Building Science 2 - Auditorium

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TABLE OF CONTENT
1.0 Introduction ..............................................................................................................................2
1.1 Aims & Objective .........................................................................................................2
1.2 Historical Background of Auditorium ................................................................3-4
1.3 Drawings of Auditorium ............................................................................................5-6
2.0 Data collection
2.1 Acoustical Elements Used.........................................................................................7
2.1.1 Sound Diffuser panels ...................................................................................7-8
2.1.2 Sound Reflector Panels ................................................................................9
2.1.3 Sound Absorber Panels ................................................................................10
2.1.4 Carpet Floorings and fabric curtain........................................................11-12
2.2 Sound Source ..................................................................................................................13-14
2.3 Sound Reflection ..........................................................................................................15-16
2.4 Sound Diffusion ............................................................................................................17-18
2.5 Sound Absorption ........................................................................................................19-24
2.6 Direct and Indirect Sound Path .............................................................................25-27
2.7 Acoustical Defects in Auditorium
2.7.1 Poor Air Tight Connection.............................................................................28
2.7.2 Mechanical Noise Problem...........................................................................29
2.7.3 External Noise from Curtain Glass ...................................................30
3.0 Conclusion.................................................................................................................................31

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4.0 Reference and Citation ......................................................................................................32-33
1.0 INTRODUCTION
The chosen auditorium, Bentley Music Auditorium is located inside the
Bentley Music Academy Building at Mutiara Damansara. This Auditorium started
operation in year 2008. This auditorium is very well known by musicians around the
world as Bentley & Co. It is the largest music instrument retailer and distributor in the
country and in turn launch the country's leading music school. A lot of renowned
musicians will hold mini concerts or music sharing sessions in this auditorium from
time to time. It is a perfect venue for small seminars and conference.
1.1 AIMS AND OBJECTIVES
The aim of this project is to expose ourselves on the actual auditorium design
layout and to learn how the design and its choice of materials will affect the
effectiveness of the acoustic properties in an auditorium.
This assignment is carried out by 8 group members consisting Tristan Yu, Roy
Yiek, Eveline Devina, Louis De Razario, Harish Kumar, Adam Tan, Lim Joe Onn and
Ong Seng Peng. Our objective is to understand how the sound propagation works in
the auditorium by analysing the data we collected from site. Besides, we are also to
make a conclusion about whether the selected case study achieve the ideal acoustic

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properties based on the analysis we did on our auditorium from several aspects such
as sound reflection, sound absorption, sound diffusion and others.
1.2 HISTORICAL BACKGROUND
The story of Bentley Music Academy begins in 1975 when founder Mr. Phua Sin
Loke opened his first music instrument store, Bentley & Co. on Masjid India in central
Kuala Lumpur, Malaysia. Little did he expect that what began over 30 years ago,
would one day turn into the largest music instrument retailer and distributor in the
country and in turn launch the country's leading music school.
In 1981 Bentley Music acquired its own building in Jalan Bukit Bintang launching
a super store with a 4-storey showroom. This store once claimed to be "the largest
music store" in the country and became a landmark in its own right. Spread over four

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levels of retail space, it has everything a musician needs, making it a music mecca on
a national and international level.
To this day Bentley Music continues to lead the way in music retailing and
continues to adapt itself to the demands of the music market with a 20,000-square-
foot Mega Store located within its new building in 2008 at Mutiara Damansara. It is in
this building that Bentley Music Auditorium is located.
This auditorium is one of the most famous places for the singers around the
world to host their music sharing session or mini live concert.

