Acoustic Studies

1. 1.0 Introduction
In a group of 8, we are required to select a venue to conduct an acoustical analysis
on the specific design of the theatre that we have chosen. Acoustic design is
important as the design of the theatre is to allow the audience to fully enjoy the stage
performance to its optimum potential without the interference of external factors or
acoustic defects. Factors such as sound intensity, sound pressure and reverberation
time may affect the quality of the performance. On the other hand, the design of the
space such as massing, arrangement of the seats and the leveling of the seats may
lead to a lost of focus of the audience towards the performance if the design is poorly
executed. A good theatre design can maximize the enjoyment of performance by the
controlling the sound propagation and eliminating external and internal noise
sources. At the end of the project, we are to demonstrate our understanding of the
brief given and present our report.
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2. 1.1 Aim and Objective
This project mainly focus on the acoustic study of the chosen auditorium in PJ JAYA
ONE, LIFE ART CENTRE.
1. To study and develop an understanding about the design of the auditorium and
the effectiveness of the chosen auditorium.
2. To study on the architectural tectonics of how the acoustical elements will affect
the quality of auditorium hall.
3. To analyze the data collected then produce a detail report by concluding the
acoustical effectiveness of the auditorium hall.
The case study is to focus on the acoustic design of chosen auditorium and
demonstrate understanding of the case study by generating analysis report of the
chosen site. Multiplicity of auditorium design approaches are to tackle different types
of auditorium and to achieve acoustical efficiency.
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3. 1.2 Site Introduction
We have selected PJ Live Art Centre as our case study to conduct our acoustical
analysis through observation, data collection and documentation. By using different
methodology to measure and test out the sound and noise of the venue, we would
have to generate a detail report of our case study.
​Figure 1.3.1 Logo Figure 1.3.2 Interior of Auditorium
Venue : PJ Live Arts Centre
Location : ​2A-3, Block K, Jaya One, Section 13,
No.72A, Jalan Universiti, 46200,
Petaling Jaya, Selangor D.E,
Malaysia
Function : Theatre, Studio
Year Built : Since ​August 2009
Total Seat : 450 seat capacity (302 pax-tiered seatings
+ 148 pax stadium seating​ balcony)
PJ Life Art Centre was chosen as our site selection due to the immense
considerations into the acoustic design and spacial qualities. We also wanted to
conduct further studies on the use of the theatre and the importance of each
components that contribute to the succession of the theatre without degrading the
quality of the space. As PJ Life Arts Centre functions as a performance theatre,
further analysis is done to understand the features and components that
accommodate both music and dance functions in the theatre.
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4. 1.3 Historical Background
The PJ Live Arts is one of the most recently established performing arts centre in the
Klang Valley. Located in Petaling Jaya, one of the most rapidly developing townships
in Selangor, the PJ Live Arts have become one of the most popular spots that hold
several types of shows and events in the performing arts genre where it has already
hosted countless sold-out shows and events since it was established. The PJ Live
Arts was set up in 2009 and it has grown from its humble beginnings into becoming
one of the preferred performing arts centres of Malaysia.
Developed to be the performing arts centre of the neighbourhood, the PJ Live Arts
have become the place where Malaysian from all walks of life come and enjoy a
show at the theatre while it has also attracted people from all over the country
through some of their most popular shows throughout the calendar year. Here is
where one will be able to enjoy shows, performances, dances and dramas while the
PJ Live Arts has also become one of the most popular stand-up comedy spaces in
the country. Its signature annual event is the Laugh Fest where it has brought
together some of the best comedians from the local and international scene together
in its biggest annual comedy event in Malaysia.
The PJ Live Arts have hosted shows that has achieved international and regional
recognition while it is also the resident venue for some of the best comedy shows the
country has ever seen that include the likes of the Comedy Club KL, the M.A.C.C
(The Malaysian Association of Chinese Comedians), the Cantus Musicus, Gardner &
Wife Theatre as well as the Sutra Dance Theatre.
The PJ Live Arts surely have come a long way to become one of the top destinations
not only within Selangor but also the country where apart from its theatre, the PJ
Live Arts also houses its own studio which is used for related events like the
Children’s Rights Reborn – with Children’s Voices by NGO Knowing Children. Apart
from that, PJ Live Arts also offer space for other related events and this include
seminars, space for product launches, workshops and rehearsals, all of which that
can be held at their studio. Apart from that, the PJ Live Arts had also recently added
a new space called the Cabaret which is focused in bringing in performances in
music, magic, stories and others.
