A Case Study On Room Acoustic

BUILDING SCIENCE II [ARC3413/BLD60803]
PROJECT 1:
AUDITORIUM:
A CASE STUDY ON ROOM ACOUSTICS
Clara Lee Pei Lin
Joy Ann Lim Ee Hsien
Kalvin Bong Jia Ying
Kennett Lim Rong Xiang
Shazleen Shafiqah
Wong Teck Poh
Yee Mae Yuen
Ar. Edwin Chan
Dr. Sujatavani Gunasagaran
0324495
0327592
0327822
0325031
0324367
0327462
0328561
EXPERIMENTALTHEATRE
UniversityMalaya
E.T.

EXPERIMENTALTHEATRE
TableofContents
E.T.
1.0
1.1
1.2
1.3
1.4
2.0
2.1
2.2
3.0
3.1
3.2
3.3
3.4
3.5
3.6
3.7
4.0
4.1
4.2
5.0
5.1
5.2
6.0
03
06
10
72
79
84
Introduction
General Information
Brief Introduction
History of E.T., UM
Context and Location
Methodology
Introduction
Measuring and Recording Equipment
Acoustical Analysis
Auditorium Design
Leveling and Arrangement of Seats and Stage
Sound Reinforcement
Acoustical Treatment and Components
Sound Propagation
Sound Defect
Noise Intrusion
Reverberation Time
Introduction
Reverberation Time Calculation
Conclusion
Experimental Theatre, University Malaya
Design Considerations and Suggestions
References

EXPERIMENTALTHEATRE
Introduction
1.0

Name of Auditorium : Experimental Theatre, University of Malaya
Address : 825, Lingkungan Budi, 50603 Kuala Lumpur, Wilayah Persekutuan
Kuala Lumpur
Type of Auditorium : Performing Arts Theatre
Year of Construction : 1965
Year of Completion : 1966
Volume : 5621 m³
Capacity : 435 pax
1.1 General Information
INTRODUCTION
1.0
Figure 1.1 : Experimental Theatre, University Malaya
03

1.2 Brief Introduction
04
The Experimental Theatre of University Malaya (E.T.) is a performing art theatre which is
suitable for stage performances and also conferences, seminars, presentations and product
launches. Even though located in a university campus, it holds events from outside parties as it
is available for rental for private and corporate functions.
Its present layout of the theatre is influenced by Richard Wagner’s original concept of
incorporating modern innovations and systems. The auditorium features tiered stalls and a
gallery. A proscenium stage with a ramp leading to basement rooms that serve as a green
room (waiting room or touch-up lounge for performers) is one of the present features of the
theatre. The front of the stage has a hydraulic platform which provides an extension when
raised and provides a space for an orchestra pit when lowered. Above the stage are gridded
structures and rigging to support the sound and lighting systems.
Figure 1.2: Interior of Experimental Theatre.

05
1.3 History of Experimental Theatre
Constructed together with the well known Dewan Tunku Canselor in 1965, University Malaya’s
Experimental Theatre was designed with heavy inspirations of Brutalist Architecture and
Modernism movement. It was designed by Dato’ Kington Loo of BEP Architects and constructed
using mainly bare concrete. It was declared a National Heritage Site in 2009 along with its
sister buildings, Dewan Tunku Canselor and the Chancellery. Restoration works commenced
on October 2009 and it was reopened to the public in 2011.
1.4 Context and Location
The Experimental Theatre (E.T.) is located within the campus of University Malaya, Kuala
Lumpur. It is located next to other university facilities such as Dewan Tunku Canselor (DTC),
The Cube Cultural Centre, and research centres. It is also surrounded by vegetation and it is
near an access road and some car parks.
Figure 1.3: Renovation works began in October
2009.
Figure 1.4: Site context of Experimental Theatre.
Figure 1.4: A new look of the theatre in March
2011.
Experimental Theatre
DTC
THE
CUBE

EXPERIMENTALTHEATRE
Methodology
2.0

2.1 Data Collection Method
Prior to site visit, we obtained the tools mention below for measuring dimensions of the theatre
and for measuring the sound intensity levels. Arrangements were made with the university’s staff to
ensure an unoccupied theatre for accurate measurements. During site visit, architectural drawings
were printed out and sketched on-site to record data and diagrams. The data collected are then
analysed of its acoustic properties.
2.2 Measuring and Recording Equipment
2.2.1 Digital Sound Meter
METHODOLOGY
2.0
Digital sound meter was used for acoustic measurement within the auditorium. The acoustic
unit of measurement is in db short for decibels. It was used to measure sound intensity levels
at various locations within the auditorium to determine the sound concentration and also the
background noise levels.
Figure 2.1. : Digital Sound Meter
06

2.2.2 Digital Single-Lens Reflex Camera (DSLR)
2.2.3 Smartphone
07
The DSLR camera was used to capture photographs of the building materials and the condition
of the auditorium for recording and analysis purposes.
Smartphones were also used as another alternative of capturing photographs of the auditorium
and its construction material. It is also used to operate a consistent single frequency sound
on the stage for readings of the sound meter to be taken at various different points of the
auditorium.
Figure 2.2: Digital Single-Lens Reflex Camera
Figure 2.3: Smartphone

2.2.4 Measuring Tape
2.2.5 Laser Distance Meter
08
The measuring tape was used to carry out the measurements of the auditorium for drawing
purposes. It was also used to measure the distance from the position of sound meter readings
taken to the stage. The measuring tape is mostly used to measure reachable areas.
The laser measuring tool was used to also measure distances in the auditorium but mainly for
distances beyond 5m due to the limitation of the measuring tape and also areas which are
hard of reach such as the height of ceiling. It is also used to determine the angle of the ceiling
of the auditorium.
Figure 2.4: Measuring tape
Figure 2.5: Laser distance meter

EXPERIMENTALTHEATRE
AcousticalAnalysis
3.0

3.1 Auditorium Design
3.1.1 Architectural Drawings and Photos
ACOUSTICAL ANALYSIS
3.0
09
Entrance (University Students) Performance Stage Ramp (Towards Basement)
VIP Entrance HallwayBack StageMale & Female Toilet

Lift Lobby (Entrance) Backstage Control Room Staircase
(From VIP Entrance Hallway)BalconyMale & Female Toilet
10

11
Back Stage House
BasementBalcony
Performance Stage House Backstage Control Room
VIP Entrance HallwayOrchestra PitBasement

