Bscience project 1 (report)

SCHOOL OF ARCHITECTURE, BUILDING & DESIGN
BACHELOR OF SCIENCE (HONS) IN ARCHITECTURE
BUILDING SCIENCE (ARC 3414 / BLD 61303)
PROJECT 1:
AUDITORIUM: A CASE STUDY
ON ACOUSTIC DESIGN
KUALA LUMPUR PERFORMING ARTS CENTRE (KLPAC)
STUDENT NAME & STUDENT ID:
AFIQAH ZAHRA ZAINOL RASHID 0315857
AMEER FARHAN RAMLAN 0319304
IZZAT ABDUL MUHAYMIN 0319437
MOHAMAD HAFIZI SIDRATUL 0315470
NIK AFIQ AMADI ABDULAH 0317749
NURIN ABDULLAH 0318596
NURINA AIDA GHIZAN 0320035
TUTOR: MR AZIM SULAIMAN

TABLE OF CONTENT
1.0 INTRODUCTION
1.1 Aim & Objective
2.0 SITE INFORMATION
2.1 Site Introduction
2.2 Site Selection Reasons
2.3 Technical Drawings
3.0 ACOUSTIC PERFORMANCE
3.1 Literature Review
3.1.1 Architecture Acoustic
3.1.2 Reverberation Time (RT)
3.2 Research Methodology
3.2.1 Acoustic Measuring Equipment
3.2.1.1 Digital Sound Level Meter
3.2.1.2 Camera
3.2.1.3 Measuring Tape
3.2.2 Methodology
3.2.3 Data Collection Procedures
3.3 Case Study
3.3.1 Materials and Properties
3.3.1.1 Furniture Material
3.3.1.2 Wall Material
3.3.1.3 Ceiling Material
3.3.1.4 Floor Material
3.4 Acoustic Tabulation and Analysis
3.4.1 Sound Source
3.4.2 Sound Intrusion
3.4.3 Sound Propagation
3.4.4 Sound Diffusion
3.4.5 Sound Absorption
3.4.6 Sound Reflection
3.4.7 Sound Reverberation
4.0 CONCLUSION
5.0 REFERENCES

1.0 INTRODUCTION
1.1 Aim & Objective
The aim and objective of this assignment is for us, in a group, to have a
better understanding on how sound and architecture correlates with
each other; through acoustics; on how sounds travels and dampened;
how the shape of the theatre effects on how sound waves dissipates;
the application of materiality and how does it effects on sound.
Through what we’ve learnt, we aim to complete the task through
extensive research on sound and acoustics; gather information through
equipment, site study, and measurements; and tabulate and calculate
the said information through calculations and research.
2.0 SITE INFORMATION
2.1 Site Introduction
Building History
KLPAC began as a wood-crafting workshop back and a sawmill back in
the 1800’s, and in 1906, KLPAC became a part of Sentul Works, the
region’s most important railway depot and workshop.
In 1945, just weeks before the end of World War II, the workshops
were heavily bombed by British B-29 bombers because it was seen as
an important rail complex for the Japanese occupiers, and soon after,
the workshops were partially rebuilt but never regained their former
glory.
In the late 1960’s, the workshop was converted into a makeshift golf
clubhouse, before the YTL Group re-designated the area as a private
community park for the benefit of the residents of its condominium
blocks in the surrounding areas, thus converting the workshop into an
arts and cultural icon.
KLPAC History
In 1995, two people that established the idea of KLPAC, Faridah
Merican and Joe Hasham, worked for theatre in beneath Dataran
Merdeka, the theatre being The Actors Studio at Plaza Putra. In 2003,
flash flood occurred in Kuala Lumpur and flooded the entirety of the
Actors Studio's underground complex, destroying it. Out of this
disaster, the arts community needed a new home, thus, KLPAC was
established.