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5. 1.4 Drawings
1.4.1 PJ Live Arts Site Plan
5

6. 1.4.2 PJ Live Arts Centre Floor Plan
Ground floor plan
First floor plan
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7. 1.4.3 Reflected Ceiling Plan
Ground floor reflected ceiling
First floor reflected ceiling plan
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8. 1.4.4 PJ Live Arts Centre Section
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9. 2.0 Literature review
2.1 Architecture Acoustics
Architectural acoustics is the process of managing how both airborne and impact
sound is transmitted and controlled within a building design. While virtually every
material within a room from furniture to floor coverings to computer screens affects
sound levels to one degree or another, wall partitions, ceiling systems and
floor/ceiling assemblies are the primary elements that designers use to control
sound.
Architectural acoustics is concerned with improving the sound in rooms through
reducing the background noise in a recording studio, improving the design of a public
address system to make speech more intelligible in railway stations, or put acoustic
treatments on walls to make music in a concert hall sound better. By researching into
new methods for measuring and predicting how sound moves within rooms and
buildings this enables us to develop innovative ways to design rooms and building
elements.
2.2 Sound Intensity Level
Sound intensity is defined as the rate of energy flow (sound power) across a unit
area. The basic units are watts/m​2​
. ​The dynamic range of human hearing and sound
intensity spans from 10​12
Watt/m2 to 10​-100
Watt/m​2​
. This span makes the absolute
value of the sound intensity impractical for normal use hence the sound intensity of
10​-12​
Watt/m​2​
, the lowest human hearable sound is used as the reference level.
Sound intensity level is referred in two different units: bel and dB (the tenth part of a
bel). Currently sound intensity level is usually , SL is defined by:
where ​SL is the sound intensity level, ​I is the intensity and ​I0 is the standard
reference sound intensity ( 10​-12​
Watt/m​2​
).
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10. 2.3 Sound Pressure Level
The sound pressure level, SPL, of a sound of root mean square pressure P​rms is
defined by
where SPL is expressed in decibels and P​o is the reference sound pressure level of
0.00002Pa. This value is chosen as it approximately corresponds to the sound
pressure of the slightest sound an ear can detect in quiet surroundings.
Sound pressure level is the quantity that is actually measured when a microphone is
placed in a sound field. The portable instrument used to measure SPL is known as a
sound level meter. Some typical sound pressure levels are shown in the figure
below.
Figure 2.3 Typical Sound Pressure Level
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11. 2.4 Sound Power Level
The sound power level, SWL or Lw is a measure of the energy output of a sound
source. The SWL is defined by
where SWL is expressed in decibels, W is the acoustic power of the source and W0
is the reference acoustic power of 10​-12​
W.
When assessing the noisiness of a machine or domestic appliance, it is not sufficient
to quote just the sound pressure level measured using the A-weighting network since
the level measured is dependent on the environment. This dependence has been
known for many years and consequently it has generally been accepted that the
sound power emitted by the machine should be determined as this is the
fundamental indication of the noise output and is virtually independent of the
environment. Some typical sound power outputs of various sources are
Figure 2.4 Typical Sound Power Level Examples
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12. 2.5 Reverberation Time
At the beginning of this century W.C. Sabine carried out a considerable amount of
research on the acoustics of auditoria and arrived at an empirical relationship
between the volume of the auditorium, the amount of absorptive material within the
auditorium and a quantity which he called the reverberation time. This relationship is
now known as the Sabine formula:
RT = ​0.161 V
A
where RT = the reverberation time defined as the time taken for a sound to decay
by 60 dB after the sound source is abruptly switched off.
V = the volume of the auditorium in m​3
A = the total absorption of the auditorium in m​2​
-sabins.
The absorption unit of 1m​2
-sabin represents a surface capable of absorbing sound
at the same rate as 1m​2​
of a perfectly absorbing surface e.g. an open window.
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13. 3.0 METHODOLOGY
3.1 Digital Sound Level Meter
​Figure 3.1.12 Image of Digital Sound Level Meter
The digital sound level meter that we used is Lutron SL - 4023SD sound level meter,
which is provided by Taylor’s University. It is a real time recorder; the weighted
sound level value is read on the meter, and able to save the data into the SD
memory card. We are using dBA due to the frequency weighting corresponds to the
way the human ear responds to the loudness of sound.
The stated sound level meter is capable of three ranges: 30 to 80, 50 to 100 and 100
to 130. It can be use for fast and slow time weighting.
3.2 Digital Camera
​ Figure 3.1.21 Image of Digital Sound Level Meter
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14. The main cameras used for this project are Canon EOS 700D and Nikon D5600. The
digital cameras were used on site to capture pictures of the auditorium, acoustic
condition and acoustical fixtures present on site. The secondary cameras are mainly
smartphone cameras, it is used to ensure that most of the photos we needed will be
taken from the site. All photos are used as evidence of our case study and for
reference purpose.
3.3 Measuring Tape
​ ​Figure 3.1.31 Image of Measuring Tape
Measuring tape were used to acquire the measurements on some details that didn’t
shown on drawings which are provided by Jaya One Management Office. It is also
used to measure the distance of the sound level meter from the sound source when
we are collecting the data for reverberation time.
