An Alternatif Acoustic Wall from Gaba-gaba

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1 P r o c e e d i n g I n t e r n a t i o n a l C o n f e r e n c e, , *, * * - * * The 4 th Green Technology Faculty of Science and Technology Islamic of University State Maulana Malik Ibrahim Malang An Alternatif Acoustic Wall from Gaba-gaba Yusfan Adeputera Yusran 1, Ary Dedy Putranto 2, Iwan Wibisono 3, Andika Citraningrum 4 1 Nusantara Architecture Lab, Department of Architecture, Brawijaya University, Malang, Indonesia; 2 Building Technology Lab, Department of Architecture, Brawijaya University, Malang, Indonesia; 3 Building Technology Lab, Department of Architecture, Brawijaya University, Malang, Indonesia; 4 Building Science Lab, Department of Architecture, Brawijaya University, Malang, Indonesia. yyusfan@yahoo.ca ABSTRACT Sago is often identified with foodstuffs without knowing that the sago palm is also one of the materials that used in the house. The part that is often used as a building material that is the leaves as roofing, sago leaf midrib as the outer wall and the sliced stalks as floor plates. But such as with the notion of the sago as a food for poor, this material is often left wasted rather than used. Sago leaf midrib usually called gaba-gaba own anatomy and fibrous porous like a sponge. From initial observations, these materials can be used as a sound reducing materials. This research was carried out initially by making a 1:10 scale and testing it by using a sound level meter (SLM) to obtain acoustic test value. From testing three models, the results shows the highest difference occured with interval 24,028 db depends on how the panels treated. This results strengthen the hypothesis of gaba-gaba as one of economically material for acoustic wall and also proves that it can be implemented as architectural element. Keywords Gaba-gaba, acoustic wall, sustainable material. 264

2 INTRODUCTION Sago palm (Metroxylon spp.) is a native plant from Indonesia. Sago s acreage in Indonesia is the world's largest sago acreage, which is about million ha or 51.3% of the million ha of world s sago area (Flach, 1997). Papua is one of the region in Indonesia which has a great potential of sago tree. In Indonesia, sago has a wide range of mention among others; rumbia, kirai (Sunda), ambulung or kersulu (Java), and lapia (Ambon). Unfortunately, sago is still often seen as a poor crop. Figure. 1. Sago plam trees (Source: Yusfan, 2012) Sago have many benefits. Sago s flour is usually used as a raw material in the manufacture of food or as a food ingredients. The flour is used for ordinary foodstuffs in Papua called papeda, also in addition for cakes and raw materials for alcohol manufacture. The leaves are used as the roof of the house, the midrib for the house wall, and the waste can be used as pulp for making paper or animal feed. In some cases of the traditional architecture in Indonesia, especially in the eastern part of Indonesia, its still founded some house that uses the roof from sago leaves and stems of sago as a wall. One of the tribes that still maintain this tradition is Alifuru tribe in Seram. Figure 2. Traditional houses of Alifuru tribe from sago material in Selumena village (left) and in Binaiya mountain (right) (Source: Wijayanto, 2013) Basically, the use of sago leaf material oftenly founded on the type of roofing. Research involving sago leaf / thatch as roofing itself has proven lowering the temperature in the room by 2.75 C (Hanan and Sujarmanto, 2011). On the walls of traditional houses, sago applied by utilizing the leaf midrib of sago which for most tribes in eastern Indonesia call it the gabagaba. The sheath has a posture similar to coconut leaf midrib. The difference identified from stem diameter and shape of the circle. When dried, its lighter than the coconut leaf midrib due to the porous material in the middle of the midrib. Research on gaba-gaba has been carried out by Kongle (2009) and proved that gaba-gaba can be used as an acoustic material. On his research, gaba-gaba treated to identify the value of sound absorption coefficient of panels from gaba-gaba powder, gaba-gaba panel in parallel fibers, and gaba-gaba panel on transverse fibers. On initial observations of the gaba-gaba, we saw an opportunity to be developed into an acoustic material that can be used to absorb noise. The existence of preliminary research conducted by Kongle (2009), will be strengthened by this research by developed it into architectural form. Therefore, through this study is expected to answer any such hypothesis by implementing the use of gabagaba architecturally as a wall on 1:10 scale model of the building and test it using a sound level meter. 265