Figure 3.1: Viewing from the stage, the
experimental theatre depicts a sense of grace and
classical elegance through warm ambience tone of
light.
Figure 3.3: The opening curtains disclosed a
performance stage deeply recessed into the wall,
giving a sense of depth in terms of visual distance.
Figure 3.2: Viewing from the balcony, the interior
wall of the theatre hall is cladded with rich plywood
to evoke a natural sense of touch and pleasant.
Figure 3.4: Opening curtains and stage effects
control panels are located at the side of the stage,
easing the backstage crews in controlling anytime.
12

Figure 3.5: Behind the balcony seatings sits a
backstage control room.
Figure 3.7: A hidden ramp that slowly leads people
down the stage to the backstage preparation area,
giving a sense of mystery and curiosity.
Figure 3.6: The backstage control room at the
balcony also serves as backstage equipment storage
room.
Figure 3.8: Below the stage, where all the
performers are getting ready or taking rest here.
13

Absorbant surfaces
3.1.2 Shape and Form of Auditorium
The auditorium is designed in a mixture of rectangular (or shoe box) and fan shapes. This
traditional shoe box form allows both side reflections and receives strong component of direct
sound whereas the concave surfaces of the hall serve to concentrate sound energy to the centre
of the space. However, the suitable position for optimum concentration of sound is still at the
centre of the theatre.
Reflective surfaces Absorbant surfaces Concentration of sound
14
Figure 3.10: The highlighted area is the best spot for optimum concentration of sound.
Figure 3.9: The form of the auditorium is mainly composed of fan and shoe box
shape.
Rectangular Fan shape

3.2 Levelling and Arrangement of Seats and Stage
The arrangement of the seats in the auditorium is arranged in concentric arc of circle efficiently
for sound range to be optimally reached at every angle. The auditorium seats are placed
within 140 degrees of sound projection which results in high recurrence sound projected. The
distance between sound source from the stage and the last row of the seats is within 22.5m
which is an ideal range for human voices to be heard clearly.
Each seats are also leveled in staggered position to allow direct sound to be received without
obstruction from absorbers and provide assurance of unobstructed views. However, there are
three-four rows of seats covered by the deep overhanging balcony which experience sound
shadow, an occurrence when sound doesn’t reach as effective as it should.
15
Sound shadow area
Figure 3.12: Sound projected through elevated seats and sound shadow area.
Figure 3.11: Seat arrangement in a concentric arc of circle.
130º

3.3 Sound Reinforcement
3.3.1 Introduction
The span of the theatre from the centre of the stage till the edge of theatre is approximately
18m long. The distance for an auditorium to function without sound reinforcement is around
15m thus this Experimental Theatre is needed to be equipped with sound reinforcement to help
deliver and amplify the sound from the performers or speaker on stage. The sound system
components present in the auditorium are:
• Line array
• Subwoofers
• Stage Monitors
• Two way wall speaker
3.3.2 System Components
3.3.2.1 Line Array
The Experimental Theater uses two main line arrays suspended from the ceiling on the left side
and right sides of the auditorium. Each has two identical speakers mounted vertically on each
other and has a retractable mechanism which allows for the height to be adjusted.
A vertical line array displays a normally wide horizontal pattern useful for supplying sound to
the majority of the audience. This type of speakers are used as it can amplify sound across a
longer distance. It also helps to reduces sound sent to the ceiling which reduces the unwanted
reflections bouncing back to the audience.
Its position on both sides of the hall allows for a balanced sound propagation on both sides
however, it allows for a higher concentration of sound towards the centre of the auditorium.
Figure 3.13: Line array speaker suspended from ceiling.
16

17
Figure 3.14: Position of line array speakers on plan.
Figure 3.15: Height of line array speakers on section.
6375mm

3.3.2.2 Subwoofer
There are two subwoofers located at each side on the stage dedicated to reinforce low pitched
audio frequencies such as bass and sub-bass from 20Hz to 80 Hz. Unlike the line array
speakers, the subwoofers come in single units as lower frequencies have slower attenuation
and can travel to the audience easier.
Again the subwoofers are positioned on both sides to achieve a wider and equal sound
distribution. The subwoofers are placed at the corners of the stage against the wall because it
helps to increase the bass output.
Figure 3.16: Subwoofer placed on stage.
Figure 3.17: Position of subwoofer speakers on plan.
18

3.3.2.3 Stage Monitor
Equipped at the front of the stage are four stage monitors that are used to amplify the sounds
of the performance and direct it back to the performers on stage to assist them in hearing their
own vocals or instruments.
The monitors also known as a foldback system are needed to prevent the performers on stage
to hear reverberated reflections bouncing from the rear wall of the auditorium which will be
delayed and distorted thus affecting their performance.
Due to the auditorium having a larger stage with great depth of 14 meters, the side of the stage
is also equipped with another stage monitor, one on each side to ensure a wider coverage at
the sides of the stage for the performers on stage. These stage monitors is mounted on the wall
rather than being placed on the ground to help distribute the sound over the large volume of
the backstage.
Figure 3.20: Position of stage monitors speakers on plan.
19
Figure 3.18: Stage monitor facing the stage. Figure 3.19: Stage monitor at the side of stage.

3.3.2.4 Two-way Wall Speaker
For the audience seated at the back of the auditorium beneath the gallery, the sound quality
and concentration might be affected due to the distance and the gallery above. Hence, sound
reinforcement is required and is placed at the low ceiling of the last third row. There are four
evenly spread two-way wall speakers fixed to the ceiling to help amplify the sound from the
stage with clarity and without any significant delay.
Figure 3.21: Two-way wall speaker attached to ceiling.
Figure 3.22: Position of two-way wall speakers on plan.
20

3.3.3 Advantages and Disadvantages of Sound Reinforcement in E.T
Advantages
• Speakers and microphones help to reinforce and amplify sound intensity across a longer
distance and a wider coverage.
• Sound reinforcement system is used to enhance or alter the sound of the sources on the
stage, such as controlling the sound reverberation time.
• Speakers such as vertical line arrays reduces sound sent to the ceiling which reduces the
unwanted reflections bouncing back to the audience.
• Sound reinforcement systems can cut through background noise produced such as traffic
from outside or mechanical services.
• Sound reinforcement systems can also help control the tone and frequencies of the sound
from the stage depending on the desired sound of the performance.
Disadvantages
• Due to the position of most of the speakers being placed at the left and right side of the
auditorium, there can be still unbalanced sound distribution in the middle of the auditorium.
• The audience might hear the original sound from the stage and the sound reproduce from
the speakers at two separate times. The ideal difference should not be more than 1/30
second.
• Technical issues or malfunctioning of systems will cause a disturbance in the sound
distribution and quality.
• If there is not enough height of the line array speakers, vertical pattern control can be lost,
allowing low and mid frequencies to project to the ceiling and stage, causing unwanted
reflections.
• The placement of the subwoofers leaning against the wall will help increase the bass boost
but might not be ideal as the bass sound quality is not the best. The ideal position should
be 8 to 12 inches away from the wall.
• Feedback sounds may be a noise source and cause disturbance during the performances
on stage.
21

