A CASE STUDY ON ACOUSTIC DESIGN
THE KUALA LUMPUR PERFORMING ARTS CENTRE
School of Architecture, Building and Design Bachelor of Science (Architecture)
BUILDING SCIENCE II ARC 3413 / BLD61303 PROJECT 1: AUDITORIUM: A CASE STUDY ON ACOUSTIC DESIGN
TUTOR : Mr. Edwin Chin Vin Yan Nurul Atika Binte Mohd Gazali Kimberly Ann Aussie Ng Kheng Soon Shefereena Isreen Aimuni Khalidah A Bakar Lee Ho Jun Rhianna Mae Storey
0320311 0323246 0325881 0318946 0325915 0326074 1007P10652 0325369
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CONTENTS 03
1. INTRODUCTION 1.1 Historical Background
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1.2 Aim & Objective
2. ACOUSTICAL PHENOMENA 2.1 Acoustical In Architecture 2.2 Sound Intensity (SIL)
10 12 20
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2.3 Reverberation, Attenuation, Echoes & Sound Shadow
3. Methodology 3.1.
Equipments
3.2.
Data Collection Method
4. Drawing & Zoning 4.1.
Kl Pac Floor Plans
4.2.
Stage 1 - Zoning
5. OBSERVATION & ANALYSIS 5.1.
Auditorium Design
5.2.
Materials
5.3.
Acoustic Treatment
5.4.
Sound Source
5.5.
Sound Path
6. NOISE 7. REVERBERATION TIME CALCULATION
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8. RECOMMENDATION 9. REFERENCES 2
1.0 INTRODUCTION
NAME
: KUALA LUMPUR PERFORMING ARTS CENTRE (KLPAC)
LOCATION
: JALAN SULTAN AZLAN SHAH, SENTUL WEST, 51100 KUALA LUMPUR, WILAYAH PERSEKUTUAN KUALA LUMPUR.
TYPE OF AUDITORIUM
: PENTAS 2
YEAR OF COMPLETION
: MAY 2005
TOTAL VOLUME
: 8,020m3
TOTAL SEATS
: 504 SEATS
The Kuala Lumpur Performing Arts Centre also known as KLPac or Pentas Seni Kuala Lumpur is one of the most established centres for the performing arts in Malaysia. It is a non-profit company whose aim is to "cultivate and sustain the performing arts for the betterment and enrichment of communities within the Klang Valley and for the Nation. Founded by Joe Hasham and Dato' Faridah Merican. Each year, KLPac and the Actors Studio plays host to more than a hundred major events, as well as many other workshops, classes, film screenings and more. Many of KLPac events are self-directed and self organised shows. The four main areas of the Kuala Lumpur Performing Arts Centre are: ➔
Pentas 1 (a Proscenium Theater): 504 seats
➔
Pentas 2 (a Black Box Theater): 192 seats depending on configuration
➔
Indicine (A film screening room): 100 seats
➔
Academy: 9 Studios for rehearsals and training.
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1.1 HISTORICAL BACKGROUND In 1995, both founders created history by building the first privately owned and operated theatre in Malaysia below Dataran Merdeka named The Actors Studio @ Plaza Putra. However in 2003, flash floods swamped KL and destroyed the underground complex entirely. In search of a new home for the arts community, they found an old warehouse that is owned by Tan Sri Francis Yeoh. The old warehouse started as a woodcrafting workshop and sawmill in the 1800s. Eventually it became part of Sentul Works in 1906, region’s most important railway depot and workshop, till it was bombed during tail end of WWII but was rebuilt in mid 1940s. In late 1960s it was then converted into a makeshift gold clubhouse but was soon abandoned in early 1990s. In 2005, KLPac was launched becoming an arts and cultural icon with an award-winning architectural design making it a historical landmark.
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1.2 AIM & OBJECTIVE The aim and objective of this report is to provide a concise and well-documented analysis that can showcase our understanding of our case study of acoustical theory in auditorium halls. Done so over the course of five to six weeks, the learning outcomes are as follows: 1.
To study and develop an understanding of auditorium through their design layout and judge its influences on the effectiveness of the acoustical design for its designated purpose.
2.
To study the general acoustical characteristics of an auditorium hall and develop a good understanding of the physical behind their functions
3.
To be able to produce a well-documented report that surmises our finding and analysis of our case study - which can then serve as an example of our accumulated knowledge of the relationship between acoustic and space.