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1.3 DRAWINGS OF AUDITORIUM
PLAN VIEW

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LEFT ELEVATION
RIGHT ELEVATION
FRONT ELEVATION REAR ELEVATION

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1.0 DATA COLLECTION
2.1 ACOUSTICAL ELEMENTS USED
Bentley Auditorium is mainly used to cater a lot of small musical
performances and seminars. Therefore, good acoustic system is being implemented
in this auditorium. The acoustical elements that can be found easily are Sound
Absorber panels, Sound Diffuser panels, Sound reflector panels, soft carpet flooring
and fabric stage curtains. All these acoustical elements are well placed and designed
in a way that the acoustic is the best when performance is going on.
2.1.1 SOUND DIFFUSER PANEL
The diffusers found in Bentley Auditorium are the random pattern
wood laths diffuser you can see on its side wall.
The highlighted area in the picture above shows the diffusers present in
the auditorium.

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Diagram
illustrating the
type of
diffuser used
in the
auditorium.

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The diffusers actually consist of two elements which comprise of
absorber and reflector that made up its sound diffusion effect, the following
diagram illustrate the concept.
WALL PANEL (PLAN VIEW)
SECTION
The uneven spacing
of dented surface
help diffuse the
sound waves to
different direction,
hence reducing the
sound intensity,
preventing it from
sound echoes.
Some of the sound wave is absorb by the fiber
glass sound insulation panel.

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2.1.2 SOUND REFLECTIVE PANEL
The reflectors are the catchy-eye panels located on top of the ceiling. With its
huge size shows its strong characteristics of giving the best reflection in the
auditorium.
Highlighted
area above
shows the reflectors present in the auditorium
Diagram illustrating the detail of reflector used in the auditorium

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2.1.3 SOUND ABSORBER PANEL
Bentley auditorium utilizes fiberglass panels for their sound absorption
requirements.
Composed of compressed mineral wool or foam, sound absorbing acoustic
panels are used to absorb sound waves which reduces general noise, clarify
speeches and limit reverberation within enclosed areas. Using acoustic panels,
it is essentially to “clean” an area of its unnecessary sound.
When sound waves travel through the air and strike the wall reducing
panels, fiberglass fibers vibrate, increasing friction among fibers. These
vibrations then reaches a point quickly where enough friction is created for
the conversion of sound energy to kinetic (heat) energy. Since kinetic energy
can’t be contained, it dissipates quickly, leaving no sound waves and,
naturally, no sound.
Fabric
Fiberglass
50mm
BricksPlaster

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2.1.4 CARPET FLOORINGS AND FABRIC CURTAIN
2.1.4.1 CARPET FLOORING
The nylon carpet flooring in the auditorium prevents hard contact with the
floor, although of no help against airborne sound transmission, and thus
attenuates impact sounds. It is, in fact, the only floor finish that absorbs
sound. The noise reduction coefficient (NRC) for typical commercial carpets is
around 0.20. The absorptivity is confined mainly to the high frequency,
however, it also helps to absorb the bass
vibration from subwoofer placedon the floor compared to hard-finish
flooring, reducing the direct impact to the floor structure.

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2.1.4.2 CURTAIN FABRIC
Fabrics include a range of textiles that are used on their own (as
curtains) or as coverings for other materials may or may not be sound
absorbing. The curtains used behind the stage in the auditorium can be
considered absorbing as they are reasonably heavy (around 500g/m2). A
heavy, flow-resistant fabric may rate NRC 0.70 or more. Provided they are not
airtight, the fabrics make an acoustically excellent finish that fully preserves
the absorptivity of the substrate.

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2.2 SOUND SOURCE
Sound systems are used to electronically amplify natural sound, also called live
sound. Traditionally, these are called sound reinforcement systems with purpose to
augment the loudness of the live sound with amplifiedsound, with the listener
hearing a combination of both. If sound system is in use, the audience is typically to
hear sound from the system. Thus, the most important consideration for the sound
system design is determining the relative importance of the four sound parameters
that make up what the listener hears: loudness, direction, frequency, and time. The
major types of loudspeaker arrangements typically used are the central loudspeaker
cluster, split cluster systems, distributed loudspeaker system, and multichannel
systems. The following diagramdiscuss about the kind of sound system present at
the site.
Speaker System: Central loudspeaker cluster system, locates the
loudspeakers above the source of live sound. It provides
directional realism toward the front of the room.
Number of speakers: 4 Full-range speakers
2 Subwoofers
The picture
beside shows
the full range
speaker.

