Reed Grass As Sustainable Sound Absorber.
SUPERVISOR DECLARATION
“I hereby declare that I have read this thesis and in my opinion this thesis is
sufficient in terms of scope and quality for the award of the degree of Bachelor of
Mechanical Engineering (Structure and Materials).”
Signature
: .................................
Supervisor
: NORYANI BINTI MUHAMMAD
Date
: .................................
REED GRASS AS SUSTAINABLE SOUND
ABSORBER
MUHAMMAD FAHMI BIN NOORDIN
This report is submitted in fulfillment of the requirements for the award
Bachelor of Mechanical Engineering (Structure and Materials)
Faculty of Mechanical Engineering
Universiti Teknikal Malaysia Melaka
JUNE 2015
ii
DECLARATION
“I hereby declare that the work in this thesis is my own except for summaries and
quotations which have been duly acknowledged.”
Signature
: .................................
Author
: MUHAMMAD FAHMI BIN NOORDIN
Date
: .................................
iii
DEDICATION
To my beloved parents.
Thank you for your care and support.
iv
ACKNOWLEDGEMENT
Alhamdulillah, praise be only to Allah S.W.T. for giving me the strength and
health to making this Final Year Project (FYP) to its completion. By his grant, I am
able to finish up this report. I like to convey my sincere gratitude neither to all UTeM
lecturers and staffs for the guidance, advice and the constructive comment
throughout this final year project.
My special thanks to the individuals that assisted me to complete my final
year project report, especially to my supervisor Madam Noryani Binti Muhammad
that provided guidance and encouragement to me. Not forgotten, expression of
gratitude to my seminar panel and my co-supervisor, Dr Azma Putra, for all the
building advices and suggestions. In addition, thanks also to Fazlin (Master student)
for her valuable guidance and “foot the bill” of the expenses that helps in completing
this report.
Lastly, a big thanks to all members or individual for their cooperation and
help in preparing this report. Thank you for their support and involvement. Do not
forget also to my friends who were doing this final year project those under the same
supervisor, for sharing our ideas when I faced some problems and difficulties in
completing the report. Without all of you, my project will not successfully finish.
v
ABSTRACT
The used of synthetic materials as acoustic absorbers are still practiced
extensively in building industry. This is because the increasing of noise level affects
people not only in the industry, but as well in the living environment. The high cost
involved in the construction and renovation of noise barriers makes the growth of
sustainable barriers necessary. Thus, researchers have now driven their attentions to
find sustainable and eco-friendly materials to be an alternative sound absorbing. This
paper discusses about the uses of reed grass to be a sustainable sound absorbing. The
usage this fabric actually will also minimize the production cost since the reed grass
is one of common natural waste materials that found across South East Asia. The
sound absorption properties of reed grass have been investigated through experiment.
Their acoustic properties were measured by using an impedance tube instrument. In
summation, the characteristic impedance and the propagation constant of the fabrics
were measured. The results shows that the reed grass has excellent acoustical
performance to be sound absorbing fabric.
vi
ABSTRAK
Penggunaan bahan-bahan sintetik sebagai bahan penyerap akustik masih
dipraktikkan secara meluas dalam industri pembinaan. Ini adalah kerana peningkatan
tahap paras bunyi yang memberi kesan kepada manusia bukan sahaja di dalam
industri, tetapi juga dalam persekitaran hidup. Penggunaan kos yang tinggi yang
dalam pembinaan dan pengubahsuaian penebat bunyi membuatkan pertumbuhan
pemampan halangan perlu diwujudkan. Oleh itu, para penyelidik kini telah memberi
perhatian untuk mencari bahan-bahan yang mampan dan mesra alam untuk dijadikan
penyerap bunyi alternatif. Kertas kerja ini membincangkan tentang penggunaan
rumput buluh untuk dijadikan penyerap bunyi. Penggunaan fabrik ini juga akan
mengurangkan kos pengeluaran kerana rumput buluh merupakan salah satu daripada
bahan-bahan buangan semula jadi yang biasa dijumpai di seluruh Asia Tenggara.
Ciri-ciri penyerapan bunyi rumput buluh ini telah dikaji melalui eksperimen. Sifat
akustik mereka diukur dengan menggunakan alat tiub galangan. Dalam eksperimen
ini, sifat akustik mereka diukur dengan menggunakan alat tiub galangan. Dalam
eksperimen ini, ciri-ciri galangan, pekali penyerapan dan tetap luang dari kain telah
diukur. Keputusan menunjukkan bahawa rumput buluh mempunyai prestasi akustik
yang sangat baik untuk menjadi bahan penyerap bunyi.
