1. CPP 301 Core Project Part I
DESIGNING OF A NOISE BARRIER
Submitted by
Lalit Aggarwal &Gayathri Lakshmi Kulukuru
Supervisor
Dr. Navin Kumar
School of Mechanical Materials & Energy Engineering
INDIAN INSTITUTE OF TECHNOLOGY ROPAR
Nov 2012
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2. CERTIFICATE
This report is submitted by Mr.Lalit Aggarwal &Ms.Gayathri Lakshmi Kulukuru detailing
the work done during the 1st semester, 2011-2012. The report written and all material taken
from other sources(books, manuals, journals,etc.) have been fully acknowledged.
Lalit Aggarwal Gayathri Lakshmi Kulukuru
P2009ME1085 P2009ME1062
SMMEE, IIT Ropar SMMEE, IIT Ropar
Date: 09-Nov-2012 Date: 09-Nov-2012
Mr. Lalit Aggarwal &Ms.Gayathri Lakshmi Kulukuru have worked under my supervision
during this semester. I have read this report; it meets the expectations and it accurately
reflects the work done by the students.
Dr. Navin Kumar
(Supervisor)
Date: 08-Nov-2012
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3. ACKNOWLEDGMENTS
The authors acknowledge the support of the Director, Defense and Research Organization
(DRDO) for giving the opportunity to work on the project. The authors acknowledge the
guidance acquired from the project work of Mr. SahilBagat performed in the previous year.
The authors acknowledge the support of their Project advisor Dr. Naveen Kumar for their
continuous guidance and support throughout the semester.
Lalit Aggarwal Gayathri Lakshmi Kulukuru
P2009ME1085 P2009ME1062
SMMEE, IIT Ropar SMMEE, IIT Ropar
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4. ABSTRACT
The project which was given to us addressed the investigation of the technical, aesthetic, and
economic feasibility of deploying special noise barrier application into baffle range of
DRDO.
So we have to suggest a most suitable design of noise and maximum sound attenuation can be
achieved under having some constraints like cost, weight and aesthetic requirements.
Sound attenuation in noise barrier depends on various parameters like (height, type of
material, top surface modification, receiver or source position and several other parameters,
barrier shapes).
There is a threefold process in which we are going to do this project.
1. Literature Survey and Theory.
2. Modeling and calculating Results.
3. Make prototypes and Verifying Results.
In Literature Survey in which there a cumulative study about the past design, all the research
done in the field and all of the different possibility is there in designing. In order to
understand the physics behind it thorough study about the theory of acoustics design is also
required.
In Modeling, Using Sysnoise software the problem will be modeled and result will be
obtained and compared with the theoretical results. Simple barrier can be solved analytically
using empirical relations but advanced barrier needs BEM or Some kind of simulation
software (SYSNOISE). The simulation will help in estimating the behavior of the noise
barrier under different parameters e.g.- changes in the barrier parameter, change in material
and other parameters.
In making Prototype and verifying results, there is series of experiments have to be
performed to see the practical behavior of the parameters involved in the formulation of the
problem which is performed using microphone and other devices.
Then all the results will be analyzed and final design will be made.
In this report we continued our work after internship work from literature survey to modeling
in matlab and taking physical readings from existing wall and on wooden barrier. Then we
compared this reading with problem formulated in Matlab and with software output. Software
we used was Oliver Lab Terrain.
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5. TABLE OF CONTENTS
ABSTRACT ........................................................................................................................... 4
Problem statement and motivation ........................................................................................ 7
INTRODUCTION .................................................................................................................. 7
REVIEW OF PAST WORK.................................................................................................... 8
Conclusion from literature ............................................................................................ 12
Work done in this semester ................................................................................................. 13
Experiment work .............................................................................................................. 13
MATLAB Programming .................................................................................................... 15
MODELLING IN OLIVE LAB TERRAIN ........................................................................... 18
Comparison of results with experimental results .............................................................. 22
Future Work ........................................................................................................................ 23
References ...................................................................................................................... 23
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6. LIST OF TABLES & FIGURES
Table 1 Literature related to insertion losses in a barrier sorted based on the parameters
being varied .......................................................................................................................... 9
Figure 1 Noise barriers with various shape edges and surface conditions............................. 8
Figure 2 Schematic of the experiment performed ................................................................ 13
Figure 3 Experimental Setup for the soft ground ................................................................ 13
Figure 4 Experiment setup for hard ground ......................................................................... 14
Figure 5Definitions of symbols used to determine Fresnel Number ‘N’ ................................ 15
Figure 6Paths considered in Lam Method ........................................................................... 16
Figure 7 Flowchart of the matlab code ................................................................................ 16
Figure 8 Matlab GUI ............................................................................................................ 17
Figure 9 Comparison of insertion losses with change in height at different frequencies ...... 18
Figure 10Comparison of insertion losses with frequency variation at different heights ........ 19
Figure 11 Variation of thickness .......................................................................................... 20
Figure 12 a) single panel barrier b) double panel barrier ......................................... 20
Figure 13 IL variation in single and double panels (frequency=1000hz) .............................. 21
Figure 14 IL variation in single and double panels (frequency=2000hz) .............................. 21
Figure 15Comparision of matlab and software results with experimental results at 500 Hertz
........................................................................................................................................... 22
Figure 16Comparisonof MATLAB and software results with Experimental results at 1000
Hertz ................................................................................................................................... 22
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7. PROBLEM STATEMENT AND MOTIVATION
Specific Aim: To design an effective and cost-efficient noise barrier for the baffle range
which can reduce the unwanted noise up to the required level.
