4.
1.1 ACKNOWLEDGEMENT
Multiple parties are credited for the completion of this project. It is thanks to Mr Azim Sulaiman
for providing us with the neccessary information through his tutorials that we were able to
understand what is needed for the completion of the report, as well as answering some of our
questions through tutorials. Also credited for our project completion is Ar. Edwin, who through
his lectures gave us a clear understanding on the fundamentals of acoustics design and its
related calculations. A special thanks to Ms. Premila of Nexus School for arranging with us the
date for site visit and making this possible. Coordinated teamwork and encouragement
between the group members are also crucial to the completion of the project.
1.2 AIM & OBJECTIVE
The main objective of this project is to gain a clear understanding on the application of
acoustic designs in an actual theatre/auditorium. Acoustic design is one of the
architectural and engineering techniques to control the behaviour of sound in an
enclosed space. The purpose is to improve sound distribution in the enclosed space by
enhancing the desired sound suited for the program. It is also for the purpose of us to
truly understand sound wave movement under certain conditions and the importance
of such.
1.3 SITE INFORMATION
Name of theatre: Nexus International School Theatre
Location: No. 1 Jalan Diplomatik 3/6 Presint 15,
62050 Putrajaya, Malaysia
Theatre type: Multi-purpose theatre
Total volume: 14578.15m3
Year of construction: 2008
Total seats: 580 fixed
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5.
1.4 HISTORICAL BACKGROUND
Nexus International School Malaysia established in 2008, Nexus International School is the first
international boarding school based in Putrajaya, Malaysia. A member of Taylor’s Education
Group (TEG), Neus International School has the backing of a company that offers well-known
educational excellence. Surrounded by a lush tropical environment the school is still within easy
reach of Kuala Lumpur City Centre (KLCC).
The school’s Performing Arts Department is furnished with a fully equipped theatre. Plans for
the theatre were included in the initial building design how it was kept running at an incomplete
state for a number of years whereby it was awaiting further financial requirements to advance.
An estimate of one million ringgit was allocated on the installment of sound improving
technology in the year 2017. This was followed by an estimate of two hundred thousand ringgit
for light technology, making it fully equipped. The theatre itself is suited for a mixed acoustical
purpose (Speech & Music).
1.5 PHOTOS
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9.
2.1 MEASURING INSTRUMENTS
Digital Sound Level Meter
9
The sound meter was used to measure the
sound levels at a particular point within the
theatre. The unit of measure is decibels
(dB). It is commonly in the form of a hand-
held instrument with a microphone and the
diaphragm of the microphone responds to
changes in air pressure caused by sound
waves.
Measuring Devices
Measurment tapes were used to obtain the
measurements of the theatre and to
measure the distance of the sound level
meter from the sound source when sound
levels data were taken.
Smart Phones
Individual members each had a smart
phone to capture personal photos that
mostly relates to the topic that they
previously choose to focus on.
Digital Camera
A digital camera was used to document
the existing context within our theatre and
to aid our after-visit analysis as well as
evidence of our visit to the theatre.
10.
2.2 DATA COLLECTION METHOD
To ensure that the site visit could be carried out smoothly and without problems, formal
arrangements were made with the authority in charge of the theatre to make sure that the
theatre would be unoccupied and available for us to use and conducting our analysis. We
documented as many details as possible during the site visit with the help of the
aforementioned tools along with all the neccessary measurements required to assist our
analysis.
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12.
3.1 AUDITORIUM DESIGN ANALYSIS
3.1.1 Sloped Floor
• Sloped floor design allow more direct angle of incidence which in turn allow less
absorption. It provide a proper sightline from the audience to the stage. It is very
important for public speaker as their audience grows, they will need to consider about
the visuality and hearability of the audience and sloped floor design will affect these
aspect.
3.1.2 Form And Massing
• Rectangular Shaped Auditorium
• The form of the auditorium is in a rectilinear shape with several angular and parallel at
the side of the auditorium. This results in poor acoustic design as parallel wall leads to
flatter echoes issue which consist of noticeable small echoes that will affect the quality
of auditorium. The sound will be more concentrated in the middle and the front.
Plan of the theatre
12
Slope floor allow more direct soundwave
13.
3.1.3 Ceiling
• Ceiling Reflector direct sound energy from stage to the seating area. Ceiling reflector is
exponentially important in rectangular-shaped design auditorium due to rectangular-
shaped designs usually lack reflection, where the ceiling reflector will increase early
reflections.