3.4 Data Collection Method
In order to conduct a sound analysis without disturbance, the visit was applied
through email and the office had made prior for us to the visit ensuring that the
auditorium would be unoccupied and allowing us to conducted a series of
investigate. With the help of all tools that had mentioned, we noted down as many
data as we can within our ability and constraints, including the auditorium’s layout
and form, noise sources, furniture, materials and notable acoustic components.
Measurements of the auditorium were also taken for drawing and calculation
purposes.
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15. 4.0 ACOUSTIC ANALYSIS
4.1 Theatre Design Analysis
4.1.1 Shape and Massing
Figure 4.1.1.1 Rectangular plan with parallel walls
End stage halls with a rectangular plan have side walls that ensure short first
reflection times, but the large parallel surfaces often result in acoustic defects, such
as flutter echoes and standing waves. The dead corner of the floor plan is cut off to
prevent excessive reflection of sound back to its source.
Figure 4.1.1.2 Excessive sound reflection at room corner
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16. 4.1.2 Levelling of Seats
A raked floor along with a raised platform for the performer, aids in useful reflections
and reduces grazing acoustic attenuations. Balconies are used to increase seating
capacity and to reduce the distance to the farthest row of seats to increase sight
lines and sound received. The balcony underside should be twice the depth of the
balcony overhang. Reflecting surfaces on the ceiling and side walls, underside of
balcony should be designed to add maximum reflected sound to the seating area on
the balcony and under it, to supplement the direct sound from the stage.
Figure 4.1.2 Raked seatings levels
4.1.3 Arrangement of Seats
Figure 4.1.3 Continental seating within 140​°​ angle
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17. Continental seating arrangement with aisleways which are accessible at both ends
allows for more seatings within the space and brings the audience closer to the
platform. ​If an aisle can be reached from one end of a row only, the seat count may
then be limited to 7 or 8​. ​The seatings are contained within a 140​° ​angle from the
center of the platform to preserve high frequency sound from the performer which
allows for optimum acoustic quality within the small theatre.​This brings in the
audience closer to the performer, establishing a more intimate experience.
4.1.4 Ceiling Reflector Panels
Figure 4.1.4.1 Ceiling Reflector Panels
Figure 4.1.4.2 Sound propagation from direct and reflected sound
A series of flat-stepped reflector panels are installed below the ceiling to provide
reflection of sound energy from the stage to the seating areas. Flat ceiling panels are
more practical to build and produces similar results as a slanted staggered ceiling.
The dimensions of the ceiling reflector panel should be 5 times the wavelength of the
lowest frequency to be reflected. As the height of the ceiling is considerably low, less
echoes are formed, hence the distribution of sound throughout the theatre is
optimized.
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18. 4.2 Sound & Noise sources
Noise is normally defined as undesirable sound yet it is indeed purely subjective,
determined by the attitude of the occupants toward the noise source. ​Noise can be
continuous, variable, intermittent or impulsive depending on how it changes over
time. Continuous noise is noise which remains constant and stable over a given time
period. Different operations or different noise sources cause the sound to change
over time. Noise is intermittent if there is a mix of relatively quiet and noisy periods.
Impulse or impact noise is a very short burst of loud noise which lasts for less than
one second. Even though, the PJ live arts centre is designed based on the acoustic
architecture and packed with acoustic equipment yet there are some noise
disturbance can be found within the theatre.
4.2.1 Outdoor noise sources
Multiple noise sources are found outside the auditorium which include the sound
generated by opening and closing of the door and continuous noise sources
produced by the people at the waiting area. The noise enters the theatre through the
doors due to the absence of the sound proofing treatments at the ground floor
entrance. In contrast, the sound lock is found at the first floor entrance which greatly
reduce the banging sound of the doors. Rubber strips are installed around each door
to seal the gap of the doors which help to reduce the noise level. Other than the
lobby area, the two exit doors located at the right side of the theatre also increases
the noise level entering the theatre. The seats near to the exits are affected and
exposed by noise disturbance that enters through the doors from the outside of the
theatre. Door dampers are attached on each door end, yet the noise generated from
the act of opening and shutting of the doors are not significantly reduce due to the
excessive weight of the door itself.
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19. Figure 4.2.1.1 The ground floor plan of the theatre and the origin of external noise
Figure 4.2.1.2 First floor plan of the theatre and the origin of external noise
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20. ​4.2.2 Indoor noise sources
Several internal noise sources have been identified inside the theatre. The
continuous noise comes from the air conditioner diffusers and ducting system which
are located within the interior spaces of theatre which include the backstage, above
the stage, the area under the balcony, the edge of the balcony and the first floor
ceiling. Under the balcony and the first floor ceiling area, linear air conditioning
diffuser system runs along the gaps of the suspended ceiling which causes a
disrupting sound of forced air. The act of opening and shutting the doors located
along the side of the theatre generates a temporary noise disturbance.