3.4 Acoustical Treatment and Components
3.4.1 Materials tabulation of Experimental Theatre, University Malaya
22
Location Component Material Description Finishes Absorption Coefficient
125Hz 500Hz 2000Hz
Stage
Walls
Brick
Brick wall
plastered on
both sides
Emulsion
paint, white
0.05 0.02 0.05
Velour
Velour
acoustic
curtain
NIL 0.05 0.40 0.60
Timber
H.W. timber
panels
(12mm thk.
plywood
panels)
NIL 0.18 0.42 0.83
Floors
Concrete
Cement
render
Polished 0.02 0.02 0.05
Timber
Timber
parquet
Varnish 0.02 0.20 0.10
Apron
Aluminium
Aluminium
grill skirting
Antique
copper,
gold faux
texture
- - -
Timber
Hardwood
timber
parquet
Varnish 0.20 0.10 0.05
Marmoleum
Vinyl
Vinyl sheet
covered over
H.W. timber
on concrete
floor
NIL 0.02 0.04 0.05
Stage
curtain
Velour
Velour
acoustic
curtain
NIL 0.05 0.40 0.60
Table 3.1: Table shows the documented materials of E.T.

Location Component Material Description Finishes Absorption Coefficient
125Hz 500Hz 2000Hz
House
Walls
Timber
12mm thk.
plywood
acoustic
timber panel
NIL 0.18 0.42 0.83
Gypsum
2 layers
of 15mm
gypsum
board on
steel studs
with 150mm
air gap filled
with 50mm
rockwool
Emulsion
paint, white
0.08 0.05 0.02
Acoustic
fibreglass
panels
Fibreglass
(72 kg/m3)
with a facing
of stretched
fabric
Stretched
fabric
0.10 0.50 0.70
Floors Carpet
10mm thk.
short pile
carpet over
concrete
floor
NIL 0.08 0.30 0.75
Ceiling Plaster
12mm thk.
GRC plaster
Emulsion
paint, white
0.20 0.18 0.15
Seating
Polyure-
thane foam
Upholstered
tip-up foam
seating
NIL 0.33 0.64 0.77
Plastic
Molded one
piece plastic
component
NIL - - -
Control
booth
Glass
1.4mm thk.
glass window
panel
NIL 0.30 0.10 0.05
Timber
Hardwood
timber
NIL 0.18 0.10 0.08
Doors Timber
Hardwood
timber flush
double door
Varnish 0.14 0.06 0.10
23

3.4.2 Material board of Experimental Theatre, University Malaya
Hardwood timber panel Aluminium grill motif
Brick wall plastered with
textured spray
Acoustic fibreglass panel
Medium pile carpet
Timber parquet floor
24
Marmoleum vinyl sheet
Plaster ceiling
Timber door panel
Gypsum board
Acoustic velour curtain
Polyutherane foam
Aluminium grill motif
Glass baluster
Aluminium railing
Medium pile carpet
Figure 3.23: Materials that can be found in E.T.

3.4.3 Materials of the walls of Experimental Theatre
Acoustic timber panels (12mm plywood panels)
Timber is a sound absorptive material. In E.T., acoustic timber panels are placed on a 2
layered 15mm gypsum drywall with 150mm air gap insulated with 50mm of rockwool foam.
The timber panels have light boxes built in and is partly covered with decorative aluminium
grills.
These panels are arranged in a jagged pattern in accordance to the gypsum drywalls to
increase surface area to absorb sound waves. Its absorptive characteristics also reduces flutter
echo. The angular design reduces the chance of incident and reflected waves from interfering
each other.
25
Figure 3.24: Acoustic timber panels are placed on
both sides of the drywall.
Figure 3.25: Decorative aluminium grills with a
lightbox in between is placed in the timber panel.
Figure 3.26: Location of timber wall panels on ground floor
plan.

Figure 3.28: Sectional detail of the wall with the timber panel highlight-
ed.
Acoustic fibreglass panels
The fibreglass panels are located at the back of the theatre on both ground floor and gallery
level. The panels only cover the middle part of the wall and not the whole wall entirely to
prevent deadening of the upper mids and high.
Fibreglass panels are effective sound absorbers. It eliminates unwanted boundary reflections
and controls excessive room reverberation. By absorbing sound waves, this can reduce
resonance within the theatre.
26
Figure 3.27: Location of timber wall panels on gallery plan.

Figure 3.29: Fibreglass panels are placed at the middle
part of the wall.
27
Figure 3.30: Location of acoustic fibreglass panels on ground
floor plan.
Figure 3.31: Sectional diagram showing the absorptive
characteristic of fibreglass panels.

Drywall (2 layers of 15mm gypsum board on steel studs and 150mm air gap with 50mm
rockwool or fibreglass in the cavity)
The drywall of the theatre is shaped in a jagged pattern to increase sound reflection from stage
towards the audience. Complemented by acoustic timber panels, the jagged pattern of walls
also prevent flutter echoes as it eliminates the parallelity of walls on flanking sides.
The rockwool foam layer inside the drywall acts as a sound absorber by inducing resonance
with the sound waves. The sound waves lose energy because the non-directional fibres traps
airborne sound more effectively compared to general insulation products which contain straight
laid glass wool with an air gap.
28
Figure 3.32: Walls layered with gypsum boards and
rockwool are used in this theatre.
Figure 3.33: Location of drywall on ground floor plan.

29
Figure 3.34: Location of drywall on gallery floor plan.
Figure 3.35: Sectional detail of the wall with the drywall highlighted.

3.4.4 Materials of the floors of Experimental Theatre
Medium pile carpet (7mm thk. - 36mm) with underlay
Medium pile carpets are covered over the concrete flooring in house as concrete is a sound
reflector which reflects and interferes with incident sound waves in the room. To prevent this,
the medium pile carpet is used to absorb impact noise created by footsteps and dropped
objects from the audience. The carpets are porous which enable sound waves to penetrate into
the pile carpet instead of being reflected back into the room.
Pile carpets are effective sound absorbers also because the individual fibres, pile tufts and
underlays have different resonant frequencies at which they absorb sound waves. The wide
range of resonant frequencies enables it to absorb a wide range of sound waves.
30
Figure 3.36: Medium pile carpet covers the floor
of E.T.
Figure 3.37: Medium pile carpet is also used on
flooring of the gallery level to reduce structure-borne
noise.

