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Procedia Engineering 53 (2013) 632 – 638
Malaysian Technical Universities Conference on Engineering & Technology 2012, MUCET 2012 Part 2 Mechanical And Manufacturing Engineering
Utilizing Sugarcane Wasted Fibers As A Sustainable Acoustic Absorber Azma Putraª*, Yasseer Abdullahª, Hady Efendyª, Wan Mohd Faridª, Md Razali Ayobª and Muhammad Sajidin Pyª ªFaculty of Mechanical Engineering Universiti Teknikal Malaysia Melaka (UTeM) Hang Tuah Jaya 76100, Melaka, Malaysia
Abstract
The use of synthetic materials as acoustic absorbers is still applied extensively in building industry. These nonbiodegradable materials do not only cause pollution to the environment, but their production also contributes significantly in emitting green house gas in the atmosphere. Corresponding research has therefore being driven to find sustainable and ecofriendly materials to be an alternative sound absorber. This paper discusses the utilization of natural fibers from sugarcane waste to be an acoustic material. Sound absorber samples from sugarcane wasted fibers are fabricated and their acoustic properties are investigated through experiment. Good acoustic performance is found at 1.2 - 4.5 kHz with average absorption coefficient of 0.65 and is comparable against that from the classical synthetic absorber. © 2013 Published by Elsevier Ltd. Ltd. © 2013The TheAuthors. Authors. Published by Elsevier Selection and peer-review under under responsibility of the Research Management & Innovation Universiti Malaysia Selection and/or peer-review responsibility of the Research Management &Centre, Innovation Centre, Universiti Malaysia Perlis Perlis. Keywords: sugarcane waste; acoustic material; sound absorber; natural fibers; absorption coefficient Introduction
1. Introduction The issue of conserving hygienic condition and environment and its relation with global warming has attracted attention of researchers for new technologies which is more environmentally friendly. Besides finding alternative energy to limit the use of fossil fuels and deforestation, attempts are also directed to create products from recyclable and sustainable materials. For application in buildings, which emphasizes sound quality in a room such as mosque, theatre hall, music studio, lecture room, cinema and meeting room, the classical abrasive and porous acoustic materials are still widely used. This room should be well controlled in order to provide good quality of speech intelligibility for the audience. Production of these synthetic materials has been known to release significant CO2 into the atmosphere compared to that of panels made from natural materials [1]. The synthetic nature of the former also creates another problem in disposition which is harmful to the environment. Continuation of their usage is therefore against the effort to realize a environment. Thus finding alternative green materials which have not only comparable capability as sound absorbers, but also bio-degradable, sustainable, abundance as well as less health risk are of interest.
* Corresponding author. E-mail address:
[email protected]
1877-7058 © 2013 The Authors. Published by Elsevier Ltd. Selection and peer-review under responsibility of the Research Management & Innovation Centre, Universiti Malaysia Perlis doi:10.1016/j.proeng.2013.02.081
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1.1. Established Works on Natural Absorbers Several works have been done concerning the ability of natural fiber to be employed as sound absorber. Koizumi et al. [2] investigated acoustical properties of bamboo fiber. This is found to have an equivalent sound absorption with glass wool. Yang et al. [3] employed rice straw-wood particle board to substitute wood. A comparison was then made with a common industrial-made plywood for analysis. It is found that the rice straw-wood particle with lower specific gravity gives better sound absorption at a range of 1 8 kHz compared to plywood and fiberboard. Alessandro and Pispola [4] tested kenaf fiber in reverberation room and the results were compared with traditional fibrous absorbers. The results are slightly poorer but still comparable if impacts on environment are taken into account. Saadatnia et al. [5] conducted an experiment on wheat and barley straws made into acoustic boards. The sound Ersoy and Kucuk [6] uncovered the potential of waste industrial tea-leaf as an acoustic material. It is shown that acoustic properties of tea-leaf-fiber increases significantly when backing with a single woven cotton cloth. For 10 mm thickness, sound absorption of tea-leaf-fiber is comparable to traditional sound absorbers i.e. polyester. Wasted ramie fiber treated and non-treated with alkalization can also produce promising result with average absorption coefficient of 0.6 at frequency range of 315 Hz - 3.2 kHz [7]. Several studies on coir fiber have also been discussed to investigate the effect of perforated