Acoustic Design

School of Architecture, Building and Design Bachelor of Science (Hons) in Architecture

Building Science I Project 1 Auditorium: A Case Study on Acoustic Design Group Members: Ahmad Ashraf 0317744 Aidan Ho Wei Suan 0326021 Caleb Soh Er Wen 0320292 Hor Ming Jack 0325145 Jack Lee Hor Kit 0325810 Ng Wyn Jane 0319440 Nik Munawwar Nik Din 0325167 Thareen Nujjoo 0324886

Tutor: Mr. Azim

A Case Study on Acoustic Design: Damansara Utama Methodist Church (DUMC)

TABLE OF CONTENTS

1.​

2.​

3.​

4.​

​Introduction 1.1 Aims & Objectives

2

1.2 Site

3

1.3 Drawings

4

​Acoustic Theory 2.1 Acoustics in Architecture

5

2.2 Sound Intensity Level

5

2.3 Reverberation, Attenuation, Echoes, and Sound Shadows

5

2.5 Acoustic Design for Auditoriums

6

​Methodology 3.1 Equipment

7

3.2 Data Collection Method

9

​Acoustic Analysis 4.1 Auditorium Design

11

4.2 Materials

18

4.3 Acoustic Treatments & Components

20

4.4 Sound & Noise Sources

29

4.5 Sound Propagations and Related Phenomena

41

5.​

​Observation, Discussions and Conclusion

​50

6.​

​References

​51

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A Case Study on Acoustic Design: Damansara Utama Methodist Church (DUMC)

1.​ Introduction ​

1.1 Aims & Objectives

The aim of this report is to document the research conducted on the acoustical design of an auditorium in order to provide an insight into the intricacies of acoustic modeling, design and implementation. The objectives of the report are as follows:

1. To conduct an in-depth exploration of the auditorium typology based on its layout, designed with an intention for a specific acoustic performance according to the needs of its functions.

2. To develop a robust understanding of the physics behind the acoustic quality of an auditorium.

3. To analyse the relationship between acoustics and the materials, spatial planning and context of an auditorium.

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A Case Study on Acoustic Design: Damansara Utama Methodist Church (DUMC)

1.2 Site

1.2.1 Basic Information Name of Auditorium : ​Damansara Utama Methodist Church (DUMC) Location

: Seksyen 13, 46200 Petaling Jaya, Selangor, Malaysia

Type of Auditorium

: Multi-purpose auditorium

Year of Construction : 2005 Year of Completion

: 2007

Total Volume

: 18655m​3

Total Seat

: 2301 seats

1.2.2 Historical Background

Damansara Utama Methodist Church (DUMC) was started in 1980 by a group of 22 professionals and 3 children from SSMC (Sungai Way-Subang Methodist Church). They started of in a shop lot premise in Damansara Uptown before moving to a factory lot in Taman Mayang in 1993 to accommodate the fast growing congregation which at this point had reached 500 people.

The Chinese congregation was started in 1996 as the first vernacular service in DUMC. At the same time, to accommodate the growing size of the congregation, more services were held each weekend. By 1998, they were having three celebrations weekly with a congregation size of 1000 worshippers.

The numbers continue to grow until 2007 when they moved to the current premise - Dream Centre. At present time, the congregation stands at 4500 worshippers weekly across seven different vernacular services.

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A Case Study on Acoustic Design: Damansara Utama Methodist Church (DUMC)

1.3 Drawings

Ground Floor Plan

First Floor Plan

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A Case Study on Acoustic Design: Damansara Utama Methodist Church (DUMC)

2. Acoustic Theory 2.1 Acoustics in Architecture Acoustic architecture, is a field of study that dabbles on the nature of sound and its manipulation within the space allotted to it.

Be it an open amphitheatre or a fully indoor auditorium, acoustic architecture attempts to optimize the sound quality for whatever activities it houses

2.2 Sound Intensity Level Sound intensity is defined as the sound​ power per unit area (watts/m​2​)

2.3 Reverberation, Attenuation, Echoes and Sound Shadows Reverberation - Persistence of ​sound after a sound is produced. A measure of sound decay through its propagation, ie ​flutter echoes​.

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A Case Study on Acoustic Design: Damansara Utama Methodist Church (DUMC)

Attenuation -

Nature/Energy level of sound as it propagates through mediums of different density and scatters to the surrounding environment.

Îą= Energy Absorbed / Incident Energy Echoes -

Sound reflection is as ubiquitous as the cosmic radiation that surrounds us always. Echoes are defined as sound reflections that is returned to the listener with a perceptible magnitude. Multiple echoes create Reverberations.

D=VT Sound Shadows - Areas that are shielded from sound waves through mediums that either absorb or reflect such waves to a considerable degree.