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The speakers used in Bentley Auditorium can be safely driven with over
1000 Watts of amplifier power. The 2-way passive 8-Ohm design uses a single
amplifier channel to deliver bi-amped performance.
A full-range loudspeaker drive unit is defined as a driver which
reproduces as much of the audible frequency range possible. It’s usually
limited to covering the audio spectrum above 100 Hz. A subwoofer is
designed for frequencies below approximately 150Hz, so they sound great on
the high and low frequencies, but poor in middle range.
The loudspeaker placement ensures both type of sound are received by
audience in the same intensity.

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2.3 SOUND REFLECTION
Incident sound wave hits the surface until the sound energy come to a zero.
Reflection of sound waves bounce off surfaces can lead to one of two phenomena -
an echo or a reverberation.
Smooth walls have a tendency to direct sound waves in a specific direction.
Subsequently the use of smooth surface in an auditorium will cause spectators to
receive a large amount of sound from one location along the wall; there would be
only one possible path by which sound waves could travel from the speakers to the
listener. The loudspeaker illuminates its entire view but only a tiny fraction of the
sound actually hits the target, the ears of the people below, the "direct sound". The
rest of the sound crashing into the walls, floor and carpet, the people, coats, and
chairs, the walls, windows and doors. Every time some part of the indirect sound hits
a surface, it is reflected. How the surfaces of the hall reflect the indirect sound
determines how the room sounds.
The floor carpet surface, wood panels on wall and aluminums panels attached
ceiling reflect almost all incident sound energy striking them. The properly concave-
shaped aluminums panels on the ceiling form a reflective surface. Concave-shaped is
especially useful, and they have one focus point which concentrate the sound
towards one direction.

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Diagram showing listeners at the front row
Diagram showing listeners at the middle row

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Based on
observation,
concave-shaped
ceiling panels
provide angle of
sound
concentration
towards the
center of the
area. While
carpet floor reflect sound from direct speaker towards the front row. The partially
wooden panels act as reflector to reflect the sound towards the center of the
audience form early reflection. Early reflections raises the apparent loudness of the
direct sound in a comfortable, natural way, much more agreeable than turning up the
volume.
Diagram showing listeners at the back row
USEFUL CEILING REFLECTOR
Diagram showing how the ceiling reflect to the audience.

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2.4 SOUND DIFFUSION
The diagrams above clearly explained the differences between
reflections, scattering and diffusion to help us understand more about the
concept of sound When the sound is spread from its source in a given
enclosed environment, how well does it spread evenly throughout the room
will depend on the sound diffusion efficiency. A good diffusive sound space
will have the same acoustic properties anywhere in the space. A poor sound
diffuser system would produce unwanted echoes. Both design and choice of
mechanism can affect sound diffusion efficiency.

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The diagram above illustrate how the different design can have
different acoustic properties in an enclosed environment. Should the
auditorium form to be designed following its floor plan, there would be some
part of the audience will receive unwanted echoes sound. It’s a preferable way
to design the ceiling in responding to the sound source and its acoustic
properties. Bentley Auditorium responded well through its design of form.
The design in Bentley auditorium actually help the even diffusion of
sound coming from the stage and speaker, through its use of aluminum
sound reflective ceiling with concave side facing the interior therefore each of
the seating zone from front to back can relatively receive the same sound
quality and equal sound intensity. As mentioned previously, the diffusers used
in Bentley Auditorium are the irregular wood patterns on the side wall. Not
only does it serves the sound diffusion function but it is also aesthetically
pleasing for its interior design.