By observing and analysis the type of acoustical design theories applied in the auditorium, we are then able to develop a better understanding on the characteristic of architectural space and how it affect the multiplicity of design approaches that can be taken for said space to be considered “acoustically efficient�. It is also important to know how different types of design and their acoustical treatment influence the sound efficiency and the overall user experience.
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2.0 ACOUSTIC PHENOMENA 2.1 ACOUSTIC IN ARCHITECTURE The main noise paths are roofs, eaves, walls, windows, door and penetrations. Sufficient control ensures space functionality and is often required based on building use. Acoustic is the term used to describe the “science of sounds”. It deals with the study of all mechanical waves in matters such as gases, liquids (air,water) or any solid, physical object that can return to its normal state after being deflected. Sound can be reflected, absorbed, transmitted and diffracted. It is comparatively different to “noise”, thought the tho are often associated and mistaken for one another by the public. The difference is in its meaning; “sounds” is any sort of vibration that can be deemed desirable, or pleasant, “noise”, on the other hand, is undesirable and often disturbing. Whilst it is often considered to be hindrance, noise in its own service,is important. For example, the sounds of fire alarm or loud music can be deemed irritable, but can also be beneficial in certain cases when its can be controlled. Understanding these differences and know how to utilize building materials, system design and technologies are key factors behind any successful acoustical design. While the science behind sound is well understood, using that knowledge to create an efficient acoustical performance within a specific building or room is a complex practice. There is ano single “solution” or “formula” that can be universally applied to any building design as each built environment offers its own unique set of acoustical parameters.
2.2 SOUND INTENSITY LEVEL (SIL) Sound energy is conveyed to our ears (or instruments) by means of a wave motion through some elastic medium (gas, liquid, or solid). At any given point in the medium, the energy content of the wave disturbance varies as well as the square of the amplitude of the wave motion. That said , it the amplitude of the oscillation is double, the energy of the wave motion is quadrupled.
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The common method in gauging this energy transport is to measure the rate at which energy is passing a certain point. This concept is dubbed as “ sound intensity”. Consider an area that is normal to direction of the sound waves. If the area is a unit, namely one square metre, the quantity of sound energy expressed in Joules that passes through the unit area in one second defines the sound intensity. The time rate of energy transfer is then referred to as its ”power” - written in the unit: “Watt” (1W equal to 1 Joule/s). In simple terms, this means that the sound intensity is the power per square meter. Normally, sound intensity is measured as a relative ratio to some standard intensity. The response of the human ear to sound waves closely follows a logarithmic function of the form “R = K logI”, where “R” is the response to a sound has an intensity of “I”, and “k” is the constant of proportionality. Thus, we define the relative sound intensity level as SL(dB) = 10log I Io The unit of Sl is called a “decibel” (abbreviated as dB). “I” is the intensity of the sound expressed in watts per meter and “io” is the references intensity defined to be 10-12 W/m². This value of “Io” is the threshold (minimum sound intensity) of hearing at 1 kHz, for a young person under the best circumstances. Notice that “I/Io” is a unit-less ratio; the intensities need only to be expressed in the same units, not necessarily W/m².
2.3 REVERBERATION, ATTENUATION, ECHOES AND SOUND SHADOWS. Sound reverberation is the persistence of sound reflection after the source of the sound has ceased. Reverberation can have both a positive and negative affect in architectural design. For example, specifying highly reflective ceiling panels directly above the stage area in an auditorium will help direct the sound toward specific seating areas, thus enhancing the room’s acoustical performance.
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However, that same reflective performance will become a negative factor of said highly reflective walls and ceiling materials are installed in the rear of the auditorium. That’s because the sound reflection from the rear of the room take too long to reach the audience, resulting in a distracting echo effect. When sound travels through a medium, its intensity diminishes with distance. In idealized materials, sound pressure (signal amplitude) is only reduced by the spreading of wave. Natural materials, however, all produce an effect which further weakens the sound. This further weakening result from scattering and absorption. Scattering is the reflection of the sound in directions other than its original direction of propagation. Absorption is the conversion of the sound energy to other forms of energy. The combined effect of scattering and absorption is called attenuation. An acoustic shadow or sound shadow is an area through which sound waves fail to propagate, due to topographical obstructions or disruption of the waves via phenomena such as wind currents, buildings, or sound barriers. A short distance acoustic shadow occurs behind a building or a sound barrier. The sound from a source is shielded by the obstruction. Due to diffraction around the object, it will not be completely silent in the sound shadow. The amplitude of the sound can be reduced considerably however, depending on the additional distance the sound must travel between source and receiver. Sound reflection occurs when wacces become off smooth, hard wall, ceiling and floor surfaces. Concave surface tend to concentrate or focus reflected sound in one are. Convex surfaces do just opposite; they tend disperse sound in multiple direction.