3 In order to make this research more effective, efficient, directional and can be studied more in depth then it is necessary to limit the problem. The main concern of this study is testing the sound absorption panels of gabagaba which has been shaped into the house. The research itself strengthen previous research that has been done by Kongle (2009). Object of this research itself is limited to a simple model house type 21 and modeled into 1:10 scale due to its easier to applicated on the actual size (for further research). Therefore, based on the background and the identification above, the general formulation of this study are; how does the potency of absorption of gaba-gaba which formed into simple model house type 21 with scale model 1:10?. Literature Review 2.1. Overview about acoustics and sound Acoustics is the study of matters relating to sound, with respect to the sense of hearing as well as the room condition that affects the sound (Gabriel, 2001). Propagation of the sound waves to the object will reflected, absorbed, or diffused, whose characteristics depend on the characteristics of the object. Propagation of sound waves on the boundary with a gap will experience diffraction (Mediastika, 2005). This is what happens to the sound in the room with the hole. According to Doelle (1985), acoustic materials and sound absorbing construction that usually used as a controller in a noisy spaces can be classified into; porous materials, absorbent panels, resonator cavity, absorbent space, and absorption by the air. Selection of the proper sound absorbing material required to produce a very satisfactory sound quality. Doelle (1990) explains that one of the sound absorbent material that always used in acoustics design as a wall hanging or as a ceiling is the porous material. The baseline characteristics of all porous materials like these are changing the sound energy into heat energy comes in the pores and absorbed, while the rest which have less energy reflected by the surface of the material. Weakening of sound that produced by a porous material depends on the flow resistance and the porosity (Attenborough in Kongle, 2009). Meanwhile, Veronina (in Kongle, 2009) identified that the pore diameter is very influential in determining the transmissibility of sound in the material Overview of gaba-gaba as acoustic material Sago is the world 's oldest staple food in the world (Ave in Flach, 1997). Sago palms are often found in peat area. In Indonesia, sago palms are often found in the Riau Islands, Sulawesi, Ambon to Papua. Stanton (in Flach, 1997) mentions some of the advantages of planting corn, such as: 1) economic, 2) sustainable, 3) good for the environment, 4) have a variety of uses, 5) strong, and 6) stabilize agroforestry system. In addition as foodstuff, some parts of the sago plant can be used as building material. Some tribes in Indonesia still uses material from sago palm such as its leaf and stem. Figure 3. An example of how gaba-gaba can be used as interior in a school in South Seram (left) and the sago leaves as roof covering (Source: Almascatie, 2007) Gaba-gaba as raw material for acoustic panels manufacturing have to be considered due to its abundance and until now it still better discarded than used. Results of research conducted by Kongle (2009) have proved that 266