Working together, The Actors Studio, YTL Corporation and Yayasan
Budi Penyayang formed the country’s first fully-integrated arts centre.
KLPAC, a non-profit organisation, opened in May 2005.
KLPAC offers theatre shows and musicals, which are directed and
most of the tome written by their own writers. KLPAC has also played a
major role in many events, and the KLPAC academy has served more
than 1500 participants in its classes, a number which includes students
from a community outreach program to members of underprivileged
communities.
2.2 Site Selection Reasons
KLPAC is one if the fully–integrated performing art centre in Kuala
Lumpur with 7, 614sq metres of built up space, comprising of two
auditoriums. One of it called Pentas 1, consists of a 504–seat
proscenium (fixed seating), equipped with one of the best materials,
sound systems, acoustic absorption, amongst other theatres in
Malaysia. Meanwhile, another auditorium (Pentas 2) consist of a 190–
seat experimental black box theatre that allows modularity. The
indicine, a 100–seat flexing space, and 9 studios, all which allows for
various uses.
The site also has an impressive long history, and possibly being the
heart of the Malaysia’s performing arts community. KLPAC almost
always has something to offer; will it be a play, a musical,
choreographies, or a musical showcase. Amongst the large amount of
studios and theatres, KLPAC also houses cafes and restaurants, as
well as a small performing arts library, and an academy that offers
workshops and seminars for everyone.
Figure 2.0 Figure 2.1 Figure 2.2
Figure 2.0: Image of Pentas 1
Figure 2.1: Image of Pentas 2
Figure 2.2: One of the 9 studios for rehearsal purposes

2.3Technical Drawings of Auditorium 1, KLPAC
Figure 2.3: First Floor Plan of Pentas 1

Figure 2.4: Second Floor of Pentas 1

Figure 2.5: Third Floor of Pentas 1

3.0 ACOUSTIC PERFORMANCE
3.1 Literature Review
3.1.1 Architectural Acoustic
Architectural acoustic is a study of achieving good sound in a
room. Room acoustic affects on how sound behaves in an
enclosed space by controlling the sound within it as to provide
the best conditions for the production and the reception of
desired sound and to negate unwanted sound, through further
analysis of the design of acoustic space; the auditoriums in
KLPAC.
3.1.2 Reverberation
Reverberation is the collection of reflected sounds from the
surfaces in an auditorium. This phenomenon is defined as the
continuous presence of an audible sound that came from a
sound source, whether active or inactive. It is occurred by
multiple reflections between the surfaces in a room.
Observation on KLPAC auditorium was purely based on
analysing the time taken for sound pressure level to decay
affecting the acoustical quality of the enclosure, which is also
known as Reverberation time.
Reverberation time of an auditorium can be calculated
dependently on the design of the auditorium – volume of the
enclosure, total surface area and material absorptions.
The formula of reverberation time is as follow:
RT – Reverberation time (sec)
V – Volume of the room (cu.m)
A – Total absorption of room surfaces (sq.m sabins)
x – Absorption coefficient of air
RT = 0.16V
A

3.2 Research Methodology
3.2.1.1 Digital Sound Level Meter
Figure 3.0: Image of Digital Sound Level Meter
By using a digital sound level meter, we were able to detect any
sound leakages due to external noises, or amenities that might
produce sound indirectly, such as air conditioning units,
ventilations, or generators.
3.2.1.2 Camera
Figure 3.1: Image of a camera
Cameras were used to take pictures of the theatres, seat
arrangements, materiality, stage equipment. The pictures then
were used as a method of documentation and proof.

3.2.1.3 Measuring Tape
Figure 3.2: Image of measuring tape
Measuring tapes were used to measure certain dimensions the
stage, the distance between seating, the distance between one
object to another.
3.2.2 Methodology
In Pentas 1, we measured the acoustics of the auditorium using a
digital sound level meter to identify sound leaks due to external
noises, and amenities such as vents and air conditioning.
Pictures of them were taken with cameras for us for identification,
research purposes, and proof. Measuring tapes were also used to
measure dimensions and distance between objects.
3.2.3 Data Collection Procedure
Before gaining access to KLPAC’s Pentas 1, we were required to
send an application email to the person in charge of the staging
to allow us to be able to do research. After the confirmation, we
were given an allotted time slot to avoid interference during
performance/set–up. In KLPAC, we were required to attend a
brief tour around the building for us to get a better understanding
on how the acoustics of KLPAC works, and learn on the
equipment and materials it took to make it all work. We were
given a brief time frame to take pictures and to measure the
sound level using the digital sound level meter to record in the
acoustics, and the measuring tape to measure in the dimensions.
We were given plans, elevations, and sections of Pentas 1
through email for us to get a better understanding of the stage
through drawings.