Usually firing ranges where soldiers are trained for the shooting at different conditions are
made out of the city so that there was no disturbance to the local residents. But some of the ranges are
within the residential areas where common people feel a lot of noise. So, to get the control over this
type of noise a noise barrier need to be designed around the range to reduce the noise up to a desirable
level.
INTRODUCTION
Increasing noise pollution will lead to an ever increasing need to control noise of all forms.
Noise barriers are the most common solution for controlling noise from surroundings and
several methods have been developed for improving their efficiency without increasing their
height.
Examples of already deployed noise barriers in India:
1. Noise Barriers in BKC, Mumbai (2010)
2. IIT Powai noise barrier (2012)
3. Commonwealth Games noise barrier (2010)
4. Sound barriers at Suman Nagar, Navghar flyovers (2012)
The vast majority of these have been vertical, reflective wall made of concrete, wood or steel.
The standard top for these walls is a “knife-edge”, providing a single diffraction edge with a
reflective diffraction zone.
Clearly, there are many other options for noise barrier shapes than vertical reflective walls
with knife-edge diffraction zone. In addition to it, there are option to make barriers
absorptive, to displace the diffraction zone through the use of a slanted section on top, or to
provide for a double- diffraction zone through the use of a T-top section and other modified
tops of the walls.
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8. REVIEW OF PAST WORK
During summer internship most of the literature work was performed and all the work is
presented in the tabular form in table 1 and table 2. During this time also complete study was
performed and the entire phenomenon was studied.
Different types of barrier that were studied are:
- Shaped Barrier
- Conventional Barrier
- T-shaped barrier
- Multiple Edge Barrier
- Arrow shape Barrier
Figure 1 illustrates various noise barriers obtained by varying the shape edges and surface
conditions.
FIGURE 1: NOISE BARRIERS W ITH VARIOUS SHAPE EDGES AND SURFACE CONDITIONS
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9. TABLE 1LITERATURE RELATED TO INSERTION LOSSES IN A BARRIER SORTED BASED ON
THE PARAMETERS BEING VARIED
Different
barrier Simple T-top y-top Cylindrical Wedge Multipl Angled edge
Parameter top shaped e edge
Barrier height D. C. David J.
HOTHERSA Oldham ,
LL, S. N. Christopher A.
CHANDLER Egan (2011)
-WILDE
AND M. N. P.J. Thorsson
HAJMIRZAE (2003)
(1990)
Takashi
Ishizuka*,
Kyoji
Fujiwara
(2003)
Change in David J. D J Oldham and C A Egan
source position Oldham , (2009)
Christopher A.
Egan (2011)
D. C. D. C. D. C.
HOTHERSA HOTHERSALL HOTHER
Receiver height LL, S. N. , S. N. SALL, S.
CHANDLER CHANDLER- N.
-WILDE WILDE AND CHANDL
AND M. N. M. N. ER-
HAJMIRZAE HAJMIRZAE(1 WILDE
(1990) 990) AND M.
N.
HAJMIR
ZAE(1990
)
Change in A. Muradali David J. D. C. C.A.
receiver and K. R. Oldham , HOTHER Egan, V
position Fyfe (1994) Christopher A. SALL, S. Chilekw
Egan (2011) N. a and D.
D. C. D. C. CHANDL J.
HOTHERSA Hothersall, D. ER- Oldham
LL, S. N. H. Crombie & WILDE (2006)
CHANDLER S. N. Chandler- AND M.