facing, multiple-layer arrangement and compression on its acoustic performance. Numerical method was established to support the experimental data. Overall, coir fiber is naturally good sound absorber at medium and high frequency at 1.5 - 5 kHz [8-12]. Investigation on the acoustic properties of arenga pinnata fibers which can be found from a palm sugar tree has been reported [13, 14]. With thickness of 40 mm, it has good sound absorption coefficient of 0.75 - 0.88 at frequency between 2 5 kHz [14]. Abdullah et al. [15] studied the acoustic properties of paddy fibers. Good sound absorption performance is found at frequency range of 2 - 3.5 kHz with absorption coefficient of 0.6 - 0.9. Fatima and Mohanty [16] experimentally investigated the sound absorption of jute fiber. It is shown that jute fiber without any treatment gives better acoustics properties compared to that with treatment at frequency 1 - 4 kHz. The flammability is also comparable to that of the conventional synthetic absorbers. Unmodified straw and reed have also been investigated for its acoustic properties. These natural non-fibrous materials are found to have a good absorption coefficient from 500 Hz 5 kHz. The prediction model is also developed [17]. This paper discusses the potential of another natural fiber to be an alternative acoustic material, namely the sugarcane 1.2. Sugarcane Fibers Sugarcane or Saccharum officinarum in its Latin name is commonly found in equatorial countries such as Brazil, India, Pakistan, Malaysia and Indonesia. On average, a hectare of sugarcane generates about 10 tons of sugarcane waste, also kn are usually burned in-situ in order to clear the field for the next crop. Some efforts have also been done to utilize the waste for paper [19]. From its physical appearances, the sugarcane (waste) consisted of tiny and soft fibers which can potentially be a good sound absorber. The soft fibers might carry the strength problem, but this can be covered if it is coupled with another strong material. Measurement using Inverted Research Microscope (IRM) in Faculty of Mechanical Engineering, UTeM shows that diameter of the sugarcane fibers ranges from 11-23 μm.
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Azma Putra et al. / Procedia Engineering 53 (2013) 632 – 638 Fig. 1.Sugarcane wasted fibers (bagasse).
2. Methodology 2.1. Sugarcane Fibers Fabrication of Absorber Sample These Construction from fibers into an absorber sample is divided into two stages, namely the pre-treatment stage and fabrication stage. In the pre-treatment stage, raw material was cut into 1 to 3 mm length. It was then sundried for 1 week and again heated in the oven at 800C for 5 minutes to let the excess water in the fiber evaporated. Later, raw material was cut into 5 to 10 mm length. In the preparation stage, the raw material was mixed with different composition of binder. Here the binders used are polyurethane and polyester. The mixture was then hot-pressed in a mould to obtain a round shape. The pressure given are just enough for the sample to take shape. This is to retain the porosity of the sample. The flow chart of this process is shown in Fig. 2. The constructed absorber sample has diameter of 33 mm to fit in the impedance tube diameter in the sound absorption test with thickness of roughly ½ inch as seen in Fig. 3. For each type of the binder used, there are four different weight composition ratios of fibers to binder; 90:10, 80:20, 70:30 and 60:40. The weight of the fibers is fixed for 1 gram and 3 grams. 2.2. Measurement of absorption coefficient The measurement of sound absorption coefficient (denoted as ) was performed in an impedance tube by applying twomicrophone transfer function method according to ISO 10534-2:2001 Prepolarized free-amplifier (GRAS 26CA). RT Pro Photon v6.34 analyzer with Dactron software was used as the data acquisition system. The signal processing of the measured data was done using Matlab. With diameter of the tube i.e. 33 mm, the reliable frequency range for this experiment is between 500 Hz to 4.5 kHz.
Pretreatment stage
Raw sugarcane fibers
Sundried for one week
Oven heat 80o C for 5 minutes
Fibers cut into 5-10 mm length
Fabrication stage
Sample fiber
Mixing with certain composition of binder
Hot press
Sound absorber sample
Fig. 2. Flow chart of absorber sample construction process
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Fig. 3. Constructed sample of sound absorber from sugarcane fibers
Fig. 4 shows the measurement setup for the test. The sample was placed at the end of the impedance tube and backed by a rigid surface. The loudspeaker feeds the white noise signal in the tube where the incident and reflected sound pressure recorded by the microphones are then processed to have the absorption coefficient of the sample. Spectrum analyzer
Computer Microphones
Removable cap (rigid)
Loudspeaker
Sample Noise generator
Amplifier
Fig. 4. Measurement setup for the sound absorption test.