3.1.5 Arrangement Of Seats
• The seats in the auditorium is arranged in fan shape to ensure a maximum number of
seats are fitted and obtain an greater sightline to stage from every seat. As spherical
wavefront will be formed when sound emit from the source, this layout helps to achieve
the most effective acoustic quality as all seats fall within the angle of the existing sound
projecting area.
Diagram highlighting the position of seats in the theatre
13
Reflection of soundwave on the ceiling
14.
3.2 MATERIALS & PROPERTIES OF THE THEATRE
In Absorptive Materials there are 3 types of Sound Absorptive Materials which are fibrous, panel
resonators and volume resonators. The Absorptive Materials transform the sound energy into
heat energy when sound passes through a material or hits a surface. Commonly Fibrous and Panel
Resonators are used in buildings.
Fibrous Materials (Porous) absorbs sound energy by pumping air through the material. It uses a
frictional drag of air moving into the tiny spaces between the fibres. This is done as the cells provide
resistance to the sound waves (energy). But this absorptive material depends on its thickness,
porosity, density and air resistance to airflow. Painting cannot be used as a finish for this material as
it prevents this porosity.
Panel Resonators are built within a membrane for e.g. Thin Plywood or Linoleum in front of a sealed
airspace containing absorbent materials. They are often used when low frequency absorption is
required. Middle and high frequency absorption is unwanted or provided by another treatment.
Volume Resonators (Cavity) is an air cavity within a massive enclosure connected to the
surroundings by a narrow neck opening. The sound causes the air in the neck to vibrate and the air
mass behind causes the entire construction to resonate at a particular frequency.
Absorption is not always proportional to the thickness of the material. It depends on the type of
material and the installation method of it.
In Nexus School Theatre’s case, it uses Materials consisting of Fibrous Materiality and Panel
Resonators for acoustic treatment.
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15.
MATERIAL NOISE REDUCTION COEFFICIENT
Stage Floors
House
125 2000500Photo Material Description
CoefficientMaterials Surface
finishes
ComponentArea
Tara flex Black
rubberised
stage
flooring
Curtain Fabric Red folded
fabric
Soft
Soft
0.02 0.04 0.05
0.1 0.4 0.5
Floors Carpet Green
needle
punch carpet
Soft 0.1 0.5 0.6
Furniture Plastic Blue and
grey plastic
shells bolted
onto metal
frames
Hard 0.07 0.14 0.14
Walls 1. Cork
Panels
Cork boards
on battens
0.15 0.65 0.35Smooth
Black
ceramic tiles
cladded
2 Ceramic
Tiles
0.01 0.01 0.02Rough
Cloth panel
walls framed
3 Cloth 0.46 1.0 1.0Soft
Wall
insulation
4
Rockwool
0.15 0.9 0.9
Ceiling Timber
Panels
Timber
board on
suspended
galvanised
iron ceiling
joists and
runners
0.1 0.74 0.61
Doors
Smooth
Timber Acoustic
timber door
with steel
framing
0.35 0.44 0.54Smooth
Drapery Red folded
heavy fabric
Fabric 0.1 0.4 0.5Soft
15
17.
3.3 ACOUSTIC TREATMENT
The Nexus School Theatre is designed to suit for Mixed Acoustical Purpose (Speech and Music).
3.3.1 Stage Flooring - Tara Flex
In the past, the stage flooring was initially comprised of Timber but to improve the sound control of
the theatre, it is replaced by Tara Flex material. A soft rubberised flooring material used as a sound
and shock absorbent with a slip resistant property. The impact sounds of people walking, running
and performing on the stage will be absorbed by the material.
Drapery
The curtains are comprised of cloth materiality, which act as sound absorbers but acoustically
transparent. They are installed within the stage and 2 exitways on the door openings. They are
placed within the exits to reduce the sound energy of the stage performance from travelling
through the openings and externally. These curtains are more heavy, dense and fuzzier than
carpets. They form an air space between itself and the wall. Its folded feature provides the curtain a
larger surface area, to absorb the sound energy emitted to them.
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18.
Flooring - Carpet
The Carpet is used as a sound absorbent material for the house’s flooring. Their soft fabric is
needle punched, which creates a lot of tiny air pockets to trap air. Softening the sound impact of
people walking and absorbing the sound transmitted from the stage.
