University Malaya
EXPERIMENTAL THEATRE
E.T.
BUILDING SCIENCE II [ARC3413/BLD60803] PROJECT 1: AUDITORIUM: A CASE STUDY ON ROOM ACOUSTICS Ar. Edwin Chan Dr. Sujatavani Gunasagaran
Clara Lee Pei Lin Joy Ann Lim Ee Hsien Kalvin Bong Jia Ying Kennett Lim Rong Xiang Shazleen Shafiqah Wong Teck Poh Yee Mae Yuen
0324495 0327592 0327822 0325031 0324367 0327462 0328561
Table of Contents
EXPERIMENTAL THEATRE
E.T. 1.0 1.1 1.2 1.3 1.4
Introduction General Information Brief Introduction History of E.T., UM Context and Location
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2.0 Methodology 2.1 Introduction 2.2 Measuring and Recording Equipment
06
3.0 3.1 3.2 3.3 3.4 3.5 3.6 3.7
10
Acoustical Analysis Auditorium Design Leveling and Arrangement of Seats and Stage Sound Reinforcement Acoustical Treatment and Components Sound Propagation Sound Defect Noise Intrusion
4.0 Reverberation Time 4.1 Introduction 4.2 Reverberation Time Calculation
72
5.0 Conclusion 5.1 Experimental Theatre, University Malaya 5.2 Design Considerations and Suggestions
79
6.0 References
84
Introduction
EXPERIMENTAL THEATRE
1.0
1.0 INTRODUCTION
1.1 General Information
Figure 1.1 : Experimental Theatre, University Malaya
Name of Auditorium : Experimental Theatre, University of Malaya Address : 825, Lingkungan Budi, 50603 Kuala Lumpur, Wilayah Persekutuan Kuala Lumpur Type of Auditorium : Performing Arts Theatre Year of Construction : 1965 Year of Completion : 1966 Volume : 5621 mÂł Capacity : 435 pax
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1.2 Brief Introduction
Figure 1.2: Interior of Experimental Theatre.
The Experimental Theatre of University Malaya (E.T.) is a performing art theatre which is suitable for stage performances and also conferences, seminars, presentations and product launches. Even though located in a university campus, it holds events from outside parties as it is available for rental for private and corporate functions. Its present layout of the theatre is influenced by Richard Wagner’s original concept of incorporating modern innovations and systems. The auditorium features tiered stalls and a gallery. A proscenium stage with a ramp leading to basement rooms that serve as a green room (waiting room or touch-up lounge for performers) is one of the present features of the theatre. The front of the stage has a hydraulic platform which provides an extension when raised and provides a space for an orchestra pit when lowered. Above the stage are gridded structures and rigging to support the sound and lighting systems.
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1.3 History of Experimental Theatre Constructed together with the well known Dewan Tunku Canselor in 1965, University Malaya’s Experimental Theatre was designed with heavy inspirations of Brutalist Architecture and Modernism movement. It was designed by Dato’ Kington Loo of BEP Architects and constructed using mainly bare concrete. It was declared a National Heritage Site in 2009 along with its sister buildings, Dewan Tunku Canselor and the Chancellery. Restoration works commenced on October 2009 and it was reopened to the public in 2011.
Figure 1.3: Renovation works began in October 2009.
Figure 1.4: A new look of the theatre in March 2011.
1.4 Context and Location
Experimental Theatre
DTC
The Experimental Theatre (E.T.) is located within the campus of University Malaya, Kuala Lumpur. It is located next to other university facilities such as Dewan Tunku Canselor (DTC), The Cube Cultural Centre, and research centres. It is also surrounded by vegetation and it is near an access road and some car parks.
THE CUBE
Figure 1.4: Site context of Experimental Theatre.
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Methodology
EXPERIMENTAL THEATRE
2.0
2.0 METHODOLOGY
2.1 Data Collection Method Prior to site visit, we obtained the tools mention below for measuring dimensions of the theatre and for measuring the sound intensity levels. Arrangements were made with the university’s staff to ensure an unoccupied theatre for accurate measurements. During site visit, architectural drawings were printed out and sketched on-site to record data and diagrams. The data collected are then analysed of its acoustic properties.
2.2 Measuring and Recording Equipment 2.2.1 Digital Sound Meter
Figure 2.1. : Digital Sound Meter
Digital sound meter was used for acoustic measurement within the auditorium. The acoustic unit of measurement is in db short for decibels. It was used to measure sound intensity levels at various locations within the auditorium to determine the sound concentration and also the background noise levels.
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2.2.2 Digital Single-Lens Reflex Camera (DSLR)
Figure 2.2: Digital Single-Lens Reflex Camera
The DSLR camera was used to capture photographs of the building materials and the condition of the auditorium for recording and analysis purposes.
2.2.3 Smartphone
Figure 2.3: Smartphone
Smartphones were also used as another alternative of capturing photographs of the auditorium and its construction material. It is also used to operate a consistent single frequency sound on the stage for readings of the sound meter to be taken at various different points of the auditorium.
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2.2.4 Measuring Tape
Figure 2.4: Measuring tape
The measuring tape was used to carry out the measurements of the auditorium for drawing purposes. It was also used to measure the distance from the position of sound meter readings taken to the stage. The measuring tape is mostly used to measure reachable areas.
2.2.5 Laser Distance Meter
Figure 2.5: Laser distance meter
The laser measuring tool was used to also measure distances in the auditorium but mainly for distances beyond 5m due to the limitation of the measuring tape and also areas which are hard of reach such as the height of ceiling. It is also used to determine the angle of the ceiling of the auditorium.
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Acoustical Analysis
EXPERIMENTAL THEATRE
3.0
3.0 ACOUSTICAL ANALYSIS
3.1 Auditorium Design 3.1.1 Architectural Drawings and Photos
Entrance (University Students)
Performance Stage
Ramp (Towards Basement)
Male & Female Toilet
Back Stage
VIP Entrance Hallway
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Lift Lobby (Entrance)
Backstage Control Room
Male & Female Toilet
Balcony
Staircase (From VIP Entrance Hallway)
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Back Stage
House
Balcony
Basement
Performance Stage
House
Backstage Control Room
Basement
Orchestra Pit
VIP Entrance Hallway
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Figure 3.1: Viewing from the stage, the experimental theatre depicts a sense of grace and classical elegance through warm ambience tone of light.
Figure 3.2: Viewing from the balcony, the interior wall of the theatre hall is cladded with rich plywood to evoke a natural sense of touch and pleasant.
Figure 3.3: The opening curtains disclosed a performance stage deeply recessed into the wall, giving a sense of depth in terms of visual distance.
Figure 3.4: Opening curtains and stage effects control panels are located at the side of the stage, easing the backstage crews in controlling anytime.
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Figure 3.5: Behind the balcony seatings sits a
Figure 3.6: The backstage control room at the balcony also serves as backstage equipment storage room.
Figure 3.7: A hidden ramp that slowly leads people
Figure 3.8: Below the stage, where all the performers are getting ready or taking rest here.
backstage control room.
down the stage to the backstage preparation area, giving a sense of mystery and curiosity.