2.4 Acoustic Design for Auditoriums Goals: a) Preservation of sound intensity (longer the better) b) Clarity in sound delivery c) Optimum reverberation time d) Prevent excessive vibrations e) Reasonably reduce external noise

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A Case Study on Acoustic Design: Damansara Utama Methodist Church (DUMC)

3. Methodology 3.1 Equipment 3.1.1 Digital Sound Level Meter

3.1.2 Digital Camera

3.1.3 Measuring Devices -

Measuring Tape, Laser Distance Measurer

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A Case Study on Acoustic Design: Damansara Utama Methodist Church (DUMC)

3.1.4 Source generator

● Bluetooth speaker + Tripod

Specifications: Max. Power Output: 3W Bluetooth Transmission Distance: 10m Bluetooth Version: 3.0 Class II, Support A2DP V1.2, AVRCP V1.4 profiles Audio Input Interface: 3.5mm audio interface, support AUX external audio input Tripod height : 1.6m ● Tone generator (phone app)

Specifications: Frequency range : 0hz - 20000hz Tested frequency : 125hz, 500hz, 2000hz 3.1.5 Human

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A Case Study on Acoustic Design: Damansara Utama Methodist Church (DUMC)

3.2 Data Collection Method

Measuring Dimensions ● Long measuring roll tape - for short and easily accessible areas up to 9m ● Laser distance measurer - for long inaccessible areas ie ceiling height

Measuring Sound Intensity Levels ● Set bluetooth speaker at the center of the stage at 1.6m height from stage floor ● Take a controlled sound level at 1m away from sound source at (125hz,500hz,2000hz) ● Take sample at 5 m away from sound source at (125hz,500hz,2000hz0

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A Case Study on Acoustic Design: Damansara Utama Methodist Church (DUMC)

● Repeat sample taking at multiples of 5m including backstage

Measuring Sound Attenuation (in children's play area) ● Set bluetooth speaker inside the children play area at 1.6m height from floor ● Set sound source and receiver at 2m away from the glass panels ● Take sample of noise level through the glass pane

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A Case Study on Acoustic Design: Damansara Utama Methodist Church (DUMC)

4. Acoustic Analysis 4.1 Auditorium Design 4.1.1 Shape of Auditorium

The auditorium is designed as a fan shape. This configuration results in a more intimate space as the audiences are brought closer to the speaker. Due to the closer proximity between the audiences and the speaker, the sound of the speaker is louder and more audible, which in turn improves the listening condition for the audience. This arrangement also creates a central focus which further contributes to a more intimate relationship between the speaker and the audience.

However, the arrangement of the auditorium, which is at 150​°​, exceeds the maximum limit of 130​° for a wide fan arrangement. This affects the audience situated beyond the suggested limit who will have to put up with a poor listening condition. Ideally, there should be no seats beyond the maximum limit for the fan shaped arrangement as it severely affects the listening condition of the audience.

The figure denotes the region which is within the 130​°​ limit.

Note the seating on both sides which fall outside this region.

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A Case Study on Acoustic Design: Damansara Utama Methodist Church (DUMC)

4.1.2 Levelling of Seats

The leveling of the seating area is of utmost importance to ensure that sound waves reach the ears of all occupants within the auditorium clearly. There are two types of seat in the auditorium which are fixed and movable seats to accommodate different occasion use. The fixed seats are placed at level terrace on the ground floor and first floor, while the movable seats are placed at the ground floor pit.

The figures above show the seat arrangement at ground floor pit, ground floor terrace and first floor terrace. Â

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A Case Study on Acoustic Design: Damansara Utama Methodist Church (DUMC)

At the ground floor pit, the sound attenuation is not resolved due to the seats that are located at the same level. The intensity of sound is decreased over time to reach the furthermost seat as the sound is absorbed in part by the seats in the first half.

The seat arrangement at ground floor pit which arranged in the same level.

The seats at the terrace on the ground floor are elevated from the ground floor pit but are not evenly allocated because there are two consecutive rows of seat positioned at the same level. With a same level positioned of seats, the propagation of sound source is reflected and diffracted by the first row seats which caused uneven distribution of sound that lead to the occurrence of undesirable acoustical defects.

The elevated seat arrangement at ground floor terrace. Â

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A Case Study on Acoustic Design: Damansara Utama Methodist Church (DUMC)

The terrace seats at the first floor are in the most effective arrangement as they are arranged in a staggered manner. Adequate sound diffusion is achieved to promote uniform distribution of sound and accentuates the natural qualities of music and speech.

There is also no sound diffraction as there are no barriers such as corners, columns, walls and beams in their path which provides an effectiveness of sound waves reaching the ear of occupants without any objects blocking or absorbing it.

The seat arrangement at first floor terrace arranged in a staggered manner.

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A Case Study on Acoustic Design: Damansara Utama Methodist Church (DUMC)

4.1.3 Arrangement of Seats

There are a total number of 2200 seats within the auditorium and they are arranged in a fan shaped configuration. This arrangement is to achieve uniform quality sound over the entire seating area because sound propagates outwards from the stage in a spherical wave front. However, some of the seats are arranged beyond the maximum limit of the fan shaped configuration which is 150 degree. A poor listening condition may occurred throughout the acoustic experience for the audience situated beyond the suggested limit seating arrangement.