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2.5 SOUND ABSORPTION
Sound absorption is the processes that result in acoustical absorption are
friction and resonance. Sound-absorbing panel affects the reverberation time and the
noise in level in the room. It works through friction when sound has access to the fine
pores and interstices that one finds in porous and fibrous material. Absorption is
frequency dependent. Porous-fibrous absorbers are most efficient in the higher
frequency and middle to low if sufficiently thick or backed by airspace. The
importance of the absorber comes to control the ambiance or reverberant field not
to exceed the room’s natural threshold, causing ‘ear fatigue’, whereby
communication will then require much more attention. Soundproofing panels will
boost the audience’s experience by improving sound clarity in an auditorium.
The sound is
absorbed by
the fiber panel
and release as
heat.
Sound is absorbed at the end of the
auditorium to prevent echoes.

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Sound Absorption Efficiency value at 500Hz

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Glass
Area: 6m
2
Absorption Coefficient: 0.04
Absorption coefficient of the surface: 0.24
Reflective Panel (Timber Door)
Area: 30m
2
Absorber Panel
Area: 60m
2
Absorption coefficient of the surface: 30
Brick Wall
Area: 60m
2
Glass
Area: 127m
2
Curtain
Area: 127m
2
ENTRANCE WALL
FACADE WALL

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CEILING
Concrete (slab)
Area: 404m
2
Absorption coefficient of the
surface: 8.08
Aluminium deck
Area: 404m
2
surface: 101
FLOOR
Concrete (slab)
Area: 404m
2
surface: 8.08
Carpet
Area: 404m
2
surface: 101

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RIGHT WALL
Absorber panel
Area: 150m
2
surface: 75
Reflector panel
Area: 76m
2
surface: 11.4
Brick wall
Area: 226m
2
surface: 6.78
Absorber panel
Area: 150m
2
surface: 75
Reflector panel
Area: 76m
2
surface: 11.4
Brick wall
Area: 226m
2
surface: 6.78
LEFT WALL

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2.6 DIRECT AND INDIRECT SOUND PATH
The perception of sound directions is attributed to the law of the first wave
front which states that the sound will usually be localized in the direction from which
the first sound wave that arrives at the listener’s location comes. The concept of
sound being divided into several components defined by perceivedacoustic qualities
is based on the idea that an impulse response can be subdivided into several
components: direct sound, the early sound reflections, the later or reverberant
sounds, and the ambient or background noises. The basic two are the direct sound
and the early sound reflections (indirect sound). Direct sound travels directly from the
source to the listener without striking any of the surfaces of the room which
contributes to sensations of loudness, clarity, and localization. It will generally
decrease as it moves further from the sound source. The early sound reflections strike
one of the room surfaces (ceiling, wall, etc.) and are reflected to the listener’s
location. Reflections that arrive within short time intervals after direct sound (less
than 80msec for music) are usually combine with the direct sound by the ear,
increasing it apparent loudness. The combination is what makes it possible to have
similar levels of loudness at seats located throughout a large room.

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2.7 ACOUSTICAL DEFECTS INAUDITORIUM
2.7.1 POOR AIR TIGHT CONNECTION
Noise from foyer open area of the building can be heard from interior. Which
will cause distraction of noise enter the auditorium if there's any function
happening inside.
One of the symptoms we discovered is the poor insulation of closed doors.
The hollow surround the door frame allows sound to pass through into the
interior from the slit easily.
We discover the door jambs comes without proper seals. Besides that, we can
feel the air movement and light shine through the door frame.
Before After
Therefore, the solution is to add seals, for example flexible material like
Neoprene. So that, when the door is shut the seal should be in line that
compress against the clean surface. The goal is be an air tight connection
from allowing air and light passing through the hollow area.

