Acoustic Transmission Analysis of Multi-Layer Absorbers

Lee, F.-C.; Chen, W.-H.

doi:10.1006/jsvi.2001.3825

Cited by 117 publications

(72 citation statements)

References 9 publications

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“…Sound absorption characteristic of porous material is not so much a function of type material but airflow resistivity and how well material construction can be executed to achieve desirable properties for sound absorbers (Lee and Chen, 2001). Ersoy and Kucuk (2009) have investigated with three different layers of tea-leaf fiber waste materials with and without backing provided by a single layer of woven textile cloth were tested for their sound absorption properties.…”

Section: Introductionmentioning

confidence: 99%

Noise Control Using Coconut Coir Fiber Sound Absorber with Porous Layer Backing and Perforated Panel

Zulkifli¹,

Zulkarnain

Nor³

2010

American Journal of Applied Sciences

106

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Problem statement: Noise control was one of the major requirements to improve the living environment. One of the methods to do that is provided by sound absorber. Commonly, multi-layer sound absorbers are applied to absorb broadband noise that was composed of perforated plates, air space and porous material. However, multi-layers sound absorbers effectiveness depends on their construction. This study was conducted to investigate the potential of using coconut coir fiber as sound absorber. The effects of porous layer backing and perforated plate on sound absorption coefficient of sound absorber using coconut coir fiber were studied. Approach: Car boot liners made from woven cotton cloth were used as type of porous layer in the study. This material has been used widely in automotive industry. Perforated plate used was machined with perforation ratio of 0.20, thickness of 1 mm and holed diameter of 2 mm. The samples were tested at the acoustic lab of the Faculty of Engineering and Built Environment, University Kebangsaan Malaysia, according to ASTM E 1050-98 international standards for noise absorption coefficient. Results: The experiment data indicates that porous layer backing can improve noise absorption coefficient at low and high frequencies with significant increasing. 20 mm thick layer coconut coir fiber with porous layer backing exhibit peak value at frequencies between 2750-2825 Hz with maximum value of 0.97. The experimental results also found that the coconut coir fiber with perforated plate gives higher value for lower frequencies range from 600-2400 Hz. The optimum value for coconut coir fiber with perforated panel is around 0.94-0.95 for the frequency range 2600-2700 Hz. Conclusion: Noise absorption coefficient of coconut coir fiber was increased at all frequency when they were backing with Woven Cotton Cloth (WCC). At low frequency, the NAC have significant increasing. This is because WCC have higher flow resistivity than coconut coir fibers, so that sound can be dissipated as it travels through material significantly. The results from the experimental tests show that it has good acoustic properties at low and high frequencies and can used to be an alternative replacement of synthetic based commercial product. By using the porous layer and perforated plate backing to coconut coir fiber, the sound absorber panel shows a good potential to be an environmentally friendly product. This innovative sound absorption panel has a bright future because they are cheaper, lighter and environmentally compare to glass fiber and mineral based synthetic materials.

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Section: Introductionmentioning

confidence: 99%

Noise Control Using Coconut Coir Fiber Sound Absorber with Porous Layer Backing and Perforated Panel

Zulkifli¹,

Zulkarnain

Nor³

2010

American Journal of Applied Sciences

106

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“…3. This differences due to porous material compressing which appear clearly at all frequencies range (Lee and Chen 2001), (Wang et al, 2008). Drop of AAC at frequency 1765-2725 Hz with value 0.67 indicated is poor in mid frequency.…”

Section: Discussionmentioning

confidence: 87%

“…The porosity of substance depends on the propagation of wave and properties of impedance which can be expressed as resistivity of the flow , number of wave , density of air and frequency of sound , (Delany and Bazley 1970).While, achieving desirable characteristic for absorption sound, through the porosity of the substance, the ability of construction and flow resistivity (Lee and Chen, 2001).…”