3.3 CASE STUDY OF KPLAC AUDITORIUM – PENTAS 1
3.3.1 KLPAC Auditorium – Pentas 1
In this case study, the focus of architectural acoustic is Pentas
1, a rectangular shaped, or a ‘shoe-box’–shaped auditorium with
mixed acoustics. There were certain compromises that had to
be made in designing the Pentas 1, as it was made for various
purposes – such as for speech and music. The volume of
Pentas 1 is roughly 8020m3,
which plays a significant role in
acoustical qualities. Further analysis will explain the material
usages in Pentas 1, which affects the acoustical phenomenon –
sound diffusion, sound diffraction and reverberation.
Figure 3.3: 3D Images of perspectives view of Pentas 1

3.3.2 Material and Properties
3.3.2.1 Furniture Material
Audience Seat

Figure 3.4: Image of the audience seat in Pentas 1

Chairs causes a great impact on the acoustics of the hall.
Sound-absorbing properties of armchairs and chairs, as well as
the audience are very important factors that have a huge
influence on the acoustic conditions of concert, theatre and
congress halls. In rooms with properly designed acoustics,
reverberation time is always the key; therefore, it is necessary to
determine exactly what this is. It is highly important to precisely
define the sound absorption coefficients for armchairs and
chairs.
The arrangement of armchairs, their shape and density of the
materials used should ensure the orchestra is always able to
hear itself in the same way, regardless of whether the hall is full
or not during recording. Perfection is when the level of acoustic
absorption with empty seats is close to that with a seated
audience, meaning that a full or empty hall always has the same
acoustic climate.
The sitting at KLPAC comprises of flip-up seats covered with
different solid colors fabric to absorb the echo of the sound. This
sound absorbing acoustical fabric is used to eliminate sound
reflections to improve speech intelligibility, reduce standing
waves and prevent comb filtering. This material can be varied in
thickness and in shape to achieve different absorption ratings
depending on the specific sound requirements.

Stage Chairs

Figure 3.5: Image of stage chairs in Pentas 1

Beneficially, a reflective front stage area provide strong early
reflections that are integrated with the direct sound and enhance
it. On the contrary, strong late reflections and reverberation,
such as from rear walls, would not integrate and may produce
echoes. To accommodate this, the stage area and front of the
hall are made reflective and absorption is placed in the seating
area and rear of the hall.
The furniture that they used at the stage are basically plastic
metal chairs. Plastic and metal are both reflective materials.
During the perfomance, the sound that produces at the stage
will not absorbed by the chairs, but it will be reflected by it.
Another main reason is because, plastic metal chairs can be
moved. So, the chairs can be rearranged into different positions
based on the situation.

Black Curtains

Figure 3.6: Image of black curtains at Pentas 1
Black curtains (black drapery, black masking or blacks), are a
staple of theatres. When used for blackout curtains, legs,
borders, tabs, black box theatres, or arena reduction curtains,
the intent is to absorb light and hide objects. Black curtains
provide designers an environment within which there are no
distracting elements, other than the show itself. Black masking
fabrics all have a matte finish so they won’t reflect light.
Sound absorption curtains won’t be able to significantly reduce
noise transmission between two adjacent spaces; they are
rather designed to improve sound quality and reduce
reverberation levels within the room that they are installed.
The acoustic curtain material at KLPAC are thick. Since we
know mass is the critical factor in absorbing sound, so the
thicker the absorption material, the more effective it will be
against a longer wavelength (lower frequency) of sound.
The curtains at KLPAC are pleated to improve the low and mid
frequency sound absorption performance of their acoustical
curtain. This will cause the fabric to be “gathered,” such that it
loops in and out (i.e. does not lay flat). To expose more sound-
absorbing surface, the pleating is as deep as possible thus
increasing effective thickness and improving low frequency
sound attenuation.
The drapery at KLPAC is spaced several inches from the wall,
so it will become more effective at absorbing longer sound
wavelengths (lower pitches). Up to a point, the deeper the
spacing, the more improvement to low frequency absorption.
The means and mechanism of mounting will not affect
acoustical performance but does determine how easy it will be
to open and close the drapery.

3.3.2.2 Wall Material
Figure 3.7: Image of concrete well
For the wall material, the walls of the auditorium are
made up of concrete, with the reason that they used
concrete is because concrete absorbs sound. A good
soundproofing wall relates to the overall ability of it to
reduce the sound transmission through it. The sound
absorption for plain cast concrete is about 0.02, indicating
that about 98% of the sound energy is reflected by the
surface. The more the concrete weighs or the denser the
concrete, the greater the sound transmission loss so the
thick concrete walls of the auditorium are really capable
of soundproofing.