vii
TABLE OF CONTENT
CHAPTER
TITLE
PAGES
DECLARATION
ii
DEDICATION
iii
ACKNOWLEDGEMENT
iv
ABSTRACT
v
ABSTRAK
vi
TABLE OF CONTENT
vii
LIST OF TABLES
x
LIST OF FIGURES
xi
LIST OF SYMBOLS
xiv
LIST OF APPENDICES
xv
CHAPTER 1 INTRODUCTION
1
1.1 Research Background
1
1.2 Problem Statement
2
1.3 Objectives
2
1.4 Research Scopes
2
CHAPTER 2 LITERATURE REVIEW
3
2.1 Introduction
3
2.2 Reed Grass (Imperata Cylindrica)
3
2.3 Sound
5
2.4 Noise Control
6
2.5 Impedance Tube (using Two-Microphone Method)
7
2.6 Sound Absorption (using natural fabrics)
8
2.7 Previous Research
10
viii
2.7.1 Specimens of chopped reeds
10
2.7.2 Absorption coefficient of Reeds
13
2.7.3 Acoustic applications
14
CHAPTER 3 METHODOLOGY
17
3.1 Introduction
17
3.2 Flowchart
18
3.3 Sample Preparation
19
3.4 Sound Absorption Coefficient Testing
21
3.4.1 Equipment of Test
22
3.4.2 Procedure of Sound Coefficient Testing
23
3.5 Air gap
24
3.6 Arrangement of samples in Impedance Tube
25
CHAPTER 4 RESULT AND DISCUSSION
27
4.1 Introduction
27
4.2 Sound Absorption Coefficient Results
27
4.3 Equation of Wavelength
28
4.4 Results on Axial Arrangement of Reeds
29
4.5 Results on Transverse Arrangement of Reeds
31
4.6 Results on Axial Arrangement of Reeds (with two fabrics)
33
4.7 Results on Cross Transverse Arrangement of Reeds
35
4.8 Sound Absorption Coefficient on Other Materials
37
4.9 Design and Fabrication of Panel
39
4.10 Discussion
40
4.10.1 Effect of Length
40
4.10.2 Effect of Sample Arrangement
41
4.10.3 Effect of Fabrics
42
ix
CHAPTER 5 CONCLUSION AND RECOMMENDATION
43
5.1 Conclusion
43
5.2 Recommendation
44
REFERENCES
45
APPENDIX A
47
APPENDIX B
49
x
LIST OF TABLES
NO.
TITLE
2.1
Acoustical properties (absorption) of some
PAGE
conventional and sustainable material
(Asdrubali and Francesco, 2007)
9
3.1
The equipment in the experiment
22
4.1
Wavelength for 2 cm and 6 cm length of the reeds
in axial arrangement
4.2
Wavelength for 2 cm and 3 cm thickness of the
reeds in transverse arrangement
4.3
34
Wavelength for 2 cm and 6 cm thickness of the
reeds in cross transverse arrangement
4.5
32
Wavelength for 2 cm and 6 cm length of the reeds
with two fabrics
4.4
30
36
Wavelength for 2 cm and 3 cm length of the
reeds and lollipop sticks
38
xi
LIST OF FIGURES
NO.
TITLE
2.1
Reed Grass (Imperata Cylindrica)
(Source: Troya M. T. 2009)
2.2
4
Two-Microphone Method
(Source: Andrew 1989)
2.3
PAGE
7
The specimens of whole reeds are presented by
four types of thickness
(Source: Mažuolis et al. 2012)
2.4
10
The process of preparing the specimens of
chopped reeds (200 mm thickness)
(Source: Mažuolis et al. 2012)
2.5
11
The process of preparing the specimens of
chopped reeds (150 mm thickness)
(Source: Mažuolis et al. 2012)
2.6
11
Chopped reeds as the specimens of a random mix
(50 mm thickness)
(Source: Mažuolis et al. 2012)
2.7
Suspended ceiling measurement
(Source: Koizumi 2002)
2.8
13
Vertical reed panel
(Source: Koizumi 2002)
2.9
12
13
Configuration of reed grass tested
(Source: Asdrubali F. 2007)
13
xii
2.10
Loose material with the average thickness is
4cm is inserted in jute sacks to obtain a layer
of sound absorbing porous material
15
(Source: Mohanty A. R. 2010)
2.11
Classroom plan with dimensions
(Source: Trematerra A 2013)
2.12
Classroom section, with height dimensions
(Source: Trematerra A 2013)
2.13
15
15
Sound absorbent panels installed in the
classroom during the test
(Source: L.V. Redman 2003)
2.14
16
Sound source in the classroom with the
measurement microphone
(Source: L.V. Redman 2003)
16
3.1
Flowchart of the research
18
3.2
Samples collected
19
3.3
Tools preparation
19
3.4
Samples were cut
20
3.5
Samples
20
3.6
Impedance tube
(Putra 2014)
3.7
21
Measurement setup
(Putra 2014)
21
3.8
(a) Sample holder (b) Calibrator
22
3.9
(a) Rigid backing (b) 1 cm air gap (c) 2 cm air gap
(d) 3 cm air gap
3.10
24
(a) Axial arrangement (b) Transverse arrangement
(c) Cross transverse arrangement
(d) Fabrics that used in axial arrangement
(with two fabrics)
25
xiii
3.11
(a) Gaps between reeds on axial arrangement
(b) Gaps between aligned reeds on transverse
arrangement
(c) Gaps between reeds on cross transverse
arrangement
4.1
Measured absorption coefficient of 2 cm length of
reeds in axial arrangement
4.2
35
Measured absorption coefficient of 6 cm thickness of
reeds in cross transverse arrangement
4.9
33
Measured absorption coefficient of 2 cm thickness
of reeds in cross transverse arrangement
4.8
33
Measured absorption coefficient of 6 cm length of
reeds with two fabrics in axial arrangement
4.7
31
Measured absorption coefficient of 2 cm length of
reeds with two fabrics in axial arrangement
4.6
31