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3.0 METHODOLOGY 3.1 EQUIPMENTS
3.1.1. Digital Camera The use of digital camera is to capture images of the existing feature or condition within our auditorium. These images would later be used as support to our analysis and also references of the analysis on how such a component contribute to external noises, such as finishing wall materials, details of acoustic wall panelling or wall treatment, position of sound source ( including speakers, poorly designed air conditioning or lighting system etc.), occupancy level and activities carried out within the auditorium.
3.1.2. MEASURING DEVICE Measuring devices is used to obtain measurement of our auditorium for drawing and calculation purposes. They were also used to measure the distance of the sound level meter from the sound source when levels were taken.
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3.1.3. Digital Sound Level Meter This device it is used to measure the sound level at a particular point within the auditorium. The unit of measure is decibels (dB).
3.2 DATA COLLECTION METHOD In order to achieve first-hand experience, formal arrangements were made prior to the visit ensuring that the auditorium would be unoccupied and allowing us to conduct a thorough investigation without disturbance. With the help of all preceding tools mentioned, we noted down as many details within our ability and constraints, including the auditorium’s layout & form, noise source, furniture, materials and notable acoustic components. Measurements of the auditorium were also taken for drawing and calculation purpose. Measurements of the auditorium were also taken for drawing and calculation purpose, along with on-site sketches of floor plans and sections for supporting any analysis.
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4.0 DRAWINGS & ZONINGS 4.1 KL PAC GROUND FLOOR PLAN
STAGE 1
CAFE
FOYER LOBBY
ENTRANCE
STAGE 2
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4.2.1 STAGE 1 - FLOOR PLANS
KLPAC PENTAS 1 GROUND FLOOR PLAN
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KLPAC PENTAS 1 FIRST FLOOR PLAN
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KLPAC PENTAS 1 SECOND FLOOR PLAN
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KLPAC PENTAS 1 SECOND FLOOR PLAN (WITH DIMENSIONS) 16
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KLPAC PENTAS 1 SECTION
4.2.2 STAGE 1 - SECTIONAL DRAWING
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KLPAC PENTAS 1 SECTION
4.3 STAGE 1 - ZONING CONTROL ROOM
AUDITORIUM SEAT
PERFORMING STAGE
BACKSTAGE
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4.3.1. Performing Stage Stage is designed in a semi-proscenium style with the stage floor levelled with the first row of audience. Along with the structural proscenium opening at 14m wide and 7.68m high. Having a variable proscenium panel that is capable of adjusting the proscenium opening from a height of 7.68m to 5.68mm. Stage depth is approximately 9m from the proscenium opening to the cyclorama and from the front end of the apron area to proscenium opening is approximately 5.5m.
4.3.2. Backstage Backstage is approximately 10m deep and 20m wide with both right and left wings from the proscenium are approximately 10m deep and 6m wide.
4.3.3. Auditorium The auditorium can seat a total of 504 patrons. While applying a front-end format seating, in which the first row of the seating for audience is on the same level as the stage floor, that comprises of flip-up seats covered with different solid-coloured fabrics. There are two main access doors for entry/exit from second floor pre-function area and walkway lights are provided.
4.3. 4. Control Room Control room for production audio, light and video is situated on the second floor within the audience and the follow spot control area is located on the third floor with a cat ladder connecting the two floors for access.
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5.0 ACOUSTIC ANALYSIS 5.1 AUDITORIUM DESIGN
5.1.1. Shape and Massing The overall shape of the auditorium is a square shaped. However, the front part of the seats have slayed wall which resulting a combination of fan-shaped and square auditorium.