The figure above shows the fan shaped configuration of seats within 150 ​°​ sound projection angle.

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A Case Study on Acoustic Design: Damansara Utama Methodist Church (DUMC)

4.1.4 Ceiling Design

The staggered ceiling configuration accommodates the inclusion of catwalks for easy access to the spotlight gantries but more importantly, it serves to contribute useful sound reflection towards the seating area, increasing the volume of the sound as it reaches the audience. The concave design of the ceiling panels further aids to direct the reflected sound waves back to the audience especially those seated at the gallery as well as the rear of the ground floor. Ultimately, the ceiling panels serve the function as a sound reflector to ensure that sound waves are distributed evenly throughout the auditorium.

The staggered ceiling helps to reflect and distribute the sound waves evenly to the back section seating in the gallery and ground floor.Â

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A Case Study on Acoustic Design: Damansara Utama Methodist Church (DUMC)

4.1.5 Sound Shadow Area

A sound shadow area is defined as an area which sound waves fail to propagate to. In the case of this auditorium, due to the position of the gallery, a sound shadow area is formed at the back section of the ground floor sitting. The gallery shrouds the people seated in this area from the sound waves produced from the house speaker arrays.

Fortunately, the sound shadow area in this auditorium is considered to be a minor issue as it is shallow. Sound waves are still propagated to the ground floor seating via reflection of the staggered ceiling panels hence no periphery audio devices are required at the back section of the ground floor to compensate for the lost of sound quality via the overhead house speakers.

The region under the gallery (highlighted in red) represents the shallow sound shadow area.Â

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A Case Study on Acoustic Design: Damansara Utama Methodist Church (DUMC)

4.2 Material Table

AREA

COMPONENT

MATERIALS MATERIAL

Stage

Walls

1. Concrete wall.

2. Canvas background.

Apron Absorber

House

SURFACE FINISHES

DESCRIPTION 1. Smooth painted concrete, 150mm thick.

2. Thin tensile canvas backdrop.

COEFFICIENT 125 Hz

Paint.

500 Hz

2000 Hz

0.01

0.01

0.02

Carpet.

5mm thick needle punch carpet.

0.03

0.05

0.35

Curtain

Heavy Cloth.

Medium velour, 50% gather, over solid backing.

0.05

0.40

0.60

Flooring

Timber parquet.

Wooden platform with large space beneath it.

0.40

0.20

0.15

Furniture

Stage set and instruments.

Proscenium opening with average stage set.

0.20

0.30

0.40

Flytower

Steel.

Steel joists/ framing.

1. Drywall.

1.Plasterboard on 25mm battens.

2. Acoustic timber wall panelling.

3. 25mm thick foam covered by scrim cloth on solid plywood backing.

Paint.

0.31

0.14

0.10

Polish.

0.18

0.42

0.83

0.90

0.54

0.88

Walls

2. Timber.

3. Foam.

Polish.

Flooring

Carpet.

5mm thick needle punch carpet.

0.03

0.05

0.35

Seating

1. Padded chairs.

1. Padded chairs with metal frame.

2. Thick cushion seats.

0.08

0.15

0.18

0.13

0.59

0.61

2. Auditorium seats.

Hand Railing

1. Steel.

1. Painted steel railing with steel cables.

Paint.

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A Case Study on Acoustic Design: Damansara Utama Methodist Church (DUMC)

Doors

Ceiling

Control Room

2. Perspex.

2. Transparent perspex panels.

Timber.

1. Solid timber double door.

2.Wood hollow core door.

Paint.

0.14

0.06

0.10

Paint.

0.30

0.15

0.10

1. Plaster on laths with airspace.

2. Gypsum plaster tiles, un-perforated with airspace.

Plaster.

0.30

0.10

0.04

Plaster.

0.45

0.80

0.65

0.30

0.10

0.05

1. Plaster 2. Gypsum Plaster.

Glass.

4mm thick window.

Padded Seat

Curtains

Acoustic Walls

Acoustic Timber Panel

Carpet

Gypsum Plaster

Plaster

Concrete

Acoustic Panels

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A Case Study on Acoustic Design: Damansara Utama Methodist Church (DUMC)

4.3 Acoustic Treatments & Components

4.3.1 Wall Panels

Placement of acoustic elements on walls of auditorium.

1. Acoustic Foam Panels The walls of the gallery of the DUMC auditorium are lined with acoustic panels of different sizes and inclined at different angles. These are designed to prevent sound, more specifically midrange and treble tones from hitting a solid surface and bouncing back to the stage and create echos, by absorbing the sound energy through the material.

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A Case Study on Acoustic Design: Damansara Utama Methodist Church (DUMC)

The panels are made up of foam placed on a plywood surface and wrapped with fabric.

Since foam and textiles are porous materials, they easily absorb sound once it hits the acoustic panel.

The top half of the foam acoustic panels are inclined at certain angles, creating a cavity between the solid wall and the plywood sheet, which makes it more effective.