31
Hardwood timber with marmoleum vinyl sheet (20mm thk. polished timber parquet on concrete)
The original flooring system of E.T. is of reinforced concrete. Reinforced concrete floor is a
reflective material which does not insulate or absorb sound waves. However, its high mass can
increase sound transmission loss of structure-borne sound.
To overcome the reflective properties of concrete, a 20mm thick polished timber parquet is laid
over most of the surface area of the stage to improve sound absorption.
Due to heavy foot traffic that would occur during a performance, the timber parquet is not
sufficient in absorbing unwanted sound. A marmoleum vinyl sheet is later covered above the
timber surface. Marmoleum vinyl sheets increases the impact time, which promotes sound
reduction. With the combination of 3 layers of flooring, unwanted noise from foot traffic is
reduced.
Figure 3.38: Marmoleum vinyl sheet covers the
stage partially but covers the entire stage apron
Figure 3.39: The original flooring of the theatre is
concrete, covered with timber parquet and an added
layer of marmoleum vinyl sheet.
3.4.5 Materials of the ceiling of Experimental Theatre
Plaster ceiling (12mm thk. GRC plaster)
The plaster ceiling is coated with white paint and is used to disperse sound from stage in a
controlled manner. The curved edges of the ceiling aids sound dispersion to the seating area.
Figure 3.40: Fibre cement boards with white paint finish is
used for the ceiling.

Figure 3.41: Curved edges are implemented to aid sound
dispersion.
3.4.6 Other materials in the Experimental Theatre
Velour acoustic curtains
The walls of the backstage are made of concrete. Hence, velour curtains are used at the
backstage to dampen sound waves and to reduce reflection of sound from the backstage
walls. The curtains will reduce reverberation and echo in a large space, as well as reduce
interference from outside noise.
The features of velour curtains to improve acoustic properties are:
Thickness
The thicker the velour curtains, the more effective it will be against longer wavelength (low
frequency) sound. However, a thickness of 25mm - 50mm is needed to effectively absorb low
frequency sounds. As this thickness is not possible and not economical, the velour curtains in
E.T. are not able to fully absorb low frequency sounds.
Figure 3.42: Velour curtains are used backstage to absorb
unwanted noise from the exterior environment.
32

Pleated curtains
To improve low and mid frequency sound absorption, the velour curtains are pleated to expose
more sound absorbing surface.
Distance from backstage wall
The flanking velour curtains are placed at a good distance of approximately 16m away from
backstage wall to increase low frequency sound absorption and reduce sound reflection.
33
Figure 3.43: Plan view of pleated curtains shows
maximisation of surface area for more sound absorbing
surface.
Figure 3.44: A distance of approximately 16 meters is allocated between the
backstage walls and the velour curtains.

34
Seating (Upholstered foam self-lifting seat with polyurethane foam)
Polyurethane foam is used because of its ability to absorb sound and prevent echoes in the case
where the theatre is not fully occupied. This material is efficient at absorbing high frequency
sounds but not efficient in absorbing low frequency sounds unless an adequate thickness is
used.
Figure 3.45: Auditorium chairs in E.T.

35
3.5 Sound Propagation
3.5.1 Introduction
Sound propagates from a point source, travels outwards in circular waves motions and its
intensity decreases via the inverse square law (the intensity is proportional to 1/(distance
squared). Utilizing the sound meter and a self-brought speaker playing at constant amplitude
and frequency, we gathered information about sound intensity level and plotted the sound
dispersion reading in the seating (Refer to Figure 3.46). We discovered that there is a small
reduction of propagation in sound energy due to the short depth and height of the auditorium
which is 18.7m and 12.5m respectively. The propagation of sound is quite consistent and equal
throughout each level of collection of data with a difference of 1 decibel in each respective
level (Refer to Figure 3.47).
Note: The readings recorded were without background mechanical noise as the management
did not allow turning on the air conditioning. Background reading recorded was 27dB.
Figure 3.46: Sound distribution in the seating area taken from the stage

3.5.2 Sound Reflection and Diffusion
Sound reflection is the return of a sound wave from a surface. It can help increase the efficiency
of the sound propagation to the audience. Careful consideration must be given during the
design of the auditorium as poor design of the reflections can result in echoes and long
reverberation which inhibit legibility of speech.
Figure 3.47: SIL readings of the auditorium.
36

37
A. Walls
Factor of Shape of Auditorium and Materiality
The shape of Experimental Theater is a combination of a shoe-boxed with the seats arranged
in a fan-shaped, and has a concave wall at the end of the auditorium. The side wall, which
is made of gypsum board (drywall), is fitted with many acoustical decorative wall panels of
different sizes and angles.
1. The hard, sound-reflecting walls reflects sound from the stage towards the center seats and
the side seats of the auditorium.
2. However, most of the sound waves are reflected to the concave wall at the end of the
auditorium.
3. To prevent and control excessive reverberation of sound, the rear concave wall is lined with
sound absorbing acoustical panels.
Figure 3.48: Reflection and absorption of sound path in auditorium.
Absorbers Reflectors

Factor of Angles
The side wall of Experimental Theater is fitted with many acoustical decorative wall panels of
different sizes and angles to aid reflecting sound from the stage to the auditorium.
1. The sound waves from the stage strike the surface of the wall panels.
2. The different angles of wall panels diffuses sound waves from the stage towards different
directions in the auditorium. This is because the angle of incidence for sound waves will
differ from the front to rear wall panels.
3. Sound waves will be spread evenly throughout the auditorium and listeners will perceive
reflected sound from many directions.
Factor of size
1. The auditorium has a high repetition of small sections of drywall and the plywood acoustic
wall panels.
2. The sharp edges of the drywall and the plywood acoustic wall panels help to diffuse the high
frequency sound which has a short wavelength and breaks and disperses sound throughout
the auditorium.
Figure 3.49: Reflected sound path in auditorium.
38

39
B. Ceiling
The experimental theater is a performing arts theatre where graduation performances, orchestral
and music recitals are held. When the theatre was renovated in 2011, efforts were done to fulfil
the acoustic requirement of music performance spaces. Additional ceiling elements such as the
tilted ceiling allows for sound from the performers to reach the audience in the upper balcony
as shown in Figure 3.50. The convex surface ceiling also disperses sound to the upper balcony
seats (Refer to Figure 3.51). The small increments and sloped angles of the ceiling has increase
the area of providing useful reflections.
Figure 3.50: Diffused sound path in auditorium.
Figure 3.51: Longitudinal section showing type of ceiling affects sound
propagation in auditorium.