-WILDE Wilde N.
AND M. N. HAJMIR
HAJMIRZAE C.A. Egan, V ZAE(1990
(1990) Chilekwa and )
D. J.
Oldham(2006)
D. C.
HOTHERSALL
, S. N.
CHANDLER-
WILDE AND
M. N.
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10. HAJMIRZAE(1
990)
Width of top David J. D. H.
Oldham , Crombi
Christopher A. e, D. C.
Egan (2011) Hothers
all& S.
D. C. N.
Hothersall, D. Chandle
H. Crombie & r-Wilde
S. N. Chandler- (1994)
Wilde C.A.
Egan, V
C.A. Egan, V Chilekw
Chilekwa and a and D.
D. J. J.
Oldham(2006) Oldham
(2006)
Cap depth D. C. TomonaoO D. H.
Hothersall, D. kuboa) and Crombi
H. Crombie & Kyoji e, D. C.
S. N. Chandler- Fujiwara Hothers
Wilde all& S.
P.J. Thorsson N.
(2003) Chandle
r-Wilde
(1994)
D. C. D J Oldham and C A Egan
Angle variation HOTHER (2009)
SALL, S.
N.
CHANDL
ER-
WILDE
AND M.
N.
HAJMIR
ZAE(1990
)
D. C.
Takashi Hothersall, D. Takashi D. C. Takashi Takashi Ishizuka*, Kyoji
Comparison Ishizuka*, H. Crombie & Ishizuka*, HOTHER Ishizuka Fujiwara (2003)
with T-top Kyoji S. N. Chandler- Kyoji SALL, S. *, Kyoji
Fujiwara Wilde(1990) Fujiwara N. Fujiwar
(2003) (2003) CHANDL a (2003)
Takashi ER-
D. C. Ishizuka*, WILDE
HOTHERSA Kyoji Fujiwara AND M.
LL, S. N. (2003) N.
CHANDLER HAJMIR
-WILDE ZAE
AND M. N. (1990)
HAJMIRZA
E (1990)
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11. barrier surface David J. David J. D. C. D. H. D J Oldham and C A Egan
variation Oldham , Oldham , HOTHER Crombi (2009)
Christopher Christopher A. SALL, S. e, D. C.
A. Egan Egan (2011) N. Hothers
(2011) CHANDL all& S.
D. C. P.J. Thorsson ER- N.
HOTHERSA (2003) WILDE Chandle
LL, S. N. AND M. r-
CHANDLER N. Wilde(1
-WILDE HAJMIR 994)
AND M. N. ZAE(1990
HAJMIRZA )
E(1990)
top surface David J. D. C. D. H. D J Oldham and C A Egan
absorption Oldham , Hothersall, D. Crombi (2009)
variation Christopher A. H. Crombie & Takashi e, D. C.
Egan (2011) S. N. Chandler- Ishizuka*, Hothers
Wilde (1990) Kyoji all& S.
D. C. Fujiwara N.
Hothersall, D. (2003) Chandle
H. Crombie & r-
S. N. Chandler- Wilde(1
Wilde 994)
C.A. Egan, V C.A.
Chilekwa and Egan, V
D. J. Chilekw
Oldham(2006) a and D.
J.
D. C. Oldham
HOTHERSALL (2006)
, S. N.
CHANDLER-
WILDE AND
M. N.
HAJMIRZAE(1
990)
M.R.
Monazzam,
Y.W.
Lam(2006)
Ground surface Muradali and D. C.
variation K. R. Fyfe Hothersall, D.
(1994) H. Crombie &
S. N. Chandler-
D. C. Wilde
HOTHERSA
LL, S. N. P.J. Thorsson
CHANDLER (2003)
-WILDE
AND M. N.
HAJMIRZA
E(1990)
~ 11 ~

12. MahdiyehNader
Perforated zadeh a,⇑,
sheet on Mohammad
diffuser Reza Monazzam
b, ParvinNassiri
b,
SamanehMome
nBellahFard
(2011)
QRD on top M.R.
Monazzam,
Y.W.
Lam(2006)
MahdiyehNader
zadeh a,⇑,
Mohammad
Reza Monazzam
b, ParvinNassiri
b,
SamanehMome
nBellahFard(20
11)
Soft TomonaoO
kuboa) and
Kyoji
Fujiwara
Reflective top D. H. D J Oldham and C A
Crombi Egan(2009)
e, D. C.
Hothers
all& S.
N.