Figure 4.2.2.1 Ground floor reflected ceiling plan and the origin of internal noise source which
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21. Figure 4.2.2.2 First floor reflected ceiling plan and the origin of internal noise source from the linear
air conditioning diffuser.
Footsteps on the carpet and stage floor, backstage area and AV room causes
impulsive noise in the theatre and affects the performance. The sprung flooring at
the stage area is made out of polyvinyl flooring backed with foam and has a flexible
surface, thus it facilitates in sound reduction which helps nullify reflection factor and it
also provides a shock absorption surface which helps to reduce the "thudding"
sounds when stepped on as well as ​enhance performance and reduce injuries. The
flooring at the audience area is finished with a layer of timber veneer which is
aesthetically pleasing however it produces higher noise level compared to a soft
carpet.
Figure 4.2.3.1 The linear air conditioning diffuser system located balcony ceiling panels
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22. Figure 4.2.3.2 Polyvinyl flooring on the stage area Figure 4.2.3.3 Timber veneer flooring on
the
seating area
Figure 4.2.3.4 Section of the PJ Live art center to show the origin of the internal noise sources from
the air conditioners diffusers and footsteps
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23. 4.3 MATERIALS
Area Component Materials Surface
Finishe
s
Coefficient (Hz)
Photo Material Description 125 500 2000
Stage Walls
(back)
Gypsum
wall
board
Coated
with black
paint
paint
finish
0.02 0.03 0.04
Walls (side) - Plaster
wall
Coated
with black
paint
paint
finish
0.02 0.03 0.04
Acoustic
panels
Acoustic
fabric
wrapped
panels
soft
fabric
0.15 0.75 0.8
Curtain Medium
velour
Thin layer
of velour
soft 0.03 0.15 0.5
Fly System Steel
battens
AFCS - 0.01 0.01 0.02
Lines AFCS - 0.01 0.01 0.02
Blocks AFCS - 0.01 0.01 0.02
Ceiling - Concrete Rough
concrete
rough 0.02 0.03 0.04
Floor Polyvinyl Black
rough
surface
laminated
onto
plywood
matte,
sheenle
ss
surface
Apron
absorber
Acoustic
panels
hung on
concrete
wall
Acoustic
fabric
wrapped
absorber
panels
soft
fabric
0.15 0.75 0.8
Arch panels Timber
panels
Perforated,
acoustic
timber
veneer
panels
smooth 0.18 0.42 0.83
Floor Floor Timber
veneer
flooring
Steel
raised
platform
with timber
flooring
smooth 0.02 0.05 0.1
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24. Walls Acoustic
panels
Acoustic
fabric
wrapped
absorber
panels
soft
fabric
0.15 0.75 0.8
Ceiling
(panels)
Timber
panels
Acoustic
timber
veneer
reflector
panels
smooth 0.19 0.25 0.37
Ceiling
(under
balcony)
Plaster
ceiling
Coated
with black
paint
paint
finish
0.02 0.03 0.04
Balcony Floor Concrete Sealed
concrete
polishe
d
0.01 0.01 0.02
Walls Concrete Rough
concrete
rough 0.02 0.03 0.04
Acoustic
panels
Acoustic
fabric
wrapped
absorber
panels
soft
fabric
0.15 0.75 0.8
Railings Metal
bars with
stainless
steel
wire
AFCS - 0.01 0.01 0.02
Audience Seats Plastic
chairs
with steel
legs
Empty (per
chair) in
sqm units
dull,
matte
0.07 0.14 0.14
With
children
(per child)
in sqm
units
0.28 0.33 0.33
With adult
(per adult)
in sqm
units
0.3 0.4 0.43
*AFCS - assume as flat concrete surface
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25. 4.4 Acoustic Treatments and Components
In live performance theatre, it functions generally as a multi-purpose space to satisfy
the acoustics and functional aspects of a theatre, due to its large volume and
capacity, the effect of reflected sounds are inevitable which would disrupt the
acoustic quality of speech, dance and music stage performance. Reflected sound
effect such as echoes are produced when a sound wave reaches the end of a
medium or encounters an obstacles, it will reflect within the theatre space. In order to
avoid this scenario, crucial acoustic treatments have to be made to improve the
sound quality in the theatre. Acoustic treatments will help to fulfil basic acoustics
criteria such as the dimensions and volume of the auditorium, seating arrangements,
shape of walls and ceilings, audience capacity and surfaces of wall and ceiling
materials have to be considered. Therefore, acoustic treatments have to be aided
with certain acoustic components which can reduce echoes and improves acoustics
in a theatre.