Figure 3.8 (left): Indication of the black acoustic panels
Figure 3.9 (right): Image of black acoustic panel

For the wall material, the walls at the front and the back of the
auditorium are made up of acoustic wall panels from bottom to
top. Specifically, they are black fabric wrapped panels. These
wall panels are soundproofing material that prevents sound from
travelling. It blocks sound from leaving or entering the
auditorium.
On the other hand, it also enhances the space’s sound quality,
which is very suitable for auditoriums as sound quality is one of
the important factors for shows. Acoustic sound panels utilize a
rigid, high-density 6-7 PCF glass fiber with an acoustically fabric
material for maximum absorption. Sound absorption is the
process by which sound waves are taken in or soaked up by soft
surfaces. They are intended to absorb unwanted noise like echo
within a space. So, it reduces the sound disturbance that would
occur during the shows. The echoes will not disturb the
audiences and intense built up of muddied sound. Furthermore,
these panels install easily on the walls, saving up to 50% time
and money on installation and since this auditorium is a low cost
building, using acoustic wall panels can help to create an
adequate acoustic auditorium environment at a reasonable cost.

Other advantages of acoustical wall fabric are that it is a
dimensional fabric that offers excellent acoustical properties,
unmatched fade resistance and a fire retardant class with a
class-A rating. It is also resistant to moisture, mildew, and rot,
bacteria and is non-allergenic so it would last for a really long
time. The wall panels are black in color to increase the quality of
lighting effects.
Figure 3.10 (left): Indication of concrete blocks and PVC tubes
Figure 3.11 (right): Images of concrete blocks and PVC tubes
While the walls on the side of the auditorium are made up of
concrete, recyclable raw materials are used as finishes. This is
the most interesting part of the auditorium since the auditorium
holds a very strong concept on sustainability. On the right wall,
not only the materials are recyclable, they are actually bits and
pieces from the history of the site, which was founded from
World War II. Their intention was to preserve the history of the
building by reusing whatever that was left. It is also one of the
efforts of building a low cost auditorium. The leftover historic
materials that they used were roof zinc and concrete blocks
while on the left wall were PVC tubes that go up to the ceiling.
These materials actually help in reflecting the sound and adding
on to the aesthetic values of the auditorium as well.
At the area of the stage, there are partition walls that are non-
fixed and are arranged according to different set ups of the
stage. The partition walls are fabric wrapped as well to maximize
sound absorption.

3.3.2.3 Ceiling Material
Figure 3.12 (left): The black fabric ceiling cloud with PVC tubes
Figure 3.13 (right): A clear diagram of the black fabric ceiling
cloud
For the ceiling of the auditorium, it uses black fabric wrapped
acoustical ceiling clouds. These ceiling clouds absorb noise and
block sound transmission. They offer outstanding control across
all frequencies as well as outstanding design flexibility. They
also solve challenging acoustical problems to aid in improving
sound quality and occupant’s enjoyment. They are unique in
combining noise and reverberation reduction with architectural
effects to add visual beauty and interest to its space. Besides
than that, they are easy to install and are low cost as well which
serves the concept. The PVC tubes on the walls actually extend
up to the ceiling, which helps to reflect the sound, and as well as
for aesthetic reasons.

3.3.2.4 Floor Material
Stage Floor

Figure 3.14: Image of the stage floor of Pentas 1

Pentas 1 uses epoxy concrete coating floor, with the intention of
creating a monolithic and exceptionally easy to clean. Being
among the most used of all surfaces, Pentas 1 stage floors
require the best in durability, impact and abrasion resistance,
easy low cost maintenance and slip-resistance, in order to
produce the best sound quality for the audience, as well as
provide the best sound quality for the musicians when
performing. Besides, Pentas 1 flooring systems also have the
beauty and high performance selection that meets exacting
requirements.