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3.1.2 Shape and Form of Auditorium The auditorium is designed in a mixture of rectangular (or shoe box) and fan shapes. This traditional shoe box form allows both side reflections and receives strong component of direct sound whereas the concave surfaces of the hall serve to concentrate sound energy to the centre of the space. However, the suitable position for optimum concentration of sound is still at the centre of the theatre.
Fan shape
Rectangular
Figure 3.9: The form of the auditorium is mainly composed of fan and shoe box shape.
Reflective surfaces
Absorbant surfaces
Concentration of sound
Figure 3.10: The highlighted area is the best spot for optimum concentration of sound.
Absorbant surfaces
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3.2 Levelling and Arrangement of Seats and Stage The arrangement of the seats in the auditorium is arranged in concentric arc of circle efficiently for sound range to be optimally reached at every angle. The auditorium seats are placed within 140 degrees of sound projection which results in high recurrence sound projected. The distance between sound source from the stage and the last row of the seats is within 22.5m which is an ideal range for human voices to be heard clearly. Each seats are also leveled in staggered position to allow direct sound to be received without obstruction from absorbers and provide assurance of unobstructed views. However, there are three-four rows of seats covered by the deep overhanging balcony which experience sound shadow, an occurrence when sound doesn’t reach as effective as it should.
130Âş
Figure 3.11: Seat arrangement in a concentric arc of circle.
Sound shadow area
Figure 3.12: Sound projected through elevated seats and sound shadow area.
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3.3 Sound Reinforcement 3.3.1 Introduction The span of the theatre from the centre of the stage till the edge of theatre is approximately 18m long. The distance for an auditorium to function without sound reinforcement is around 15m thus this Experimental Theatre is needed to be equipped with sound reinforcement to help deliver and amplify the sound from the performers or speaker on stage. The sound system components present in the auditorium are: • • • •
Line array Subwoofers Stage Monitors Two way wall speaker
3.3.2 System Components 3.3.2.1 Line Array
Figure 3.13: Line array speaker suspended from ceiling.
The Experimental Theater uses two main line arrays suspended from the ceiling on the left side and right sides of the auditorium. Each has two identical speakers mounted vertically on each other and has a retractable mechanism which allows for the height to be adjusted. A vertical line array displays a normally wide horizontal pattern useful for supplying sound to the majority of the audience. This type of speakers are used as it can amplify sound across a longer distance. It also helps to reduces sound sent to the ceiling which reduces the unwanted reflections bouncing back to the audience. Its position on both sides of the hall allows for a balanced sound propagation on both sides however, it allows for a higher concentration of sound towards the centre of the auditorium.
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Figure 3.14: Position of line array speakers on plan.
6375mm
Figure 3.15: Height of line array speakers on section.
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3.3.2.2 Subwoofer
Figure 3.16: Subwoofer placed on stage.
There are two subwoofers located at each side on the stage dedicated to reinforce low pitched audio frequencies such as bass and sub-bass from 20Hz to 80 Hz. Unlike the line array speakers, the subwoofers come in single units as lower frequencies have slower attenuation and can travel to the audience easier. Again the subwoofers are positioned on both sides to achieve a wider and equal sound distribution. The subwoofers are placed at the corners of the stage against the wall because it helps to increase the bass output.
Figure 3.17: Position of subwoofer speakers on plan.
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3.3.2.3 Stage Monitor
Figure 3.18: Stage monitor facing the stage.
Figure 3.19: Stage monitor at the side of stage.
Equipped at the front of the stage are four stage monitors that are used to amplify the sounds of the performance and direct it back to the performers on stage to assist them in hearing their own vocals or instruments. The monitors also known as a foldback system are needed to prevent the performers on stage to hear reverberated reflections bouncing from the rear wall of the auditorium which will be delayed and distorted thus affecting their performance. Due to the auditorium having a larger stage with great depth of 14 meters, the side of the stage is also equipped with another stage monitor, one on each side to ensure a wider coverage at the sides of the stage for the performers on stage. These stage monitors is mounted on the wall rather than being placed on the ground to help distribute the sound over the large volume of the backstage.
Figure 3.20: Position of stage monitors speakers on plan.
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3.3.2.4 Two-way Wall Speaker
Figure 3.21: Two-way wall speaker attached to ceiling.
For the audience seated at the back of the auditorium beneath the gallery, the sound quality and concentration might be affected due to the distance and the gallery above. Hence, sound reinforcement is required and is placed at the low ceiling of the last third row. There are four evenly spread two-way wall speakers fixed to the ceiling to help amplify the sound from the stage with clarity and without any significant delay.
Figure 3.22: Position of two-way wall speakers on plan.
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3.3.3 Advantages and Disadvantages of Sound Reinforcement in E.T Advantages • Speakers and microphones help to reinforce and amplify sound intensity across a longer distance and a wider coverage. • Sound reinforcement system is used to enhance or alter the sound of the sources on the stage, such as controlling the sound reverberation time. • Speakers such as vertical line arrays reduces sound sent to the ceiling which reduces the unwanted reflections bouncing back to the audience. • Sound reinforcement systems can cut through background noise produced such as traffic from outside or mechanical services. • Sound reinforcement systems can also help control the tone and frequencies of the sound from the stage depending on the desired sound of the performance.
Disadvantages • Due to the position of most of the speakers being placed at the left and right side of the auditorium, there can be still unbalanced sound distribution in the middle of the auditorium. • The audience might hear the original sound from the stage and the sound reproduce from the speakers at two separate times. The ideal difference should not be more than 1/30 second. • Technical issues or malfunctioning of systems will cause a disturbance in the sound distribution and quality. • If there is not enough height of the line array speakers, vertical pattern control can be lost, allowing low and mid frequencies to project to the ceiling and stage, causing unwanted reflections. • The placement of the subwoofers leaning against the wall will help increase the bass boost but might not be ideal as the bass sound quality is not the best. The ideal position should be 8 to 12 inches away from the wall. • Feedback sounds may be a noise source and cause disturbance during the performances on stage.
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3.4 Acoustical Treatment and Components 3.4.1 Materials tabulation of Experimental Theatre, University Malaya
Location
Component
Material
Brick
Velour Walls
Timber
Apron
Stage curtain
Finishes
Brick wall Emulsion plastered on paint, white both sides Velour acoustic NIL curtain H.W. timber panels (12mm thk. NIL plywood panels)
Absorption Coefficient 125Hz
500Hz
2000Hz
0.05
0.02
0.05
0.05
0.40
0.60
0.18
0.42
0.83
Concrete
Cement render
Polished
0.02
0.02
0.05
Timber
Timber parquet
Varnish
0.02
0.20
0.10
Aluminium
Aluminium grill skirting
Antique copper, gold faux texture
-
-
-
Varnish
0.20
0.10
0.05
NIL
0.02
0.04
0.05
NIL
0.05
0.40
0.60
Floors Stage
Description
Hardwood timber parquet Vinyl sheet covered over Marmoleum H.W. timber Vinyl on concrete floor Velour Velour acoustic curtain Timber
Table 3.1: Table shows the documented materials of E.T.