3.3.2 Walls
Cork Panels (Acoustic Panelling)
The Cork Panels are battened to the theatre’s walls above the floor level to act as Acoustic Panels.
These panels will absorb the sound energy travelled to them. Consisting of little holes, which acts
as air pockets, trapping the air within them. The sound (energy) will be dispersed from these panels.
They are also built above the floor level to prevent them from being damaged and connecting the
sound from the walls to the floor. Therefore these panels act as sound insulation to prevent the
sound from travelling through the wall by sound absorption means.
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19.
Rockwool Panels
The walls of the theatre are structurally made out of Rockwool, a mineral fibre. The Rockwool wall
consist of a sponge built between 2 wooden panels attached to a concrete slab. The spongy
mineral fibre creates a lot of tiny air pockets, which absorbs the sound energy travelled through
them. Preventing the sound from going through the walls externally. It disperses the sound energy,
giving the time for it to decay.
Fabric Walls
Cloth panels are framed and attached to certain parts of the house walls and the control room’s
interior. They act as sound absorbers to absorb the direct sound energy travelling from the stage.
The control room’s interior walls are filled with this material in order to provide the room’s privacy by
reducing the noise transmittance from the stage into the space.
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20.
3.3.3 Ceiling- Timber Panels
The ceiling panels are comprised of timber, employing the same principles as the walls as sound
travels upwards. By principles is that when sound is travelled upwards, the panels absorb the sound
and reflected them back towards the audience. It is also used for aesthetic purposes.
3.3.4 Acoustic Doors
The doors are comprised of timber panels with steel framing and double seals. Timber is used to
reflect the sound waves emitted by the stage performance. Double seals are used to seal the air
gaps of the doors to prevent the sound from travelling through these gaps.
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21.
3.4 SOUND SOURCES & PROPAGATION
3.4.1 SOUND SOURCE
Sound source are subjects producing sound waves into the environment within the range of
frequencies than can be perceived by the human ear.
Sound Source A
The sound amplification system in the theatre is the main sound source. The stage is the main
performing area where the sound is produced and transmitted towards the audience. The purpose
of this system is used to strengthen the sound level when the sound is too weak to be heard, to
provide amplified sound for overfull audience and to minimize sound reverberation.
There are total of 8 speakers hanging top of the front stage and total of 4 speakers positioned
individually on the stage area.
Position of speakers shown on plan
Position of speakers shown in photo
21
22.
Loudspeakers are adjusted and controlled through a processor in a control room located above the
audience seating. The speaker’s volume have been adjusted before performances show starts.
The top speakers produce higher volume of sound to make sure it is transmitted to the audience
seating at the back area of the theatre. The bottom speakers on front stage produce sounds of a
lower volume which directed to the audience seating in front which is located nearer to the sound
source.
Section of the functioning speakers
SPECIFICATION A
PRODUCT BRAND Yamaha CM10V
Floor Monitor
Speaker
DIMENSION ( w x h x d ) 560mm x 353mm x
277mm
FREQUENCY RANGE 71Hz – 20kHz
WEIGHT 13.3 kg
POWER RATING 125w (noise)/
250w(pgm)/
500w(peak)
PLACEMENT Floor
22
23.
SPECIFICATION B
PRODUCT BRAND Yamaha C112VA Full
Range Speaker
DIMENSION ( w x h x d
)
416mm x 620mm x
329mm
FREQUENCY RANGE 68Hz – 16kHz
WEIGHT 21.8 kg
POWER RATING 175w (noise)/
350w(pgm)/
700w(peak)
PLACEMENT Ceiling
SPECIFICATION C
PRODUCT BRAND Yamaha IF2112/64
DIMENSION ( w x h x d
)
378mm x 695mm x
454mm
FREQUENCY RANGE 55Hz – 20kHz
WEIGHT 21.8 kg
POWER RATING 300w (noise)/
700w(pgm)/
1400w(peak)
PLACEMENT Ceiling
23
24.
Sound Source B
The sound source of this is the least evident and originates from the audience themselves.
Audience’s in and out movement from the theatre, adjusting of seats and small chatters contribute
to sounds in the auditorium and can be kept minimum by announcement and reminders before
and during intermissions
Sound Source : Audience
24
25.
3.4.2 SOUND CONCENTRATION
The sound concentration zone of the auditorium can be determined through the measurement of
the sound intensity level (SIL) from the sound source. There is a distinct sound concentration at the
front & middle of the auditorium.