Chandle
r-
Wilde(1
994)
CONCLUSION FROM LITERATURE
Going through all the research papers and by seeing their comparative study, it was vaguely
suggested that T-type barrier having absorptive coating suits best to get maximum sound
abatement.
Since for a single barrier height/cost ration peaks at 3meter so height of T-top barrier should
be taken 3meter and width of the top can be taken as 1 meter so that aesthetically is looks
good and having maximum sound abatement.
Till internship the project was not having any practical touch and in this research paper
experiments were conducted and results was compared to get the real and practical touch
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13. WORK DONE IN THIS SEMESTER
EXPERIMENT WORK
SCHEMATIC
FIGURE 2: SCHEMATIC OF THE EXPERIMENT PERFORMED
Figure 2 shows the basic schematics of the experiments that were performed and it shows
various parameter that is involved during calculations.
EXPERIMENT ON SOFT GROUND FOR AN EXISTING WALL
FIGURE 3 : EXPERIMENTAL SETUP FOR THE SOFT GROUND
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14. Figure 3 shows the experiment that was performed on an existing wall at the fuel-zap in IIT
Ropar to get the basic insight of the insertion loss values obtained. The material of the wall is
concrete with a height of 170 cm and thickness of 22 cm. The parameters that are varied in
this experiment are frequency (varied between 100-1000Hz at an interval of 100 Hz) and
receiver distance (varied between 3-15m from the wall) while keeping all other parameters
constant. The source height and receiver height are kept in the shadow region with values of
50 cm and 100 cm respectively.
EXPERIMENT ON HARD GROUND
FIGURE 4EXPERIMENT SETUP FOR HARD GROUND
The experiment was performed on a finite barrier on hard ground to enable comparisons as
most of the analytical solutions are for hard ground. Figure 4 shows the experimental setup of
the experiment. The material of the barrier is wood with a height of 90 cm, width of 108 cm
and thickness of 2 cm. The parameters that are varied in this experiment are frequency
(varied between 100-1000Hz at an interval of 100 Hz) and receiver distance (varied between
0-16m from the barrier) while keeping all other parameters constant. The source height and
receiver height are kept in the shadow region with values of 50 cm and 83 cm respectively.
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15. MATLAB PROGRAMMING
THEORY: LAM’S METHOD USING MAEKAWA’S CURVE
Maekawa introduced an empirically based diffraction model that provides the insertion loss
due to a thin-walled barrier in terms of the Fresnel number.Maekawa then suggested that the
insertion loss for a finite-length barrier could be determined by multiple application of this
curve to the diffraction paths around the barrier and then summing the energy contributions
of these paths.
Maekawa‟s curve can be represented by the following two equations:
where N is Fresnel Number given by
Where (A+B-d) is the path difference and λ is the wavelength. The symbols are defined as
shown in the Figure 5.
FIGURE 5 DEFINITIONS OF SYMBOLS USED TO DETERMINE FRESNEL NUMBER ‘N’
Lam improved on Maekawa‟s method by summing complex pressures, instead of energies, of
each diffraction path around the barrier. This was done to incorporate the phase interaction
and interference between the paths, the absence of which, Lam suggested, was the cause of
the poor agreement between Maekawa‟s method and experimental results.
A semi-infinite barrier is equivalent to a 2D geometry. Diffraction Paths considered for a
semi-infinite thin barrier are as shown in Figure 6.
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16. FIGURE 6 PATHS CONSIDERED IN LAM METHOD
The barrier insertion loss is given by:
Mi represents the insertion loss value from Maekawa‟s curve for the ithpath. The subscript „o‟
refers to the direct path (from the source to receiver) and the subscript „r‟ refers to the ground
reflected path (from the source image to receiver).
The Lam method fell short when the receivers were in the proximity of the line-of-sight, and
when parallel geometries in 2D were considered. This is due to the fact that this method does
not predict a unique phase shift at the diffraction edge for each path.
GUI IMPLEMENTATION
FIGURE 7: FLOWCHART OF THE MATLAB CODE
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17. A MATLAB GUI has been made for calculating the insertion loss. It includes analysis for an
input data.
A GUI (graphical user interface) allows users to perform tasks interactively through controls
such as buttons and sliders. Within MATLAB®, GUI tools enable you to perform tasks such
as creating and customizing plots, fitting curves and surfaces, and analyzing and filtering
signals.
Figure 8 shows the typical GUI that was modeled in the Matlab using Lam‟s equation.
Parameters that were involved in GUI are barrier height, Source and receiver height, source
and receiver distance, and frequency of the sound.