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5.2 MATERIALS
COMPONENT
WALLS
BLACK FABRIC WRAPPED PANEL
CEILING CLOUD
WOOLEN CARPET
MATERIAL
PHOTO 125HZ
500HZ
2000HZ
0.01
0.015
0.02
0.35
1.20
1.07
0.45
0.8
0.65
0.02
0.14
0.60
CONCRETE
FABRIC
CONCRETE,
METAL
CARPET
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COMPONENT
STAGE FLOOR
CHAIR
MATERIAL
125HZ
500HZ
2000HZ
EPOXY CONCRETE
0.01
0.015
0.02
UPHOLSTE RY FABRIC
0.60
0.015
0.93
0.05
0.40
0.60
0.36
0.31
0.39
CURTAIN
FABRIC
WOODEN BLOCK
HARD WOOD
PHOTO
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component
material
SOUND DIFFUSER
PVC, CONCRETE
SOUND REFLECTION PANEL
ZINC
SOUND INSULATION
BRICK WALL
PHOTO
125hz
500HZ
2000HZ
0.01
0.02
0.035
0.48
1.0
1.0
0.03
0.03
0.05
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5.3 ACOUSTIC TREATMENT 5.3.1. Performing Stage
Figure 5.3.1.1 Floor plan showing sound absorption in concrete walls
Figure 5.3.1.2 diagram show that the wall absorb the sound wave and produce minimum reverberation
The auditorium wall is covered with sound absorbent materials to reduce the reverberation in the auditorium and percentage of creating echo. This material helps to absorb and soften the sound waves produced from the stage. This in result will create a better sound quality for the audience. Pentas 1 auditorium is the biggest stage in KLPAC. The type of material that is used for pentas 1 for sound absorption is concrete wall. Concrete walls may be a good sound absorber but do not act as a good sound insulator. Thus, high frequency sounds coming from Pentas 2 or other rooms can occasionally be heard in Pentas 1. The concrete wall in Pentas 1 is layered with black paint. The color of the wall does not play a huge role in sound absorbance but it helps to control the temperature in the enclosed auditorium. The speed of sound actually increases as the temperature goes up . The wall is a flat surface layered with wooden blocks on one side and PVC concrete tubes on the other for trapping sound . The idea behind the technique of materials used is to keep the sound from bouncing off in an enclosed space. If the concrete walls were left bare, sound reflections would create undesirable echoes.
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5.3.2. PVC Tube
Figure 5.3.2.2 alignment of PVC TUBE
Figure 5.3.2.3 PVC TUBE Figure 5.3.2.1 sound wave direction to PVC tube And scatter the sound wave to audience
Apart from the concrete walls, material sustainability for materials used in the theatre is highly kept into consideration and most of the finishes are made up of reused materials. Before the building was used as KLPAC it was a railway station and today part of the building, including original materials have lasted from before World War ll. Although parts of the building have been renovated, history of the place still remains and is evident through the old building material. There are two different wall finishes and they both play a different role in terms of acoustic purposes. PVC tubes placed on the concrete wall are not just used for aesthetic values but also act as a sound diffuser. The height of the PVC tubes extend all the way to the ceiling and the surface of the tubes are convex shaped. When a direct sound wave hits the tube, it will distribute the sound wave equally to the audience. The PVC tubes are also hollow inside and this helps to compress direct large sound waves and absorb base sounds. Therefore, the PVC tubes help to distribute small frequency sound waves equally to the audience and at the same time compresses large frequency sound waves. The wall behind will able to absorb the remaining sound waves .
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5.3.3. Wooden Block and Corrugatd Metal
Figure 5.3.3.2 the side of wall that function as a diffuser
Figure 5.3.3.1 Sound wave direction that hit the wooden Block and scatter the sound wave to the audience
Figure 5.3.3.3 wooden block
The wall on the opposite side of the theatre is covered with corrugated metal and wooden blocks. The zinc metal plates are reused from the roof of the old railway station . The surface of the metal is corrugated which is a mixture of concave and convex surfaces, allowing it to act as a good sound reflector. It helps to reflect low frequency sounds around the theatre. Wooden blocks are scattered on the wall surface below the corrugated metal. These blocks are made from small pieces of leftover wood that are formed into a box shape. Wood is a light material and its smooth surface helps to dampen sound particularly well. But wood cannot work alone in sound absorption, so when the sound hits the wooden block, some of sound is scattered and some would be absorbed by the concrete wall. Hence, the wooden blocks help to diffuse high frequency sounds. Both of the side walls use different design strategies but they still serve an equal acoustic experience to the audience in terms of sound diffusion and reflection. Therefore, only a low cost is required to maximize the acoustic treatment because of well thought of design strategies.