4.4.1 Theatre Stage Floor (Polyvinyl)
Figure 4.4.1.1 Polyvinyl is used as a material for the floor stage for acoustic treatments purposes.
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26. Polyvinyl used as a stage flooring material has a cushioning effect which reduces
finish wear and sound transmission. Polyvinyl material absorbs sound vibrations in a
way which it soaks up incoming sound energy so that less sound is transmitted
within the auditorium.
Figure 4.4.1.2 Auditorium stage is installed at the front of audience according to plan view.
Figure 4.4.1.3 Cross section diagram of a polyvinyl stage material.
Higher frequency noise is controlled by mass of the floor system which are concrete
and plywood that is overlaid on the concrete slab. ​Other than that, polyvinyl that has
a rough surface is overlaid on the plywood so that it is highly resistant from
scratching and overcomes lower frequencies which are the footfalls of people
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27. walking and dancing on stage. It also add on a layer of softness to the stage floor
hence reducing the impact of footfalls as a form of protection to the performers.
Polyvinyl are typically black as it does not distract users from enjoying the
performance.
4.4.2 Flooring (Timber Veneer Flooring)
Figure 4.4.2.1 Timber veneer is used as flooring for auditorium to attenuate noise transmission.
Figure 4.4.2.2 Plan of PJ Live Arts auditorium indicates timber veneer flooring.
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28. Timber veneer is used as the flooring for the theatre to reduce noise transmission to
acceptable levels. Timber veneer flooring used for sound reduction is often laid on
with an acoustic underlay to absorb sound in a moderate level. It is able to reduce
lower sound frequencies vibrations in order to avoid low frequency sounds to vibrate
the slabs and walls of the auditorium. The absorption of low frequency sounds can
be affected by the depth of the floor slab and the perimeter of the floor. The reason
of it is because sound wave is able to travel across the floors and walls into adjacent
spaces.
Figure 4.4.2.3 Cross section of a timber veneer flooring.
Timber veneer flooring with and acoustic underlay will often provide about 10 dB to
20 dB attenuation. Acoustic underlayment is able to absorb sound produced by
percussive sound of footfalls and provide a feeling of solidity to the timber flooring.
The acoustic underlayment is fixed to the sub-floors of the timber veneer flooring.
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29. 4.4.3 Curtain (Medium Velour)
Figure 4.4.3.1 Medium velour fabric used as sound absorption material for auditorium stage curtain
Figure 4.4.3.2 Five layers of stage curtains are located at the back of the auditorium stage in section
view.
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30. Fabric curtains located at the both sides of the stage functions to block the view
towards the backstage and helps to control the reverberation by absorbing excessive
sound and eliminating the acoustic reflection off glass. It is a movable material, when
sound hits the curtain, the fabric will be moves slightly to reduce the reverberation.
Medium velour is a medium weight and closely woven fabric that is usually used for
stage curtains, theatre masking and acoustical sound absorption purposes. Medium
velour fabric curtains are unable to reduce noise transmission significantly between
two adjacent spaces, they are designed to enhance sound quality and to reduce
sound reverberation levels. Medium velour fabrics as a sound absorption acoustic
curtain has to be thick to absorb sound effectively. In order to reduce lower sound
frequencies, the medium velour fabric in the theatre is within the necessary thickness
of 25.4mm to 50.8mm.
On the other hand, medium velour fabrics are highly porous to trap sound energy for
noise reduction. Besides that, pleated medium velour fabric helps to improve sound
absorption of low and mid frequency sound. Pleated fabric causes the fabrics to
pleat together in a way which it loops in and out to increase the sound absorbing
surfaces which improves the low sound frequency absorption.
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31. 4.4.4 Acoustic Wall Panels (Acoustic Fabric Wrapped Panels)
Figure 4.4.4.1 Acoustic wall panels are installed at the walls of auditorium for sound absorption.
Figure 4.4.4.2 Plan view of PJ Live Arts auditorium indicates the locations of acoustic wall panels.
The surface of this auditorium is mainly covered by acoustic wall panels, which are
an absorptive material. The first layer of fabric of the panels absorb a tiny amount of
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32. sound energy when it passes through the fabric and its underlying high-density foam
is used to control and reduce the reverberation time. Other than that, it absorbs the
sound after it has passed over the audience and prevent echoes from occurring.
Figure 4.4.4.3 Cross section of an acoustic wall panel.
The material of the wall panel layering also affects the sound absorption. In this
case, the surface of the wall panelling is fabric, followed by the foam core and last
will be plywood. Foam is a porous and soft material that can absorb high frequency
sound. Plywood is used to absorb low frequency sound.
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33. 4.4.5 Timber Panels (Acoustic Timber Veneer Panels)
Figure 4.4.5.1 Acoustic timber veneer panels are installed on top of the auditorium ceiling.
