School of Architecture, Building and Design Center for Architecture Studies in Southeast Asia (MASSA) Bachelor of Science (Honours) in Architecture Building Science II Assignment 1: Auditorium - A Case Study on Acoustic Design
Tutor: Ar.Edwin Yean Liong Chan Group members: Benjamin Lew Jowyn Ooi Yin Yi Lim Lih Han Lim Zhi Kang Lock Tian Jiun Loh Shu Wei Yeoh Han Joo Yeow Wan Yee Yong Zhi Kang
0331583 0330897 0326573 0330914 0327636 0331016 0330959 0331154 0327791
Table of Content 1.0 Introduction ·············································································································································································· 1 - 6 1.1 Historical Background 1.2 Information on Experimental Theatre 1.3 Context and Location 1.4 Architectural Drawings 2.0 Methodology ············································································································································································· 7 - 9 2.1 Data Collection and Site Observation Process 2.1.1 Sound Concentration and Sound Pressure Level 2.1.2 Noise Intrusion and Sound Absorption 2.1.3 Materiality and Massing Studies 2.2 Limitation 3.0 Architecture and Building Acoustics of Experimental Theatre, University Malaya ·································································· 10 - 60 3.1 Sound Propagation and Behaviour in Experimental Theatre, UM 3.2 Acoustical Phenomenon 1 - Direct and Indirect Sound Path 3.2.1 Sound Reflection and Diffusion 3.2.2 Echoes 3.2.3 Flutter Echoes 3.3 Acoustical Phenomenon 2 - Sound Shadow 3.4 Acoustical Phenomenon 3 - Sound Absorption 3.5 Acoustical Phenomenon 4 - Noise Intrusion 3.5.1 Noise Analysis 3.5.2 Noise Source in Experimental Theatre, UM 3.5.3 Noise Control in Experimental Theatre, UM 3.5.4 Background Noise 3.6 Acoustical Phenomenon 5 - Reverberation in Enclosed Space 3.6.1 Introduction to Reverberation Time 3.6.2 Reverberation Calculation 4.0 Conclusion ············································································································································································ 61 - 63 5.0 References ············································································································································································ 64 - 66
1.0 Introduction
Experimental Theatre, University Malaya | 1
1.0 | Introduction
1.1 Historical Background Built in the mid-sixties together with the Dewan Tunku Canselor (DTC). Both the DTC and E.T. were designed and constructed by Dato’ Kington Loo of BEP Architects. Designed with a strong inuence of Brutalist architecture and the Modernist movement, the building was constructed mainly from a bare concrete structure. It was declared a National Heritage in early 2009. Renovation works commenced in year 2009 and was reopened in April 2011.
1.2 Information about Experimental Theatre
Figure 1.1.1 Historical photo of Experimental Theatre
The layout of the present Experimental Theatre builds upon Richard Wagner's original concept, incorporating modern innovations and systems. It features a proscenium stage, with a ramp leading to basement rooms that serve as a green room (waiting room or touch-up lounge for performers). In front of the stage is a hydraulic platform, which when raised serves as an extension to the front of the stage, and when lowered as an orchestra pit. Hidden above the stage is a structure of grids and rigging to accommodate modern sound and lighting systems. The auditorium consists of tiered stalls and a gallery (balcony or raised seating platform). The theatre hall are available for rental (private and corporate functions). The theatres are suitable for stage performance, conferences, seminars, presentations and product launches. It can accommodate about 435 pax. The theatres are well-known, extremely well-equipped.
Figure 1.2.1 Undergone renovation work in 2009
Figure 1.2.2 Looks after renovation in April 2011 Experimental Theatre, University Malaya | 2
1.0 | Introduction
1.3 Context and Location The Experimental Theatre is located in Lingkungan Budi, Kuala Lumpur, Wilayah Persekutuan Kuala Lumpur, in within the campus of University Malaya. It is situated just beside the infamous Tunku Dewan Canselor (DTC) and surrounded by softscape that soften the hardness of the brutalic structure. Since the accessibility and linkage of vehicular circulation around the campus is good provided with suďŹƒcient car parks, the monolithic concrete structure can be easily found.
Figure 1.3.2 Perspective view from front of Experimental Theatre
Figure 1.3.1 Location of Experimental Theatre in Google map plan view
Figure 1.3.3 Perspective view from back of Experimental Theatre
Experimental Theatre, University Malaya | 3
1.0 | Introduction
1.4 Architectural Drawings (Scale 1: 500)
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5 B’ Figure 1.4.1 Ground Floor Plan Legend 1. Entrance (students and audience access) 2. Washrooms 3. Performance stage 4. Backstage 5. Ramp 6. VIP entrance hallway
Figure 1.4.2 First Floor Plan Legend 1. Lift lobby 2. Washrooms 3. Backstage control room 4. Balcony 5. Staircase (leads to VIP entrance hallway) 6. VIP entrance hallway
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1.0 | Introduction
1.4 Architectural Drawings (Scale 1: 500)
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Legend 1. Backstage 2. Balcony 3. House 4. Basement 5. Aisle
Figure 1.4.3 Section A-A’
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Legend 1. Performance stage 2. Stage apron 3. House 4. Basement 5. Orchestra pit 6. Backstage control room 7. VIP entrance hallway
Figure 1.4.4 Section B-B’
Experimental Theatre, University Malaya | 5
1.0 | Introduction
Figure 1.5.1 View from balcony
Figure 1.5.2 Control panel located at the side of stage
Figure 1.5.3 A hidden ramp which leads people to backstage preparation area
Figure 1.5.4 View from stage
Figure 1.5.5 Performance stage
Figure 1.5.6 Backstage preparation area
Experimental Theatre, University Malaya | 6
2.0 Methodology
Experimental Theatre, University Malaya | 7
2.0 | Methodology
2.1 Data Collection and Site Observation Process 2.1.1 Sound Concentration and Sound Pressure Level Sound level was measured using sound level meter to identify the magnitude of a constant sound source in different points and location across the audience seats. Sound produced by hair dryer is used as the constant sound source.
Figure 2.1.1.1 Usage of sound level meter
2.1.2 Noise Intrusion and Sound Absorption Identification of both exterior and interior noise were taken into consideration. High heels is used to test the potential noise caused by certain floor materials while outdoor noise were noted down to determine if the wall insulation and cavity system is working properly. Every detailed source of noise was noted down.
Figure 2.1.2.1 Photography and usage of laser meter
2.1.3 Materiality and Measurement Different usage of materiality were recorded along with its dimensions using laser meter. Photographs were taken at marked locations on plan for report usage. Drawings were obtained from the authorities and were retraced to obtain accurate dimensions to study the relationship between sound to distance. Moreover, the dimension of the materials were extracted from the drawings for RT calculation.
Figure 2.1.3.1 Measuring dimension through traced drawings using software Experimental Theatre, University Malaya | 8
2.0 | Methodology
2.2 Limitation Acoustic Analysis of Space Since most of the sound that is propagating into the curve zone will not reflect back into the main shoe box area, together with existence of absorption materials such as the velour curtain, sound attenuation happens inside the curve space with only minor insignificant sound reflection escaped. Thus the curve stage in negligible to the data collected in the shoe box zone. The noise analysis will be mainly focus in the enclosed space region as well due to limitation of access into private authorization area such as control room, green rooms, break rooms and air-conditioning room etc.