Section: Introductionmentioning

confidence: 99%

Acoustic Properties of Innovative Material from Date Palm Fibre

ALRahman

Raja²,

Rahman³

et al. 2012

American Journal of Applied Sciences

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Problem statement: An organic material is one of the major requirements to improve living environment and the invention of materials need to consider for the best solution. This study presents an experimental investigation on pure porous from Date Palm Fibre (DPF). The effectiveness of sound absorbers depends on structural architecture of this material. This study was conducted to examine the potential of using date palm fibre as sound absorber. The effects of porous layer thicknesses, densities and compression on Acoustic Absorption Coefficient (AAC) of sound absorber using date palm fibre were studied. Approach: Rigid frame Johnson-Allard Model for various sample thicknesses was used in this study. The measurements were conducted in impedance tube on normal incidence acoustic absorption. The date palm fibre was mixed with latex which used for physical treatment on this material. Acoustic absorption behaviour of a porous material with different thicknesses was studied as well as samples with same thickness but different densities. In addition, samples with same properties but different period of compression time were inspected. The tests were in accordance to ISO 10534-2 and ASTM E1050-98 international standards for Acoustic Absorption Coefficient (AAC). Results: The experimental data indicates that two peak values of AAC is 0.93 at 1356Hz for sample with 50 mm thickness, also the AAC at high frequency for same thickness is 0.99 at 4200-4353 Hz that means able to improve acoustic absorption coefficient at low and high frequencies with significant increasing. Meanwhile, another experimental results were acquired for AAC of date palm fibre, with samples thicknesses of 35 mm at different densities .The results show that denser sample (11 Kg m −3 ) has higher AAC value of 0.83 at 1934-2250 Hz as compared to less dense sample (9.92 Kg m −3 ) with AAC value 0.84 at 2443-2587 Hz . Conclusion: Acoustic absorption coefficient AAC of date palm fibre was increased at all frequencies when the thickness of sample was increased, particularly at low frequencies less than 1200 Hz. The introduction of latex on the samples adds stiffness, so that sound can be dissipated significantly as it travels through material. Results from the experimental tests show that date palm fibre has good acoustic properties at low and high frequencies and can be used as an alternative replacement to conventional product. Increasing density of the samples, increase the AAC as well. The innovative acoustic absorption panel has a good potential because they are cheaper and lighter in comparison to asbestos and rock wool industrial materials.

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“…The inner porous layer attenuated the sound energy and prevented the sound from recombining. 7 Lee and Swenson also showed that the multilayer absorber assembly with two layers of PP backed with air spaces provided better absorption than a single layer. 8 It was reported that the multilayer absorber composed of PP and porous material had better absorption than that of PP and air gap at both low and high frequencies.…”

Section: Introductionmentioning

confidence: 97%

“…Multilayer absorber composed of porous material may distinctly promote the sound absorption and shift the resonance frequencies towards lower frequency bands. 7 Chen et al chose four surface shapes of commercially available porous materials, i.e., triangle, semicircle, convex rectangle and plate shapes for analysis over a 1200 Hz band. The fibrous material with triangle, semicircle, or convex shapes had better sound absorption than those with a plate shape.…”

Section: Introductionmentioning

confidence: 99%

Analysis on Multiple Perforated Plate Sound Absorber Made of Coir Fiber

Ayub¹,

Fouladi²,

Ghassem³

et al. 2014

IJAV

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Current studies are aiming to improve the sound absorption of coir fiber by implementing combinations of Perforated Plates (PPs) and air gaps. The Atalla and Sgrad model along with Johnson-Allard model and Acoustic Transmission Analysis (ATA) approach are used to estimate the absorption coefficient of the combination. Measurements are conducted in impedance tube to validate the analytical results. Outcomes show that the absorption coefficient of the panel is governed by the porosities of the implemented PPs. Reduction in the porosity of the face PP causes the incident sound to reflect back whereas higher porosity encourages the sound to enter and be absorbed gradually in the inner compartments. For the case of multilayer panels with two PPs, the best result is obtained when the inner PP has low porosity and is backed with an air gap. Absorption in high and low frequency bands are enhanced by having highly porous material and a thick layer of air gap in front of and behind the inner PP, respectively. This study shows that the high-frequency absorption is enhanced further in panels that include three PP layers. The study suggests fabricating panels containing two or three PPs with gradual reduction of porosity from the face PP to the inner ones, while the inner most PP has low porosity and is backed with air gap.

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Acoustic Transmission Analysis of Multi-Layer Absorbers

Cited by 117 publications

References 9 publications

Noise Control Using Coconut Coir Fiber Sound Absorber with Porous Layer Backing and Perforated Panel

Noise Control Using Coconut Coir Fiber Sound Absorber with Porous Layer Backing and Perforated Panel

Acoustic Properties of Innovative Material from Date Palm Fibre

Analysis on Multiple Perforated Plate Sound Absorber Made of Coir Fiber

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