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A Case Study on Acoustic Design: Damansara Utama Methodist Church (DUMC)

Retrieved from: http://www.troldtekt.com/Product-properties/Good-acoustics/Acoustics-for-advanced/Different-a bsorber-types

2. Acoustic Timber Panels

Retrieved from: http://www.stil-acoustics.co.uk/Timber-Acoustic/Linear.html

The lower half of the ground floor walls, are cladded with acoustic timber panels for absorption of low frequency sounds.

Groove panels are cavity absorbers, they act as a perforated panel by absorbing sound through the linear slits on the face of the panel, which are connected to large cutouts in the back. A layer of mineral fibre is provided behind the panel in order to dampen the

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A Case Study on Acoustic Design: Damansara Utama Methodist Church (DUMC)

sound energy, while a cavity between the wall and the panel creates resonance due to air vibration. These, combined to the perforations create a Helmholtz absorber.

Alterations in acoustic performance are made possible by changing the distance between the grooves or the perforation pattern, the cavity depth and the choice of absorbent material. Smaller groove width usually increases acoustic performance.

3. Padded Walls

The rear walls of the auditorium are covered in a layer of foam and fabric. These walls act as sound absorbers due to the porosity of the materials, to prevent reflection of sound waves back toward the stage which is echo.

The padded walls are also located on the balcony strip, which is where the air conditioning diffusers are. This is an attempt to absorb and dampen the sound caused by the diffusers.

4. Dry Walls Dry walls are located on the sides of the stage, being hard surfaces, they have very low absorption abilities and are used to reflect sound coming from the stage back to the audience.

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A Case Study on Acoustic Design: Damansara Utama Methodist Church (DUMC)

In order to prevent any flutter that could occur during sound reflection, walls parallel to the dry walls are avoided.

4.3.2 Flooring

Carpeted area of the auditorium.

Carpeted Floor Majority of the floor in the Dream Centre auditorium is covered in a layer of carpet. The needle punched carpet that is utilised is created by having barbed needles punched into a matted layer of fiber, that form a mat of surface fibre.

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A Case Study on Acoustic Design: Damansara Utama Methodist Church (DUMC)

This carpeting is sound absorbent, dampening impact and sounds that are a result of the dense foot traffic. It is also porous and absorbs sound energy and reduces reflections and echoes.

Between the carpet and the existing concrete floor, a thin floor underlayment is used to provide further cushioning from footsteps and impacts, and prevent the transmission of floor vibrations. The underlayment is comprised of 2 layers, a flexible solid mass barrier, a soft foam portion that prevents the vibrations and is to be faced toward the ground.

4.3.3 Curtains

Placement of curtains in auditorium.

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A Case Study on Acoustic Design: Damansara Utama Methodist Church (DUMC)

Velour Curtains These are heavy sound-absorbing curtains that are located in strategic locations of the auditorium in order to dampen sound efficiently. Curtains are located at 2 types of areas; At entry points to the auditorium and at the stage.

Curtains are found at access points in order to diminish sounds coming from the opening and closing of doors as people walk in and out of the auditorium, and also to stop sound from escaping the space and leaking into the external area.

At the stage, curtains serve the purpose of aesthetics & concealment, as well as to reduce the reflection of sound, and ultimately echoes. These curtains also stop sound that is made backstage from being heard in the auditorium.

However, to naturally propagate sound more efficiently and effectively, the backdrop curtain of the stage should be removed, and replaced with a more acoustically reflective in order for sound to bounce of it and back to the audience.

4.3.4 Seating

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A Case Study on Acoustic Design: Damansara Utama Methodist Church (DUMC)

Padded Theatre Seating The auditorium feature 2 styles of seating, fixed folding theatre seating at the back of the auditorium and movable seating at front.

The seating and audience of an auditorium are usually the main points of sound absorption in the room. Because of this, it is crucial to correctly plan and predict the absorption coefficient of these components. Therefore, the design and material of the aforementioned seating has to be planned properly.

Both types of seating are padded and clad in a fabric in order to absorbs sound and dampen sound energy, which in turn diminishes echos.

4.3.5 Ceiling

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A Case Study on Acoustic Design: Damansara Utama Methodist Church (DUMC)

Plaster & Plasterboard Ceiling The ceiling is primarily plaster-coated and formed of plasterboards. Plaster has a hard surface that has poor acoustic absorption qualities and therefore sound bounces off it and back towards the ground. This ceiling has been designed in such a way as to properly deflect the sound in the right direction towards the audience, and avoid surfaces parallel to avoid flutter echoes.

This false plaster ceiling also functions to conceal ventilation system and the the fly system inside which is comprised mainly of lighting rigs.

4.3.6 Stage

1. Timber Parquet Flooring Wood floors are utilised for stage use as they are resilient and can withstand foot traffic, as well as produce a longer reverberation time due to it being a hard, acoustically reflective surface. Reverberation can be the cause of various issues if not appropriately suited to the space or use, however in this case it is justified as it causes sound from the stage sound more full.