Measured absorption coefficient of 3 cm thickness
of reeds in transverse arrangement
4.5
29
Measured absorption coefficient of 2 cm thickness
of reeds in transverse arrangement
4.4
29
Measured absorption coefficient of 6 cm length of
reeds in axial arrangement
4.3
26
35
Comparison of measured absorption coefficient of
reeds and lollipop sticks
37
4.10
Absorber panel
39
4.11
Measured absorption coefficient of 2 cm and 6 cm
length of reeds in axial arrangement
4.12
40
Comparison of the measured value of absorption
coefficient of rigid backing samples with different
41
arrangement
4.13
Examples of sound insulated panels
(Source: AcousticsFREQ 2011)
42
xiv
LIST OF SYMBOL
°F
=
Fahrenheit
=
Absorption Coefficient
T60
=
Reverberation Time
V
=
Volume
c
=
Speed of Wave
%
=
Percentage
f
=
Frequency of Sound Wave
λ
=
Wavelength
xv
LIST OF APPENDICES
NO.
TITLE
A
Gantt chart of PSM I and PSM II
B
Results of Absorption Coefficient for Different
Arrangement
PAGE
47
49
xvi
1
CHAPTER 1
INTRODUCTION
1.1
RESEARCH BACKGROUND
Until todays, the used of synthetic materials as acoustic absorbers are still practiced
extensively in building industry. This is because the increasing of noise level affects
people not only in the industry, but also in the living environment. A sustainable
material is produced usually from natural or recycled materials and its production
requires a small amount of energy. It makes special use of non-renewable resources
and delivers a low environmental impact (Ersoy S. 2008). Therefore, researchers have
now driven their attentions to find sustainable and eco-friendly materials to be an
alternative sound absorbing. The need for new applications by addressing acoustic
problems has been constantly growing.
Thus, the sound absorption properties of reed grass have been investigated. One of
the reason is the reed grass are able to provide up to 80% absorption in a relatively
broad frequency range (Asdrubali F. 2007). By increasing the layer thickness, this
range can be expanded to the lower frequency regime. It has been found that the higher
absorption properties of the tested samples are obtained sealing the reeds.
Generally, this research is about the potential use of reed grass as a sustainable
noise absorber among the others natural materials by using the suitable testing method.
2
1.2
PROBLEM STATEMENT
In the final age, noise control was one of the major requirements to improve the
living environment. For example, in the construction sector. The high cost involved in
the building and renovation of noise barriers makes the growth of sustainable barriers
necessary. One of the methods to execute that is provided by sound absorber. This
survey was directed to look into the potency of using reed grass (Imperata Cylindrica)
as sound absorbing. Different with the experiments before, this experiment using 3cm
length of the reed grass that arranged in vertical arrangement.
1.3
OBJECTIVES
The objectives of this research are:
1. To design and fabricate reed grass as sustainable sound absorber.
2. To measure the sound absorption coefficient of the panel using the impedance tube.
1.4
RESEARCH SCOPES
The scope of project are:
1. Material preparation, design and fabrication.
2. Measurement of sound absorption coefficient in impedance tube.
3
CHAPTER 2
LITERATURE REVIEW
2.1
INTRODUCTION
This chapter will discuss the literature review in order to gain enough
information that can be used to complete the research. It will includes the introduction
of reed grass, usage of reed grass, overview of research in noise control in industry
and also the analysis method used in previous research works. There are many
advantages from the reed grass such as low density, cheap in cost, the availability, and
biodegradable. Hence, the usage of reed grass has increased because of these
advantages. The data’s include in this chapter are taken from thesis, books, journals,
and any academic articles that are related to the research topic and will be clearly cited.
2.2
REED GRASS (Imperata Cylindrica)
Reed grass or scientific name Imperata Cylindrical. Reed is tall woody
perennial grass with hollow slender stems and sharp leaves. They can grow to a height
of 1.5 meters. The leaves are green, long and straight with parallel veins and pointy at
the final stage. The border of the leaves is rather piercing and cause injury if not careful
when wielding it. The blooms are white, mild and smooth clump. Its stems called
rhizomes typical scaly and sharp, and grow creeping on the earth. In Indonesia it is
traditional medicinal plant used as treatment for lowering high blood pressure and pain
relieving (Chee 2012).