40
It can be analysed from Figure 3.52 that the upper gallery area does not receive direct sound
as the glass railings block and obstruct the sound from reaching. To counter this problem, line
array speakers that are hung from the ceiling provide sound reinforcement which in turn allow
direct sounds to the audience in the upper gallery. (Refer to Figure 3.53). The deep overhang
of the gallery has obstructed and decrease the acoustical quality for audience. Two way wall
speakers have been installed below the gallery to assist with sound propagation.
Figure 3.52: Cross section showing type of ceiling affects sound propagation in auditorium.
Figure 3.53: Obstruction of sound propagation in auditorium.
Convex surface
ceiling
Sound Reflection
Sound Reflection

Subwoofers are placed on the floor levels as it emits low pitched audio frequencies (Refer to
Figure 3.54). Low frequency of sounds are less subjected to diffraction after striking a surface of
small architectural elements. Thus the cantilevered floor slab of the balcony would not scatter
and impart odd tonal distortion to the sound as the subwoofer emits low frequency sound.
41
Figure 3.54: Reflections made from sound reinforcement.

42
3.5.3 Sound Delay and Echo
Sound Delay and Echo 1
Echo = (R1
+ R2
) - D
0.32
= 13.3 + 12.3 + 13
0.32
= 39.4 ms
The time delay for this position is 39.4ms, where direct sound is reinforced by the direct sound.
No echo is heard.
Figure 3.55: Sound delay and echo 1
13000
12300
13300
Direct Sound
Sound Source
Sound Recipient
Indirect Sound
38900
23100 79007900
18300510011400
34800

43
Echo = (R1
+ R2
) - D
0.32
= 7.3 + 6.4 - 3.6
0.32
= 31.6 ms
No echo is heard.
Direct Sound
Sound Source
Sound Recipient
Indirect Sound
6400
7300
3600

44
Echo = (R1
+ R2
) - D
0.32
= 15 + 1 + 15.8
0.32
= 0.63 ms
No echo is heard.
Direct Sound
Sound Source
Sound Recipient
Indirect Sound
15000
1000
15800

The upper balcony will not receive sound echo without the aid of sound reinforcement as direct
sound to the balcony is blocked by the glass railing (Refer to Figure 3.57).
In conclusion, the Experimental Theater has acceptable sound delay as a performing arts
theatre as all the readings of sound delay has less than 100 milliseconds.
Direct Sound
Sound Source
Sound Recipient
Indirect Sound
150002400
45

3.6 Sound Defect
3.6.1 Sound Shadow
Acoustic shadows or sound shadows are regions in which the frequency regions of sound are
altered as sound undergoes diffraction effects around large pillars and corners or underneath
a low balcony (Richard E. Berg, 1995).
In the Experimental Theatre of University Malaya, sound shadow occurs at the seatings beneath
the gallery level without the usage of sound reinforcement. There is a slight change in the
quality of sound as the obstructed design did not consider the transmission of sound to the far
end of the auditorium from the stage.
However, the sound shadow effect is not felt as much at these spaces as sound reinforcement
systems - speakers are installed at the top of the stage and at the ceiling at the furthest back
of the theatre.
3.6.2 Sound shadow in Experimental Theatre, University Malaya
In our case study of UM’s experimental theatre, sound shadow regions can be identified at the
seatings under the gallery level.
As mentioned earlier in the topic of sound propagation, sound intensity at the back is lower
as compared to the area closer to the stage. A sound intensity difference of 4 to 5dB can be
measured from the back rows to the middle rows of the auditorium. Besides the difference
in distance, this is also because the back rows of the seats are covered by the overhang of
the balcony level. Audience within this region will experience a slight sound disruption as the
sound quality transferred from the stage to the back rows of the theatre is not at its fullest and
optimal value.
46
Figure 3.59: Plan indicates the seatings affected by the sound
shadow region.

47
In concert halls, the acoustic quality below a large balcony is often reduced compared to the
acoustic quality of the main volume. This is caused by significant differences in the reverberated
energy behavior between these two volumes even though it can provide a much immersive and
pleasant viewing experience.
Our case study has a deep balcony of approximately 4.3m. The audience seated under this
balcony might suffer from a lack of acoustical quality as the opening aperture between its
volume to the main house of the auditorium is small - approximately 2 metres.
Figure 3.60: Sound intensity levels (dB) shows the significant
difference at different areas of the plan.
Figure 3.61: Section which demonstrates the
dimension of the sound shadow region.

When a sound source is emitted from the stage, the sound travels through air and towards
the audience seated before the stage. The sound paths travel directly from the sound source to
the audience is effective until the middle portion of the seating rows where it is aided further by
the side wall and ceiling by reflecting the sound source and distributes sound at a further range
from the stage. However, a lack of reflected sound path enters the space below the balcony
where sound shadow occurs. Hence, a different quality of sound is experienced.
Figure 3.62: Section which demonstrates travel path of sound to the audience
seatings.
48

3.6.3 Considerations taken to mitigate the effects of sound shadow
Sound reinforcement systems
Sound travelling within the sound shadowed region will be attenuated as sound waves are
diffracted by the pillars, and the low balcony. Therefore the amplitude of sound is reduced. As
a way to overcome this, E.T. makes use of speakers for sound reinforcement. 4 speakers are
installed below the fascia segment of the balcony. During a speech or a singing performance,
these speakers will be used to provide equal clarity of sound to the be transferred to the
audience at the back row seats affected by the sound shadow region.
Figure 3.63: Sound reinforcement system installed on the
ceiling of the seating under the gallery level.
49
Figure 3.64: Plan indicating a total of four sound speakers
are placed at the sound shadow region, to ensure equal sound
quality.

Sloped floor
The floor is angled 7.4 degrees off from the entry floor after the stage. This floor design is
desirable as it increases the angle of incidence of sound waves and thus the audience receives
more direct sound from the sound source during an ongoing performance. Sloped (raked)
floor also benefits the audience as the sloped floor improves sight lines as well as fidelity in the
seating area. However, this may prove to be counter-intuitive as the sloped floor is covered with
absorptive medium pile carpet, where the increase in exposed surface area of the material will
incerease the sound absorption in the auditorium.
Figure 3.65: Diagram depicts how sound travels to the two
levels in the theatre.
Figure 3.66: Diagram shows the floor is at a gradient
of 7 degrees off starting from the horizontal entry floor
level.
50

3.6.4 Flutter echo
Flutter echo is a condition which occurs in acoustical spaces whereby two parallel surfaces
reflecting sound between one another are far enough apart that audiences can hear the
reflections between them as distinct echoes. The audible effect is in many cases a sort of
“fluttering” sound as the echoes occur in rapid succession. Flutter echo is a problem caused
by longer reflections.
In the E.T., flutter echo cannot be identified due to several conscious designs of the auditorium.
3.6.5 Considerations taken to eliminate flutter echo
Room shape
The plan geometry of the E.T. composes the shape of a fan auditorium layout. The side walls
are splayed out to not only accommodate a greater seating area but to also encourage sound
reflection. The side walls spanning 4.7 metres is angled by 60 degrees following the wide
aperture opening of the stage.
Figure 3.67: Diagram illustrates how the sound waves are
reflected back as cancellation or with increased amplitude
from the wall.
51
Figure 3.68: 60° spread out from the walls and the almost fan
layout of the auditorium.