Auditorium Floor
Figure 3.15: Image of the auditorium floor of Pentas 1
The material used in the flooring of auditorium is woolen carpet
as it is a very good absorptive material made of 80% wool and
20% nylon. The floor had a black finishes to absorb the light so it
will not disturbing the performer when they perform the shows.
There are several reasons of the usage of woolen carpet in this
auditorium. Firstly, it provides quality as woolen carpet is
carefully tested for its performance, consistency, performance,
and overall adherence to strict product specifications. In terms of
comfort, woolen carpet is a naturally lustered fiber that is
appealing to the eye and allows for a soft and comfortable
appearance on the floor, as well as provides a warm and
comfortable environment for the audience. Other than that,
woolen carpet’s natural luster and gentle light reflection
characteristics give Pentas 1 an elegant and peaceful
background. Last but not least, Pentas 1 promises audiences’
safety. So, the usage of woolen carpet is essential as it is
naturally flame resistant and does not come in contact with fire.
It has the ability to self extinguish itself.
Woolen carpet is the antithesis of hard, echoing surfaces. Sound
waves are effectively absorbed and deflected by the carpet and
by the padding under the carpet, and the level of sound
absorption can be enhanced with a thicker pad.

3.4 Acoustic Analysis
3.4.1 Sound Source

Figure 3.16: Identification of sound sources found in Pentas 1

INDICATION SOUND SOURCE SPECIFICATION
Speaker/Microphone Product name
Power Handling
Frequencies
Response
Input
Configuration
Sound Pressure
Level
Placement
Meyer Sound
UPJ-1P
Meyer Sound
UPM-1P
Meyer Sound
UMS-1P
Meyer Sound
UPA-1P
50-100W
65Hz-20kHz
70v – 100v
35-45dB
Wall / Ceiling
Electric Appliances Product name
Power Handling
Frequencies
Response
Sound Pressure
Level
Placement
Fresnel
3.3kW
200Hz
30 – 40 dB
Ceiling

Figure 3.17: Table of sound source and its specification

3.4.2 Sound Intrusion
Pentas 1 is designed in a way that sound insulates and
mechanical noise control are fixed at certain area to negate
background noise, such as heavy rain. Thus, rain noise isolation
is also fixed in to achieve speech intelligibility within an enclosed
environment without sound amplification, relying only on natural
sound for propagation.
3.4.3 Sound Propagation
When sound is released from a source point, it propagates
outwards in a spherical wave front and the sound waves can be
reflected, refracted, diffracted or attenuated by the medium it
hits. As an architect, it is important to take into account the
design and materiality used to achieve the perfect acoustics.
Figure 3.18: Propagation of sound in the air
Air is the most common medium through which air travels. When
a vibrating object moves forward, it pushes and compresses the
air in front of it and forming a region of high pressure called
compression, which moves away from the vibrating object
whereas when the object moves backwards, it creates a region
of low pressure called rarefaction. As the object moves to and
fro rapidly, it produces a series of compressions and
rarefactions in the air, which makes the sound to propagate in
the medium.
There are a few acoustical phenomena that can be found in
KLPAC, which are:-
• Sound diffusion
• Sound absorption
• Sound reflection

3.4.4 Sound Diffusion
When sound bounces off a hard flat surface, it will be scattered
and the energy remains very much intact resulting in discrete
echoes. These echoes will produce destructive effects such as
comb filtering; flutter echoes and standing waves, which disrupt
the quality of speech intelligibility and music clarity.
Figure 3.19: Sound diffusers can be seen on the both sides of
the walls of Pentas 1, KLPAC by using DIY items such as PVC
pipes and white boxes.
From Figure 3.18, KLPAC installed a very unique piece that not
only for aesthetics, but it is also used as sound diffuser panels.
The uneven surfaces of the walls will not absorb the sound.
Instead, it will preserve the energy by dispersing them across
the room thus making it livelier.
Figure 3.20: Due to the uneven and hard surfaces, sound
energy is dispersed, instead of being absorbed.

3.4.5 Sound Absorption
Sound absorption refers to the process by which a structure,
material or object takes in sound energy when sound waves are
encountered, as contradicting to reflecting the energy. Part of
the absorbed energy is transformed into heat energy and part is
transmitted through the absorbing body. Soft, porous materials
such as acoustic fabric panels, foam chairs are used to
absorbed sound energy.
Figure 3.20 Figure3.21
Figure 3.21: Shows the absorption characteristics of a foam used
Figure 3.21: Table of material absorption coefficient

3.4.6 Sound Reflection

Figure 3.22: Shows the reflection of sound versus direct sound
The reflection of sound follows the law "angle of incidence
equals angle of reflection", sometimes called the law of
reflection. The same behavior is observed with light and other
waves, and by the bounce of a billiard ball off the bank of a
table. Hard surfaces such as concrete walls, floorings and cloud
acoustic panels are used to reflect direct sound thus dispersing
the sound equally in the auditorium.