Figure 2.2.1 Main enclosed space region of the theatre
Figure 2.2.2 Entrance of the administrative office
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3.0 Architecture and Building Acoustics of Experimental Theatre, University Malaya
Experimental Theatre, University Malaya | 10
3.0 | Architecture and Building Acoustics of Experimental Theatre, University Malaya
3.1 Sound Propagation and Behaviour in Experimental Theatre, UM When designing an enclosed space, like auditorium, architects are needed to take in consideration with the control of sound in the designated space to provide the best condition and high quality for the production and the reception of desirable sound in a same time eliminating the unwanted sound and noise within and outside of the enclose space. The study of the sound in an enclosed space can be simplified by imaginary sound “rays”, where it’s perpendicular to the advancing wavefront, travelling in straight lines in every direction within the space.This approach is called geometric acoustic in architectural acoustics, which similar to the behaviour of sound waves towards light rays. In ETUM, we have analysed its sound propagation and behaviour and there are a few that we managed to note it down, namely the: 1. 2. 3. 4. 5. 6. 7. 8.
Sound Diffraction or Bent Sound Sound Absorption by Surface Treatment Direct Sound Sound Dispersion Sound Reflection Sound Transmission Sound Conducted by the Structure Sound Dissipation within the Structure
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2 1
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Figure 3.1.1 Sound propagation and behaviour in ETUM Experimental Theatre, University Malaya | 11
3.0 | Architecture and Building Acoustics of Experimental Theatre, University Malaya
3.1 Sound Propagation and Behaviour in Experimental Theatre, UM
Figure 3.1.2 SIL readings taken along fixed interval points of ground floor with sound source from stage
Figure 3.1.3 SIL readings along fixed interval points of upper floor with sound source from stage
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3.0 | Architecture and Building Acoustics of Experimental Theatre, University Malaya
3.2 Acoustical Phenomenon 1 - Direct and Indirect Sound Path 3.2.1 Sound Reflection and Diffusion - Floor Area Design
Sound Absorbing Surface Sound Reflecting Surface 60°
60°
Figure 3.2.1.1 Sound reflection path according to the theatre form
The theatre form implemented the rectangular shoebox with fan-shaped seats arrangement with concave end wall. It aided in controlling the sound propagation and behaviours within the theatre easier. The placement of two hard splayed side walls reflect sound energy towards the end concave surface which prevents late reflection by absorbing the sound energy.
Figure 3.2.1.2 Sound reflection path at different angular surfaces
The concrete side wall of the ETUM are mounted with highly reflective acoustic wall panels of different angled facade surfaces. With the intention to aid in reflecting sound, the sound energy strikes the flat surface of the hard wall panels and reflect in various directions to enhance the sound diffusion more evenly in the theatre.
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3.0 | Architecture and Building Acoustics of Experimental Theatre, University Malaya
3.2 Acoustical Phenomenon 1 - Direct and Indirect Sound Path 3.2.1 Sound Reflection and Diffusion - Floor Area Design
Figure 3.2.1.3 Seats arranged in a concentric arc segment of circle
The configuration of the seats in the theatre is arranged in a concentric arc segment of circle (fan shape) efficiently for sound range to be optimally reached at every angle. The theatre seats are orientated within 140 degrees of sound projection which results in high recurrence of sound projected. The distance between sound source from the stage and the last row of the seats is within 22.5m, which is ideal range for human voices to be heard clearly.
Figure 3.2.1.4 The levelling of auditorium
The implementation of staggered seatings in ETUM are designated to allow the sound waves from the sound source to be transferred clearly to the audience without obstruction and provide assurance of unobstructed views. The slope created in the theatre floor is around 8 degree which is an optimum degree to create a comfortable sightlines for the audiences, at the same time to prevent direct blockage of sound by any physical parts of audiences. Experimental Theatre, University Malaya | 14
3.0 | Architecture and Building Acoustics of Experimental Theatre, University Malaya
3.2 Acoustical Phenomenon 1 - Direct and Indirect Sound Path 3.2.1 Sound Reflection and Diffusion - Vertical Elements Design
Figure 3.2.1.6 Zig zag arrangement of acoustic wall panels at side wall
Sound Absorbing Surface
Sound Reflecting Surface
Figure 3.2.1.5 Diffused high frequency sound path in the theatre
Vertical Elements The repetitive zig zag arrangement of several small section of dry walls and acoustic wall panels which allows sound to have many reflective surfaces. The pointed edges of the acoustic wall panels provides sufficient scattering to reduce ‘glare’ and create diffusivity of the sound waves which benefits in diffuse the high frequency sound which has a short wavelength and disperse sound to provide a more uniform spatial distribution of sound energy to achieve desirable acoustic performance throughout the theatre.
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3.0 | Architecture and Building Acoustics of Experimental Theatre, University Malaya
3.2 Acoustical Phenomenon 1 - Direct and Indirect Sound Path 3.2.1 Sound Reflection and Diffusion - Vertical Elements Design
Convex ceiling
Figure 3.2.1.8 Curvy sidewall to roof ceilings form finishes with fibre cement boards with white paint finish.
Sound source
Incident sound
Reflected and dispersed sound
Figure 3.2.1.7 Section showing form of the ceiling edge on the edge of the wall affecting the sound specific behaviour
Vertical Elements The plaster ceiling which painted with white paint is used to disperse sound from stage in a steep angle. The curve edges of the ceiling aids in better sound dispersion to the balcony seating area. It also eliminates sharp corners which prevent echoes that may occur from long reflections.
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3.0 | Architecture and Building Acoustics of Experimental Theatre, University Malaya
3.2 Acoustical Phenomenon 1 - Direct and Indirect Sound Path 3.2.1 Sound Reflection and Diffusion - Ceiling Design
Sound Absorbing Surface Sound Reflective Surface Sound Reflection
Figure 3.2.1.9 Sound propagation reflected follow the ceiling form design
Figure 3.2.1.10 The small increments and sloped angles of the ceiling
Ceiling Ceiling height is usually determined by the overall room volume that is required. A ceiling is too high in a room may create undesirable late reflections. To avoid potential flutter echo, the ceiling should not be parallel to the floor. The ceiling of experimental theatre geometry itself is designed to direct sound to the rear hall and to diffuse it all over the hall. The effective ceiling form design reflect the sound propagation evenly to every part of seating area in auditorium expect for the sound shadow area which is under the balcony. The convex surface ceiling disperses sound to middle seating area and the upper balcony seats.The rear part of ceiling design allows for sound from the performers to reach the audience in the upper balcony. The small increments and sloped angles of the ceiling has increase the area of providing useful sound direction.
