Bentley Music Auditorium Acoustic Studies

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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 Bricks Plaster

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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 placed on 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 amplified sound, 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 diagram discuss 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: 6m2

Absorption Coefficient: 0.04

Absorption coefficient of the surface: 0.24

Reflective Panel (Timber Door)

Area: 30m2



Absorber Panel

Area: 60m2


Absorption coefficient of the surface: 30

Brick Wall Area: 60m

2



Glass

Area: 127m2



Curtain

Area: 127m2



ENTRANCE WALL

FACADE WALL

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CEILING

Concrete (slab)

Area: 404m2


Absorption coefficient of the

surface: 8.08

Aluminium deck

Area: 404m2



surface: 101

FLOOR

Concrete (slab)

Area: 404m2



surface: 8.08

Carpet

Area: 404m2



surface: 101

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RIGHT WALL

Absorber panel

Area: 150m2



surface: 75

Reflector panel

Area: 76m2



surface: 11.4

Brick wall Area: 226m

2



surface: 6.78

Absorber panel

Area: 150m2



surface: 75

Reflector panel Area: 76m

2



surface: 11.4

Brick wall

Area: 226m2



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 perceived acoustic 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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4.0 REFERENCE 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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Bentley Music Auditorium Acoustic Studies

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