4 gaba-gaba can be used as a sound absorber panel material. In his research, gaba-gaba treated as panels from gaba-gaba powder, gabagaba panel with parallel fibers and gaba-gaba panel with transverse fiber. These panels are then tested using the impedance tube method consists of PVC Pipe (diameter D = 4 inch) with a length of 4 m, 1 microphone, preamplifire, audio function generator (AFG), oscilloscope, and a computer with sound forge 6.0 software to analize sound signals spectrum that detected by a microphone. Research material consists of: gaba-gaba, sago glue, and pipe glue.from the results, it was concluded among other things: Lowest absorption coefficient is 0.83 on transverse fibers panel with thickness of 3 cm and the highest on the panel with sago with thickness of 3 cm and the reflection coefficient from to 0.17 and the value of the transmission coefficient between to 0, Treatment of gaba-gaba as a panel are highly influential for determining coefficient of acoustic. Absorption coefficient was highest at gaba-gaba panels with pipe glue and the smallest on the panel with parallel fiber sheath. Acoustic coefficient depends on the thickness of the panel where the panel thicker will higher the coefficient of acoustic. The frequency of the sound of acoustic influence coefficients. Table 1. Comparison of the absorption coefficient between Gaba-gaba panels with parallel and transverse fibers Sound Intensity (db) Absorption coefficient of gaba-gaba panel Parallel fibers Transverse fibers 125 0, , , , , , , , (source: Kongle, 2009) Figure 4. Gaba-gaba sliced vertically and horizontally To complement the research that has been done before, so in this research the treatment of gaba-gaba be simulated in house form so that in addition to strengthening the hypothesis, also will be obtained one method of gaba-gaba composition that most appropriate when applied as an acoustic material in the house form METHODS Gaba-gaba which had dried initially will peeled to get the middle part. Then its cut to obtain a similar diameter with a thickness of 1 cm. This thick representing the actual models (10 cm) that can be conditioned as insulation element (not a stand-alone wall). Gaba-gaba edges then arranged vertically so that it becomes a wall. Mockups was designed using size 52.5 cm x 40 cm as a representation of the type 21 (5.25 x 4 m) and made square without any space in it. In this research, these models will be conditioned into 3 models. Early stage mockups (model 1) was established by using a full wall material of gaba-gaba, roofs of alang-alang as a representation of rumbia roof and the floor and ceiling from plasterboard. This model is then tested using a sound level meter to get the acoustic test model 1 (ATR 1). On model 2 mockups, the treatment differentiated with plasterboard wall on the inside and outside of the model. This model was tested to obtain the acoustic test results of model 2 (ATR 2). On model 3 mockups, similar to the previous 267

5 model but with some addition of residential openings such as windows and door. This model was tested to obtain the results of the acoustic test model 3 (ATR 3). Each test to get ATR follows such a technical methods that is: 1. Measuring the intensity of the sound that occurs during daylight hours on the highway as a representation of most noisy sound intensity. This measurement was conducted on July 24, 2013 at the side of MT Haryono, Malang road at 10:10 am. Furthermore, it was simulated using a handheld mobile as representation of interval highway noise when crowded. 2. Measuring the intensity of sound that occurs in the maket models I, II and III to obtain the average intensity of sounds that occur in the mockups. In each model was performed 50 times test to get an average sound. Results of measurements of each model are recorded and then divided so as to get a valid average noise figure. The tools used in this study are: - Mockup models, - Sound level meter Lutron SL 4010, - Equipment noise source (samsung GT 5510) RESULTS This research ran for four months. Description of research activities described consecutively of following activities: Testing Model I Model I is an initial model in this research. This model is made from gaba-gaba which cutted parallely 1 cm as a representation of wall thickness of 10 cm. Its cutted parallely because once done by transverse, it was not strong enough to be arranged into panels. Moreover, it uses more material if the panel arranged transversely. Parallel piece is easier to construct and more able to resist lateral and vertical loads. All of these pieces then glued using adhesive glue. Figure 5. Gaba-gaba s slice and wall panel from it Part of the panel that has been glued formed into square model 50 x 30 cm and 42 x 30 cm each two pieces. These sheets are then put together to get a wall model. Figure 6. Testing model I On the top of this model was closed with gabagaba panel with a thickness of 1 cm to represent acoustic ceiling, while the bottom of the model was closed by using fiber cement board as a representation of the cement floor. Model I testing session conducted at the Science Laboratory, Department of Architecture UB with initially stimulating sound condition on the road when crowded. Measurements were carried out at the edge of highway to get real noise conditions that occurs at the peak. From the measurement results, obtained an average noise by 74 db. The first measurement was conducted on July 24, 2013 using a sound source (highway representation) with 74 db noise and two Sound Level Meter 268