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3.0 | Architecture and Building Acoustics of Experimental Theatre, University Malaya
3.2 Acoustical Phenomenon 1 - Direct and Indirect Sound Path 3.2.1 Sound Reflection and Diffusion - Ceiling Design
a)
c)
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Figure 3.2.1.11 Sound reflected to the front seating area from the front ceiling surfaces Sound Absorbing Surface
Figure 3.2.1.12 Sound reflected to the central seating area from the middle part of ceiling surfaces Sound Reflective Surface
Sound Reflection
Figure 3.2.1.13 Sound reflected to the upper seating area from the rear ceiling surfaces
Area of Sound Reflection
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3.0 | Architecture and Building Acoustics of Experimental Theatre, University Malaya
3.2 Acoustical Phenomenon 1 - Direct and Indirect Sound Path 3.2.1 Sound Reflection and Diffusion - Ceiling Design
a) + b) = Sound reflected on surface (1) Surface (1)
Based on the ceiling design analysis diagrams, the ceiling surface (1) contributes in reflecting greater sound to the audience located in the front row seating area due to the composition of the concave and convex surface. The short distance between the stage and the front row allows direct sound to travel to the audience. Figure 3.2.1.14 Sound reflection of surface (1) from the stage to the front row c) + d) + e) + f) = Sound reflected on surface (2) Surface (2)
As the sound travels to the middle and back row, direct sound attenuates as sound loses its energy when it travels further. The ceiling surface is designed to reflect most of the sound to the back and middle row in order to reinforce the attenuated direct sound. Surface (2) has a certain sloped angles of ceiling height to ensure even dispersion of sound to different required angle. Sound distribution in Experimental Theatre of UM can be considered as even because based on the analysis, the recorded sound readings of the front row and back rows are relatively similar with only minor difference.
Figure 3.2.1.15 Sound reflection of surface (2) from the stage to the back row
Sound Absorbing Surface
Sound Reflective Surface
Sound Reflection
Area of Sound Reflection
Direct Sound
Ceiling Surface Experimental Theatre, University Malaya | 19
3.0 | Architecture and Building Acoustics of Experimental Theatre, University Malaya
3.2 Acoustical Phenomenon 1 - Direct and Indirect Sound Path
a)
3.2.2 Echoes Reflected sound reinforces direct sound if the time delay is within 30 m/sec. When time delay exceeds 40 m/sec for speech and 100 m/sec for music perceived as a sound distinct from that travelling directly from source to listener is deemed as an echo. Calculation of sound time delay at different points around the theatre can be made to determine if echo existed when a constant sound source is present. a)
Sound source with sound reflected by walls to possible furthest listener location: Times delay = (R1 + R2 - D) / 0.32 = (14 + 14 - 16) / 0.32 = 37.5 m/sec
b)
Sound source with sound reflected by walls to random listener location: Times delay = (R1 + R2 - D) / 0.32 = (16.5 + 9 - 11.5) / 0.32 = 43.75 m/sec
c)
Sound source with sound reflected by walls to random listener location : Times delay = (R1 + R2 - D) / 0.32 = (14.3 + 16 - 6.7) / 0.32 = 73.75 m/sec
On point b) and c), there is potential of hearing echo from a speech since the time delay exceeds 40 m/sec. Late reflection occurs where the time taken for sound to travel back is longer when the distance is further away from the rear. To prevent echoes at front, experimental theatre treated the rear walls with sound absorption materials so that most of the sound is absorbed at the rear and the reflected sound is insignificant to cause echo. Hence, the audience around point b) and c) can freely enjoy the performances with the absence of the echoes.
b) Sound source Listener
c)
Figure 3.2.2.1 Sound time delay on different location in the house Experimental Theatre, University Malaya | 20
3.0 | Architecture and Building Acoustics of Experimental Theatre, University Malaya
3.2 Acoustical Phenomenon 1 - Direct and Indirect Sound Path 3.2.2 Echoes
Reflected sound reinforces direct sound if the time delay is within 30 m/sec. When time delay exceeds 40 m/sec for speech and 100 m/sec for music perceived as a sound distinct from that travelling directly from source to listener is deemed as an echo.
a)
Calculation of sound time delay at different points around the theatre can be made to determine if echo existed when a constant sound source is present. a)
b)
Sound source with sound reflected by walls to possible furthest listener location: Times delay = (R1 + R2 - D) / 0.32 = (8.3 + 8.3 - 10) / 0.32 = 20.63 m/sec
b)
Sound source with sound reflected by walls to random listener location : Times delay = (R1 + R2 - D) / 0.32 = (7.1 + 7.5 - 4) / 0.32 = 33.13 m/sec
Point a) and b) shows time delay which is beneficial for reflected sound to reinforce direct sound. Instead of having reflected sound as an echo, the reflected sound helps people to hear more clearly and to provide better experience.
Listener Figure 3.2.2.2 Sound time delay on different location in the house
As conclusion from analysis on both plan and section, the Experimental Theatre has acceptable sound time delay as performing arts centre since all the calculated sound delay are below 100 m/sec and will not cause echo for speech since sufficient absorptive materials are provided. Experimental Theatre, University Malaya | 21
3.0 | Architecture and Building Acoustics of Experimental Theatre, University Malaya
3.2 Acoustical Phenomenon 1 - Direct and Indirect Sound Path 3.2.3 Flutter Echoes
Sound propagates into the backstage area Sound propagates within the backstage area Velour curtains prohibited the sounds to enter back the house Figure 3.2.3.1 Potential existence of flutter echoes at backstage area
Figure 3.2.3.2 Velours design and stage optimum height to prevent flutter echoes to affect the performance
Flutter echo is a condition which occurs in acoustical spaces whereby two parallel surfaces reflecting sound between one another are far apart enough 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. For our experimental theatre, there is still potential presence of minimal flutter echoes in the transitional spaces and the stage area as the design of the ceiling and floor are in a relatively parallel manner. Even though, there is potential for flutter echoes to happen, the audience can still enjoy a good performances as the flutter echoes is weak enough to not propagate into the house due to several conscious designs of our experiment theatre which are the enclosed space shape and height, ceiling design, wall design, floor area design and use of suitable materiality in different surfaces of the enclosed space.
Figure 3.2.3.3 Ramp leads to break rooms and services area of the theatre Experimental Theatre, University Malaya | 22
3.0 | Architecture and Building Acoustics of Experimental Theatre, University Malaya
3.3 Acoustical Phenomenon 2 - Sound Shadow
For this case study, the shallow sound shadow region is concentrated mainly in the seatings beneath the gallery. Based on the sound intensity level recorded, the readings show that the sound intensity at the back is slightly lower than the front area which positioned closer to the stage, with a difference of 4-5 dB. This is contributed by 2 factors, the increase in distance from the sound source as mentioned in the previous sound propagation topic and its location covered by the overhang of the gallery balcony above.Therefore, it results in the formation of sound shadow which causes the audiences in the region experiencing disrupted sound and sound quality which is not at its optimal value.