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5.3. 4. Flooring
Figure 5.3.4.2 audience floor
Figure 5.3.4.1 zoning of wool carpet and epoxy Concrete wall
Figure 5.3.4.3 stage floor
In Pentas 1 there are two different flooring material. For the stage flooring, epoxy concrete coating is used whereas the audience floor is covered by wool carpet. The wool carpet is black in color and it's soft and smooth texture produces a comfortable environment for the audience. The carpet improves the sound quality in the auditorium because it acts as a sound absorber and helps to reduce the impact of noise such as audience entering or exiting the auditorium, dropping of items, and moving furniture or equipment etc. Air Is transmitted by vibration of air molecules and sound waves are absorbed by the wool carpet instead of being reflected back to the surface. This is because the material of the wool carpet consists of individual fibers and pile tufts which produce several resonant frequencies which absorb sound . The stage floor is different from the audience floor as it is an epoxy concrete floor and is layered with a layer of black paint. It creates a focus towards the stage while the reflected light creates an elegant environment. This surface is slip-resistant and is easy to maintain due to the fact that the floor has a low absorbance value and reflects the sound wave to audience. This also allows the musician to produce the best quality of sound for the audience.
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5.3.5. Chairs (Audience Seats)
Figure 5.3.5.1 placement of chair in the auditorium
Figure 5.3.5.2 Blue arrows indicate soundwaves while the red arrows show sound wave absorbed by the chair
Other than using walls and floors for dampening sound waves throughout the room surfaces, each auditorium chair has individual sound absorption. Furthermore, the smooth and flat surface of the chair provides comfort for the audience. The auditorium chairs are of tip up type creating minimal noise. The shape and material of the chair also determines the sound quality of the auditorium hall. Each chair is covered with a sound absorbent fabric which ensures that the presence or absence of the audience won’t affect the reverberation time.
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5.3.6. Brickwall
Figure 5.3.6.1 audience view to stage
Figure 5.3.6.2 noise been reflect to the atmosphere by brick wall
At the back of the stage, brick wall was still well preserved from the old railway station since the wwii. The brick are coated a layer of black paint to give a good protection and serve
as
an
aesthetic
purpose.
The choice of preserving the brickwall is because brick are naturally thick and dense which help to block sound wave passing through. Hence, it helps to prevent the external noises enter to auditorium which minimise the distraction to the audience. Beside that, the size of the brick will also affect the insulation purpose. The thicker the material, the more challenging for a sound wave to pass through it. Thus, auditorium less likely to hear the sound from the other side of the wall. Because of its bold characteristic, the direct sound wave hit the brick wall unabling the absorption of sound wave instead the sound wave will bounce off to the surrounding. However, to prevent any leak of the sound wave penetrate into the auditorium, the brick wall should be well maintain due to the aging of the building.
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5.3.7. Black Curtain & Ceiling
Figure 5.3.7.1 diagram show the curtain is a absorbent material
The black curtains of KLPAC are sound absorbers where they are placed onstage for blackout curtains. While the curtain doesn’t completely reduce the sound between two different spaces, it helps improve the sound quality and reduce the reverberation level of the
theatre.
The thick and heavy fabric curtain absorb excessive sound. Fabric acoustic curtains feature a core material of naturally fire resistant wool fabric that is sandwich between a decorative fabric and a blackout liner. It reflects thermal energy and black light while creating an elegant surrounding for the audience.
Figure 5.3.7.2 ceiling of the auditorium
The ceiling of the auditorium consists of black fabric wrapped ceiling clouds. They prevent sound from escaping out of the room, absorbs noise and increase sound quality to the audience. Capable in stopping sound reflection in large areas, black fabric offers outstanding control across all frequencies as well design flexibility being architecturally decorative.
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5.3.8. Wall Panels
Figure 5.3.8.1 the sound wave created from the stage been absorbed to fabric wrap panel
Figure 5.3.8.2 direction of sound wave to the fabric wrap panel
Black acoustic panels are located behind the theatre. Fabric panels are the ideal choice for controlling excessive reverberations in the theatre setting and delivering back premium sound quality. Acoustic wall panels are sound absorbent, mounted directly to the wall consisting of medium density core with a fabric finish. When the sound waves hit the surface, they are absorbed through soft surfaces and bounce back to surrounding. Therefore the audience will not experience sound delay and echoes behind the black acoustic panel on the concrete wall.
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5. 4 SOUND SOURCE Sound sources are subjects emitting sound waves into the environment which are percepted as pleasurable sounds or taken in as noise depending on the frequency level received by the human ear.
5. 4.1. Primary Sound Source The sound amplification system in the theatre is the main sound source,, producing sound waves which dominate the largest part of the audience hearing. This system is used for the following purposes : -
To reinforce the sound level when the sound is too weak to be heard
-
To provide amplified sound for overflow audience
-
To minimize sound reverberation
The original system arrangement for Pentas 1 would be a centrally located system, with a single cluster of loudspeakers over the sound source.This system is practical and realistic as the amplified sound produced is coming from the same direction as the actual sound source. There are a total of ten speakers located on the top of the front of the stage. The two speakers
at
the
center
are
positioned
vertically at a 30 degree angle facing the center audience seating. The four speakers on each side are horizontally positioned above each other, forming a concave projection
Figure 5.4.1.1 Vertical positioned speakers located at the top front of the stage
towards the audience.