The stage apron is constructed of a different, but similar-functioning material, which is a laminated MDF-flooring. It has similar acoustic qualities, but costs less than solid timber.

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A Case Study on Acoustic Design: Damansara Utama Methodist Church (DUMC)

2. Carpet Apron Absorber Similar to the auditorium flooring, the apron is clad with a carpeting finish. However, the underlayment is not required as prevention of floor vibrations is not required. The apron absorber absorbs sound reflected from the auditorium that has bounced back towards the stage.

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A Case Study on Acoustic Design: Damansara Utama Methodist Church (DUMC)

4.4 Sound & Noise Sources

The auditorium is designed to produce and contain sound within its enclosed space via the Audio Visual (“AV”) system installed. The control deck for the AV system is located at the centre of the upper seating area for optimal sound monitoring. The sound produced in the auditorium is contained via sound absorbing walls, seats, carpets, and doors that minimizes sound leakages to the outside, whilst also keeping external noises at a minimum.

The term “Sound” and “Noise” may be confused and can be subjectively defined based on the effects it has on a particular person. Noise is generally defined as sound that is unpleasant to the listener. Sound and Noise are both “decibel-independent”; a low db noise is still considered as noise whereas a high db sound is still considered sound.

Both external and internal noises need to be considered when attempting noise suppression in the design of an auditorium. External noise is defined as noise that originates from outside the auditorium, and internal noise is defined as noise produced from within the auditorium, most commonly from instruments, materials, and electrical appliances.

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A Case Study on Acoustic Design: Damansara Utama Methodist Church (DUMC)

4.4.1 Sound Sources

Internal sounds are amplified via the auditorium’s built in AV system, comprising of the input and output components. The input components include dynamic utility microphones, condenser microphones, electric pickups for guitars and bass and direct input from electric musical instruments like keyboards. Output components include amplifiers, array speakers (ceiling mounted) and stage monitors.

Dynamic Microphone

Condenser Microphone

Electromagnetic Guitar Pickup

Type, Location, and Number of Speakers Speakers are used to amplify the sounds created on stage to the audiences and are monitored and controlled by a sound engineer in the sound booth. The speakers are mounted in an angled array from the ceiling at a height of approximately 7 meters from the ground.

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A Case Study on Acoustic Design: Damansara Utama Methodist Church (DUMC)

Speaker Arrays There are 3 speaker arrays suspended from the ceiling directly in front of the stage directed to the centre, left and right sides of the hall to ensure a balanced transmission of sound to the entire hall. The speakers are configured in a 9 – 8 – 9 configuration whereby there are 9 speakers for each left and right arrays and 8 speakers in the centre array.

The speakers are installed in such a manner to avoid reflection from the flat floor which can produce inconsistent amplification should the speakers be on ground level.

Arrangement of Suspended Array Speakers 32

A Case Study on Acoustic Design: Damansara Utama Methodist Church (DUMC)

Subwoofers Alternating between the 3 arrayed speakers are subwoofers that boosts the lower frequency range of the sound, typically below 100 Hz. There is a total of 4 subwoofers which are also suspended from the ceiling of the stage. Instead of being configured in an array similar to the speakers, the 4 subwoofers are installed as single units as lower frequencies have slower attenuation and can easily reach the audiences.

However, the output source of the subwoofers is pointed towards the concrete wall behind it to produce indirect sounds which will be reflected to the audiences via the angled ceiling. This method further reduces the attenuation of lower frequency sounds.

Subwoofer Placement and Configuration 33

A Case Study on Acoustic Design: Damansara Utama Methodist Church (DUMC)

Monitors Monitor speakers function to provide feedback to the performers on stage which are situated in the blind spot area of the speakers.

It is placed on the stage floor facing the performers to ensure that they can hear the sound they produce to help with synchronisation between different instruments during performance.

Location of Floor MonitorsÂ

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A Case Study on Acoustic Design: Damansara Utama Methodist Church (DUMC)

4.4.2 External Noises

Most of the external noise comes from the hallway areas surrounding the hall including from the entrance foyer and the cafeteria on the right side of the auditorium, at approximately ~50dB. However, the external noise from the cafeteria is reduced to an approximated ~30dB when the door is completely shut.

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A Case Study on Acoustic Design: Damansara Utama Methodist Church (DUMC)

There is also a back door behind the stage area which opens up directly to the outside of DUMC. Since the door is not configured with a sound lock, external noise from the parking and construction around the area can be heard quite significantly from the stage at around ~60dB. The level of noise is also dependent on the event taking place in the auditorium. During Sunday services for example, when some of the doors are left partially opened and more congregants are around in the hallway, there is significant increase in external noise as compared to other days.

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A Case Study on Acoustic Design: Damansara Utama Methodist Church (DUMC)

4.4.3 Internal Noises

Internal noise in the auditorium are mostly created by the sounds of electrical equipment such as the AV deck, server, air conditioning, and minor static noise from fluorescent lighting. These noises are constantly present when the hall is in use, but are often dwarfed by the sound of events taking place on stage.