Figure 3.3.1 Plan showing the difference in sound intensity level at the sound shadow region and other regions
In concert halls, the acoustic quality below a large balcony is often reduced compared with the acoustic quality of the main volume. This is caused by significant differences in the reverberated energy behavior between these two volumes.The main difference is a global lack of reverberated energy under the balcony. (Rouch, Jérémy & Galland, Marie-Annick & Schmich-Yamane, Isabelle, 2013)
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3.0 | Architecture and Building Acoustics of Experimental Theatre, University Malaya
3.3 Acoustical Phenomenon 2 - Sound Shadow The balcony depth of University Malaya Experimental Theatre is approximately 3.5m. The aperture for the sound energy to pass through from the main volume of the hall to the region below the balcony is 1.9m. For balcony design, Beranek (1962) suggested a rule-of-thumb for concert halls that the depth beyond the overhang should not exceed the height of the opening, ratio of depth to height overhang proportion criteria D/H ≤1 so that the volume below the balcony does not acoustically ‘decoupled’ from the main volume. The D/H ratio of the case study is 1.8 which is still acceptable as the ratio of depth to opening for multipurpose theatre is not as strict for concert hall and will only have a little more impact on the persons seated deep under a balcony of the sound shadow area. Also, the balcony did not protrude too deeply in the air-space of the hall thus the the quality of sound under the balcony is only affected in a slight degree.
Figure 3.3.2 Size of the balcony and sound shadow region
When sound travels from the source located at the stage, the direct sound travels to the middle region of the hall effectively and is further enhanced by the reflective sound paths from the ceiling and walls to reach homogeneity in sound. However, region underneath the balcony is far beyond reach for the direct sound waves and cannot receive useful reflected sound from the ceiling and are shielded from the reverberant sound, forming a sound shadow phenomenon where the audience experiences a drop in sound quality and intensity. Figure 3.3.3 Section showing the sound shadow region being shielded from both direct and reflected sound, with sound source located on the stage
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3.0 | Architecture and Building Acoustics of Experimental Theatre, University Malaya
3.3 Acoustical Phenomenon 2 - Sound Shadow Considerations made to mitigate the effects of sound shadow Experimental Theatre is a practical multi-purpose hall to be used as a performing arena for theatre plays, pop music, and classical music or opera, which all need different acoustical conditions. A solution for enhancing the reverberated energy below the balcony to tackle sound shadow defect and to achieve different acoustical conditions is to inject amplified sound picked up in the main volume by sound reinforcement system. Simple electroacoustic channels is performed in this case. Each channel is composed of a microphone in the main volume, and four loudspeakers under the balcony. There are four two-way ceiling mounted speakers installed on the balcony soffit for the region under the balcony to enhance sound intensity in the area in order to reach overall sound homogeneity and to improve sound clarity.
Figure 3.3.4 Plan showing the equally spaced out placement of speakers in order to reach sound homogeneity in the sound shadow area
Figure 3.3.5 Electro-acoustic enhancement system installed under the balcony Experimental Theatre, University Malaya | 25
3.0 Architecture | Architecture and and Building Building Acoustics Acoustics of of University Experimental Malaya Theatre, Experiential University Theatre Malaya
3.4 Acoustical Phenomenon 3 - Sound Absorption GROUND FLOOR PLAN
SECTION A-A’
SECTION B-B’
Marmoleum vinyl sheet Timber parquet
Needle punch non woven carpet
Glass panel
Velour acoustic curtains
Acoustic fabric fibreglass panels
Plaster ceiling
Timber acoustic panels
Polyurethane seats Timber doors
Drywall
Medium pile carpet Figure 3.4.1 Architectural drawings of Experimental Theatre which indicating all materials Experimental Theatre, University Malaya | 26
3.0 Architecture | Architecture and and Building Building Acoustics Acoustics of of University Experimental Malaya Theatre, Experiential University Theatre Malaya
3.4 Acoustical Phenomenon 3 - Sound Absorption 3.4.1 Materiality (Stage) in Experimental Theatre, UM Hardwood Timber with Marmoleum Vinyl Sheet (20mm thk. Polished Timber Parquet on Concrete) The original flooring system of E.T. is of reinforced concrete which is a reflective material. It does not insulate or absorb sound waves. However, its high mass can increase sound transmission loss of structure-borne sound. As a solution to overcome the reflective properties of concrete, a 20 mm thick polished timber parquet is laid over most of the surface of the stage to enhance sound absorption. Due to the high possibility of foot traffic occuring during a performance, the timber parquet is not sufficient in absorbing excess sound. Therefore, a marmoleum vinyl sheet is later covered above the timber surface. Marmoleum vinyl sheets increases the impact time, which in turn promotes sound reduction. With the combination of 3 layers of flooring, unwanted noise from foot traffic is reduced.
Figure 3.4.1.1 Marmoleum vinyl sheet
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3.0 Architecture | Architecture and and Building Building Acoustics Acoustics of of University Experimental Malaya Theatre, Experiential University Theatre Malaya
3.4 Acoustical Phenomenon 3 - Sound Absorption 3.4.1 Materiality (Stage) in Experimental Theatre, UM Plaster Ceiling (12mm thk. GRC Plaster) The plaster ceiling is coated with white paint and is used to disperse sound from the stage in a controlled manner. The curved edges of the ceiling aids sound dispersion to the seating area, enabling the audience to hear sounds more clearly. sound from stage reflected sound
Figure 3.4.1.2 Curved edges are implemented to aid sound dispersion
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 3.4.1.3 Velour curtains are used backstage to absorb unwanted noise from the exterior environment Experimental Theatre, University Malaya | 28
3.0 Architecture | Architecture and and Building Building Acoustics Acoustics of of University Experimental Malaya Theatre, Experiential University Theatre Malaya
3.4 Acoustical Phenomenon 3 - Sound Absorption 3.4.1 Materiality (Stage) in Experimental Theatre, UM Pleated Curtains To improve low and mid frequency sound absorption, the velour curtains are pleated to expose more sound absorbing surface. This will cause the fabric to be “gathered,” such that it loops in and out. The pleating should be as deep as possible in order to expose more sound-absorbing surface, thus increasing effective thickness and improving low frequency sound attenuation.