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Figure 5.4.1.2 Primary Sound Source : Speakers
Figure 5.4.1.3 Position of Speakers
Figure 5.4.1.4 Section of the functioning speakers
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Loudspeakers are adjusted and controlled through a processor and this is done from the control room or control panel located above the audience seating. The speaker volumes have been calculated and are adjusted before performances whereby the top speakers produce a higher volume of sound to ensure it is propagated to the audience seating at the back part of the theater. The bottom speakers produce sounds of a lower volume as it is directed to the audience seating in front which is located nearer to the sound source. During some productions, the speakers would be arranged in a stereophonic system which includes two or more clusters of loudspeakers around the proscenium opening and on either side of the audience seating. This system imitates a realistic environment and preserves the illusion that the sound is coming from the original, unamplified source. When this system is used, side fill speakers are placed in these main places : 1. 2. 3.
Aisle of theatre Side of stage Lighting bar on either side of stage
Depending on the positioning of the sub speakers, a delay tower is used to ensure sound waves emitted reach the audience at the same time. Speakers placed at the back aisle of the theater will have a longer delay. Speakers are occasionally clipped onto the lighting bars either on the sides of the front part of the theatre or at the back for backstage crew.
Figure 5.4.1.5 Placement of lighting bars on the front of the theatre
Figure 5.4.1.6 Placement of Sub Speakers on the backstage lighting bars
The number and placement of additional speakers depends heavily on the type of production and the budget of the production team.
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Sound Source Speakers
Electrical Appliance
Product Name
Specification
Meyer Sound UPJ-1P (Permanently rigged)
Power Handling
50W - 100W
Frequency Response
65Hz - 20Hz
Meyer Sound UPM-1P
Input Configuration
70v - 100v
Meyer Sound UMS-1P
Sound Pressure Level
35dB - 45dB
Meyer Sound UPA-1P
Placement
Wall / Ceiling
Fresnel
Power Handling
3.3W
Frequency Response
200Hz
Sound Pressure Level
30dB - 40dB
Placement
Ceiling
Figure 5.4.1.7 Table of sound source and its specification
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5. 4.2. Secondary Sound Source Electrical appliances such as the AC system and lighting fixes
contribute to the total
internal sound produced in the theatre. AC vents are located at the right side of the backstage above the chiller room. A motor from the room and air travelling through the vents produce low frequency sounds that could be considered background noise during performances and are quite prominent when there is still silence in the theatre. Light fixes such as spotlights produce a certain buzzing sound for the first five minutes of being switched on but mostly do not affect performances.
Figure 5.4.2.1 Secondary Sound Source : AC Vents
Figure 5.4.2.2 Position of AC Vents on the side of the backstage
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5. 4.3. Tertiary Sound Source This sound source is the least evident
and originates from the audience themselves.
Audience movement in and out of the theatre, adjusting of seats and small chatter contribute to sounds in the hall and can be kept minimum by announcements and reminders before and during intermissions.
Figure 5.4.3.1 Tertiary Sound Source : Audience
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5.5 SOUND PATH 5.5.1. Sound Concentration The measurements of Pentas 1 were taken from a fixed sound; outputting approximately 500Hz tune at 90dB. The measurement of the sound intensity levels (SIL) from the sound source show that there is a distinct sound concentration zone can be found at the centre of Pentas 1 with the reading of 74dB.
Figure 5.5.1 The SIL measurement of Pentas 1.
The SIL readings are high at the back right and left corner of Pentas 1 due to the location of the speakers located on top of each respective sections resulting in amplified sound in the specific area.
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Sound from the speakers are more intense at the direction they are pointing at, which in return cover its own area that overlap over another. This results audiences sitting in the darker area in the diagram to receive a higher sound amplitude which is recommendable to sit (fig 5.4.1)
Figure 5.5.1.1 Sound coverage and path of speakers
Figure 5.5.1.2 sound path and reflection from sound source on the stage
On the other side, seats in the corners of front right and left side of the hall (fig 5.4.2) is nearby walls of diffusion walls. However, these diffusion walls reflect certain incident of sound simultaneously whereby audiences get distracted while receiving direct sound from the stage. Horizontal shape of plane walls reflects sound ray at constant angle under law of reflection. This is not efficient way of dispersing sound and does not promote concentration of sound efficiently.