3.4.7 Sound Reverberation
Reverberation is defined as the prolongation of the reflected
sound. When a sound ceases in space, the sound wave will
continue to be reflected to hard surfaces until it loses enough
energy and dies out. Reverberation Time (RT) is the number of
seconds it takes for the reverberant sound energy to die down to
60dB of its original value from the instant of the sound signal
stops. Sound reverberation depends only on the volume of the
space and acoustically absorptive quality of the room’s finishes.
Figure 3.23: Certain materials play a very important role
in the acoustics architecture.

Calculation of reverberation time:
Surface Material Area (m²) Absorption
(500Hz)
Abs. Unit (m²)
Wall Acoustic fabric
panels
161 0.44 70.84
Wall Concrete with
zinc
135 0.02 2.7
Wall Concrete with
PVC
135 0.02 2.7
Ceiling Concrete with
fabric clouds
802 0.02 16.04
Floor Concrete with
epoxy coating
802 0.02 16.04
Occupants - 506 0.46 232.76
Total Absorption (A) 341.08
Figure 3.24: KLPAC’s Pentas 1 total absorption of sound
Figure 3.25: Reverberation time (RT) calculation in
seconds at 500Hz
From the calculation above, Kuala Lumpur Performing Art Center’s
(KLPAC) Pentas 1 has an above average reverberation time by 3.76
seconds because of the usage of various materials, which is quite high
compared to other auditoriums and could produce echoes. Materials
such as roof zincs and PVC pipes were used as a decorative purpose
on the walls of the auditorium which affects the reverberation because
they have hard surfaces that reflects the sound waves instead of
absorbing them. Softer materials like acoustic fabric panels; fabric
cloud ceilings and woolen carpets are a good example of better
acoustics absorptive fabrics to reduce the sound reverberation of the
auditorium.
𝑅𝑇 =
0.16𝑉
𝐴
𝑅𝑇 =
0.16 × 8020
341.08
𝑹𝑻 = 𝟑. 𝟕𝟔𝒔

4.0 CONCLUSION
As a conclusion for the research, we’ve learnt that KLPAC has an above
average reverberation time, which is quite high compared to other echo-
producing auditoriums, and offers a fully–integrated performing art centre,
equipped with one of the best materials, sound systems, acoustic
absorption, amongst other theatres in Malaysia, along with an impressive
long history, and the significance of being the heart of the Malaysia’s
performing arts community, KLPAC almost always has something to offer.

5.0 REFERENCE
1. Absorption Data. (2017). Retrieved 28 April 2017, from
http://www.acoustic.ua/st/web_absorption_data_eng.pdf

2. McMullan, R. (2017). Environmental Science in Building (7th ed.).
Basingstoke: Palgrave.

3. Reflected Sound - Reverberation. (2017). Acoustical Surfaces. Retrieved
28 April 2017, from
https://www.acousticalsurfaces.com/acoustic_IOI/reverberation.htm

4. Grondzik, W.T. & Kwok, A.G (2015). Mechanical and Electrical Equipment
for Buildings. New Jersey: John Wiley & Sons

5. www.ideo.pl, i. (2017). Seating systems, stadium seats, arena seating -
Forum Seating / News / 2015 / Acoustics as important as ergonomics.
[online] Forumseating.com. Available at:
http://www.forumseating.com/news/a2015/art,164,acoustics-as-
important-as-ergonomics.html [Accessed 1 May 2017].

6. mominzaki (2017). Auditorium Acoustics. [online] Slideshare.net.
Available at: https://www.slideshare.net/mominzaki/auditorium-
acoustics-33230112 [Accessed 1 May 2017].

7. Rosebrand.com. (2017). Black Curtains (Black Masking) from Rose Brand.
[online] Available at: http://www.rosebrand.com/subcategory471/black-
curtains-masking.aspx) (http://acousticsfreq.com/sound-control-
acoustic-curtain/ [Accessed 1 May 2017].

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