Figure 3.4.2.29 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. The drapery will also become more effective at absorbing longer sound wavelengths (lower pitches) if it is spaced several inches from the wall or window.
source of external noise
source of external noise
Figure 3.4.2.30 A distance of approximately 16 meters is allocated between the backstage walls and the velour curtains
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 3.4.2.31 Polyurethane foam seating Experimental Theatre, University Malaya | 29
3.0 Architecture | Architecture and and Building Building Acoustics Acoustics of of University Experimental Malaya Theatre, Experiential University Theatre Malaya
3.4 Acoustical Phenomenon 3 - Sound Absorption 3.4.2 Materiality (House) in Experimental Theatre, UM Walls (including mezzanine)
Figure 3.4.2.1 Timber Acoustic Panels
Figure 3.4.2.2 Plastered concrete column with white emulsion paint ďŹ nish
Seating
Figure 3.4.2.8 Polyurethane foam seating
Floor
Figure 3.4.2.3 Acoustic fabric panel
Figure 3.4.2.4 Aluminium Grill Framing on Timber panel
Ceiling
Figure 3.4.2.9 Plastic armrest
Figure 3.4.2.10 Plaster ceiling
Figure 3.4.2.5 Gypsum board with air gap with white emulsion paint ďŹ nish
Figure 3.4.2.6 Short pile carpet
Figure 3.4.2.7 Needle punch non-woven carpet
Mezzanine
Figure 3.4.2.11 Glass railing with aluminium handrail
Figure 3.4.2.12 Glass panel with timber frame for control room
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3.0 Architecture | Architecture and and Building Building Acoustics Acoustics of of University Experimental Malaya Theatre, Experiential University Theatre Malaya
3.4 Acoustical Phenomenon 3 - Sound Absorption 3.4.2 Materiality (House) in Experimental Theatre, UM Acoustic Timber Panels (12mm Plywood Panels) Timber is a low frequency 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 are covered with decorative aluminium grills and have light boxes built in. To absorb sound waves, the surface area is increased by arranging them in a jagged pattern in accordance to the gypsum drywalls. This in turn reduces flutter echo which reduces the chance of incident and reflected waves from interfering each other. Figure 3.4.2.13 Timber Acoustic Panels
Figure 3.4.2.15 Location of timber wall panels on ground floor plan
Figure 3.4.2.16 Location of timber wall panels on gallery plan
Figure 3.4.2.14 Timber Acoustic Panels
Figure 3.4.2.17 Sectional detail of the wall with the timber panel highlighted
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3.4 Acoustical Phenomenon 3 - Sound Absorption 3.4.2 Materiality (House) in Experimental Theatre, UM Acoustic Fabric Fibreglass Panels The fibreglass panels are located at the back of the theatre on both ground floor and gallery level. To prevent deadening of the upper mids and high, the panels only cover the middle part of the wall and not the whole wall entirely. These fiberglass panels feature an innovative combination of dimensionally stable glass fiberboard, with a resilient perforated co-polymer face sheet with heat-formed edges. They are also effective sound absorbers. They eliminate unwanted boundary reflections and controls excessive room reverberation. By absorbing sound waves, this can reduce resonance within the theatre. Figure 3.4.2.18 Acoustic fabric panels on the back walls of the ground floor and balcony
Figure 3.4.2.20 Location of acoustic fabric fibreglass panels on ground floor plan
Figure 3.4.2.19 Acoustic fabric panel
Figure 3.4.2.21 Sectional diagram showing the absorptive characteristic of fibreglass panels
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3.4 Acoustical Phenomenon 3 - Sound Absorption 3.4.2 Materiality (House) in Experimental Theatre, UM Drywall (2 Layers of 15mm Gypsum Board on Steel Studs and 150mm Air Gap with 50mm Rockwool or Fibreglass in the Cavity) To increase sound reflection from stage towards the audience, the drywall of the theatre is shaped in a jagged pattern. Complemented by acoustic timber panels, the unique pattern of the walls also prevent flutter echoes as it eliminates the parallelity of walls on flanking sides. Drywall has a solid core made of gypsum. 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 3.4.2.23 Location of drywall on ground floor.
Figure 3.4.2.22 Walls layered with gypsum boards and rockwool are used in this theatre
Figure 3.4.2.24 Location of drywall on gallery floor plan
Figure 3.4.2.25 Sectional detail of the wall with the drywall highlighted
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3.4 Acoustical Phenomenon 3 - Sound Absorption 3.4.2 Materiality (House) in Experimental Theatre, UM 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. Therefore, the medium pile carpet is used to absorb impact noise created by footsteps and dropped objects from the audience. The carpets are permeable which enables sound waves to penetrate into the pile carpet instead of being reflected. 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 continuous range of frequencies enables it to absorb a wide range of sound waves.
Figure 3.4.2.26 Medium pile carpet
Figure 3.4.2.27 Needle punch non-woven carpet
Figure 3.4.2.28 Short pile carpet
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3.4 Acoustical Phenomenon 3 - Sound Absorption 3.4.3 Material Specifications in Experimental Theatre, UM Absorption CoeďŹƒcient Location
Component
Walls
Stage
Material
Description
Finishes 125Hz
500Hz
2000Hz
Reinforced concrete
Reinforced concrete wall plastered on both sides
Emulsion paint, black
0.01
0.01
0.02
Velour
Velour acoustic curtain
NIL
0.05
0.40
0.60
Timber
H.W. timber panels (12mm thk. plywood panels)
NIL
0.18
0.42
0.83
Gypsum
2 layers of 15mm gypsum board on steel studs with 150mm air gap ďŹ lled with 50mm rockwool
Emulsion paint, white
0.08
0.05
0.02
Concrete
Cement render
Polished
0.02
0.02
0.05
Timber
Timber parquet
Varnish
0.02
0.20
0.10
Aluminum
Aluminum grill skirting
Antique copper, gold faux texture
-
-
-
Timber
Hardwood timber parquet
Varnish
0.20
0.10
0.05
Floors
Apron
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3.4 Acoustical Phenomenon 3 - Sound Absorption 3.4.3 Material Specifications in Experimental Theatre, UM Absorption Coefficient Location
Component
Material
Description
Finishes 125Hz
500Hz
2000Hz
Apron
Marmoleum Vinyl
Vinyl sheet covered over H.W. timber on concrete floor
NIL
0.02
0.04
0.05
Stage curtain
Velour
Velour acoustic curtain
NIL
0.05
0.40
0.60
Stage
Figure 3.4.3.1 Table showing Stage materials of the Experimental Theatre
Walls
Figure Velour curtains
Floor & Apron
3.4.3.2 acoustic
Figure 3.4.3.3 Plastered concrete wall with black emulsion paint finish
Figure 3.4.3.4 Gypsum wall panels with white emulsion paint finish
Figure Polished floor
3.4.3.5 Figure 3.4.3.6 concrete Timber parquet
Figure 3.4.3.7 Figure Marmoleum vinyl sheet Aluminium skirting
3.4.3.8 grill
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3.4 Acoustical Phenomenon 3 - Sound Absorption 3.4.3 Material Specifications in Experimental Theatre, UM
Absorption Coefficient Location
Component
Material
Description
Finishes 125Hz
500Hz
2000Hz
Timber
12mm thk. plywood acoustic timber panel
NIL
0.18
0.42
0.83
Gypsum
2 layers of 15mm gypsum board on steel studs with 150mm air gap filled with 50mm rockwool
Emulsion paint, white
0.08
0.05
0.02
Acoustic fibreglass panels
Fibreglass (72 kg/m3) with a facing of stretched fabric
Stretched fabric
0.10
0.50
0.70
Floors
Carpet
10mm thk. short pile carpet over concrete floor
NIL
0.08
0.30
0.75
Ceiling
Plaster
12mm thk. GRC plaster
Emulsion paint, white
0.20
0.18
0.15
Walls
House
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3.4 Acoustical Phenomenon 3 - Sound Absorption 3.4.3 Material Specifications in Experimental Theatre, UM Absorption CoeďŹƒcient Location
Component
Material
Description
Finishes 125Hz
500Hz
2000Hz
Plastic
Molded one piece plastic component
NIL
-
-
-
Polyurethane foam
Upholstered tip-up foam seating
NIL
0.33
0.64
0.77
Glass
1.4mm thk. glass window panel
NIL
0.30
0.10
0.05
Timber
Hardwood timber
NIL
0.18
0.10
0.08
Timber
Hardwood timber ush double door
Varnish
0.14
0.06
0.10
Seating
House Control booth
Doors
Figure 3.4.3.9 Table showing House materials of the Experimental Theatre
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3.5 Acoustical Phenomenon 4 - Noise Intrusion 3.5.1 Noise Analysis
The acoustic analysis of noise in buildings can be viewed from as standpoint of three different relationship which is the sound source, sound path and sound receiver. Sound source
Sound path
Sound receiver
Figure 3.5.1.1 Transmission of sound.