4
Reed grass can find in the vicinity of Southeast Asia, Africa, India, Australia
and tropical climes, such as North America, Central America and South America. In
fact, the grasses are growing in some temperate areas, such as New Zealand and Japan.
They thrive in countries that received rainfall in excess of 1,000 mm per year. Reed
grass also lives in countries prone to flooding and fire resistant (Chee 2012).
Consequently, the reed grass are easily spread into sandy areas, such as coastal, desert
and watery habitats, such as swamps and river valleys. High growth rates have the reed
grass quickly spread throughout the new country as a new pilot that threaten
agriculture and plantation sectors.
The scientific name is selected from the remembrance services grass
pharmacist Italy, namely Ferrante Imperato (1550-1631). He is actively involved in
the field of natural resources and the author Dell'Historia Naturale. Another name for
them is the weeds in Indonesia, kunai in Papua New Guinea, co tranh (Vietnam), Eye
and gogon (Philippines), yet-mei (Myanmar) and O - kha (Thailand). They are also
known as congress and satin tail in English (Chee 2012).
Figure 2.1: Reed Grass (Imperata Cylindrica)
(Source: Troya M. T. 2009)
5
2.3
SOUND
Sound is the sensation of hearing. It is any pressure variation (in air, water, or
other medium) that the human ear can detect. Sound is developed when a source
defines the air closest to it in motion. For instance, when a tuning fork is taken, it
vibrates, causing the air around it to move back and forth creating a variation in normal
atmospheric pressure. Then it will create alternate layers of expansion and contraction
to move off from the vibrating source. These compression waves can we say as sound.
The pressure fluctuation (amplitude) determines the loudness and the number of
fluctuations its frequency.
Sound waves move around in the air at a speed which is temperature dependent.
The velocity of sound is about 1130 feet per second at 70°F. The frequency of sound
is measured in cycles per second, and is called Hertz (Hz). The human hearing range
is about 20 to 20,000 Hz (Mueller 2001).
The wavelength of a frequency is announced by the Greek symbol λ and is
calculated by splitting up the focal ratio of sound by the frequency. For comparison,
the wavelength of 20 Hz at 70°F is 56.5 Ft. and 20,000 Hz at 70°F is approximately
11/16 In. long (Mueller 2001). Hence we see that high frequencies have short
wavelengths and low frequencies have long wavelengths.
6
2.4
NOISE CONTROL
Noise is can be defined as any unwanted sound. Noise may be continuous or
erratic depending upon the source. It annoys, distracts and generally upsets the
environment. Noise affects people in a bit of ways. If sufficiently intense, noise may
damage hearing or health, interfere with work tasks, interfere with speech
communication, interrupt sleep, or cause irritation.
Noise can be controlled by addressing their origin, track or recipient. Noise
control at the source. A noise source is created by the motility of a solid, liquid, or gas.
A solid source may be quoted if its manner of performance is shifted so that it moves
less. Liquid and gaseous sources may be piped down by reducing flow velocity,
smoothing flow, and attenuating pressure pulsations (Zulkifli R. 2010).
Control at the source by planning while the merchandise is in the design stage
is often the most cost effective and least expensive control measure. Most corrective
measures for an existing noise control problem utilizes changes in the path. Solutions
for path noise control include barriers, enclosures, silencers, and dampers, vibration
dampening, and vibration isolation.
Thus, we can state that noise control can result in improved worker
communication, increased productivity, higher tone of work output and a quieter, safer
environment. This involves the use and application of sound absorption materials,
acoustic shields and barriers, acoustic enclosures and silencers.
7
2.5
IMPEDANCE TUBE (using Two-Microphone Method)
The methods to use an impedance tube with two microphones is to obtain the
acoustic features of materials samples. This setup can also be utilized to assess the
absorption coefficient in-situ on road surfaces, as a non-destructive alternative to fit
drilled out road samples into the tube. Besides that, impedance tubes can also be
applied to receive the non-acoustic parameters of a porous material using multiple
microphones and transfer function computations.
This setup also can be used to measure the absorption coefficient in-situ on
road surfaces, as a non-destructive alternative to fit drilled out road samples into the
tube (Andrew 1989). Moreover, impedance tubes can also be used to obtain the nonacoustic parameters of a porous material using multiple microphones and transfer
function calculations.
The two-microphone method is shown schematically in Figure 2.2 below. A
sample of the material to be tested is placed in a sample holder and mounted to one
end of a straight tube. A rigid plunger with an adjustable depth is placed behind the
sample to provide a reflecting surface. A sound source, typically a high-output acoustic
driver, is connected at the opposite end of the tube. A pair of microphones is mounted
flush with the inner wall of the tube near the sample end of the tube.