It also shows the graphical variation of the variation in one parameter by taking 5 other
parameter constant and vary 6th one.
FIGURE 8 MATLAB GUI
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18. MODELLING IN OLIVE LAB TERRAIN
ABOUT THE SOFTWARE
THEORY
The acoustic calculations are made by the software based on Hadden& Pierce Diffraction 3D
model implemented with finite impedances faces using Salomons semi-analytical method
including ground effects. Multiple barrier diffraction is calculated in a recursive way at any
diffraction order.Ground effect is included using the One Parameter Theory of Chessell based
on Delany and Bazley.
LIMITATIONS
The thickness of the barrier cannot be reduced to a value less than 3cm. The numerical values
of the readings are available only at octave and 1/3rd octave frequencies. Any other parameter
except frequency cannot be varied in the same model.
ANALYSIS MADE
VARIATION OF HEIGHT
PARAMETERS
Barrier Material: mineral wool
Barrier type: Thin Barrier
Receiver Height= 50 cm
Source Height= 50cm
Source distance=5m
35
30
Insertion Loss(in dB)
25
20
1000 Hz
15
1995 Hz
10
3981 Hz
5
0
0 1 2 3 4 5
Barrier height(in m)
FIGURE 9: COMPARISON OF INSERTION LOSSES WITH CHANGE IN HEIGHT AT DIFFERENT
FREQUENCIES
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19. 35
30
25
Insertion Loss(in dB)
20 h=1m
h=2m
15
h=3m
10 h=4m
5
0
2 2.5 3 3.5 4
-5
log(frequency(in Hz))
FIGURE 10: COMPARISON OF INSERTION LOSSES WITH FREQUENCY VARIATION AT
DIFFERENT HEIGHTS
It can be seen that the insertion loss increases with increase of barrier height. From the figure
7, it can be seen that the variation of the insertion loss values is not much when it is changed
from a height of 3m to 4m.
VARIATION OF THICKNESS
MASS LAW
When sound is incident upon a wall or partition, some of it will be reflected and some will be
transmitted through the wall. The transmission loss obtained can be determined using mass
law at a particular frequency.
Where m=mass density and
f=frequency
PARAMETERS
Barrier Material: mineral wool
Flow resistivity=20000 Pas/m2
Barrier Height = 2m
Receiver Height= 1 m
Source Height = 1 m
Source distance=2m
~ 19 ~

20. Frequency=1500 Hz
30
25
20
Insertion Loss(in dB)
thickness_3cm
15
thickness_3.5cm
thickness_4cm
10 thickness_4.5cm
5
0
0 10 20 30 40 50 60
-5
Receiver distance (in m)
FIGURE 11 VARIATION OF THICKNESS
From figure 8 it can be clearly seen that the value of insertion loss doesn‟t vary much with
the receiver distance for thickness values greater than the optimum value calculated from the
mass law (≈2.5cm).
SINGLE VS DOUBLE PANELS
FIGURE 12 A) SINGLE PANEL BARRIER B) DOUBLE PANEL BARRIER
PARAMETERS
Barrier Material: mineral wool
Flow resistivity 20000 Pas/m2
Barrier Height 2m
Barrier Thickness 20cm single
10 cm double
Receiver Height 1m
Source Height 1m
Source distance 2m
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21. 45
Frequency = 1000 Hz
40
35
single panel
30
25
double
Insertion Loss(in dB)
20 panel_gap20cm
15 double panel_gap
30cm
10
5 double
panel_gap50cm
0
0 2 4 6 8 10 12
Receiver distance(in m)
FIGURE 13 IL VARIATION IN SINGLE AND DOUBLE PANELS (FREQUENCY=1000HZ)
45
40
35 Frequency = 2000 Hz
Insertion Loss(in dB)
30
single panel
25
double panel gap
20 20 cm
double panel_gap
15
30cm
10 double
panel_gap50cm
5
0
0 2 4 6 8 10 12
Receiver distance (in m)
FIGURE 14 IL VARIATION IN SINGLE AND DOUBLE PANELS (FREQUENCY=2000HZ)
From the figures 13 and 14 it can be clearly seen that double panel barriers are more effective
in sound reduction compared to single panel barrier and the insertion loss increases with
increase in gap between the two panels.