Sound Source Sound source can be divided into three subcategories which are: a) Occupant activity in a building b) Environmental sound that is produced outside a building c) Operation of the mechanical and electrical services in a building Sound source can be divided into two different groups: a) Outdoor Noise - Noise produced by transportation such as road traffic, railway lines, motor boats and aircraft. - Mechanical equipments such as cooling towers, compressors, machinery - Rainfall and thunder b)
Interior Noise - Noise produced by people through their activities and movement such as noises from the radios and televisions, slamming of doors and dragging of furniture - Building noise produced by machines and household equipments - Noise produced by industrial buildings such as manufacturing and production
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3.5 Acoustical Phenomenon 4 - Noise Intrusion 3.5.1 Noise Analysis
Sound Path There are two ways that sound can transmit: a) Air-borne Sound Transmission Sound is transmitted through the air from its source. b) Structure-borne Sound Transmission Sound caused by the structural vibrations through solid parts of a building structure which transmitted directly through a medium to a detection device or to human ear. Sound Receiver In sound transmission process, the sound receiver can be a person, rooms in a building or a building. Effects of Noise Noise (around the range of 65 dB) in an auditorium may cause these following physical and psychological effects: a) Noise during performances, recitals or rehearsals may hinder concentration. b) Noise causes distraction which may affect production rate and quality of people. c) Interference caused by noise during a speech may cause general annoyance or misinformation. d) Mental effects may occur among performers such as increased anxiety and nervousness. Therefore, a desirable acoustical environment is critical in creating a great sound experience in an auditorium. Noise needs to be kept at a non-existant or minimum level to prevent disruption during events or performances in an auditorium.
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3.5 Acoustical Phenomenon 4 - Noise Intrusion 3.5.2 Noise Source in Experimental Theatre, UM
The Experimental Theatre of University Malaya houses events and performances, ranging from dance performances, singing performances to small orchestra performances. However, noise is not kept at a non-existent or minimum level at the exterior and also the interior of the auditorium. For the case study, the source of noise pollution to the Experimental Theatre of University Malaya is categorised into outdoor and interior noises. The outdoor noise sources involve the factors of exterior environment and human activities and movement while the interior noise sources involve the factors of human activities and movement as well as machinery and equipments. Furthermore, the source of noise pollution is also categorised by either air-borne or structure-borne sound transmission.
Air-borne Sound Transmission Structure-borne Sound Transmission
Figure 3.5.2.1 The ground floor plan shows the location of noise sources by air-borne and structure-borne sound transmission.
Air-borne Sound Transmission Structure-borne Sound Transmission
Figure 3.5.2.2 The first floor plan shows the location of noise sources by air-borne and structure-borne sound transmission. Experimental Theatre, University Malaya | 41
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3.5 Acoustical Phenomenon 4 - Noise Intrusion 3.5.2 Noise Source in Experimental Theatre, UM Outdoor Noise - Exterior Environment The Experimental Theatre of University Malaya is located along Lingkungan Budi which is a two-way road highly accessible by vehicles like buses, cars and motorcycles. Exposure of road traďŹƒc noise to the close proximity of the auditorium entrance causes noise pollution to the inside of the building. The noise source is transmitted through air-borne transmission and the building itself acts as the receiver of noise. Furthermore, illegal parking of motorcycles along the side of the auditorium and construction work at the back of the auditorium produce high noise pollution. Both of the noise sources are transmitted through air and also vibrates through solid parts of the building structure, virtually multiplying the area of the sound radiating surface.
Air-borne Sound Transmission Structure-borne Sound Transmission
Figure 3.5.2.3 Vehicles often pass along Lingkungan Budi which is in front of the auditorium.
Figure 3.5.2.4 Illegal parking of motorcycles along the side of the auditorium.
Figure 3.5.2.5 Construction work at the back of the auditorium.
Figure 3.5.2.6 The section shows the sound energy from construction work is transmitted through air and also vibration into the slab and walls of the auditorium.
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3.5 Acoustical Phenomenon 4 - Noise Intrusion 3.5.2 Noise Source in Experimental Theatre, UM Outdoor Noise - Exterior Environment Air-borne noise is transmitted along a continuous air paths such as gaps around door and window openings which can be identiďŹ ed in the Experimental Theatre. The roller shutter of the service room located next to the stage is not sealed which creates gaps around the door while the windows at the staircase core are opened throughout the day. Therefore, the gaps and window openings allow outdoor noise to pass into the auditorium.
Legend 1. Illegal parking of motorcycles 2. Construction work 1
2
Figure 3.5.2.7 Visible gap from the inside of the auditorium.
Figure 3.5.2.8 Windows at the side of the auditorium are opened.
Figure 3.5.2.9 Windows at the staircase core are opened.
Figure 3.5.2.10 The ground oor plan shows the location of outdoor noise sources from exterior environment.
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3.5 Acoustical Phenomenon 4 - Noise Intrusion 3.5.2 Noise Source in Experimental Theatre, UM Outdoor Noise - Human Activities and Movement Noise generated by activities can be transmitted into the auditorium as there is a lack of buer zone between the main entrance and the auditorium. Conversations and light chatters can be heard near the back of the auditorium if activities occur at the lobby and reception area.
Figure 3.5.2.11 Lobby and reception area of the Experimental Theatre
Figure 3.5.2.12 The ground oor plan shows the lobby and reception area that noise can be produced from human activities and movement and transmitted to the auditorium.
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3.5 Acoustical Phenomenon 4 - Noise Intrusion 3.5.2 Noise Source in Experimental Theatre, UM Interior Noise - Human Activities and Movement Interior noise is generated by impact of the physical contact with a surface. The noise generated may be insignificant but it might cause general annoyance to the users of the auditorium. Specific noise sources generated by human movement within the auditorium: a) Stepping on the timber plaque flooring material b) Walking up and down the steps c) Usage of auditorium chairs d) Stepping on the carpet covered timber platform e) Door slams f) Stepping on the small ramp at the balcony area g) Office work in the projection room h) Opening and closing of roller shutter i) Rehearsals from linked Dewan Tunku Canselor
Figure 3.5.2.13 Timber plaque as flooring material for the backstage.