Acoustic timber veneer panels for acoustic treatments just like other wooden
materials by reflecting sound waves. The surfaces of acoustic timber veneer panels
are easily made to channel sound reflections. Acoustic timber veneer panels conduct
sound waves better in a longitudinal direction rather than perpendicular direction to
it. When sound waves travel in all directions and encounter an obstacle in its path for
instance ceiling surfaces, hence sound waves will be reflected. The travel direction
of reflected sound is same as the angle of the original sound striking any hard
surface. Hence, this applies to acoustic timber veneer panels as well. In a musical
performance or speech auditorium, the acoustic timber veneer timber panels are
installed in an angled tiered formation for sound waves to be reflected from the stage
to the audience seating areas.
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34. Figure 4.4.5.2 Cross section of an acoustic timber veneer timber panels.
Figure 4.4.5.3​ ​Section of the PJ Live Arts auditorium shows the position of acoustic timber veneer
timber panels.
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35. 4.4.6 Speakers
Figure 4.4.6.1 Point Speakers
Sets of point source speakers are placed in a single row facing the audience above
the stage. Types of speakers used include line array loud speakers and subwoofer
speakers.
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36. Figure 4.4.6.2 Subwoofer Speakers
The function of a subwoofer speaker is to reproduce low-pitched audio frequencies
known as bass.
Speaker specifications:
Model VRX918SP
18 in. High Power
Powered Flying Subwoofer
System Power Rating 1500 Watts Peak
Frequency Range 31 Hz – 220 Hz
Dimensions (H x W x D) 508 mm x 597 mm x 749 mm
Frequency Response (±3 dB) 34 Hz – 220 Hz
Net Weight 38.5 kg
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37. Figure 4.4.6.3 Line array loudspeaker.
Speaker specifications:
Model VRX928LA - 8 in. Two-Way
Line Array
Loudspeaker System
System Power Rating 400 W / 800 W / 1600W
Frequency Range (-10dB) 70 Hz - 20 kHz
Dimensions (H x W x D) 230 mm x 420 mm x 270 mm
Frequency Response (±3 dB) 85 Hz - 19 Hz
Coverage Pattern 100 x 15 nominal
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38. Net Weight 12.7 kg
Figure 4.4.6.4 Standing Portable Speakers
Portable speakers used in the theatre vary in placement from show to show.
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39. Figure 4.4.6.5 Portable speaker.
Speaker specifications
Model JBL EON 515 -​ ​Portable Self-Powered
15”,Two-Way, Bass-Reflex Design
System Power Rating 450W continuous
900W peak
Frequency Range (-10dB) 39Hz - 20kHz
Dimensions (H x W x D) 685 x 438 x 366mm
Frequency Response (±3 dB) 42Hz - 18kHz
Coverage Pattern 100​° H, 60° V nominal
Net Weight 14.8kg
39

40. Figure 4.4.6.6 Placement of the different types of speakers shown on an inverted ceiling plan.
Figure 4.4.6.7 Placement of the different types of speakers shown in a section view.
40

41. Sound reflections on hard surfaces such as walls, ceilings and floors will affect
listening experience. The use of digital speaker sound system will help to reduce
bass or low sound frequencies in the listening position of audience. Besides that,
speakers are used as sound amplification to reinforce sound level when sound is too
weak to be heard. Speaker system also functions to provide artificial reverberation in
rooms that are too dead for satisfactory listening. The type of speaker system used
in the PJ Live Arts auditorium is a distributed system. A distributed speaker system is
where a number of overhead loudspeakers being installed through the auditorium.
Distributed speaker system is used to overflow sound to the audience in the
auditorium. A distributed speaker system is effective to majority of the audience to
gain adequate sound quality.
The speaker system that is used in PJ Live Arts auditorium is a centrally located
system. A centrally located speaker system is a number of loudspeakers being
installed in a single cluster arrangement as a sound source. This system provides
maximum sound realism to the audience as the amplified sound is direct from the
same the direction as the original source.
Unfortunately, the speaker system unable to solve the prolonged reverberation time
of the standing sound waves. Standing sound waves are low frequency resonances
that take place between two parallel reflecting surfaces. Acoustic qualities of
speakers are affected by many factors such as distance of speakers from audience,
relationship of direct sound and reflected sound, audience absorption of direct
sound, delayed reflected sounds and the duplication of sound source by speakers. In
order to support audible sound levels, the audience seating areas have to be placed
as close as possible to the speaker. The reason of this is to minimizes the sound
attenuation and provide more direct sound path to the audience.
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42. 4.5 Sound Propagation and Related Phenomena
4.5.1 Sound Concentration
The measurement of the sound intensity level (SIL) from the sound source shows
that there is a little difference in dB from different sides of the theatre.