~ 21 ~

22. COMPARISON OF RESULTS WITH EXPERIMENTAL RESULTS
PARAMETERS
Barrier Material: wood
Barrier Height=90 cm
Barrier Width=105 cm
Barrier Thickness= 2cm
Receiver Height= 80 cm
Source Height= 50 cm
FIGURE 15 COMPARISION OF MATLAB AND SOFTWARE RESULTS WITH EXPERIMENTAL
RESULTS AT 500 HERTZ
FIGURE 16COMPARISONOF MATLAB AND SOFTWARE RESULTSWITH EXPERIMENTAL
RESULTSAT 1000 HERTZ
From the figures 15 and 16 it can be seen that the results from the software are in coherence
with those of the experimental results within acceptable error limits. It can also be seen there
is a considerable variation in the results obtained from MATLAB program, the reasons of
which can be attributed to the assumptions made in the theoretical model, where it considers
the barrier is semi-infinite with negligible thickness and which doesn‟t include the effect of
the material of the barrier.
~ 22 ~

23. FUTURE WORK
Some part of the project is completed in B.Tech-1 project which was in this semester and this
project will be continued in coming semester also as B.Tech-2 project.
The things which are planned for coming semester are:
1. In current work, Material selection for the barrier was not suggested so work will be
done in this context in the upcoming semester.
2. In current work, output from the software of single and double panels was compared
but there physical modelling was not done. It will be includedin the further studies.
3. The software which is presently used has certain limitations due to which one cannot
vary the shape of the barrier. The new software SYSNOISE, which is BEM/FEM
software, was purchased for getting more accurate results and help in physical
modelling of the system.
4. In current study the MATLAB formulations are donefor a semi-infinite, thin barrier.
In 2nd part the more focus will be made in including parameters like thickness,
finiteness, etc.
5. In our next work formation of the optimization problem will be included and will be
solved using different optimization techniques.
REFERENCES
Web site reference
1. http://sciencedirect.com/
2. http://www.acoustax.com/noise-barrier-specs.php
3. http://www.acousticalsurfaces.com/wall_barrier/wall_barrier.htm
4. http://www.nrc-cnrc.gc.ca/eng/ibp/irc/bsi/85-sound-tranmission.html
5. http://articles.timesofindia.indiatimes.com/2012-05-17/mumbai/31747986_1_noise-
barrier-noise-levels-sumaira-abdulali
6. http://www.nrc-cnrc.gc.ca/eng/ibp/irc/bsi/85-sound-tranmission.html
7. http://www.otlterrain.com/
Research Papers
[1] R.O.Feher, proc.Ann.Nat. Noise Abatement Symp.,1951,p-98
[2] A.Muradali and K.R Fyfe,A study of 2d and 3d barrier insertion loss using
improved diffraction based methods, applied acoustics,vol.53,no-1-3,pp 49-75,1998
[3] D. C. HOTHERSALL, S. N. CHANDLER-WILDE AND M. N. HAJMIRZAE,
Efficiency of Single Noise barrier, Journal of Sound and Vibration (1991) 146(2),
303-322.
~ 23 ~

24. [4] David J. Oldham , Christopher A. Egan.. A parametric investigation of the
performance of T-profiled highway noise barriers.. Applied Acoustics 72 (2011)
803–813
[5] C.A. Egan, V Chilekwa and D. J. Oldham, Top edge treatment to enhance the
performance of a noise,Acoustics Research Unit, University of LiverpoolLiverpool,
L69 3BX, United Kingdom
[6] Watts, G.R., Barrier design to reduce road traffic noise. Proceedings of the
Institution of Civil Engineers, 2002. 53(2): p. 79- 86.
[7] Takashi Ishizuka, KyojiFujiwara,Performance of noise barriers with various edge
shapes and acoustical conditions.. Applied Acoustics 65 (2004) 125–141.
[8] MahdiyehNaderzadeh, Mohammad Reza Monazzam, ParvinNassiri,
SamanehMomenBellahFard, Application of perforated sheets to improve the
efficiency of reactive profilednoise barriers, Applied Acoustics 72 (2011) 393–398.
[9] A. Muradali and K. R. Fyfe, A Study of 2D and 3D Barrier Insertion Loss using
Improved Diffraction-based Methods, Applied Acoustics, Vol. 53, No. I-3, pp. 49-
15, 1998
[10] Maekawa, Z., Noise reduction by screens. Applied Acoustics, 1968, 1, 157-
173.
[11] Pontus J. Thorsson,Combined effects of admittance optimisationon both
barrier and ground, Applied Acoustics 64 (2003) 693–711.
[12] D J Oldham and C A Egan, The development of a practical top edge device for
a noise barrier, 16th international congress on noise and vibration July 2009.
~ 24 ~