Figure 3.5.2.14 Steps to the stage from the seating level.
Figure 3.5.2.15 Auditorium chairs in the house.
Figure 3.5.2.16 Carpet covered timber platform.
Figure 3.5.2.17 Main entrance door at one side of the auditorium.
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3.5 Acoustical Phenomenon 4 - Noise Intrusion 3.5.2 Noise Source in Experimental Theatre, UM Interior Noise - Human Activities and Movement Door exits from the ground floor and first floor level of the auditorium creates impact noise when there are door slams.
Figure 3.5.2.18 The ground floor plan shows the door slams that transmit structure-borne noise as vibrations through the walls and slab of the auditorium.
Figure 3.5.2.19 The first floor plan shows the door slams that transmit structure-borne noise as vibrations through the walls and slab of the auditorium.
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Figure 3.5.2.22 Window of the projection room at the back of the balcony area is opened.
Figure 3.5.2.23 Roller shutter of service room at the backstage produces noise.
Figure 3.5.2.24 Passage to Dewan Tunku Canselor which is linked with the backstage of the auditorium.
Figure 3.5.2.25 Sound of rehearsals from Dewan Tunku Canselor can be heard at the linked backstage of the auditorium.
Figure 3.5.2.26 Small ramp at the balcony area.
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.
Figure 3.5.2.27 Lighting equipment above the stage.
Figure 3.5.2.28 Lighting equipment at the balcony level.
Figure 3.5.2.29 performances.
Spotlight
for
stage
Figure 3.5.2.30 The plan shows the location of machinery and equipments. Experimental Theatre, University Malaya | 47
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3.5 Acoustical Phenomenon 4 - Noise Intrusion 3.5.2 Noise Source in Experimental Theatre, UM
Interior Noise - Human Activities and Movement
3
5
Legend 1. Stepping on the timber plaque flooring material 2. Walking up and down the steps 3. Usage of auditorium chairs 4. Stepping on the carpet covered timber platform 5. Door slams 6. Opening and closing of roller shutter 7. Rehearsals from linked Dewan Tunku Canselor
5
4
3
5
2
2
1 2
1
Legend 1. Door slams 2. Stepping on the small ramp 3. Office work in the projection room
5 5
5 1
5
5
5 6
5
5
7
7
Figure 3.5.2.20 The ground floor plan shows the location of interior noise sources from human activities and movement.
Figure 3.5.2.21 The first floor plan shows the location of interior noise sources from interior environment.
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3.5 Acoustical Phenomenon 4 - Noise Intrusion 3.5.2 Noise Source in Experimental Theatre, UM Outdoor Noises
Air-borne Sound Transmission
Structure-borne Sound Transmission
Vehicular traffic along Lingkungan Budi
√
Illegal parking of motorcycles
√
√
Construction work
√
√
Lobby and reception area
√
Interior Noises
Air-borne Sound Transmission
Structure-borne Sound Transmission
Stepping on the timber plaque flooring material
√
Walking up and down the steps
√
Usage of auditorium chairs
√
Stepping on the carpet covered timber platform
√
Door slams
√
Stepping on the small ramp at the balcony area
√
Office work in the projection room
√
Opening and closing of roller shutter
√
Rehearsals from linked Dewan Tunku Canselor
√
Lighting equipments
√ Figure 3.5.2.31 List of outdoor and interior noises and their type of sound transmission in Experimental Theatre, University Malaya. Experimental Theatre, University Malaya | 49
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3.5 Acoustical Phenomenon 4 - Noise Intrusion 3.5.3 Noise Control in Experimental Theatre, UM To reduce the eect of noise in an auditorium, certain measures can be taken which is known as noise control. Noise control measures that can be taken includes: a) Suppression of noise at the source b) Town / site planning c) Architectural design d) Mechanical and electrical design e) Structural design f) Organisation of work spaces g) Sound absorption h) Masking noise i) Sound Insulation
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3.5 Acoustical Phenomenon 4 - Noise Intrusion 3.5.3 Noise Control in Experimental Theatre, UM Introduction Noise control measures that are taken in the Experimental Theatre of University Malaya includes: a) Organisation of space b) Sound absorption c) Sound insulation Organisation of Space The two intermediate spaces act as a sound-lock to separate the auditorium space from the external environment. The corridor with the width of 1.5m isolates the noise produced in the amenities area from transmitting into the house. During events and performances, the corridor with the width of 7m will be mostly unoccupied, it then acts as a buffer zone to prevent noise from exterior traffic to enter the house. Therefore, the buffer zones decrease the air-borne noise transmission that could reach into the auditorium.
Amenities area Exterior noise from vehicular traffic
Figure 3.5.3.1 Corridor beside the auditorium on the ground floor level serves as a buffer zone.
Figure 3.5.3.2 Corridor beside the auditorium on the ground floor level serves as a buffer zone to separates the auditorium from the service spaces.
Figure 3.5.3.3 Corridor behind the auditorium on the lower ground floor level serves as a buffer zone.
Figure 3.5.3.4 The ground floor plan shows the buffer zones on both sides of the auditorium.
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3.5 Acoustical Phenomenon 4 - Noise Intrusion 3.5.3 Noise Control in Experimental Theatre, UM Sound Absorption Noise control actions are taken using the principle of sound absorption. Soft, uneven materials are employed to reduce interior noise. For instances, the concrete floors of the Experimental Theatre is carpeted with short 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. Moreover, 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 the stage and the marmoleum vinyl sheet covers the timber surface for the front part of the stage. Furthermore, velour curtains can also be found around a perimeter on the stage. During events and performances, these curtains are used to reduce noise levels from the backstage and the exterior environment by absorbing low frequency sounds.
Figure 3.5.3.5 Short pile carpet covers the floor of the house.
Figure 3.5.3.6 Marmoleum vinyl sheet as part of the flooring layer on the stage.
Figure 3.5.3.7 Velour acoustic curtain hanging around the stage.
Figure 3.5.3.8 The ground floor plan shows the position of velour curtains.
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3.5 Acoustical Phenomenon 4 - Noise Intrusion 3.5.3 Noise Control in Experimental Theatre, UM Sound Absorption Apart from that, acoustic panels can be found along some parts of the wall within the auditorium. Acoustic panels deal more with the mid and high frequencies in a room like the Experimental Theatre. Acoustic panels are sound absorbing panels that control and reduce noise, eliminate slap echo and control comb filtering in a room, reduce, but not entirely eliminate, resonance within the auditorium.
Sound Insulation Double wall creates an air cavity which serves as sound insulation. The sound insulation 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. The Experimental Theatre has two pockets of air cavity on each side of the auditorium between its wall with a gap of 150mm.
Figure 3.5.3.9 Acoustic panels on the wall behind the balcony area.
Figure 3.5.3.10 Sound absorption to acoustic panel.
Figure 3.5.3.11 The ground floor plan shows the position of wall with air cavity.