Wall panels
The side wall panels of E.T. are arranged at an angle and outfitted with decorative ornaments
as well as integrated with lighting components. Not only that, these panels provides necessary
angle for the reflection of sound. These plywood panels span 1.1 metre long and is repeated
throughout the spaces of the wall and are tilted at an angle of 4 degrees to angle the sound
coming from the stage. As the angle of incidence of sound waves is the same as the angle of
reflection, these non-parallel arrangements allow for a variety of patterns of sound path, thus
eliminating flutter echo.
52
Figure 3.69: The rhythmic arrangements of the
acoustical decorative wall panels.
Figure 3.70: The materiality of the angular drywall
and plywood panels.
Figure 3.71: Plan shows the jagged arrangement of the wall
panels.

Ceiling
The convex ceiling design at the corner of the E.T. enables sound dispersion, resulting in an
more even distribution of sound throughout the theatre. It also eliminates sharp corners which
prevents unwanted echoes that may occur from long reflections.
Figure 3.72: E.T.’s convex corner ceiling design. Figure 3.73: E.T.’s convex corner ceiling design.
53
Besides that, the smooth ceiling of the E.T. is not made parallel to the floor. It is arranged in a
jagged position that reflects incident sound. This prevents flutter echoes because there are no
parallel surfaces on the ceiling compared to the floor.
Figure 3.74: Section indicating the sound waves energy diminishing as it gets
absorbed by absorptive surfaces.

54
Figure 3.75: The convex design of the ceiling is an acoustical element into
reflecting sound waves throughout the theatre space. The sound wave are dispersed
and scattered to be thoroughly distributed throughout the experimental theatre.
Convex ceiling surface design

3.7 Noise Intrusion
3.7.1 Introduction
Noise is an undesirable and unwanted sound, usually judged from the perspective of an
recipient.
Noise can be categorized as continuous, variable, impulsive or intermittent depending on
how it changes over time. Continuous noise is noise that remains constant and stable over a
given time period. Different operations or different noise sources can also cause the sound
to change. Noise is intermittent if there is a mix of relatively quiet and noisy time periods.
Impulsive or impact noise is a very short burst of loud noise which lasts for less than a second.
In an auditorium, noise can be crucial to the quality of a performance or an event as it may
create disruption and unpleasantness to the hearing experience.
3.7.2 Effects of Noise
The Experimental Theatre of University Malaya houses events and performances, ranging from
dance performances, singing performances to small orchestra performances.
Noise (around the range of 65 dB) in an auditorium may cause these following physical and
psychological effects:
1. Noise during performances, recitals or even rehearsals may hinder concentration
2. Noise causes distraction which reduces efficiency and decreases attention, which will
affect production rate and quality
3. Interference caused by noise during a speech will cause general annoyance and might
cause misinformation
4. Mental effects might occur among performers such as increased anxiety and nervousness;
or even physical effects such as bodily fatigue
Therefore, a desirable acoustical environment is critical in creating a great sound experience.
Noise needs to be kept at a non-existant or minimum level to prevent disruption during events.
Figure 3.76: Experimental Theatre of University Malaya.
55

3.7.3 Noise Analysis
The analysis of noise for noise control action can be translated into a relationship of a source
and receiver, connected by a path.
Sound sources can be divided into three categories:
1. Occupants activity
2. Operation of building’s M&E services
3. Environmental sound produced outside a building
For noise sources, two main groups can be identified:
1. Outdoor/exterior noise
• noises produced by transportation such as road traffic, railway lines, motor boats,
aircraft etc.
• mechanical equipments such as compressors, cooling towers, construction equipment
noise, machinery etc.
• rainfall and thunder
2. Interior noise
• noises produced by people through their activities such as noises from radio/
television, loud conversation, slamming of doors, dragging furniture, babies crying,
etc.
• building noises produced by machines and household equipment
• noise produced in certain industrial buildings by manufacturing or production
processes
These noise (or sound in general) can be transmitted in two ways:
1. Airborne
2. Structure-borne
In noise control, the sound receiver can be a building or a room in a building as well as a
person. Actions can be taken to reduce noise based on this relationship of sound transmission.
Figure 3.11: The transmission of sound.
Sound source Sound path Sound receiver
56

57
3.7.4 Noise sources in Experimental Theatre, University Malaya
Outdoor noise - exterior environment
The Experimental Theatre (E.T.) of University Malaya is located next to a two-way road -
Lingkungan Budi. The other side of the auditorium is the school compound, which is generally
empty.
The vehicles passing by the street causes transportation noise in the building.
This noise source is transmitted through airborne as well as structure-borne transmission.
In this case, the building itself acts as a receiver of noise.
Figure 3.77: Map shows the location of E.T. and its
surroundings.
Figure 3.78: Lingkungan Budi and the lack of
sound barriers.
Figure 3.79: The sidewalk of Lingkungan Budi is
used for bicycles.

58
Airborne noise is transmitted along a continuous air paths such as openings and cracks around
doors, which can be identified in E.T. The service roller door located next to the stage is not
sealed, which becomes a noise source as the opening is permeable to the exterior noise.
Figure 3.80: The visible gap from the inside of the E.T.
Figure 3.83: Plan shows the location of the service roller doors as one of
the main source of outdoor noise.
Figure 3.81: Service roller door that is not sealed
which allows airborne noise.
Figure 3.82: Exposed condition of the service door.

59
Outdoor noise - weather
Due to the exposed manner of the building, noise effects caused by weather i.e. rain, thunder
or storm will be heard in the auditorium as there is a lack of soundproofing.
However, the usage of roofing materials can reduce the noise level caused by weather
conditions. The roof of the E.T. is reinforced concrete (RC) slab with an approximate thickness
of 300mm. This results in an approximate STC value of 65, which can reduce the noise of an
extreme weather situation i.e. thunderstorm (120dB) to 55dB. This noise level will still be heard
in the auditorium, but not very detrimental to the acoustic experience.
Figure 3.84: Section shows the RC slab of the E.T.
Figure 3.85: Plan shows possible noise source during
unfavourable weather conditions.