Figure 2.2: Two-Microphone Method
(Source: Andrew 1989)
“I hereby declare that I have read this thesis and in my opinion this thesis is
sufficient in terms of scope and quality for the award of the degree of Bachelor of
Mechanical Engineering (Structure and Materials).”
Signature
: .................................
Supervisor
: NORYANI BINTI MUHAMMAD
Date
: .................................
REED GRASS AS SUSTAINABLE SOUND
ABSORBER
MUHAMMAD FAHMI BIN NOORDIN
This report is submitted in fulfillment of the requirements for the award
Bachelor of Mechanical Engineering (Structure and Materials)
Faculty of Mechanical Engineering
Universiti Teknikal Malaysia Melaka
JUNE 2015
ii
DECLARATION
“I hereby declare that the work in this thesis is my own except for summaries and
quotations which have been duly acknowledged.”
Signature
: .................................
Author
: MUHAMMAD FAHMI BIN NOORDIN
Date
: .................................
iii
DEDICATION
To my beloved parents.
Thank you for your care and support.
iv
ACKNOWLEDGEMENT
Alhamdulillah, praise be only to Allah S.W.T. for giving me the strength and
health to making this Final Year Project (FYP) to its completion. By his grant, I am
able to finish up this report. I like to convey my sincere gratitude neither to all UTeM
lecturers and staffs for the guidance, advice and the constructive comment
throughout this final year project.
My special thanks to the individuals that assisted me to complete my final
year project report, especially to my supervisor Madam Noryani Binti Muhammad
that provided guidance and encouragement to me. Not forgotten, expression of
gratitude to my seminar panel and my co-supervisor, Dr Azma Putra, for all the
building advices and suggestions. In addition, thanks also to Fazlin (Master student)
for her valuable guidance and “foot the bill” of the expenses that helps in completing
this report.
Lastly, a big thanks to all members or individual for their cooperation and
help in preparing this report. Thank you for their support and involvement. Do not
forget also to my friends who were doing this final year project those under the same
supervisor, for sharing our ideas when I faced some problems and difficulties in
completing the report. Without all of you, my project will not successfully finish.
v
ABSTRACT
The used of synthetic materials as acoustic absorbers are still practiced
extensively in building industry. This is because the increasing of noise level affects
people not only in the industry, but as well in the living environment. The high cost
involved in the construction and renovation of noise barriers makes the growth of
sustainable barriers necessary. Thus, researchers have now driven their attentions to
find sustainable and eco-friendly materials to be an alternative sound absorbing. This
paper discusses about the uses of reed grass to be a sustainable sound absorbing. The
usage this fabric actually will also minimize the production cost since the reed grass
is one of common natural waste materials that found across South East Asia. The
sound absorption properties of reed grass have been investigated through experiment.
Their acoustic properties were measured by using an impedance tube instrument. In
summation, the characteristic impedance and the propagation constant of the fabrics
were measured. The results shows that the reed grass has excellent acoustical
performance to be sound absorbing fabric.
vi
ABSTRAK
Penggunaan bahan-bahan sintetik sebagai bahan penyerap akustik masih
dipraktikkan secara meluas dalam industri pembinaan. Ini adalah kerana peningkatan
tahap paras bunyi yang memberi kesan kepada manusia bukan sahaja di dalam
industri, tetapi juga dalam persekitaran hidup. Penggunaan kos yang tinggi yang
dalam pembinaan dan pengubahsuaian penebat bunyi membuatkan pertumbuhan
pemampan halangan perlu diwujudkan. Oleh itu, para penyelidik kini telah memberi
perhatian untuk mencari bahan-bahan yang mampan dan mesra alam untuk dijadikan
penyerap bunyi alternatif. Kertas kerja ini membincangkan tentang penggunaan
rumput buluh untuk dijadikan penyerap bunyi. Penggunaan fabrik ini juga akan
mengurangkan kos pengeluaran kerana rumput buluh merupakan salah satu daripada
bahan-bahan buangan semula jadi yang biasa dijumpai di seluruh Asia Tenggara.
Ciri-ciri penyerapan bunyi rumput buluh ini telah dikaji melalui eksperimen. Sifat
akustik mereka diukur dengan menggunakan alat tiub galangan. Dalam eksperimen
ini, sifat akustik mereka diukur dengan menggunakan alat tiub galangan. Dalam
eksperimen ini, ciri-ciri galangan, pekali penyerapan dan tetap luang dari kain telah
diukur. Keputusan menunjukkan bahawa rumput buluh mempunyai prestasi akustik
yang sangat baik untuk menjadi bahan penyerap bunyi.