6 (SLM). One speaker of SLM (SLM 1) inserted into the mockups and the other (SLM 2) are outside the model to measure the noise level of the sound source. From 50 times testing of Model I, obtained interval db between the SLM 1 andslm 2. Testing Model II Model II is a development model of model I by adding a fiber cement sheet on some parts of the model I. The addition was done on the outside wall of the model I to represent the real cement wall and the inside to represent ceiling. This attachment glued using PVAc wood glue and mixed with calcium powder. Figure 8. Testing model III Comparison Testing Results Model I, II and III Figure 7. Testing model II Almost similar to the test performed on the model I, that is by calculating the interval between the SLM 1 and SLM 2. From the test results to the model II, obtained intervals of db. Testing Model III This model is a model development of model II with by adding a door and window openings. Moreover, the addition of a thatched roof made to get the model oh house. From the test results to the model III, obtained intervals of db between SLM 1 and SLM 2. Figure 9. Comparison testing results of model I, II, and III From the test results of the three models showed that the highest interval obtained on the model II. CONCLUSION Conclusions from the results of tests performed on the three models shows that: 1. Test results comparised by sound level meter (SLM) to model I (gaba-gaba cube), model II (gaba-gaba cube coated with plasterboard) and model III (model house type 21) shows differentiation in sound intensity. The highest difference occurred in model II with interval db. Treatment to the mockup determines the amount of sound absorption. 269

7 2. The panel types which the best to use in this research is made up of gaba-gaba sliced parallely and then glued. This method is better due to in addition to the intensity of the absorbed sound quite well, also it could strengthen the structure. The recommended way is formed gaba-gaba into hexagonal pieces. As for suggestions that can be used as basis for developing the research, such as : 1. Need for continuing this research implemented on the model 1:1. It will greatly affect the actual sound absorption. 2. Need for further research on how to preserve gaba-gaba panel so that not easily damaged by bugs and weather. Conference of SENVAR Held in Brawijaya University November Kongle, L. P Kajian Kinerja Absorbsi Bising Panel Akustik Gaba-Gaba Limbah Pelepah Pohon Sagu. Program Magíster Sistem Teknik Konsentrasi Teknologi Pengelolaan dan Pemanfaatan Sampah/ Limbah Perkotaan. Jurusan Ilmu-Ilmu Teknik. Fakultas Teknik Universitas Gadjah Mada. Tesis: Tidak dipublikasikan. Mediastika, C. E Akustika Bangunan: Prinsipprinsip dan Penerapannya di Indonesia. Jakarta: Erlangga. Mediastika, C. E Kualitas Akustik Panel Dinding Berbahan Baku Jerami. Dimensi. Journal Of Architecture And Built Environment, Vol. 36 p , No. 2, December 2008, ISSN x. ACKNOWLEDGMENT We would like to express our gratitude to BPPT FT UB in funding this research. This research also supported by Department of Architecture. Also to Mr. Agus Sulistio, Ms. Dhia Rosanti, Ms. Dewi Widya and Mrs. Rahmat Khoirul for their contribution in research progress. REFERENCES Doelle, L. L Akustik Lingkungan. Terjemahan oleh: Lea Prasetia. Jakarta: Erlangga. Flach, M Sago palm (Metroxylon sagu Rottb.) Promoting the conservation and use of underutilized and neglected crops. 13. Institute of Plant Genetics and Crop Plant Research, Gatersleben/International Plant Genetic Resources Institute, Rome, Italy. diakses melalui ftp://ftp.cgiar.org/ipgri/publications/pdf/238.pdf pada tanggal 24 Maret Gabriel, J. F Fisika Lingkungan. Jakarta: Hipokrates. Hanan, H. dan Sujarmanto The Impact of Modern Roof Material to the Traditional House of Batak Toba. Proceedings of The 12 th International 270