Noise is also created by the materials used in the auditorium when activities are conducted, such as walking on the timber flooring on stage, the opening and closing of the doors, the spring-loaded folding seats, as well as the opening and closing of the sliding doors at the children’s section.

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A Case Study on Acoustic Design: Damansara Utama Methodist Church (DUMC)

Air Conditioning The biggest issue with conditioning the air for a space as large as the DUMC Auditorium is that it produces a high amount of noise when high velocity blowers supply air into the space, usually coupled with jet diffusers. However, the use of these type of blowers are necessary as the diffusers are placed only around the perimeter of the upper tier due to the high ceiling. Hence, a powerful stream of cool air needs to be pumped into the centre from this perimeter array of jet diffusers, producing noticeable noise.

Different types of diffusers are used in the auditorium depending on the functionality, either return or supply of air.

Return For return / intake air, single deflection return diffusers are used in different sizes depending on its location. For first floor return air diffusers, a larger version is used to return air placed at the ceiling.

Return Air DiffuserÂ

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A Case Study on Acoustic Design: Damansara Utama Methodist Church (DUMC)

Supply For the supply of air, two types of diffusers are implemented in the design, namely louver blade diffusers and the rounded jet diffusers. The normal louver blades diffusers are installed where the ceiling is lower such as the area below the upper tier. The blades deflect in all four directions to spread the supply of air evenly. This type of diffuser still produces noticeable noise, but at a much lower level relative to the jet diffusers.

Louvered Blade DiffuserÂ

Jet DiffuserÂ

Jet diffusers are used to supply air to the center of the auditorium where normal louvered diffusers would be inadequate due to the high ceiling.

They are placed at the perimeter of the upper tier pointed towards the center of the auditorium and produces loud noise during operation. Based on observation during the visit, the noise produced by only half of these diffusers on was approximately ~55 dB.

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A Case Study on Acoustic Design: Damansara Utama Methodist Church (DUMC)

Lighting Layout, Types of Lighting Fixtures, Functions Most of the lighting fixtures in the auditorium are recessed lighting using fluorescent energy saving light bulbs that are embedded in the high ceiling of the center atrium. There are also strips of fluorescent tubes installed as up lights that are suspended used to light up the ceiling of the upper tier seating area.

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A Case Study on Acoustic Design: Damansara Utama Methodist Church (DUMC)

The main issue with fluorescent bulbs is the buzzing noise it produces which can average at around ~35 dB. However, the noise produced from the lighting fixtures are often dwarfed by the noise of the air conditioning system.

On top of the lighting for the audience seating areas, there are also stage lighting which include spotlights installed at specific locations depending on its functions.

Sound Locks The hall does not implement a sound lock at the entry/exit points. Hence, external noise may penetrate from time to time depending on the intensity of the noise. However, the hall uses heavy curtains on the doors to suppress external noise, which may be adequate for a multi-purpose hall. The curtains also act as sound absorbers to prevent sounds from the inside of the hall to leak to the exterior hallways.

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A Case Study on Acoustic Design: Damansara Utama Methodist Church (DUMC)

4.5 Sound Propagations and Related Phenomena

4.5.1 Sound Reflection

Reflection is often used in room acoustics to efficiently distribute and reinforce the sound waves heard by the audience. More often than not, only 10% of what is heard in a room is from direct sound; the other 90% is aided by reflective surfaces to redirect more sound waves to the audience.

Audience members receive sound from both direct sound and reflected sound waves.Â

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A Case Study on Acoustic Design: Damansara Utama Methodist Church (DUMC)

The above diagram shows the ineffectiveness of the sound paths when the waves reflect off everything.Â

These reflections should be kept under control so as not to bombard audience members with too much noise to the point of discomfort or to create echoes. This can be done by easily covering the right surfaces with sound-absorbing material.

Smooth surfaces reflect sound waves coherently, while rough surfaces would reflect the waves in many different directions, and porous surfaces absorb waves.

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A Case Study on Acoustic Design: Damansara Utama Methodist Church (DUMC)

The ceiling of the auditorium is staggered in such a fashion that imitates the reflective effects of a concave surface. Concave surfaces can cover a wider area of sound wave distribution so that the sound waves get reflected to both the lower and upper levels as well as farther-seated audience members.

Audience members seated more than 15m away from the performer or speaker should require the aid of reflected sound waves of the sound source.

4.5.2 Echoes and Sound Delay

Echoes occur when the audience hears the reflected sound from a source with a notable delay time after hearing the direct sound.

By using the formula of [ R​1 + R​2 -​ D = delay distance ] we can find out the delay time of ​ sound waves at a certain point in the auditorium by later substituting values in the formula [ t = s/v ] specifically meaning [ delay time = delay distance / speed of sound ]

R​1​ = Incident distance R​2​ = Reflection distance D = Direct distance T​D​ = Delay time V​S​ = Speed of sound Thus, Delay time, [ T​D​ = ( R​1 + ​ R​2 ​ D ) / V​S​ ] measured in milliseconds (ms).