vii
TABLE OF CONTENT
CHAPTER
TITLE
PAGES
DECLARATION
ii
DEDICATION
iii
ACKNOWLEDGEMENT
iv
ABSTRACT
v
ABSTRAK
vi
TABLE OF CONTENT
vii
LIST OF TABLES
x
LIST OF FIGURES
xi
LIST OF SYMBOLS
xiv
LIST OF APPENDICES
xv
CHAPTER 1 INTRODUCTION
1
1.1 Research Background
1
1.2 Problem Statement
2
1.3 Objectives
2
1.4 Research Scopes
2
CHAPTER 2 LITERATURE REVIEW
3
2.1 Introduction
3
2.2 Reed Grass (Imperata Cylindrica)
3
2.3 Sound
5
2.4 Noise Control
6
2.5 Impedance Tube (using Two-Microphone Method)
7
2.6 Sound Absorption (using natural fabrics)
8
2.7 Previous Research
10
viii
2.7.1 Specimens of chopped reeds
10
2.7.2 Absorption coefficient of Reeds
13
2.7.3 Acoustic applications
14
CHAPTER 3 METHODOLOGY
17
3.1 Introduction
17
3.2 Flowchart
18
3.3 Sample Preparation
19
3.4 Sound Absorption Coefficient Testing
21
3.4.1 Equipment of Test
22
3.4.2 Procedure of Sound Coefficient Testing
23
3.5 Air gap
24
3.6 Arrangement of samples in Impedance Tube
25
CHAPTER 4 RESULT AND DISCUSSION
27
4.1 Introduction
27
4.2 Sound Absorption Coefficient Results
27
4.3 Equation of Wavelength
28
4.4 Results on Axial Arrangement of Reeds
29
4.5 Results on Transverse Arrangement of Reeds
31
4.6 Results on Axial Arrangement of Reeds (with two fabrics)
33
4.7 Results on Cross Transverse Arrangement of Reeds
35
4.8 Sound Absorption Coefficient on Other Materials
37
4.9 Design and Fabrication of Panel
39
4.10 Discussion
40
4.10.1 Effect of Length
40
4.10.2 Effect of Sample Arrangement
41
4.10.3 Effect of Fabrics
42
ix
CHAPTER 5 CONCLUSION AND RECOMMENDATION
43
5.1 Conclusion
43
5.2 Recommendation
44
REFERENCES
45
APPENDIX A
47
APPENDIX B
49
x
LIST OF TABLES
NO.
TITLE
2.1
Acoustical properties (absorption) of some
PAGE
conventional and sustainable material
(Asdrubali and Francesco, 2007)
9
3.1
The equipment in the experiment
22
4.1
Wavelength for 2 cm and 6 cm length of the reeds
in axial arrangement
4.2
Wavelength for 2 cm and 3 cm thickness of the
reeds in transverse arrangement
4.3
34
Wavelength for 2 cm and 6 cm thickness of the
reeds in cross transverse arrangement
4.5
32
Wavelength for 2 cm and 6 cm length of the reeds
with two fabrics
4.4
30
36
Wavelength for 2 cm and 3 cm length of the
reeds and lollipop sticks
38
xi
LIST OF FIGURES
NO.
TITLE
2.1
Reed Grass (Imperata Cylindrica)
(Source: Troya M. T. 2009)
2.2
4
Two-Microphone Method
(Source: Andrew 1989)
2.3
PAGE
7
The specimens of whole reeds are presented by
four types of thickness
(Source: Mažuolis et al. 2012)
2.4
10
The process of preparing the specimens of
chopped reeds (200 mm thickness)
(Source: Mažuolis et al. 2012)
2.5
11
The process of preparing the specimens of
chopped reeds (150 mm thickness)
(Source: Mažuolis et al. 2012)
2.6
11
Chopped reeds as the specimens of a random mix
(50 mm thickness)
(Source: Mažuolis et al. 2012)
2.7
Suspended ceiling measurement
(Source: Koizumi 2002)
2.8
13
Vertical reed panel
(Source: Koizumi 2002)
2.9
12
13
Configuration of reed grass tested
(Source: Asdrubali F. 2007)
13
xii
2.10
Loose material with the average thickness is
4cm is inserted in jute sacks to obtain a layer
of sound absorbing porous material
15
(Source: Mohanty A. R. 2010)
2.11
Classroom plan with dimensions
(Source: Trematerra A 2013)
2.12
Classroom section, with height dimensions
(Source: Trematerra A 2013)
2.13
15
15
Sound absorbent panels installed in the
classroom during the test
(Source: L.V. Redman 2003)
2.14
16
Sound source in the classroom with the
measurement microphone
(Source: L.V. Redman 2003)
16
3.1
Flowchart of the research
18
3.2
Samples collected
19
3.3
Tools preparation
19
3.4
Samples were cut
20
3.5
Samples
20
3.6
Impedance tube
(Putra 2014)
3.7
21
Measurement setup
(Putra 2014)
21
3.8
(a) Sample holder (b) Calibrator
22
3.9
(a) Rigid backing (b) 1 cm air gap (c) 2 cm air gap
(d) 3 cm air gap
3.10
24
(a) Axial arrangement (b) Transverse arrangement
(c) Cross transverse arrangement
(d) Fabrics that used in axial arrangement
(with two fabrics)
25
xiii
3.11
(a) Gaps between reeds on axial arrangement
(b) Gaps between aligned reeds on transverse
arrangement
(c) Gaps between reeds on cross transverse
arrangement
4.1
Measured absorption coefficient of 2 cm length of
reeds in axial arrangement
4.2
35
Measured absorption coefficient of 6 cm thickness of
reeds in cross transverse arrangement
4.9
33
Measured absorption coefficient of 2 cm thickness
of reeds in cross transverse arrangement
4.8
33
Measured absorption coefficient of 6 cm length of
reeds with two fabrics in axial arrangement
4.7
31
Measured absorption coefficient of 2 cm length of
reeds with two fabrics in axial arrangement
4.6
31