SIL measurement in auditorium without any sound
SIL measurement in auditorium with spotlight cooling fan on only
47dB
44dB
42dB
45dB
40dB
36dB
32dB
30dB
29dB
25dB
STAGE
25
26.
Therefore, the sound concentration zone is created through the auditorium’s diamond form. Due
to the direction of the front ceiling timber panel, this reflects the sound to the front and middle part
of the auditorium as the back ceiling timber panel has no acoustic value.
SIL measurement in auditorium with music on.
Sound Reflection Diagram. The design of the auditorium reflects the sound path towards the middle & front area
68dB
75dB
78dB
69dB
70dB
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27.
3.4.3 SOUND REFLECTION
The surface of the auditorium has been altered with the right materials to reflect and absorb the
right amount of sound reflected to the audience for the better acoustic quality.
Smooth surfaces reflects waves coherently while rough surface would reflect the waves in many
different directions. Porous surface will absorb sound waves. Timber perforated acoustics panels
are placed on the sides and back of the auditorium to absorb the sound waves. Carpet is used to
cover the floor of auditorium to help in absorbing the sound waves while preventing internal noises.
Timber panels on the ceiling of the auditorium are added to reflect the sound waves. But only the
front panels has acoustic property while the back panel does not. On the wall of the auditorium,
ceramic tiles are placed from floor to 750mm height to reflect the sound waves to audience and
preventing the sound waves to be absorbed by the carpet flooring.
Diagram of auditorium with absorbers & reflectors placing
Sound propagation at front row 2, proving sufficient sound reflected
27
28.
Sound propagation at middle row 7, proving more than sufficient sound reflected
Sound propagation at back row 13, proving lack of sound reflected
28
29.
3.4.4 SOUND ECHOES & SOUND DELAY
Echoes are the distinctive repetition of a sound. Reverb is when the reflected sound wave reaches
the audience ear in less than 0.1 seconds after original sound wave. In theatre design, the longest
acceptance delay time for speech is 40ms and a delay time of 100ms for music & performance.
Time delay = (5.6m+5.7m-4m)/0.34s
= 21.5ms
A time delay of 21.5ms towards front row 2 is acceptable for speech orientated auditorium
Time delay = (8m+5.6m-8.3m)/0.34s
= 15.6ms
A time delay of 10.6ms towards back row 13 is acceptable for speech orientated auditorium
Time delay = (11.4m+6.7m-14.5m)/0.34s
= 10.6ms
A time delay of 15.6ms towards middle row 7 is acceptable for speech orientated auditorium
In conclusion, the sound delay in the NEXUS auditorium is still within control even in different
seatings. This also shows that the auditorium is suitable for speech usage but not very good for
musical purposes. Echo is not a problem in the auditorium as it is handled properly through
certain design strategies.
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30.
3.5 NOISE INTRUSION
Sound in general can be described as a vibration that travels through a medium to a person’s ear.
However, the term ‘noise’ is often considered to be a disturbance which brings unpleasantness.
The degree of desirable depends on various qualities including the frequency, continuity, volume,
time of occurrence, place and even the personal state of mind of the listener.
3.5.1 EXTERNAL NOISES
There are multiple origins of noise at the external of Nexus International School Auditorium which
are vehicular noise along the main road, the sound produced by the opening and closing of doors,
the sound of conversation taking place outside the auditorium, potential noise from the soccer field
and also potential noise coming from the musical classrooms just outside the main entrance of the
auditorium. The noise produced from the musical classroom just outside the auditorium can enter
visa the doors. However, there is a sound lock within the inner and outer door at the main entrance
of the auditorium. This serves to trap the sound waves within the sound lock and prevent them
from interfering with the event inside, bringing the noise level from the outside down to less then
25dB for the seats nearby the door.
Besides, there is an exterior alley running along the sides of auditorium that many occupants such
as crews and price receivers used to get to the front or the back of the auditorium without creating
disturbance to the audience. However, any noise from the walkway can be heard in the auditorium
due to the lack of sound proofing on the doors and sound locks. Thus, the seats closer to the doors
are exposed to roughly 50dB of noise disturbance. Door dampers are attached on each end,
however the noise of opening and closing of the doors are not reduced because of its excessive
weight.
Sound lock within the inner and outer doors
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31.