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A Case Study on Acoustic Design: Damansara Utama Methodist Church (DUMC)

[ ( R​1 + ​ R​2 ​ D ) / V​S​ = T​D​ ] 1. (25.2 + 4.0 - 27.4) / 344

= 5.2ms

2. (22.6 + 5.6 - 25.0) / 344

= 9.3ms

3. (17.6 + 9.4 - 22.6) / 344

= 12.8ms

4. (13.4 + 12.0 - 19.0) / 344 = 18.6ms 5. (9.6 + 19.6 - 18.6) / 344

= 32.8ms

6. (8.6 + 14.8 - 11.6) / 344

= 40.1ms

For speech, the longest acceptable delay time is 40ms (14m); for music, the longest acceptable delay time is 100ms (34m). The auditorium, for the most part, falls within the acceptable range for delay time for both speech and music purposes.

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A Case Study on Acoustic Design: Damansara Utama Methodist Church (DUMC)

4.5.3 Reverberation

Reverberation affects acoustic qualities of a certain space to give it a ‘dry’ or ‘wet’ sound, a by-product of, respectively, short and long reverberation times (seconds).

Desirable reverberation times in a given space are engineered purposefully, where as shown below, help accentuate sound qualities:

Retrieved from: http://www.industrial-electronics.com/measurement-testing-com/architectual-acoustics-2-SOUND-ABSORPTI ON-2.html

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A Case Study on Acoustic Design: Damansara Utama Methodist Church (DUMC)

4.5.3.1 Effective Surface Area

What proceeds is finding the reverberation time of DUMC on 3 octaves of 125Hz, 500Hz and 2000Hz to analyse the range and extent of reverb in the hall. The findings can then tell us if the acoustics correspond with the multi-purpose usage

EFFECTIVE SURFACE AREA

MATERIALS

SOUND ABSORPTION COEFFICIENT 125 Hz

500 Hz

2000 Hz

Concrete wall

0.01

0.01

0.02

1605.3

Carpet

0.03

0.05

0.35

192.7

Curtain

0.05

0.40

0.60

206.9

Timber parquet

0.40

0.20

0.15

950.7

1. Drywall

0.31

0.14

0.10

116.7

2. Timber

0.18

0.42

0.83

144

3. Foam

0.9

0.54

0.88

171

1. Padded chairs

0.08

0.15

0.18

2. Auditorium seats

0.13

0.59

0.61

1. Timber double door

0.14

0.06

0.10

2. Timber core door

0.30

0.15

0.10

1. Plaster

0.30

0.10

0.04

2. Gypsum Plaster

0.45

0.80

0.65

Glass window

0.30

0.10

0.05

1431.50

1483.73

1853.68

378.8

213

32.4 15.4

1193 930

24.7

Σ (m​2​ x coefficient)

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A Case Study on Acoustic Design: Damansara Utama Methodist Church (DUMC)

4.5.3.1 RT​60 of DUMC ​ This shows the measurement of how long it would take a sound to decay 60dB, suitable for use in large halls, within context of DUMC. Using Sabine’s formula here are the results:

RT = ​0.16V A RT = Reverberation Time (s) V = Volume of Hall (m​3​) A = Total absorption of room surface (m​2​)

125Hz

RT = ​0.16(18655) 1431.5 RT = 2.08s

500Hz

RT = ​0.16(18655) 1483.73 RT = 2.01s

2000Hz

RT = ​0.16(18655) 1853.68 RT = 1.61s

Given the volume of the hall, these reverberation times are slightly above the desired values of a multipurpose hall, although certain pockets of spaces have a more pronounced effect on the dampening of transmitted sound. Furthermore, Sabine’s formula tends to overestimate the reverberation time from variables unaccounted for.

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A Case Study on Acoustic Design: Damansara Utama Methodist Church (DUMC)

4.5.4 Acoustical Defects and Design Issues DUMC advertises itself as a multi-purpose hall, falling on the higher end of the optimum RT measure across the frequency band, making it better suited for music. Unassisted and unamplified speech suffers greatly, factoring in the distance needed for sound to travel from centre stage to the 1st floor remote seats

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A Case Study on Acoustic Design: Damansara Utama Methodist Church (DUMC)

4.5.4.1 Design Factor Big halls are a problem in factoring in design strategies to for multi-purposes. The DUMC stretches wider than 140​° resulting in undesirable seating spots. In the case of unassisted sound, at the average volume of a grown adult speech (85Hz - 150Hz), the ambient sound intensity of the hall (45Hz) lowers intelligibility. Below is a table of sound intensity level analysis at different ranges, across three octaves as well:

Distance (m)

Sound Intensity Level (dB) 125Hz

500Hz

2000Hz

1

60.8

74.7

86.2

5

54.7

69.2

79.5

10

47.0

62.5

72.7

15

45.5

55.0

67.4

20

46.0

54.2

66.6

25

45.2

50.5

64.6

Note that the mean of the values correspond to the inverse-distance law that states that for every doubling of distance from the incident sound, 6.02 dB is loss in a direction.