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Location
Component
Material
Timber
Walls
Gypsum
Acoustic fibreglass panels
House
Floors
Carpet
Ceiling
Plaster Polyurethane foam
Seating Plastic
Control booth
Doors
Glass
Description
Finishes
125Hz
500Hz
2000Hz
0.18
0.42
0.83
0.08
0.05
0.02
0.10
0.50
0.70
0.08
0.30
0.75
0.20
0.18
0.15
NIL
0.33
0.64
0.77
NIL
-
-
-
NIL
0.30
0.10
0.05
12mm thk. plywood NIL acoustic timber panel 2 layers of 15mm gypsum board on Emulsion steel studs paint, white with 150mm air gap filled with 50mm rockwool Fibreglass (72 kg/m3) Stretched with a facing fabric of stretched fabric 10mm thk. short pile carpet over NIL concrete floor 12mm thk. Emulsion GRC plaster paint, white Upholstered tip-up foam seating Molded one piece plastic component 1.4mm thk. glass window panel
Absorption Coefficient
Timber
Hardwood timber
NIL
0.18
0.10
0.08
Timber
Hardwood timber flush double door
Varnish
0.14
0.06
0.10
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3.4.2 Material board of Experimental Theatre, University Malaya
Hardwood timber panel
Aluminium grill motif
Marmoleum vinyl sheet
Brick wall plastered with textured spray
Medium pile carpet
Gypsum board
Acoustic fibreglass panel
Timber parquet floor
Acoustic velour curtain
Plaster ceiling
Polyutherane foam
Glass baluster Aluminium railing
Timber door panel
Aluminium grill motif
Medium pile carpet
Figure 3.23: Materials that can be found in E.T.
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3.4.3 Materials of the walls of Experimental Theatre Acoustic timber panels (12mm plywood panels) Timber is a sound absorptive material. In E.T., acoustic timber panels are placed on a 2 layered 15mm gypsum drywall with 150mm air gap insulated with 50mm of rockwool foam. The timber panels have light boxes built in and is partly covered with decorative aluminium grills. These panels are arranged in a jagged pattern in accordance to the gypsum drywalls to increase surface area to absorb sound waves. Its absorptive characteristics also reduces flutter echo. The angular design reduces the chance of incident and reflected waves from interfering each other.
Figure 3.24: Acoustic timber panels are placed on
Figure 3.25: Decorative aluminium grills with a
both sides of the drywall.
lightbox in between is placed in the timber panel.
Figure 3.26: Location of timber wall panels on ground floor plan.
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Figure 3.27: Location of timber wall panels on gallery plan.
Figure 3.28: Sectional detail of the wall with the timber panel highlighted.
Acoustic fibreglass panels The fibreglass panels are located at the back of the theatre on both ground floor and gallery level. The panels only cover the middle part of the wall and not the whole wall entirely to prevent deadening of the upper mids and high. Fibreglass panels are effective sound absorbers. It eliminates unwanted boundary reflections and controls excessive room reverberation. By absorbing sound waves, this can reduce resonance within the theatre.
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Figure 3.29: Fibreglass panels are placed at the middle part of the wall.
Figure 3.30: Location of acoustic fibreglass panels on ground floor plan.
Figure 3.31: Sectional diagram showing the absorptive characteristic of fibreglass panels.
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Drywall (2 layers of 15mm gypsum board on steel studs and 150mm air gap with 50mm rockwool or fibreglass in the cavity) The drywall of the theatre is shaped in a jagged pattern to increase sound reflection from stage towards the audience. Complemented by acoustic timber panels, the jagged pattern of walls also prevent flutter echoes as it eliminates the parallelity of walls on flanking sides. The rockwool foam layer inside the drywall acts as a sound absorber by inducing resonance with the sound waves. The sound waves lose energy because the non-directional fibres traps airborne sound more effectively compared to general insulation products which contain straight laid glass wool with an air gap.
Figure 3.32: Walls layered with gypsum boards and rockwool are used in this theatre.
Figure 3.33: Location of drywall on ground floor plan.
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Figure 3.34: Location of drywall on gallery floor plan.
Figure 3.35: Sectional detail of the wall with the drywall highlighted.
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3.4.4 Materials of the floors of Experimental Theatre Medium pile carpet (7mm thk. - 36mm) with underlay Medium pile carpets are covered over the concrete flooring in house as concrete is a sound reflector which reflects and interferes with incident sound waves in the room. To prevent this, the medium pile carpet is used to absorb impact noise created by footsteps and dropped objects from the audience. The carpets are porous which enable sound waves to penetrate into the pile carpet instead of being reflected back into the room. Pile carpets are effective sound absorbers also because the individual fibres, pile tufts and underlays have different resonant frequencies at which they absorb sound waves. The wide range of resonant frequencies enables it to absorb a wide range of sound waves.
Figure 3.36: Medium pile carpet covers the floor of E.T.
Figure 3.37: Medium pile carpet is also used on flooring of the gallery level to reduce structure-borne noise.
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Hardwood timber with marmoleum vinyl sheet (20mm thk. polished timber parquet on concrete) The original flooring system of E.T. is of reinforced concrete. Reinforced concrete floor is a reflective material which does not insulate or absorb sound waves. However, its high mass can increase sound transmission loss of structure-borne sound. To overcome the reflective properties of concrete, a 20mm thick polished timber parquet is laid over most of the surface area of the stage to improve sound absorption. Due to heavy foot traffic that would occur during a performance, the timber parquet is not sufficient in absorbing unwanted sound. A marmoleum vinyl sheet is later covered above the timber surface. Marmoleum vinyl sheets increases the impact time, which promotes sound reduction. With the combination of 3 layers of flooring, unwanted noise from foot traffic is reduced.
Figure 3.38: Marmoleum vinyl sheet covers the stage partially but covers the entire stage apron
Figure 3.39: The original flooring of the theatre is concrete, covered with timber parquet and an added layer of marmoleum vinyl sheet.
3.4.5 Materials of the ceiling of Experimental Theatre Plaster ceiling (12mm thk. GRC plaster) The plaster ceiling is coated with white paint and is used to disperse sound from stage in a controlled manner. The curved edges of the ceiling aids sound dispersion to the seating area.
Figure 3.40: Fibre cement boards with white paint finish is used for the ceiling.
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Figure 3.41: Curved edges are implemented to aid sound dispersion.
3.4.6 Other materials in the Experimental Theatre Velour acoustic curtains The walls of the backstage are made of concrete. Hence, velour curtains are used at the backstage to dampen sound waves and to reduce reflection of sound from the backstage walls. The curtains will reduce reverberation and echo in a large space, as well as reduce interference from outside noise. The features of velour curtains to improve acoustic properties are: Thickness The thicker the velour curtains, the more effective it will be against longer wavelength (low frequency) sound. However, a thickness of 25mm - 50mm is needed to effectively absorb low frequency sounds. As this thickness is not possible and not economical, the velour curtains in E.T. are not able to fully absorb low frequency sounds.