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3.5 Acoustical Phenomenon 4 - Noise Intrusion 3.5.4 Background Noise Good quality of room acoustics and noise control are critical for auditorium spaces to ensure the users can clearly hear, understand and enjoy performances and events. To ensure a favorable acoustical environment for auditoriums or theatres, the recommended noise criteria level should not exceed 25-30. The background noise is estimated to be at a level of 40 dB due to the noise sources a shown in this chapter of case study. The Experimental Theatre of University Malaya with an occupancy of 435 seats and octave band center frequency of 500Hz, the noise level matches the noise criteria (NC) of an auditorium. Hence, this indicates that the selected case study has an acceptable background noise level due to optimum noise control and suďŹƒcient soundprooďŹ ng.
Figure 3.5.4.1 Recommended noise criteria level for type of space (and acoustical requirements).
Figure 3.5.4.2 Graph shows the noise criteria (NC) curve.
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3.6 Acoustical Phenomenon 5 - Reverberation 3.6.1 Introduction to Reverberation Time As a sound is made, it will bounce off surfaces such as floor, wall, ceiling, furniture repeatedly. As the reflections mix, the phenomenon known as reverberation is created. As the source of sound stops, the reverberant sound level decays over a period of time. This reverberation decays as reflections hit surfaces which absorb sound such as chairs, curtains and even people. The reverberation time of a room or space is defined as the time it takes for sound to decay by 60dB after the original sound source has stopped. This 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 Thus, the Reverberation Time (RT) can be calculated by using Sabine’s Formula:
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
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3.6 Acoustical Phenomenon 5 - Reverberation 3.6.2 Reverberation Calculation Volume of the Experimental Theatre With the uneven levels of the experimental theatre, the volume calculation involves dividing the theatre into segments for calculation.
F E
Estimated Floor area of each segment (m3):
D
A: 283.6m2 B: 50.9m2 C: 77.02m2 D: 135.26m2 E: 46.35m2 F: 85.67m2
C B
A
Estimated Volume of each segment (m3) : A: B: 440.79m3 C: D: 1082.1m3 E: 326.3m3 F: 517.45m3 Total Volume of the Experimental Theatre (m3): 6281.38m3
3374.84m3 539.9m3
Figure 3.6.2.1 GF Plan: Divided segments for volume calculation
F E
D
C B
A
Figure 3.6.2.2 Section BB: Divided segments for volume calculation
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3.6 Acoustical Phenomenon 5 - Reverberation 3.6.2 Reverberation Calculation Surface Area of Floor Materials To find A, the total absorption of room surfaces, involves the materials for the floor, wall, ceiling, and other materials. Each material has their own absorption coefficient.
B A
Total Absorption, A s : sA
2 (sq.m sabins) = S (Area of surfaces, m )x
αs
(Absorption coefficient of surface)
D
C
D
E 500 Hz
Component
Surface Area (m2)
A
Short pile carpet flooring
472.64
B
Needle punch non-woven thin carpet
5.03
0.25
1.26
C
Marmoleum vinyl sheet over hardwood timber flooring on concrete
198.07
0.04
7.92
D
Hardwood timber parquet on concrete
129.34
0.07
9.05
E
Polished concrete
79.29
0.01
0.79
Figure 3.6.2.3 GF Plan: Floor materials on Ground floor
Absorption Coefficient
Abs Units (m2 sabins)
0.3
141.792 A
Total
Figure 3.6.2.4 GF Plan: Floor materials on First floor
160.81 Experimental Theatre, University Malaya | 57
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3.6 Acoustical Phenomenon 5 - Reverberation 3.6.2 Reverberation Calculation Surface Area of Wall Materials
A C 500 Hz Component
Surface Area (m2)
Absorption CoeďŹƒcient
Abs Units (m2 sabins)
A
Acoustic timber panels
223.4
0.42
93.83
B
Acoustic fabric ďŹ breglass panels
59.11
0.5
29.56
C
Drywall
76.3
0.05
3.82
Total
Figure 3.6.2.5 Section BB: Location of Wall Materials
A
B
C
127.21
Figure 3.6.2.6 Section AA: Location of Wall Materials
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3.6 Acoustical Phenomenon 5 - Reverberation 3.6.2 Reverberation Calculation C Area of Floor Materials B 500 Hz Component
Surface Area (m2)
Absorption CoeďŹƒcient
Abs Units (m2 sabins) A
A
Velour curtain
367.94
0.4
147.18
B
Auditorium seats (Unoccupied)
237.54
0.64
152.03
C
Timber doors
10.08
0.05
0.50
D
Glass windows
4.65
0.04
0.19
E
Glass railings
23.43
0.04
0.94
F
Plaster ceiling
595.38
0.18
107.17
Figure 3.6.2.7 Ground oor plan: Highlighted miscellaneous materials
F D
Total
E
A
408.01
Figure 3.6.2.8 Section BB: Highlighted miscellaneous materials
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3.0 Architecture | Architecture and and Building Building Acoustics Acoustics of of University Experimental Malaya Theatre, Experiential University Theatre Malaya
3.6 Acoustical Phenomenon 5 - Reverberation 3.6.2 Reverberation Calculation
After obtaining V values and A values, the Reverberation Time (RT) can be calculated by using Sabine’s Formula:
RT
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
Volume of the Experimental Theater: 6281.38m3 Total absorption: Absorption of Floor Materials + Wall Materials + Other Materials =160.81 + 127.21 + 408.01 = 695.03 sq.m sabins
RT =
Figure 3.6.2.9 The Reverberation Time of Experimental Theatre on the chart of Optimum Reverberation Times of different venue volumes.
0.16 ( 6281.38) 696.03
= 1.44s
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4.0 Conclusion
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4.0 | Conclusion
4.1 Building Acoustics of Experimental Theatre, UM
Uses
Small Rooms ( 750 m3 )
Medium Rooms ( 750 - 7500 m3 )
Large Rooms ( > 7500 m3 )
Speech
0.75
0.75 - 1.00
1.00
Multi-purpose
1.00
1.00 - 1.50
1.00 - 2.00
Music
1.50
1.50 - 2.00
2.00 or more
Figure 4.1.1 Recommended reverberation time (RT) according to usage and volume. Highlighted is E.T.’s category and its recommended RT.
Application of acoustics in architecture for a building is definitely important where it should be able to perform well to provide comfort and suitability for occupants. Every surfaces, forms and textiles matters since they contribute to the behaviour of sound propagation, proper noise control measurements should be taken as design strategies to create an efficient auditorium equipped with proper acoustic features without assistance of sound reinforcements. Based on our calculation using the Sabine formula, Experimental Theatre, UM has a volume of 6281.38 m3 and a reverberation time of 1.44s. Due to its high volume, E.T. is suitable to be used for both speech and music performances. As a conclusion, E.T. is suitable to be used as a multi-purpose theatre since it has an optimum RT where the prolonged sound does not cause significant disturbance (echo) for speech and at the same time benefits by prolonging the music to a desirable extend where the sound does not die out immediately.
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“The great problem of the concert hall is that the shoebox is the ideal shape for acoustics but that no architect worth their names wants to build a shoebox.�, once said by a visionary architect - Rem Koolhaas.
5.0 References
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5.0 | References
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5.0 | References
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