3. Result and Discussion Figs. 5 and 6 plot the acoustic absorption of 1 gram sugarcane waste fibers using polyurethane and polyester, respectively. The results show that the composition of binder (up to 40%) does not significantly affect the performance of above 3.5 kHz. The absorption coefficient increases until it reaches the value of 4.5 kHz at 0.78. This applies for both types of binders. Fig. 7 shows the absorption coefficient for samples with higher densities. The thickness is maintained as ½ inch while the fiber weight is increased to three times i.e. 3 grams. Since the binder does not affect the absorption performance significantly, only results using one binder with different compositions are discussed. Unlike the results in Figs. 5 and 6, the weight composition of binder and fibers does show significant effect. However, no consistent trend is shown from the results. It is expected for 1 gram of fibers (Figs. 5 and 6) to also show this phenomenon. This might be due to the process during the cold press of which notes should be taken. Here it is found that composition of 70:30 gives the best acoustic performance with > 0.5 at frequency 1- 4.5 kHz.
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Azma Putra et al. / Procedia Engineering 53 (2013) 632 – 638 1 60:40 70:30 80:20 90:10
0.9
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0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 500
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Fig. 5. Measured absorption coefficient of 1 gram sugarcane fibers using polyurethane.
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0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 500
.
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Fig. 6. Measured absorption coefficient of 1 gram sugarcane fibers using polyester.
Fig. 8 compares the samples having 1 gram and 3 grams weight fibers with the same composition of binder, i.e. 70:30. It can be seen that more fibers give better sound absorption. This can be explained as the denser the acoustic panel, the greater the flow resistivity. The airflow resistance becomes high because of fiber arrangement inside the panel is too close and effectively. It shows that the denser absorber sample overcomes t > 0.5 starting from 1.2 kHz with average absorption coefficient of 0.65. Fig. 9 compares the acoustic performance of sugarcane absorber sample with that of 3 layers of woven cloth absorber used for automotive application. The results shown that with the same thickness, sugarcane absorber performance is comparable to the corresponding commercial product.
Azma Putra et al. / Procedia Engineering 53 (2013) 632 – 638 1 0.9
absorption coefficient
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0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 500
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1500
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Fig. 7. Measured absorption coefficient of 3 grams sugarcane fibers using polyurethane.
1 0.9
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absorption coefficient
0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 500
1000
1500
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Fig. 8. Effect of density on sound absorption (fiber-binder weight composition 70:30).
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woven cloth sugarcane fiber
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0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 500
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Fig. 9. Comparison of sound absorption coefficient of sugarcane absorber with that of woven cloth sound insulator.
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4. Conclusion Utilization of sugarcane wasted fibers as an alternative sound absorbing material has been investigated. The effect of binder composition and fiber density are discussed with the former affects only for the 3 grams fibers and the latter to give better absorption coefficient. It is found that acoustical performance of the sugarcane absorber with thickness of ½ inch is comparable with that of commercial sound insulator with average absorption coefficient of 0.65 at frequency 1.2 - 4.5 kHz. References [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15]
[F. T. Koizumi, N. Tsujiuchi, and A. Structures and Composites, 2002, pp. 157-166. H.S. Yang, D.J. Kim, and H.J. 86, 2003, pp. 117-121. F. G. Pispola, and Exposition on Noise Control Engineering, Brazil, 2005. M. Saadatnia, G. Ebrahimi, and M. percentage o S. Ersoy and H. -leaf2009, pp. 215-220. R. R. Zulkifli, Zulkarnain, and M.J. American Journal of Applied Sciences, vol: 7, no: 2, 2010, pp. 260-264. M.J. Mohd Nor, M. Ayub, R. Zulkifli, N. Amin, and M.H. Journal of Applied Sciences, vol: 7, no: 9, 2010, pp. 1285-1290. M.H Fouladi, M.J Mohd Nor, M. Ayub, and Z.I. 71, 2010, pp. 241-249. M.H. Fouladi, M. Ayub, and M.J. A. Khuriati, E. Komaruddin, and M. Berkala Fisika, vol: 9, no: 1, 2006, pp. 15-25. Zulfian and M.S. Kimia dan Lingkungan, vol:7, 2009, pp. 94-98. L. Ismail, M.I Ghazali, S. Mahzan, and A.M.A and Technology, vol:67, 2010, pp. 804-806. Y. Abdullah, A. Putra, H. Effendy, W.M. Farid, and M.R.
enhanced reverberation
-59.
-42.
fibers from dried paddy straw as a sustainable
[16] S. Fatima, and A.R. Applied Acoustics, vol:72, 2011, pp. 108-114. [17] D.J. Oldham, C.A. Egan, and R.D. Cookson, -363. [18] www.arti-india.org. 15 July 2012. [19] fact of cane fields sugarcane www.canefieldsusa.com/canefields_usa_facts_on_sugarcane_paper.html. 15 July 2012. [20] ISO 10534-2:2001. Acoustic-Determination od sound absorption coefficient and impedance tubes Part 2: Transfer function method, 2001.