60
Outdoor noise - people’s activities
Noise generated by activities can be transmitted into the auditorium as well as there is a lack of
buffer zone between the main entrances and the auditorium. Conversations and light chatters
can be heard near the back of the auditorium if activities occur at the lobby.
Figure 3.86: Lobby and reception area of E.T.
The door (right) is one of the two main entrances of E.T.
Figure 3.87: Plan shows the main entrance and the lobby of
E.T. and sound may transmit to the auditorium.

61
Outdoor noise - building structure
The architectural feature located on the facade of the sides of the E.T. may be a sunshading
devide but could also present itself as a noise source. As it is part of the building structure,
structure-borne noise in the auditorium can be generated as condenser units of air conditioners
are placed near to the facade element.
Figure 3.88: The facade element and the
condenser unit.
Figure 3.89: Protruding elements along the side of
the auditorium.
Figure 3.90: Plan shows the location of the element.
Figure 3.91: Structure-borne noise when a mechanical
equipment is located close to a buildng strcucture.

62
Interior noise - people activities and movement
Interior noise is generated by impact of the physical contact with a surface.
Specific noise sources generated by human movement can be identified in E.T:
1. Auditorium chairs
2. Timber ramp at the gallery/balcony level
3. Hinge of doors
4. Door slam stopper
The noise generated is a low but noticeable creaking sound which might cause general
annoyance among people.
Figure 3.92: The auditorium chairs in the house.
(A)
Figure 3.94: Ramp at the balcony level. (C)
Figure 3.93: The steps to the seating level from the
stage. (B)
Figure 3.95: The door slam stopper of the main
entrance door. (D)

63
Figure 3.96: Ground floor plan shows the location of B and D.
Figure 3.97: Gallery level plan shows the location of C.
Interior noise - machinery and equipments
The equipments employed for lighting such as spotlights and stage lights produce a buzzing
sound which indicates a lack of maintenance.
Interior noise is also generated by the HVAC system. The expel of cold air through the diffuser
grills causes a noise level that is noticeable.

64
Figure 3.98: Lighting equipment above the stage.
(A)
Figure 3.100: Diffusers of A/C and mechanical air
intake openings. (C)
Figure 3.99: Lighting equipment (spotlight) for
stage performances. (B)
Figure 3.101: Lighting equipment on the gallery
level. (D)
Figure 3.102: Plan shows the location of machinery and
equipments.

65
3.7.5 Noise control
To reduce the effect of noise in an auditorium, certain measures can be taken which is known
as noise control.
Noise control can be acted upon the sound transmission relationship i.e. source > path >
receiver.
Noise control measures that can be taken includes:
1. Suppression of noise at the source
2. Town/site planning
3. Architectural and structural design
4. Mechanical and electrical design
5. Organisation of work spaces
6. Sound absorption/masking
7. Sound insulation

66
3.7.6 Noise control in Experimental Theatre, University Malaya
Organisation of spaces
Two hallways (one on each side) separate the auditorium space from the external environment.
The 1.5 metres wide hallway isolates the noise caused by services from the auditorium.
The other hallway has a width of 7 metres and is a void space occupied by a staircase to the
balcony level.
This decreases the airborne noise that could reach the auditorium.
Figure 3.103: Walkway of E.T. serves as buffer
zone.
Figure 3.104: The buffer zone separates the
auditorium from the service spaces.
Figure 3.105: Gallery level plan shows the buffer zones on the
sides of the auditorium.

67
Sound absorption
Noise control actions are taken using the principle of sound absorption. Soft, uneven materials
are employed to reduce interior noise. For example, the concrete floors of the auditorium is
carpeted with medium pile carpet to reduce the sound of footsteps. Pile carpets are effective
sound absorbers as the individual fibres, pile tufts and underlays have different resonant
frequencies at which they absorb sound waves. The wide range of resonant frequencies enables
it to absorb a wide range of sound waves.
Different materials are applied on the stage of the auditorium to reduce foot traffic noise as
well. A 20mm thick polished timber parquet is laid over most of the stage and a marmoleum
vinyl sheet is covering the timber surface for the front part of the stage.
Figure 3.106: The carpet used to cover the flooring of the
auditorium.
Figure 3.107: The different flooring layers of the stage of
E.T.

Velour curtains can also be found around a perimenter on the stage. During performances,
these curtains are used to reduce noise levels from the back stage and the exterior environment
by absorbing low frequency sounds.
Figure 3.108: Velour acoustic curtain hanging around the
stage of E.T.
68
Figure 3.109: Ground floor plan indicates the position of
these curtains.

69
Sound insulation
Double wall creates an air cavity which serves as sound insulation. This is known as the mass-
air-mass system, which is usually applied as a method of soundproofing.
A large cavity of air is usually introduced in this system, which performs better than a smaller
air cavity. Generally, a large air cavity also performs better as sound insulation than two
smaller air cavities.
E.T. has two pockets of air cavity on each side of the auditorium between its walls with a gap
of 150mm.
Figure 3.110: Ground floor plan indicates the position of the
wall with air cavity.

70
3.7.7 Background noise
Quality acoustical characteristics are important in auditorium spaces so that performances
and presentations can be clearly heard and understood. For performance spaces and general
presentation spaces, recommended noise criteria (NC) rating ranges from NC–20 to NC–30;
recommended sound transmission class (STC) rating ranges from STC 40 to STC 50.
Background noise is estimated to be at a level of 40dB due to the noise sources as shown in
chapter 3.7.4.
E.T. with an occupancy of 435 seats and octave band center frequency of 500Hz, the noise
level does not match the NC of an auditorium, which is around the range of 30s.
This indicates that the selected case study has an undesirable background noise level caused
by noise intrusions and the lack of soundproofing.
Figure 3.111: Graph shows the noise criteria
(NC) curve.

EXPERIMENTALTHEATRE
ReverberationTime
4.0

4.1 Introduction
The reverberant sound in a room will fade away due to the sound energy bouncing off and being
absorbed by multiple surface on the room. Thus, the reverberation time is defined as the time for
the sound pressure level in a room to decrease by 60dB from its original level after the sound is
stopped. It is dependent on the following variables:
1. The volume of the enclosure (distance)
2. The total surface area
3. The absorption coefficients of the surfaces
Hence, the reverberation time can be calculated by using the Sabine Formula;
RT = 0.16V
A
where, 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
REVERBERATION TIME
4.0
72
4.2 Reverberation Time Calculation
4.2.1 Volume of Experimental Theatre
Figure 4.1: Division of floor area for calculation of volume.