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5.5.2. Sound Incident (Direct sound)
Figure 5.5.2.1 Front row audience nearest to the sound source
Audience in the front row receives the highest incident of sound amplitude with louder volume as they are nearer to the sound source.
Figure 5.5.2.2 Middle row audience receiving moderate incident of sound
Audience in the middle rows receives a moderate incident of sound amplitude and volume from the sound source.
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Figure 5.5.2.3 Back row audience furthest from the stage of sound source
Audience in the last rows receive the lowest incident of sound amplitude as they are the furthest from the sound source.
5.5.3. Sound Reflection (Indirect sound)
Figure 5.5.3.1 First row audience receiving indirect which is insignificant compared to direct sound
Reflected sound in the front rows of the audience aren’t as significant as they’re nearby the sound source
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Figure 5.5.3.2 Back and middle row audience receiving indirect sound reflected from ceiling
Audience sitting in middle and last back rows receives sound reflected from the ceiling. Horizontal ceiling reflects sound at constant angle under law of reflection - which is inefficient, as there are limited amount of short delayed reflection.
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5.5.4. Sound Diffusion
Figure 5.5.4.1. Sound hitting a diffuser and being reflected back in many different directions
Figure 5.5.4.1 explains how sound diffusion may be achieved with the aid of surface irregularities and scattering elements. Adequate sound diffusion is essential in many types of rooms in order to promote uniform distribution of sound, accentuate the natural qualities of music and speech and preventing the occurrence of undesirable acoustical defects. Unlike absorption, diffusers preserve the liveliness of the room as they do not absorb much sound energy, but dispersing it instead, spreading the energy around the room. A sound diffuser is an acoustic panel used to treat echoes and reflections. A diffuser jumbles up these reflections to avoid reflected sound from returning back into the room directly or having echoes.
Figure 5.5.4.3. Hollow pipes that act as diffuser panels and bass trapper.
Figure 5.5.4.2. The location of sound diffuser panels in Pentas 1.
Figure 5.5.4.4. Wooden blocks arranged all the way up. .
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Application of Wooden Blocks as diffuser panels.
Figure 5.5.4.6. Horizontal and vertical planes scattered the diffused sound in different directions.
Figure 5.5.4.5. How sound travels within Pentas 1 thus amplifying the sound at right side of the hall.
An ideal acoustic diffuser is a surface that causes an incident sound wave from any direction to be evenly scattered in all directions. Having the same function as skyline diffuser, they are able to scatter sound across two planes: horizontal (left & right) and vertical (up & down). This two-dimensional scattering broadens the soundscape and provide greater distribution of amplitude of sound.
Wooden block Concrete
Figure 5.5.4.7. Shows how the sound scattered after hitting the planes.
The diffusion panels are placed along the side walls of Pentas 1 all the way up high to kill echoes.
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Application of Hollow Pipe as diffuser panels.
Figure 5.5.4.8. Direction of the sound dispersed within Pentas 1.
Figure 5.5.4.9. Highlighting the small gaps in between the PVC hollow pipe.
The PVC hollow pipes are arranged closely together leaving a small gap (highlighted in figure 5.5.4.9) in between to allow sound at certain frequency to be dispersed into many direction when hitting the convex surface of the hollow pipes to provide better sound quality, especially to the right side of the hall.
PVC hollow pipe Concrete
Figure 5.5.4.10. Shows how the sound scattered after hitting the planes.
When sound is reflected from convex surfaces, the geometry of the surface will push back the energy to disperse outwards and encourage uniform distribution of sound.
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5.5.5. Sound Absorption When a sound wave hit a particular surface, its kinetic energy is converted into a small amount of heat energy which dissipates.
Figure 5.5.5.1. Rock wool material is used as the main absorber panel.
Figure 5.5.5.2. Besides acting as diffuser panel, PVC hollow pipes also act as bass trap.
Figure 5.5.5.3. Absorbency path.
Acoustical absorption abilities of a material are expressed by the sound absorption coefficient, Îą, (alpha), as a function of the frequency. Îą ranges from 0 (total reflection) to 1.00 (total absorption). Application of bass traps helps to absorb much of this excess sound energy, thereby reducing the amount of acoustic interference that occurs in the room. The more traps are added, the more of these excess reflections are absorbed, which further reduces the interference (or possible echoes), thus flattening the frequency response of Pentas 1.