This simple experiment is conducted with a tone a generator with the specific frequencies and at constant volume, although the air-conditioning (ambient) proved a challenge to ensure controlled variables.

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A Case Study on Acoustic Design: Damansara Utama Methodist Church (DUMC)

4.5.4.2 Flutter Echoes The monitor room on the first floor might prove unpleasant to the surrounding seatings, a result of flutter echoes that are reflected off of the parallel unpadded concrete walls that contain the room.An overhead flat ceiling that sits (less than 17m) above the monitor room is less susceptible to flutter echo but may still cause unwanted reflected sound out and upwards.

Diagram above shows the section of near parallel surfaces that gives chance for the occurrence of echo.

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A Case Study on Acoustic Design: Damansara Utama Methodist Church (DUMC)

A zooming in of the space shows vertical parallel surfaces that are not lined with absorbent material. Horizontal flutter echo greatly occurs in this space.

4.5.4.3 Sound Shadows The last four rows of the ground floor fixed seats will experience a dead sound experience, caused by the surrounding absorbent materials and the extended corridor overhead that blocks out reflected sound off the ceiling.

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A Case Study on Acoustic Design: Damansara Utama Methodist Church (DUMC)

The phenomenon is known as sound shadows. These instance can be detected in a few spaces of the hall, some for the better:

The stairway casts sound shadows near toilet entrances. This increases the perception of privacy.

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A Case Study on Acoustic Design: Damansara Utama Methodist Church (DUMC)

and some for the worse:

These top row remote seating areas fall almost out of sight lines. The erected perspex railings are not only a barrier of sight, but sound as well.

4.5.4.4 Sound Transmission Anomalies The pillars that support the extended corridor above can be designed and placed in a more strategic manner, avoiding the risk of sound shadows and unwanted diffraction to the row fixed seating arranged behind the 6 pillars.

Shown in red are pillars that are obstacles for sound transmission. Blue are seatings that are directly affected.

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A Case Study on Acoustic Design: Damansara Utama Methodist Church (DUMC)

4.5.5 DUMC as a Mixed-Use Auditorium

DUMC works well as a multipurpose hall as a whole, where weekly services comprise of musical hymns and sermons, with an engineered reverberation time that falls well within the range of a 100,000m3 hall. The ground floor is elevated toward the back to position the fixed seats within sight lines while the ceiling panels serve as sufficient reflectors to redirect sound toward the raked seatings on the upper floor, also well within sight lines.

This enables incident and reflected sound to be received by the ears across the hall.

The need to accommodate both the desirable qualities of music and speech leaves room for criticism as well.

Assisted sound is managed through the utilisation of multiple speakers, increasing SIL to better project sound across distances from centre stage, relying less on the careful consideration of sound redirection. Unassisted speeches are muffled when seating on the last four rows of the hall, almost blending into the ambient sound at 43dB.

The bottom row under the extended terrace are affected by loud air-conditioning at 45dB and is noticeable during speeches. In addition to that, the last four rows fall under sound shadows from the terrace above, where aural experience tends to feel ‘dead’, being contained in a sound-absorbent surrounding. In accommodating the need for ample seating and amplified music, this is where the experience falls flat.

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A Case Study on Acoustic Design: Damansara Utama Methodist Church (DUMC)

5.0 Observation, Discussions and Conclusion

Through the observations and measurements taken, we can conclude that as a multipurpose hall that primarily focuses on speeches and music, the acoustic design of the auditorium is optimized for such activities.

By prioritizing mid to high frequency sounds while muffling low frequency sounds, the DUMC auditorium is able to reduce vibrations that would otherwise be transferred throughout the church itself, which may disturb other activities that are going on in other rooms. While unassisted speech doesn’t perform well in this auditorium it is not much of a problem as speeches are expected to be conducted with the aid of speakers at all times.

This project has allowed us to understand the acoustic design response based on the typology and function of the DUMC auditorium and how specific adjustments are needed to cater to the programmatic demands of an auditorium in general. The analysis has made clear the relationship between acoustics and the materials, spatial planning and context of an auditorium. The understanding of these relationships and concepts would greatly benefit us in future design projects especially when acoustics are taken into consideration.

The group would like to extend its utmost appreciation to Mr. Azim and Mr. Edwin who have actively assisted throughout the group’s journey in completing this project.

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A Case Study on Acoustic Design: Damansara Utama Methodist Church (DUMC)

6.0 References ●

http://www.sxsevents.co.uk/about/resource-hub/explanatory-articles/sound-delay-explain ed

●

http://www.theatresolutions.net/auditorium-seating-layout/#theater-forms

●

http://www.industrial-electronics.com/measurement-testing-com/architectual-acoustics-2SOUND-ABSORPTION-2.html

●

Parkin, P. (1972). Acoustics of Concert and Multi-Purpose Halls. Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences, 272(1229), 621-625. Retrieved from http://www.jstor.org/stable/74099

●

http://hyperphysics.phy-astr.gsu.edu/hbase/Acoustic/revmod.html

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