Figure 3.42: Velour curtains are used backstage to absorb unwanted noise from the exterior environment.
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Pleated curtains To improve low and mid frequency sound absorption, the velour curtains are pleated to expose more sound absorbing surface.
Figure 3.43: Plan view of pleated curtains shows maximisation of surface area for more sound absorbing surface.
Distance from backstage wall The flanking velour curtains are placed at a good distance of approximately 16m away from backstage wall to increase low frequency sound absorption and reduce sound reflection.
Figure 3.44: A distance of approximately 16 meters is allocated between the backstage walls and the velour curtains.
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Seating (Upholstered foam self-lifting seat with polyurethane foam) Polyurethane foam is used because of its ability to absorb sound and prevent echoes in the case where the theatre is not fully occupied. This material is efficient at absorbing high frequency sounds but not efficient in absorbing low frequency sounds unless an adequate thickness is used.
Figure 3.45: Auditorium chairs in E.T.
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3.5 Sound Propagation 3.5.1 Introduction Sound propagates from a point source, travels outwards in circular waves motions and its intensity decreases via the inverse square law (the intensity is proportional to 1/(distance squared). Utilizing the sound meter and a self-brought speaker playing at constant amplitude and frequency, we gathered information about sound intensity level and plotted the sound dispersion reading in the seating (Refer to Figure 3.46). We discovered that there is a small reduction of propagation in sound energy due to the short depth and height of the auditorium which is 18.7m and 12.5m respectively. The propagation of sound is quite consistent and equal throughout each level of collection of data with a difference of 1 decibel in each respective level (Refer to Figure 3.47). Note: The readings recorded were without background mechanical noise as the management did not allow turning on the air conditioning. Background reading recorded was 27dB.
Figure 3.46: Sound distribution in the seating area taken from the stage
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Figure 3.47: SIL readings of the auditorium.
3.5.2 Sound Reflection and Diffusion Sound reflection is the return of a sound wave from a surface. It can help increase the efficiency of the sound propagation to the audience. Careful consideration must be given during the design of the auditorium as poor design of the reflections can result in echoes and long reverberation which inhibit legibility of speech.
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A. Walls Factor of Shape of Auditorium and Materiality The shape of Experimental Theater is a combination of a shoe-boxed with the seats arranged in a fan-shaped, and has a concave wall at the end of the auditorium. The side wall, which is made of gypsum board (drywall), is fitted with many acoustical decorative wall panels of different sizes and angles. 1. The hard, sound-reflecting walls reflects sound from the stage towards the center seats and the side seats of the auditorium. 2. However, most of the sound waves are reflected to the concave wall at the end of the auditorium. 3. To prevent and control excessive reverberation of sound, the rear concave wall is lined with sound absorbing acoustical panels.
Absorbers
Reflectors
Figure 3.48: Reflection and absorption of sound path in auditorium.
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Factor of Angles The side wall of Experimental Theater is fitted with many acoustical decorative wall panels of different sizes and angles to aid reflecting sound from the stage to the auditorium. 1. The sound waves from the stage strike the surface of the wall panels. 2. The different angles of wall panels diffuses sound waves from the stage towards different directions in the auditorium. This is because the angle of incidence for sound waves will differ from the front to rear wall panels. 3. Sound waves will be spread evenly throughout the auditorium and listeners will perceive reflected sound from many directions.
Figure 3.49: Reflected sound path in auditorium.
Factor of size 1. The auditorium has a high repetition of small sections of drywall and the plywood acoustic wall panels. 2. The sharp edges of the drywall and the plywood acoustic wall panels help to diffuse the high frequency sound which has a short wavelength and breaks and disperses sound throughout the auditorium.
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Figure 3.50: Diffused sound path in auditorium.
B. Ceiling The experimental theater is a performing arts theatre where graduation performances, orchestral and music recitals are held. When the theatre was renovated in 2011, efforts were done to fulfil the acoustic requirement of music performance spaces. Additional ceiling elements such as the tilted ceiling allows for sound from the performers to reach the audience in the upper balcony as shown in Figure 3.50. The convex surface ceiling also disperses sound to the upper balcony seats (Refer to Figure 3.51). The small increments and sloped angles of the ceiling has increase the area of providing useful reflections.
Figure 3.51: Longitudinal section showing type of ceiling affects sound propagation in auditorium.
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Convex surface ceiling
Sound Reflection
Figure 3.52: Cross section showing type of ceiling affects sound propagation in auditorium.
Sound Reflection
It can be analysed from Figure 3.52 that the upper gallery area does not receive direct sound as the glass railings block and obstruct the sound from reaching. To counter this problem, line array speakers that are hung from the ceiling provide sound reinforcement which in turn allow direct sounds to the audience in the upper gallery. (Refer to Figure 3.53). The deep overhang of the gallery has obstructed and decrease the acoustical quality for audience. Two way wall speakers have been installed below the gallery to assist with sound propagation.
Figure 3.53: Obstruction of sound propagation in auditorium.
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Subwoofers are placed on the floor levels as it emits low pitched audio frequencies (Refer to Figure 3.54). Low frequency of sounds are less subjected to diffraction after striking a surface of small architectural elements. Thus the cantilevered floor slab of the balcony would not scatter and impart odd tonal distortion to the sound as the subwoofer emits low frequency sound.
Figure 3.54: Reflections made from sound reinforcement.
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3.5.3 Sound Delay and Echo Sound Delay and Echo 1 Echo = (R1 + R2) - D 0.32 = 13.3 + 12.3 + 13 0.32 = 39.4 ms The time delay for this position is 39.4ms, where direct sound is reinforced by the direct sound. No echo is heard.
38900 23100
7900
5100
7900
13300
34800
18300
13000
11400
12300
Direct Sound Indirect Sound Sound Source Sound Recipient
Figure 3.55: Sound delay and echo 1
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Sound Delay and Echo 2 Echo = (R1 + R2) - D 0.32 = 7.3 + 6.4 - 3.6 0.32 = 31.6 ms The time delay for this position is 31.6ms, where direct sound is reinforced by the direct sound. No echo is heard.
7300
6400
3600
Direct Sound Indirect Sound Sound Source Sound Recipient
Figure 3.56: Sound delay and echo 2
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Sound Delay and Echo 3 Echo = (R1 + R2) - D 0.32 = 15 + 1 + 15.8 0.32 = 0.63 ms The time delay for this position is 0.63ms, where direct sound is reinforced by the direct sound. No echo is heard.
1000
15000 15800
Direct Sound Indirect Sound Sound Source Sound Recipient
Figure 3.57: Sound delay and echo 3
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Sound Delay and Echo 4 The upper balcony will not receive sound echo without the aid of sound reinforcement as direct sound to the balcony is blocked by the glass railing (Refer to Figure 3.57).