Figure 4.2: Division of floor to height area for calculation of volume.
Estimated Floor Area (m2
)
A : 76.4 m2
B : 177.9 m2
C : 76.3 m2
D : 40.2 m2
E : 253 m2
Estimated Volume (m3
)
A : 439 m3
B : 1316.5 m3
C : 618 m3
D : 311.6 m3
E : 2934.8 m3
Total Volume of Experimental Theatre (m3
): 5621 m3
73

4.2.2 Area of Floor Materials
500Hz is used as a standard of measurement as musical performances usually fall under the
category of this frequency and this auditorium is mostly used as a performing art space.
Component
Surface
Area (m2
)
500 Hz
Absorption
Coefficient
Abs Units
(m2
sabins)
A
Marmoleum vinyl sheet over hardwood
timber flooring on conrete
152.7 0.04 6.12
B Hardwood timber parquet on concrete 100.3 0.07 7.02
C Carpet flooring 330.6 0.30 99.18
Total 112.32
74
Figure 4.3: Flooring material on ground floor. Figure 4.4: Flooring material on first floor.

4.2.3 Area of Wall Materials
Component
Surface
Area (m2
)
500 Hz
Absorption
Coefficient
Abs Units
(m2
sabins)
A Acoustic timber panels 222.8 0.42 93.6
B Acoustic fibreglass panels 42 0.5 21.0
C Drywall 75 0.05 3.75
Total 118.35
75
Figure 4.5: Wall material on back of the auditorium wall.
Figure 4.6: Wall material on the sides of the auditorium wall.

4.2.3 Area of Other Materials
Component
Surface
Area (m2
)
500 Hz
Absorption
Coefficient
Abs Units
(m2
sabins)
A Plaster ceiling 563.8 0.18 101.5
B Velour curtain 372.9 0.4 149.2
C Timber doors 10.3 0.05 0.52
D Glass windows 9 0.04 0.36
E Auditorium Seats (Unoccupied) 208.8 0.64 133.6
F Glass Railings 21.9 0.04 0.88
Total 386.1
76
Figure 4.7: Other materials on ground floor. Figure 4.8: Other materials on first floor.
Figure 4.9: Other materials labelled on section.

4.2.4 Reverberation Time
Using the Sabine Formula,
RT = 0.16V
A
where, RT = reverberation time (sec)
V = volume of the room (cu.m)
A = total absorption of room surfaces (sq.m sabins)

Volume = 5621 m3
Total abs unit = 112.32 + 118.35 + 386.1
= 616.8 m2
sabins
∴ RT = 0.16 (5621)
616.8
= 1.46 secs
The reverberation time for Experimental Theatre is 1.46 seconds which shows that the auditorium
does serve its function as a performing arts theatre althought it may not be necessarily be good
for speeches and conferences which do also take place in the auditorium. However, it should
also noted that the high reverberation time could be mainly influenced by the large volume of
the space which is 5621m3
. This is due to the backstage area having a high double volume
space in comparison to the volume of the auditorium seating itself.
Figure 4.10: The table shows where the Experimental Theatre lies in the optimum reverberation
different types of auditorium and halls.
E.T
77

EXPERIMENTALTHEATRE
Conclusion
5.0

5.1 Experimental Theatre, University Malaya
CONCLUSION
5.0
Table 5.1 : Recommended reverberation time (RT) according to usage and volume. Highlighted is
E.T.’s category and its recommended RT.
79
The case study has taught us the importance and application of acoustics in architecture
for a building to be able to perform its stated function i.e. auditorium. Every surface in the
building matters in regard to the propagation of sound and therefore details should be
considered and conscious design strategies should be applied to create a fully functioning
auditorium.
Based on our calculation using the Sabine formula, E.T. has a volume of 5621m3
and
a reverberation time of 1.46s, due to its high volume. Therefore, E.T. is mostly suitable for live
and instrumental perfomances as the RT is just enough to provide for an acoustic experience
for musical performances. The auditorium is not suitable for uses such as speeches or lectures
however as sound absorption is loosely applied, which can reduce echoes in the auditorium,
allowing for clarity of speech. Experimental Theatre of University Malaya proves to be a
functional auditorium for perfoming arts, but not without certain shortcomings that can be
overcomed.
There are still defects in regards to its conditions which can result in a decrease of
quality of its acoustics. Discussed further are actions and design considerations that can be
taken, whether to reduce noise intrusion into the auditorium, or to increase the reverberation
time of Experimental Theatre.
Uses Small Rooms
(750m3
)
Medium Rooms
(750 - 7500m3
)
Large Rooms
(>7500m3
)
Speech 0.75 0.75 - 1.00 1.00
Multi-purpose 1.00 1.00 - 1.25 1.00 - 2.00
Music 1.50 1.50 - 2.00 2.00 or more

5.2 Design Considerations and Suggestions
5.2.1 Buffer zone between lobby and main entrances
By creating - or extending - a buffer zone for the main entrance of the auditorium, the air gap
created will be a good sound insulation to prevent noise from entering the auditorium any time
of the day.
5.2.2 Upgrading the main entrance doors to be soundproof / Adding soundlock
The same problem can also be mitigated by improving the soundproof properties of the main
entrance doors. Soundlock prevents sound leakage in or out from a room.
80
Figure 5.1: Creating a buffer zone by joining the walls.
Figure 5.2: Velour acoustic curtain hanging around the
stage of E.T.
Figure 5.3: The condition of the
current main entrance door.

5.2.3 Machinery & equipments type
Currently, the HVAC system of E.T. is one of the contributors of background noise in the
auditorium. Having air forced out from the diffusers can create noise, and paired with a lack
of maintenance, the air conditioning system may generate noise that will disrupt the acoustic
experience of the auditorium. The placement of the return air inlet close to the supply air outlet
seems to be counter-intuitive as well. A more suitable air conditioning system can be applied
to reduce the level of background noise experienced.
5.2.4 Changing materials to encourage sound reflection
One of the ways to increase reverberation time is to decrease the total absorption of room
surfaces. For example, the acoustic fibreglass panel at the back defeats the purpose of the
concave shape of the wall as it is a absoptive material. Reducing or removing it can increase
the reverberation time in E.T.
81
Figure 5.4: Current air conditioning system.
Figure 5.5: Concave wall at the back is covered with
absorptive material.

5.2.5 Sound barrier
Sound barrier can be added to the exterior of the auditorium at the risk of losing visibility to the
building. This can mitigate traffic noise with proper implementation.
Figure 5.6: Lack of sound barrier from the traffic.
82

EXPERIMENTALTHEATRE
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