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2.7.2 MECHANICAL NOISE PROBLEM
The air vents is right on top of the ceiling hiding behind the aluminums panels
producing whooshing of air create noise and make it difficult to focus at a
certain time when the room is quiet.
An annoying whooshing sound from the vents outlet are usually result of
small openings and tight grillwork that restrict the airflow from the aluminums
panel.
Due to the fact that music room need nearly twice the rate of fresh air
exchange as a classroom of equal size. As a result, vent openings need to be
large with open grillwork. Thus, small vents and heavily screened grills is
required to replace if possible.
Small vent outlet

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2.7.3 EXTERNAL NOISE FROM CURTAIN GLASS
One of the major defects in this auditorium is that it is not completely sound
proof from the external noise. This is because of the selection of material at the front
part (exterior façade) of the hall. The front part of the auditorium hall is a huge
curtain glass panels.
The reason for the choice of material is for the esthetic purpose from the
exterior of the building and also to provide sufficient lighting into the interior of the
building. However,
one downside of this
decision is that
exterior noise will be
able to penetrate
into the auditorium
hall. It is even more
obvious as there is a
construction work
going on at the
opposite of the
auditorium.

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2.0 CONCLUSION
Based on our findings, we have concluded that Bentley Auditorium has
installed plenty of materials, new methods of controlling the sound effectively
that gave us the opportunity to find out deeper about. We analysed deeply
about the right combination of both sound absorption and diffusion. This
combination can transform the acoustics of virtually any room into a world-
class auditorium. While learning about the acoustics in Bentley Auditorium, we
discovered some poor noise control in the room that is cause by the noise
pollution from the exterior affecting the internal sound, thus we proposed a
few solutions for that issue. An auditorium should take into consideration
towards future planning. This problem doesn’t affect the auditorium as much,
as it is perfectly usable. The fact that this auditorium is made from low
budget but still ideal for its current function. In terms of materials and
construction system involved, it creates an overall great listening experience.
Therefore, it shows that effective sound control could produce a great
environment for listening in the building.

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4.0REFERENCE AND CITIATION
Astralsound. (2003). Bass Loudspeaker Position in PA Systems. Retrieved from
www.astralsound.comBentley Music Academy Sdn Bhd (2016). A Brief History.
Retrieved from http://www.bma.com.my
Cavanaugh, J. W., Tocci, G. C., & Wilkes, J. A. (2010). Architectural Acoustics Principles
and Practice. USA: John Wiley & Sons, Inc.
Dare, Tyler. (2005, May 13). Multipurpose Auditorium. Retrieved from
https://courses.physics.illinois.edu
Egan, M. D. (2000). Architectural Acoustics. USA: J. Ross Publishing.
GraceNote Design Group. (2013). Acoustics 101 for Architects. Retrieved from
www.sound-image.com
Graves, R. S., & Zarr, R. R. (1997). Insulation Materials, Testing, and Applications (3rd
Ed.). US: ASTM International.
Harris, Cyril M. (2012). Noise Control in Buildings: A Practical Guide for Architects and
Engineers. NY: McGraw-Hill.
Kinetics Noise Control. Architectural Acoustics. Retrieved from
http://www.kineticsnoise.com
Mehta, M., Johnson, J., & Rocafort, J. (1999). Architectural Acoustics: Principles and
Design. USA: Upper Saddle River.
Neufert, Ernst, & Peter. (2012). Neufert Architects’ Data. Oxford: Wiley-Blackwell.
PS15 Loudspeaker. (2015). Retrieved from www.Audiologic.uk
The University of Hong Kong Libraries. (1996). Auditorium Acoustic Design, Hong Kong
Academy for Performing Arts. Retrieved from
http://ebook.lib.hku.hk/CADAL/B38631787.pdf

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Theatre Project Consultants. Types and Forms of Theatres. Retrieved from
www.http://theatreprojects.com
University of Salford. (2017). Architectural and Building Acoustics. Retrieved from
http://www.salford.ac.uk
Wenger. (2000). Acoustic Problems & Solutions for Rehearsal and Practice Spaces.
Retrieved from www.wengercorp.com

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