2400
15000
Direct Sound Indirect Sound Sound Source Sound Recipient
Figure 3.58: Sound delay and echo 4
In conclusion, the Experimental Theater has acceptable sound delay as a performing arts theatre as all the readings of sound delay has less than 100 milliseconds.
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3.6 Sound Defect 3.6.1 Sound Shadow Acoustic shadows or sound shadows are regions in which the frequency regions of sound are altered as sound undergoes diffraction effects around large pillars and corners or underneath a low balcony (Richard E. Berg, 1995). In the Experimental Theatre of University Malaya, sound shadow occurs at the seatings beneath the gallery level without the usage of sound reinforcement. There is a slight change in the quality of sound as the obstructed design did not consider the transmission of sound to the far end of the auditorium from the stage. However, the sound shadow effect is not felt as much at these spaces as sound reinforcement systems - speakers are installed at the top of the stage and at the ceiling at the furthest back of the theatre.
3.6.2 Sound shadow in Experimental Theatre, University Malaya In our case study of UM’s experimental theatre, sound shadow regions can be identified at the seatings under the gallery level. As mentioned earlier in the topic of sound propagation, sound intensity at the back is lower as compared to the area closer to the stage. A sound intensity difference of 4 to 5dB can be measured from the back rows to the middle rows of the auditorium. Besides the difference in distance, this is also because the back rows of the seats are covered by the overhang of the balcony level. Audience within this region will experience a slight sound disruption as the sound quality transferred from the stage to the back rows of the theatre is not at its fullest and optimal value.
Figure 3.59: Plan indicates the seatings affected by the sound shadow region.
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Figure 3.60: Sound intensity levels (dB) shows the significant difference at different areas of the plan.
In concert halls, the acoustic quality below a large balcony is often reduced compared to the acoustic quality of the main volume. This is caused by significant differences in the reverberated energy behavior between these two volumes even though it can provide a much immersive and pleasant viewing experience. Our case study has a deep balcony of approximately 4.3m. The audience seated under this balcony might suffer from a lack of acoustical quality as the opening aperture between its volume to the main house of the auditorium is small - approximately 2 metres.
Figure 3.61: Section which demonstrates the dimension of the sound shadow region.
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When a sound source is emitted from the stage, the sound travels through air and towards the audience seated before the stage. The sound paths travel directly from the sound source to the audience is effective until the middle portion of the seating rows where it is aided further by the side wall and ceiling by reflecting the sound source and distributes sound at a further range from the stage. However, a lack of reflected sound path enters the space below the balcony where sound shadow occurs. Hence, a different quality of sound is experienced.
Figure 3.62: Section which demonstrates travel path of sound to the audience seatings.
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3.6.3 Considerations taken to mitigate the effects of sound shadow Sound reinforcement systems Sound travelling within the sound shadowed region will be attenuated as sound waves are diffracted by the pillars, and the low balcony. Therefore the amplitude of sound is reduced. As a way to overcome this, E.T. makes use of speakers for sound reinforcement. 4 speakers are installed below the fascia segment of the balcony. During a speech or a singing performance, these speakers will be used to provide equal clarity of sound to the be transferred to the audience at the back row seats affected by the sound shadow region.
Figure 3.63: Sound reinforcement system installed on the ceiling of the seating under the gallery level.
Figure 3.64: Plan indicating a total of four sound speakers are placed at the sound shadow region, to ensure equal sound quality.
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Sloped floor The floor is angled 7.4 degrees off from the entry floor after the stage. This floor design is desirable as it increases the angle of incidence of sound waves and thus the audience receives more direct sound from the sound source during an ongoing performance. Sloped (raked) floor also benefits the audience as the sloped floor improves sight lines as well as fidelity in the seating area. However, this may prove to be counter-intuitive as the sloped floor is covered with absorptive medium pile carpet, where the increase in exposed surface area of the material will incerease the sound absorption in the auditorium.
Figure 3.65: Diagram depicts how sound travels to the two levels in the theatre.
Figure 3.66: Diagram shows the floor is at a gradient of 7 degrees off starting from the horizontal entry floor level.
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3.6.4 Flutter echo Flutter echo is a condition which occurs in acoustical spaces whereby two parallel surfaces reflecting sound between one another are far enough apart that audiences can hear the reflections between them as distinct echoes. The audible effect is in many cases a sort of “fluttering” sound as the echoes occur in rapid succession. Flutter echo is a problem caused by longer reflections. In the E.T., flutter echo cannot be identified due to several conscious designs of the auditorium.
Figure 3.67: Diagram illustrates how the sound waves are reflected back as cancellation or with increased amplitude from the wall.
3.6.5 Considerations taken to eliminate flutter echo Room shape The plan geometry of the E.T. composes the shape of a fan auditorium layout. The side walls are splayed out to not only accommodate a greater seating area but to also encourage sound reflection. The side walls spanning 4.7 metres is angled by 60 degrees following the wide aperture opening of the stage.
Figure 3.68: 60° spread out from the walls and the almost fan layout of the auditorium.
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Wall panels The side wall panels of E.T. are arranged at an angle and outfitted with decorative ornaments as well as integrated with lighting components. Not only that, these panels provides necessary angle for the reflection of sound. These plywood panels span 1.1 metre long and is repeated throughout the spaces of the wall and are tilted at an angle of 4 degrees to angle the sound coming from the stage. As the angle of incidence of sound waves is the same as the angle of reflection, these non-parallel arrangements allow for a variety of patterns of sound path, thus eliminating flutter echo.
Figure 3.69: The rhythmic arrangements of the acoustical decorative wall panels.
Figure 3.70: The materiality of the angular drywall and plywood panels.
Figure 3.71: Plan shows the jagged arrangement of the wall panels.
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Ceiling The convex ceiling design at the corner of the E.T. enables sound dispersion, resulting in an more even distribution of sound throughout the theatre. It also eliminates sharp corners which prevents unwanted echoes that may occur from long reflections.
Figure 3.72: E.T.’s convex corner ceiling design.
Figure 3.73: E.T.’s convex corner ceiling design.
Besides that, the smooth ceiling of the E.T. is not made parallel to the floor. It is arranged in a jagged position that reflects incident sound. This prevents flutter echoes because there are no parallel surfaces on the ceiling compared to the floor.
Figure 3.74: Section indicating the sound waves energy diminishing as it gets absorbed by absorptive surfaces.
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Convex ceiling surface design
Figure 3.75: The convex design of the ceiling is an acoustical element into reflecting sound waves throughout the theatre space. The sound wave are dispersed and scattered to be thoroughly distributed throughout the experimental theatre.
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3.7 Noise Intrusion 3.7.1 Introduction Noise is an undesirable and unwanted sound, usually judged from the perspective of an recipient. Noise can be categorized as continuous, variable, impulsive or intermittent depending on how it changes over time. Continuous noise is noise that remains constant and stable over a given time period. Different operations or different noise sources can also cause the sound to change. Noise is intermittent if there is a mix of relatively quiet and noisy time periods. Impulsive or impact noise is a very short burst of loud noise which lasts for less than a second. In an auditorium, noise can be crucial to the quality of a performance or an event as it may create disruption and unpleasantness to the hearing experience.