Measured absorption coefficient of 3 cm thickness
of reeds in transverse arrangement
4.5
29
Measured absorption coefficient of 2 cm thickness
of reeds in transverse arrangement
4.4
29
Measured absorption coefficient of 6 cm length of
reeds in axial arrangement
4.3
26
35
Comparison of measured absorption coefficient of
reeds and lollipop sticks
37
4.10
Absorber panel
39
4.11
Measured absorption coefficient of 2 cm and 6 cm
length of reeds in axial arrangement
4.12
40
Comparison of the measured value of absorption
coefficient of rigid backing samples with different
41
arrangement
4.13
Examples of sound insulated panels
(Source: AcousticsFREQ 2011)
42
xiv
LIST OF SYMBOL
°F
=
Fahrenheit
=
Absorption Coefficient
T60
=
Reverberation Time
V
=
Volume
c
=
Speed of Wave
%
=
Percentage
f
=
Frequency of Sound Wave
λ
=
Wavelength
xv
LIST OF APPENDICES
NO.
TITLE
A
Gantt chart of PSM I and PSM II
B
Results of Absorption Coefficient for Different
Arrangement
PAGE
47
49
xvi
1
CHAPTER 1
INTRODUCTION
1.1
RESEARCH BACKGROUND
Until todays, the used of synthetic materials as acoustic absorbers are still practiced
extensively in building industry. This is because the increasing of noise level affects
people not only in the industry, but also in the living environment. A sustainable
material is produced usually from natural or recycled materials and its production
requires a small amount of energy. It makes special use of non-renewable resources
and delivers a low environmental impact (Ersoy S. 2008). Therefore, researchers have
now driven their attentions to find sustainable and eco-friendly materials to be an
alternative sound absorbing. The need for new applications by addressing acoustic
problems has been constantly growing.
Thus, the sound absorption properties of reed grass have been investigated. One of
the reason is the reed grass are able to provide up to 80% absorption in a relatively
broad frequency range (Asdrubali F. 2007). By increasing the layer thickness, this
range can be expanded to the lower frequency regime. It has been found that the higher
absorption properties of the tested samples are obtained sealing the reeds.
Generally, this research is about the potential use of reed grass as a sustainable
noise absorber among the others natural materials by using the suitable testing method.
2
1.2
PROBLEM STATEMENT
In the final age, noise control was one of the major requirements to improve the
living environment. For example, in the construction sector. The high cost involved in
the building and renovation of noise barriers makes the growth of sustainable barriers
necessary. One of the methods to execute that is provided by sound absorber. This
survey was directed to look into the potency of using reed grass (Imperata Cylindrica)
as sound absorbing. Different with the experiments before, this experiment using 3cm
length of the reed grass that arranged in vertical arrangement.
1.3
OBJECTIVES
The objectives of this research are:
1. To design and fabricate reed grass as sustainable sound absorber.
2. To measure the sound absorption coefficient of the panel using the impedance tube.
1.4
RESEARCH SCOPES
The scope of project are:
1. Material preparation, design and fabrication.
2. Measurement of sound absorption coefficient in impedance tube.
3
CHAPTER 2
LITERATURE REVIEW
2.1
INTRODUCTION
This chapter will discuss the literature review in order to gain enough
information that can be used to complete the research. It will includes the introduction
of reed grass, usage of reed grass, overview of research in noise control in industry
and also the analysis method used in previous research works. There are many
advantages from the reed grass such as low density, cheap in cost, the availability, and
biodegradable. Hence, the usage of reed grass has increased because of these
advantages. The data’s include in this chapter are taken from thesis, books, journals,
and any academic articles that are related to the research topic and will be clearly cited.
2.2
REED GRASS (Imperata Cylindrica)
Reed grass or scientific name Imperata Cylindrical. Reed is tall woody
perennial grass with hollow slender stems and sharp leaves. They can grow to a height
of 1.5 meters. The leaves are green, long and straight with parallel veins and pointy at
the final stage. The border of the leaves is rather piercing and cause injury if not careful
when wielding it. The blooms are white, mild and smooth clump. Its stems called
rhizomes typical scaly and sharp, and grow creeping on the earth. In Indonesia it is
traditional medicinal plant used as treatment for lowering high blood pressure and pain
relieving (Chee 2012).