Figure 4.5.1 Record of SIL measurement on both ground floor plan of the theatre and the balcony
Comparing with both ground and balcony level of the theatre, the SIL found on first
floor is slightly higher. It appears that smaller volume of space found in this theatre
allows the first floor to receive the sufficient reflection of sound waves from the
ceiling panel, which amplifies the sound received. While on the ground floor, due to
the presence of sound shadow and parallel walls, sound is concentrated more at the
front and middle part.
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43. 4.5.2 Sound reflection (Horizontally)
Trajectory of sound waves should be properly planned to allow a better experience in
the theatre. Reflection of sound is one of the way in transferring sound waves
efficiently to the audience. The amount of sound waves have to be controlled to
avoid the production of echos and other acoustic issues.
Figure 4.5.2.1 The reflection of sound at parallel walls
The design of straight walls allow sound waves to be reflected at a perpendicular
angle against the walls. Higher intensity of sound level at the middle part of the
theatre as compared to other area. This explains the concentration of SIL diagram as
mentioned above.
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44. Figure 4.5.2.2 The design consideration in reducing reflected sound waves
It is shown that more absorbance materials are used throughout the theatre on each
side of the walls so that reverberation time can be reduced and also to prevent the
production of echoes coming from the sound source.
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45. 4.5.3 Sound Reflection (Vertically)
Timber panels
Ceiling reflectors are used to efficiently direct sound waves to the back of the
audiences. This helps in bringing sound waves further back. However, absorbent
materials need to be used in order to avoid unnecessary echo due to resultant
reflected sound.
Sound reflection can also be shown through sections. A more detailed picture of how
angle of sound waves are being reflected at the ceiling reflectors to user at different
area can be seen.
Figure 4.5.3.1 Propagation of sound towards user sitting in the front row
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46. Figure 4.5.3.2 Propagation of sound wave towards user sitting in the middle row
Figure 4.5.3.3 Propagation of sound wave towards user sitting at the balcony (first floor)
46

47. 4.5.4 Sound Shadow
Figure 4.5.4 Propagation of sound wave towards user sitting under the balcony
The diagram further explains the disadvantages of user sitting under the balcony.
Where sound shadow is formed, user under it will not be able to enjoy the
performance or speech to the fullest due to the lack of design application in bringing
sound waves further back and under.
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48. 4.5.5 Sound Echo and Delay
Sound echo and reverb are caused by sound bouncing off various room surfaces.
However, the experience of repetition of sound (echo) is disturbing and does not
help in sound propagation. Absorption or diffusion is used to removed echo
contained within a space.
In an theatre design, a time delay of 40msec for speech oriented theatre and a time
delay of 100msec for performance oriented theatre is deemed as echo. They are the
distinct repetition of the original sound.
Short Range
Time delay
= (7.8m + 8.4m - 3.6m)/0.34s
= 37.1ms
A time delay of 37.1ms is still acceptable for a speech oriented theatre
48

49. Mid Range
Time delay
= (10.1m + 7.8m - 9.1m)/0.34s
= 25.9ms
A time delay of 25.9msec is acceptable for a speech oriented theatre
49

50. Far range
Time delay
= (11.9m + 3.9m - 11m)/0.34s
= 14.1ms
A time delay of 14.1msec is still acceptable for a speech oriented theatre
The time delay for PJ Live Arts is still within control even at different seatings. Echo
is not a big issue for the auditorium as it is handled properly through certain design
strategies.
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51. 4.5.6 Flutter Echoes
Flutter echo is an energy that’s trapped between two parallel surfaces that places
opposite to each other. A flutter echo can be diagnosed with a sharp hand-clap,
when the repeating reflections form a fluttering noise that give the problem its name.
Figure 4.5.6.1 Diagram shows the flutter echos in the auditorium without absorbent wall
Figure 4.5.6.2 Diagram shows the flutter echos in the auditorium with absorbent wall
Without the absorbent wall, the repeating reflections on the parallel walls form a
flutter echos. The absorbent material absorb and decrease the flutters echoes.
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52. Figure 4.5.6.3 Diagram above shows flutter echoes of the theatre without ceiling panels
Figure 4.5.6.4 Diagram above shows flutter echoes of the theatre with ceiling panels
Without the ceiling panels, flutter echoes will happen as the ceiling and floor is
opposite and parallel to each other. The ceiling reflector panels were installed in
specific angle to prevent flutter echoes in the auditorium.