3.7.2 Effects of Noise The Experimental Theatre of University Malaya houses events and performances, ranging from dance performances, singing performances to small orchestra performances. Noise (around the range of 65 dB) in an auditorium may cause these following physical and psychological effects: 1. Noise during performances, recitals or even rehearsals may hinder concentration 2. Noise causes distraction which reduces efficiency and decreases attention, which will affect production rate and quality 3. Interference caused by noise during a speech will cause general annoyance and might cause misinformation 4. Mental effects might occur among performers such as increased anxiety and nervousness; or even physical effects such as bodily fatigue Therefore, a desirable acoustical environment is critical in creating a great sound experience. Noise needs to be kept at a non-existant or minimum level to prevent disruption during events.
Figure 3.76: Experimental Theatre of University Malaya.
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3.7.3 Noise Analysis
Sound source
Sound path
Sound receiver
Figure 3.11: The transmission of sound.
The analysis of noise for noise control action can be translated into a relationship of a source and receiver, connected by a path. Sound sources can be divided into three categories: 1. Occupants activity 2. Operation of building’s M&E services 3. Environmental sound produced outside a building For noise sources, two main groups can be identified: 1. Outdoor/exterior noise • noises produced by transportation such as road traffic, railway lines, motor boats, aircraft etc. • mechanical equipments such as compressors, cooling towers, construction equipment noise, machinery etc. • rainfall and thunder 2. Interior noise • noises produced by people through their activities such as noises from radio/ television, loud conversation, slamming of doors, dragging furniture, babies crying, etc. • building noises produced by machines and household equipment • noise produced in certain industrial buildings by manufacturing or production processes These noise (or sound in general) can be transmitted in two ways: 1. Airborne 2. Structure-borne In noise control, the sound receiver can be a building or a room in a building as well as a person. Actions can be taken to reduce noise based on this relationship of sound transmission.
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3.7.4 Noise sources in Experimental Theatre, University Malaya Outdoor noise - exterior environment The Experimental Theatre (E.T.) of University Malaya is located next to a two-way road Lingkungan Budi. The other side of the auditorium is the school compound, which is generally empty. The vehicles passing by the street causes transportation noise in the building. This noise source is transmitted through airborne as well as structure-borne transmission. In this case, the building itself acts as a receiver of noise.
Figure 3.77: Map shows the location of E.T. and its surroundings.
Figure 3.78: Lingkungan Budi and the lack of sound barriers.
Figure 3.79: The sidewalk of Lingkungan Budi is used for bicycles.
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Airborne noise is transmitted along a continuous air paths such as openings and cracks around doors, which can be identified in E.T. The service roller door located next to the stage is not sealed, which becomes a noise source as the opening is permeable to the exterior noise.
Figure 3.80: The visible gap from the inside of the E.T.
Figure 3.81: Service roller door that is not sealed which allows airborne noise.
Figure 3.82: Exposed condition of the service door.
Figure 3.83: Plan shows the location of the service roller doors as one of the main source of outdoor noise.
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Outdoor noise - weather Due to the exposed manner of the building, noise effects caused by weather i.e. rain, thunder or storm will be heard in the auditorium as there is a lack of soundproofing. However, the usage of roofing materials can reduce the noise level caused by weather conditions. The roof of the E.T. is reinforced concrete (RC) slab with an approximate thickness of 300mm. This results in an approximate STC value of 65, which can reduce the noise of an extreme weather situation i.e. thunderstorm (120dB) to 55dB. This noise level will still be heard in the auditorium, but not very detrimental to the acoustic experience.
Figure 3.84: Section shows the RC slab of the E.T.
Figure 3.85: Plan shows possible noise source during unfavourable weather conditions.
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Outdoor noise - people’s activities Noise generated by activities can be transmitted into the auditorium as well as there is a lack of buffer zone between the main entrances and the auditorium. Conversations and light chatters can be heard near the back of the auditorium if activities occur at the lobby.
Figure 3.86: Lobby and reception area of E.T. The door (right) is one of the two main entrances of E.T.
Figure 3.87: Plan shows the main entrance and the lobby of E.T. and sound may transmit to the auditorium.
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Outdoor noise - building structure The architectural feature located on the facade of the sides of the E.T. may be a sunshading devide but could also present itself as a noise source. As it is part of the building structure, structure-borne noise in the auditorium can be generated as condenser units of air conditioners are placed near to the facade element.
Figure 3.88: The facade element and the condenser unit.
Figure 3.89: Protruding elements along the side of the auditorium.
Figure 3.90: Plan shows the location of the element.
Figure 3.91: Structure-borne noise when a mechanical equipment is located close to a buildng strcucture.
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Interior noise - people activities and movement Interior noise is generated by impact of the physical contact with a surface. Specific noise sources generated by human movement can be identified in E.T: 1. Auditorium chairs 2. Timber ramp at the gallery/balcony level 3. Hinge of doors 4. Door slam stopper The noise generated is a low but noticeable creaking sound which might cause general annoyance among people.
Figure 3.92: The auditorium chairs in the house.
Figure 3.93: The steps to the seating level from the
Figure 3.94: Ramp at the balcony level. (C)
Figure 3.95: The door slam stopper of the main
(A)
stage. (B)
entrance door. (D)
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Figure 3.96: Ground floor plan shows the location of B and D.
Figure 3.97: Gallery level plan shows the location of C.
Interior noise - machinery and equipments The equipments employed for lighting such as spotlights and stage lights produce a buzzing sound which indicates a lack of maintenance. Interior noise is also generated by the HVAC system. The expel of cold air through the diffuser grills causes a noise level that is noticeable.
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Figure 3.98: Lighting equipment above the stage.
Figure 3.99: Lighting equipment (spotlight) for
Figure 3.100: Diffusers of A/C and mechanical air
Figure 3.101: Lighting equipment on the gallery
(A)
intake openings. (C)
stage performances. (B)
level. (D)
Figure 3.102: Plan shows the location of machinery and equipments.
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3.7.5 Noise control To reduce the effect of noise in an auditorium, certain measures can be taken which is known as noise control. Noise control can be acted upon the sound transmission relationship i.e. source > path > receiver. Noise control measures that can be taken includes: 1. Suppression of noise at the source 2. Town/site planning 3. Architectural and structural design 4. Mechanical and electrical design 5. Organisation of work spaces 6. Sound absorption/masking 7. Sound insulation
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3.7.6 Noise control in Experimental Theatre, University Malaya Organisation of spaces Two hallways (one on each side) separate the auditorium space from the external environment. The 1.5 metres wide hallway isolates the noise caused by services from the auditorium. The other hallway has a width of 7 metres and is a void space occupied by a staircase to the balcony level. This decreases the airborne noise that could reach the auditorium.
Figure 3.103: Walkway of E.T. serves as buffer zone.
Figure 3.104: The buffer zone separates the auditorium from the service spaces.
Figure 3.105: Gallery level plan shows the buffer zones on the sides of the auditorium.