4
Reed grass can find in the vicinity of Southeast Asia, Africa, India, Australia
and tropical climes, such as North America, Central America and South America. In
fact, the grasses are growing in some temperate areas, such as New Zealand and Japan.
They thrive in countries that received rainfall in excess of 1,000 mm per year. Reed
grass also lives in countries prone to flooding and fire resistant (Chee 2012).
Consequently, the reed grass are easily spread into sandy areas, such as coastal, desert
and watery habitats, such as swamps and river valleys. High growth rates have the reed
grass quickly spread throughout the new country as a new pilot that threaten
agriculture and plantation sectors.
The scientific name is selected from the remembrance services grass
pharmacist Italy, namely Ferrante Imperato (1550-1631). He is actively involved in
the field of natural resources and the author Dell'Historia Naturale. Another name for
them is the weeds in Indonesia, kunai in Papua New Guinea, co tranh (Vietnam), Eye
and gogon (Philippines), yet-mei (Myanmar) and O - kha (Thailand). They are also
known as congress and satin tail in English (Chee 2012).
Figure 2.1: Reed Grass (Imperata Cylindrica)
(Source: Troya M. T. 2009)
5
2.3
SOUND
Sound is the sensation of hearing. It is any pressure variation (in air, water, or
other medium) that the human ear can detect. Sound is developed when a source
defines the air closest to it in motion. For instance, when a tuning fork is taken, it
vibrates, causing the air around it to move back and forth creating a variation in normal
atmospheric pressure. Then it will create alternate layers of expansion and contraction
to move off from the vibrating source. These compression waves can we say as sound.
The pressure fluctuation (amplitude) determines the loudness and the number of
fluctuations its frequency.
Sound waves move around in the air at a speed which is temperature dependent.
The velocity of sound is about 1130 feet per second at 70°F. The frequency of sound
is measured in cycles per second, and is called Hertz (Hz). The human hearing range
is about 20 to 20,000 Hz (Mueller 2001).
The wavelength of a frequency is announced by the Greek symbol λ and is
calculated by splitting up the focal ratio of sound by the frequency. For comparison,
the wavelength of 20 Hz at 70°F is 56.5 Ft. and 20,000 Hz at 70°F is approximately
11/16 In. long (Mueller 2001). Hence we see that high frequencies have short
wavelengths and low frequencies have long wavelengths.
6
2.4
NOISE CONTROL
Noise is can be defined as any unwanted sound. Noise may be continuous or
erratic depending upon the source. It annoys, distracts and generally upsets the
environment. Noise affects people in a bit of ways. If sufficiently intense, noise may
damage hearing or health, interfere with work tasks, interfere with speech
communication, interrupt sleep, or cause irritation.
Noise can be controlled by addressing their origin, track or recipient. Noise
control at the source. A noise source is created by the motility of a solid, liquid, or gas.
A solid source may be quoted if its manner of performance is shifted so that it moves
less. Liquid and gaseous sources may be piped down by reducing flow velocity,
smoothing flow, and attenuating pressure pulsations (Zulkifli R. 2010).
Control at the source by planning while the merchandise is in the design stage
is often the most cost effective and least expensive control measure. Most corrective
measures for an existing noise control problem utilizes changes in the path. Solutions
for path noise control include barriers, enclosures, silencers, and dampers, vibration
dampening, and vibration isolation.
Thus, we can state that noise control can result in improved worker
communication, increased productivity, higher tone of work output and a quieter, safer
environment. This involves the use and application of sound absorption materials,
acoustic shields and barriers, acoustic enclosures and silencers.
7
2.5
IMPEDANCE TUBE (using Two-Microphone Method)
The methods to use an impedance tube with two microphones is to obtain the
acoustic features of materials samples. This setup can also be utilized to assess the
absorption coefficient in-situ on road surfaces, as a non-destructive alternative to fit
drilled out road samples into the tube. Besides that, impedance tubes can also be
applied to receive the non-acoustic parameters of a porous material using multiple
microphones and transfer function computations.
This setup also can be used to measure the absorption coefficient in-situ on
road surfaces, as a non-destructive alternative to fit drilled out road samples into the
tube (Andrew 1989). Moreover, impedance tubes can also be used to obtain the nonacoustic parameters of a porous material using multiple microphones and transfer
function calculations.
The two-microphone method is shown schematically in Figure 2.2 below. A
sample of the material to be tested is placed in a sample holder and mounted to one
end of a straight tube. A rigid plunger with an adjustable depth is placed behind the
sample to provide a reflecting surface. A sound source, typically a high-output acoustic
driver, is connected at the opposite end of the tube. A pair of microphones is mounted
flush with the inner wall of the tube near the sample end of the tube.
Figure 2.2: Two-Microphone Method
(Source: Andrew 1989)