3.5.2 INTERNAL NOISES
Not only from the external, there are also noise sources from the interior of the auditorium such as
the footsteps on carpeted floor and on the stage as well as the spotlights. The carpeted floor
reduces echo, however the noise of footsteps can not be reduced as the flooring material used is
timber. On the stage of the auditorium, which is paved with a layer of timber veneer for aesthetics,
causes incessant thudding sounds when stepped on. The air gap below its concrete platform
which is used for amplifying the subwoofers below the stage is contributing to the noise of the
footfalls. The air-conditioners in this auditorium do not produce noise. Instead, it is the Ellipsoidal
Reflector Spotlights that are producing loud noises as the spotlights are equipped with cooling fans
to prevent overheating.
Entrance to the side alleys The walkway of the side of the auditorium
Carpeted floor Tara Flex flooring stageEllipsoidal Reflector Spotlight
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33.
4.0 REVERBERATION TIME CALCULATION
Sabine Formula: RT = 0.16V/A
Where. RT: Reverberation Time (sec)
V: Volume of the room
A: Total Absorption of Room Surface
1 STAGE
Floor
A = 115.43m2
α = 0.04
Aα = 4.617m2
Curtain
A = 139.92m2
α = 0.4
Aα = 55.968m2
Note
A : Area
α : Absorption Coefficient
Aα : Absorption Surface
2 HOUSE
Floor
A = 2090.93m2
α = 0.5
Aα = 1045.465m2
Furniture
A = 1611.55m2
α = 0.14
Aα = 225.617m2
Wall
a. Cork Panel
A = 222.46m2
α = 0.65
Aα = 144.6m2
b. Rockwool
A = 111.83m2
α = 0.9
Aα = 100.647m2
Ceiling (Timber Panel)
a.
A = 1121.66m2
α = 0.74
Aα = 830.03m2
b.
A = 1121.66m2
α = 0.1
Aα = 112.17m2
Door
A = 18.6m2
α = 0.44
Aα = 8.185m2
Drapery
A = 5.04m2
α = 0.4
Aα = 2.016m2
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34.
CALCULATIONS
∑ Stage = 4.617 + 55.968
= 60.59m2
∑ House = 1045.47 + 225.62 + 144.6 + 100.65 + 830.03 + 112.17 + 8.185 + 2.016
= 2468.74m2
V = 14578.15m3
A = ∑ Stage + ∑ House
= 60.59m2 + 2468.74m2
= 2529.33m2
RT = 0.16V/A
= 0.16 (14578.15)/2529.33
= 0.92 seconds
The Nexus International School Theatre has a reverberation time of 0.92 seconds, making it more
suitable as a space for speech and lectures but making it not optimal for a music performance,
resulting in the addition of speakers to aid in that regard.
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36.
5.1 RECOMMENDATIONS
36
Maintenance
Scheduled maintenance
should be done, to fix loose
screws, greasing door hinge
and the handle to minimise
unwanted noise that would
affect of disrupt the acoustic
experience in the theatre.
Lights
Consideration to start using
less quiet fans to cool down
the lights would be a good
step towards preventing
internal noise intrusion,
especially since the lights
wo u l d b e sw i t c h e d o n
constantly.
Replacing old panels
According to the person we
interviewed, he said the old
panels loses its function
overtime and replacing it
regularly would help to
improve the acoustical issue.
Reduce absorbent
The Nexus International
School Theatre would benefit
from reducing the amount of
absorbent materials as it
would be able to increase the
reverberation time of the
theatre, making it more
s u i t a b l e f o r a m u s i c
performance.
37.
5.2 CONCLUSION
Overall, this project is an eye opener to us and it is a huge learning experience for the nine of us. It
lets us understand the performance of acoustic design is dependant on the function of the
auditorium, and utilising said design to make the users feel comfortable. The layout of the space as
well as materials of the structure such as walls, floors, chairs, curtains, ceilings etc. can affect the
acoustic inside and can even efficiently affect the sound from the outside.
Based on our analysis and calculations, Nexus Theatre has a considerably low reverberation time,
with a similarly short sound delay, making it a suitable space for giving speeches or talks, but much
less suitable for something like a musical performance, as it lacks the richness of sound for the
audience in this theatre. With that said, the speakers somewhat make up for this problem.
To conclude this case study, we very much understand about how the acoustic design such as
architectural layout and materials used can play a very large role to control the desired sound and
unwanted noise caused by various sources, and how it affects the people using the theatre. This
project has benefit us as future architects to design a more effetive and comfortable space for
people in the future, especially for something underappreciated such as acoustics.
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