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Sound absorption Noise control actions are taken using the principle of sound absorption. Soft, uneven materials are employed to reduce interior noise. For example, the concrete floors of the auditorium is carpeted with medium pile carpet to reduce the sound of footsteps. Pile carpets are effective sound absorbers as the individual fibres, pile tufts and underlays have different resonant frequencies at which they absorb sound waves. The wide range of resonant frequencies enables it to absorb a wide range of sound waves.
Figure 3.106: The carpet used to cover the flooring of the auditorium.
Different materials are applied on the stage of the auditorium to reduce foot traffic noise as well. A 20mm thick polished timber parquet is laid over most of the stage and a marmoleum vinyl sheet is covering the timber surface for the front part of the stage.
Figure 3.107: The different flooring layers of the stage of E.T.
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Velour curtains can also be found around a perimenter on the stage. During performances, these curtains are used to reduce noise levels from the back stage and the exterior environment by absorbing low frequency sounds.
Figure 3.108: Velour acoustic curtain hanging around the stage of E.T.
Figure 3.109: Ground floor plan indicates the position of these curtains.
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Sound insulation Double wall creates an air cavity which serves as sound insulation. This is known as the massair-mass system, which is usually applied as a method of soundproofing. A large cavity of air is usually introduced in this system, which performs better than a smaller air cavity. Generally, a large air cavity also performs better as sound insulation than two smaller air cavities. E.T. has two pockets of air cavity on each side of the auditorium between its walls with a gap of 150mm.
Figure 3.110: Ground floor plan indicates the position of the wall with air cavity.
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3.7.7 Background noise Quality acoustical characteristics are important in auditorium spaces so that performances and presentations can be clearly heard and understood. For performance spaces and general presentation spaces, recommended noise criteria (NC) rating ranges from NC–20 to NC–30; recommended sound transmission class (STC) rating ranges from STC 40 to STC 50. Background noise is estimated to be at a level of 40dB due to the noise sources as shown in chapter 3.7.4. E.T. with an occupancy of 435 seats and octave band center frequency of 500Hz, the noise level does not match the NC of an auditorium, which is around the range of 30s. This indicates that the selected case study has an undesirable background noise level caused by noise intrusions and the lack of soundproofing.
Figure 3.111: Graph shows the noise criteria (NC) curve.
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Reverberation Time
EXPERIMENTAL THEATRE
4.0
4.0 REVERBERATION TIME
4.1 Introduction The reverberant sound in a room will fade away due to the sound energy bouncing off and being absorbed by multiple surface on the room. Thus, the reverberation time is defined as the time for the sound pressure level in a room to decrease by 60dB from its original level after the sound is stopped. It is dependent on the following variables: 1. The volume of the enclosure (distance) 2. The total surface area 3. The absorption coefficients of the surfaces Hence, the reverberation time can be calculated by using the Sabine Formula;
RT = 0.16V A where,
RT = reverberation time (sec) V = volume of the room (cu.m) A = total absorption of room surfaces (sq.m sabins) x = absorption coefficient of air
4.2 Reverberation Time Calculation 4.2.1 Volume of Experimental Theatre
Figure 4.1: Division of floor area for calculation of volume.
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Figure 4.2: Division of floor to height area for calculation of volume.
Estimated Floor Area (m2) A B C D E
: 76.4 m2 : 177.9 m2 : 76.3 m2 : 40.2 m2 : 253 m2
Estimated Volume (m3) A B C D E
: 439 m3 : 1316.5 m3 : 618 m3 : 311.6 m3 : 2934.8 m3
Total Volume of Experimental Theatre (m3): 5621 m3
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4.2.2 Area of Floor Materials 500Hz is used as a standard of measurement as musical performances usually fall under the category of this frequency and this auditorium is mostly used as a performing art space.
Figure 4.3: Flooring material on ground floor.
Figure 4.4: Flooring material on first floor.
Component
Surface Area (m2)
A
Marmoleum vinyl sheet over hardwood timber flooring on conrete
B C
500 Hz Absorption Coefficient
Abs Units (m2 sabins)
152.7
0.04
6.12
Hardwood timber parquet on concrete
100.3
0.07
7.02
Carpet flooring
330.6
0.30
99.18 Total
112.32
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4.2.3 Area of Wall Materials
Figure 4.5: Wall material on back of the auditorium wall.
Figure 4.6: Wall material on the sides of the auditorium wall.
Component
Surface Area (m2)
A
Acoustic timber panels
B C
500 Hz Absorption Coefficient
Abs Units (m2 sabins)
222.8
0.42
93.6
Acoustic fibreglass panels
42
0.5
21.0
Drywall
75
0.05
3.75 Total
118.35
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4.2.3 Area of Other Materials
Figure 4.7: Other materials on ground floor.
Figure 4.8: Other materials on first floor.
Figure 4.9: Other materials labelled on section.
Component
Surface Area (m2)
A
Plaster ceiling
B
500 Hz Absorption Coefficient
Abs Units (m2 sabins)
563.8
0.18
101.5
Velour curtain
372.9
0.4
149.2
C
Timber doors
10.3
0.05
0.52
D
Glass windows
9
0.04
0.36
E
Auditorium Seats (Unoccupied)
208.8
0.64
133.6
F
Glass Railings
21.9
0.04
0.88 Total
386.1 76
4.2.4 Reverberation Time Using the Sabine Formula,
RT = 0.16V A
where, RT = reverberation time (sec) V = volume of the room (cu.m) A = total absorption of room surfaces (sq.m sabins) Volume = 5621 m3 Total abs unit = 112.32 + 118.35 + 386.1 = 616.8 m2 sabins ∴ RT = 0.16 (5621) 616.8
= 1.46 secs
E.T
Figure 4.10: The table shows where the Experimental Theatre lies in the optimum reverberation different types of auditorium and halls.
The reverberation time for Experimental Theatre is 1.46 seconds which shows that the auditorium does serve its function as a performing arts theatre althought it may not be necessarily be good for speeches and conferences which do also take place in the auditorium. However, it should also noted that the high reverberation time could be mainly influenced by the large volume of the space which is 5621m3. This is due to the backstage area having a high double volume space in comparison to the volume of the auditorium seating itself. 77
Conclusion
EXPERIMENTAL THEATRE
5.0
5.0 CONCLUSION
5.1 Experimental Theatre, University Malaya Uses
Small Rooms (750m3)
Medium Rooms (750 - 7500m3)
Large Rooms (>7500m3)
Speech
0.75
0.75 - 1.00
1.00
Multi-purpose
1.00
1.00 - 1.25
1.00 - 2.00
Music
1.50
1.50 - 2.00
2.00 or more
Table 5.1 : Recommended reverberation time (RT) according to usage and volume. Highlighted is E.T.’s category and its recommended RT.
