenols (tannins) which cause high resistance to fungal and termites, and high resistance to fire. In addition, STL are hollow and cellular in nature and thus perform well as acoustic and thermal insulators. Three different grades of STL were studied and the acoustic property was analyzed in terms of sound absorption coefficient and transmission loss. Experimental measurements of sound absorption coefficient in impedance tube are conducted. It was found that finest STL fiber grade exhibits better acoustic performance among others. Furthermore, the effect of latex binder on the acoustic property of STL fiber was also analyzed. Results suggest that the types of binder such as polyurethane and latex influenced the acoustic performance of STL fiber.

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