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53. 4.6 Reverberation Time Calculation
As (chair)
= [(0.37m x 0.26m) + (0.3m x 0.41m)] x 0.14
= [0.10m² + 0.12m²] x 0.14
= 0.04 m² sabins
No. of chairs = 412 chairs
As (chair)
= 0.04 x 412
= ​16.48 m² sabins
Surface area of ground floor (timber veneer flooring)
= [(8.15m x 3.34m) + (8.23m x 3.35m) + (12.22m x 9.53m) + (16.2m x 5.9m) +
(2.24m x 3.12m)]
= 27.22m² + 27.57m² + 116.46m² + 71.98m² + 6.99m²
= 250.22m²
Surface area of stage (polyvinyl)
= [(8.15m x 3.34m) + (8.23m x 3.35m) + (2.24m x 3.12m) + (3.12m x 9.53m)] -
11.82m
= 27.22m² + 27.57m² + 6.99m² + 29.73m² - 11.82m²
= 79.69m²
Surface area of balcony (concrete floor)
= (6.42m x 0.92m) x2
= 11.82m²
As (timber veneer flooring)
= 250.22m² x 0.05
= ​12.51 m² sabins
As (polyvinyl)
= 79.69m² x 0.08
= ​6.38 m² sabins
As (sealed concrete flooring)
= 11.82m² x 0.01
= ​0.12m² sabins
Surface area of ceiling (rough concrete)
= [(8.15m x 3.34m) + (8.23m x 3.35m) + (12.22m x 9.53m) + (16.2m x 5.9m) +
(2.24m x 3.12m)]
= 27.22m² + 27.57m² + 116.46m² + 71.98m² + 6.99m²
= 250.22m²
Surface area of ceiling under balcony (plaster ceiling)
= [(8.15m x 3.34m) + (8.23m x 3.35m) + (2.24m x 3.12m) + (3.12m x 9.53m)]
= 27.22m² + 27.57m² + 6.99m² + 29.73m²
53

54. = 91.51m²
Surface area of ceiling (timber panels)
= [(2.74m x 1m) x 27] + [(2.74m x 0.71m) x 6)]
= 73.98m² + 11.67m²
= 85.65m²
As (rough concrete ceiling)
= 250.22m² x 0.03
= ​7.51 m² sabins
As (plaster ceiling)
= 91.51m² x 0.03
= ​2.75 m² sabins
As (ceiling timber panels)
= 85.65m² x 0.25
= ​21.41 m² sabins
Surface area of wall (stage)
= (16.5m + 5.97m + 5.97m) x 7.05m
= 28.44m x 7.05m
= 200.05m²
Surface area of wall (audience)
= (11.73m + 4.10m + 10.34m + 4.57m + 17.46m) x 11.9m
= 48.2m x 11.9m
= 573.58m²
As (acoustic panel - wall​)
= (200.05m² + 573.58m²) x 0.75
= ​580.22 m² sabins
Surface area of curtain
= (16.5m + 5.97m + 5.97m) x 7.05m
= 28.44m x 7.05m
= 200.05m²
As (curtain)
= 200.05m² x 0.15
= ​30.01 m² sabins
Total As
= (16.48 + 12.51 + 6.38 + 0.12 + 7.51 + 2.75 + 21.41 + 580.22 + 30.01) m² sabins
= 677.39 m² sabins
Volume of theatre
= (101.25m² x 7.05m) + (226.52m² x 11.9m)
54

55. = 713.81m³ + 2695.59m³
= ​3373.4m³
RT
= 0.16V/A
= 0.16 x 3373.4/677.39
= ​0.8 seconds
5.0 Conclusion
For a general use of a theatre catering for speech and performance purposes, a
reverberation time of 1.5-2s is optimum. While in PJ Live Arts, the reverberation time
is considered as low, as only suitable for a recording studio, or even as a classroom
(< 1s). Design considerations should be taken care of to increase the reverberation
time within the theatre, such as to replace some of the absorbance material with
reflective materials.
55

56. 6.0 References
ROGERS, H. (2005). Acoustic Architecture: Music and Space in the Video
Installations of Bill Viola. Twentieth-Century Music, 2(2), 197-219.
doi:10.1017/S1478572206000260
Muecke, M. W., & Zach, M. S. (Eds.). (2007). Essays on the Intersection of Music
and Architecture (Vol. 1). Lulu. com.
Baumann, D. (2011). Music and Space: A Systematic and Historical Investigation
Into the Impact of Architectural Acoustics on Performance Practice Followed by a
Study of Handel's Messiah. Peter Lang.
Born, G. (Ed.). (2013). Music, sound and space: transformations of public and
private experience. Cambridge University Press.
Seddeq, H. S. (2009). Factors influencing acoustic performance of sound absorptive
materials. Australian Journal of Basic and Applied Sciences, 3(4), 4610-4617.
Yokota, T., Sakamoto, S., & Tachibana, H. (2002). Visualization of sound
propagation and scattering in rooms. Acoustical science and technology, 23(1),
40-46.
Pierce, A. D. (1981). Acoustics: an introduction to its physical principles and
applications (Vol. 678). New York: McGraw-Hill.
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