The case study has taught us the importance and application of acoustics in architecture for a building to be able to perform its stated function i.e. auditorium. Every surface in the building matters in regard to the propagation of sound and therefore details should be considered and conscious design strategies should be applied to create a fully functioning auditorium. Based on our calculation using the Sabine formula, E.T. has a volume of 5621m3 and a reverberation time of 1.46s, due to its high volume. Therefore, E.T. is mostly suitable for live and instrumental perfomances as the RT is just enough to provide for an acoustic experience for musical performances. The auditorium is not suitable for uses such as speeches or lectures however as sound absorption is loosely applied, which can reduce echoes in the auditorium, allowing for clarity of speech. Experimental Theatre of University Malaya proves to be a functional auditorium for perfoming arts, but not without certain shortcomings that can be overcomed. There are still defects in regards to its conditions which can result in a decrease of quality of its acoustics. Discussed further are actions and design considerations that can be taken, whether to reduce noise intrusion into the auditorium, or to increase the reverberation time of Experimental Theatre.
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5.2 Design Considerations and Suggestions 5.2.1 Buffer zone between lobby and main entrances By creating - or extending - a buffer zone for the main entrance of the auditorium, the air gap created will be a good sound insulation to prevent noise from entering the auditorium any time of the day.
Figure 5.1: Creating a buffer zone by joining the walls.
5.2.2 Upgrading the main entrance doors to be soundproof / Adding soundlock The same problem can also be mitigated by improving the soundproof properties of the main entrance doors. Soundlock prevents sound leakage in or out from a room.
Figure 5.2: Velour acoustic curtain hanging around the stage of E.T.
Figure 5.3: The condition of the current main entrance door.
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5.2.3 Machinery & equipments type Currently, the HVAC system of E.T. is one of the contributors of background noise in the auditorium. Having air forced out from the diffusers can create noise, and paired with a lack of maintenance, the air conditioning system may generate noise that will disrupt the acoustic experience of the auditorium. The placement of the return air inlet close to the supply air outlet seems to be counter-intuitive as well. A more suitable air conditioning system can be applied to reduce the level of background noise experienced.
Figure 5.4: Current air conditioning system.
5.2.4 Changing materials to encourage sound reflection One of the ways to increase reverberation time is to decrease the total absorption of room surfaces. For example, the acoustic fibreglass panel at the back defeats the purpose of the concave shape of the wall as it is a absoptive material. Reducing or removing it can increase the reverberation time in E.T.
Figure 5.5: Concave wall at the back is covered with absorptive material.
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5.2.5 Sound barrier Sound barrier can be added to the exterior of the auditorium at the risk of losing visibility to the building. This can mitigate traffic noise with proper implementation.
Figure 5.6: Lack of sound barrier from the traffic.
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References
EXPERIMENTAL THEATRE
6.0
6.0 REFERENCES BOOKS Egan, M. D. (2007). Architectural Acoustics. J.Ross Publishing. ARTICLES Acoustic. (n.d.). Absorption Coefficients. Retrieved October 11, 2018, from http://www. acoustic.ua/st/web_absorption_data_eng.pdf B. Y. Kinzey & H. M. Sharp. (1963). Environmental Technologies in Architecture. Retrieved from October 13, 2018, from http://www.industrial-electronics.com/measurement-testing-com/ architectual-acoustics-3-0.html Cern Accelerating Science. (n.d.). Material Data. Retrieved October 11, 2018, from https:// cds.cern.ch/record/1251519/files/978-3-540-48830-9_BookBackMatter.pdf D. Y. Maa. (2005). The Flutter Echoes. Retrieved October 11, 2018, from https://asa.scitation. org/doi/abs/10.1121/1.1916161?journalCode=jas N. W. Adelman-Larsen. (2014). Rock and Pop Venues Acoustic and Architectural Design. Retrieved October 13, 2018, from http://www.springer.com/978-3-642-45235-2 R. E. Berg. (1995). Acoustic Problems. Retrieved from October 14, 2018, from https://www. britannica.com/science/acoustics/Acoustic-problems#ref527632 R. L. Hanson. (2013). Reverberation Characteristics of Sound Pictures Sets and Stages. Retrieved October 11, 2018, from https://asa.scitation.org/doi/pdf/10.1121/1.1901936?class=pdf The Arc. (n.d.). Acoustics: Room Criteria. Retrieved October 11, 2018, from https://web.iit. edu/sites/web/files/departments/academic-affairs/Academic%20Resource%20Center/pdfs/ Workshop_-_Acoustic.pdf University of Malaya Library Bulletin. (2011). Kekal Abadi. Retrieved October 11, 2018, from https://umlib.um.edu.my/publications/kekal-29-1-2011.pdf Z. George. (2011). Operation Resurrection: Launch Report. Retrieved October 11, 2018, from http://operationresurection.blogspot.com/2011/03/launch.html
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WEBSITES Contrado. (2016, February 16). What is Velour and How Does it Differ from Velvet? Retrieved October 11, 2018, from https://www.contrado.co.uk/blog/what-is-velour/ Gustafs. (n.d.). Acoustic Academy. Retrieved October 11, 2018, from https://gustafs.com/ architect-support/acoustics-academy/ Hyper Physics. (n.d.). Reverberation Time. Retrieved October 12, 2018, from http://hyperphysics. phy-astr.gsu.edu/hbase/Acoustic/revtim.html JCW Acoustics Supplies. (n.d.). Absorption Coefficients of Common Building Materials and Finishes. Retrieved October 11, 2018, from https://soundproofyourhome.com/absorptioncoefficient-chart/ K. Rick. (2016). Point Source, Line Arrays or Column Speakers: What’s Best for Your Church? Retrieved October 12, 2018, from https://pro.harman.com/insights/enterprise/hospitality/ house-of-worship/point-source-li ne-arrays-or-column-speakers-whats-best-for-your-church/ R. Hugh. (2007). All You Wanted to Know About Subwoofers. Retrieved October 12, 2018, from https://www.soundonsound.com/sound-advice/all-you-wanted-know-about-subwoofers Sound Proofing Company. (n.d.). The Triple Leaf Effect & Air Cavity Depth. Retrieved October 12, 2018, from https://www.soundproofingcompany.com/soundproofing101/triple-leafeffect/ Sweetwater. (2001). Flutter Echo. Retrieved October 14, 2018, from https://www.sweetwater. com/insync/flutter-echo/ Theatre Solutions Inc. (n.d.). Auditorium Design 101: The Complete Guide. Retrieved October 12, 2018, from http://www.theatresolutions.net/auditorium-design/#seating University of Malaya. (n.d.). Dewan Tunku Canselor. Retrieved October 11, 2018, from http:// cultural.um.edu.my/facilities-and-services/facilities University of Salford Manchester. (n.d.). Concert Hall Acoustics: Art and Science. Retrieved October 12, 2018, from http://www.acoustics.salford.ac.uk/acoustics_info/concert_hall_ acoustics/?content=shape U.S. Department of Transportation Federal Highway Administration. (n.d.). The Audible Landscape: A Manual for Highway Noise and Land Use. Retrieved October 12, 2018, from https://www.fhwa.dot.gov/ENVIRonment/noise/noise_compatible_planning/federal_ approach/audible_landscape/al04.cfm
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