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6.0 NOISE Noise is a subset of sound, which is undesirable or obnoxious. Noise is a sound that is unpleasant to hear. Unlike sound that is pleasant and clearly audible, noise is unpleasant, deafening, and incomprehensible though audible. There are a number of ways that noise intrudes into a specific enclosed area. Noise pollution can hinder performance intelligibility and greatly reduce the ability for an audience to hear and understand what is being delivered. In auditoriums, noise pollution can come from a wide array of sources, external or internal sources.
6.1 External Noise External noise is unwanted sound generated around from outside the space and that which is capable of causing distraction and disruption of activities and proceedings within the auditorium. In Pentas 1, there are multiple origins of noise produced by :-
Figure 6.1.1 Indicates the location of origin of exterior noise produced by movement of people outside the hall
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6.1.1 Outdoor events happening outside the auditorium As klpac is a preserved site, most of the areas in KLPac is an outdoor space which is occasionally being used for outdoor activities. Intruding outside noise is conducted into the auditorium through the windows and existing single layer red bricks act
as a wall
separating the outdoor and indoor spaces.
Figure 6.1.1.1 Location of outdoor events or activities which is right on the side of Pentas 1 backstage
Figure 6.1.1.2 Circular windows which can be seen from outside are covered with black painted plasterboard in the auditorium to avoid confusion between light and light sources
6.1.2 Opposite auditorium As both auditorium are located side by side, it is very important to ensure a good sound proofing system in order to prevent unwanted sound heard by audiences during performance or when the space is being used. In Pentas 1, sound from Pentas 2 can be heard when loud noise is produced in Pentas 2
PENTAS 2
PENTAS 1
Figure 6.1.2.1 The location of Pentas 1 and Pentas 2
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6.1.3 Adjoining corridors Noise produced by people walking or talking outside Pentas 1 corridors located along the left and right side of the auditorium. This can be reduced by increasing the sound proofing ability as the noise produced are conducive to sound reverberation.
Figure 6.1.3.1 Corridors located outside Pentas 1
6.2 Internal Noise Internal noise is unwanted sound generated from inside the space. There are a number of ways that noise intrudes into the auditorium. In Pentas 1, sound chambers allocated at each entrances and exit doors are designed to trap sound waves coming from outside.
Figure 6.2.1 Indicates the location of origin of interior noise produced by movement of people inside the hall, air conditioner diffusers and profile fixtures.
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6.2.1 Sound of Folding Theatre Seats When unfolding or folding the seats, it produces squeaking or rasping sound of the hinges. This may interrupt the audience especially when there are latecomers entering the auditorium during the performance.
Figure 6.2.1.1 Folding theatre seats
6.2.2 Sound of Footsteps Carpet is a sound absorber material that can reduce the sound of walking by 25 to 34 decibels. The reverberation time in a carpeted room is halved compared to a space with hard flooring, creating a soft atmosphere. However the staircase in Pentas 1 are constructed with aluminium stair tread nosing creating a safe walking surface for the audience but at the same time, it produces sound of footsteps that may interrupt performance.
Figure 6.2.2.1 Staircases with aluminium nosing which is one of the sources of noise.
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6.2.3 Profile Fixtures Buzzing sound of lighting profile fixtures when it is switched on. The interrupted current can produce a vibration within the light bulb filament or within the switch itself, which can cause a humming or buzzing noise of lighting fixtures. It takes up to one hour to stop buzzing. The technicians will switch the lights on earlier so that by the time the performance starts, the noise does not interrupt the audience.
Figure 6.2.3.1 Profile fixtures
6.2. 4 Air Conditioner Diffuser In Pentas 1, the air conditioner is a centralized type where the one visible in the auditorium is the diffusers. This type of air conditioning system has a quieter operation because the compressor-bearing unit is located outside , the indoor noise level from its operation is much lower. However when the auditorium is in silence, you can hear the sound of the diffusers as air is forced out from the vents.
Figure 6.2.4.1 Air conditioner diffuser that produces unwanted sound
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6.2.5 Sound of Door Opening The usage of acoustic doors act as a sound barrier to noise getting in or out, working both ways in controlling the sound of people moving in and out of the auditorium. The sound heard from outside is reduced with this installation however if the sound is too loud, it can still be heard by the audience especially those who site near the entrance doors.
Figure 6.2.5.1 Acoustic door located at the back side of the auditorium
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7.0 REVERBERATION TIME CALCULATION
Z
Y
X
W3
W1
W2 W
Figure 7.0.1 Position of calculated walls
7.1 Volume Volume of theatre = (260 x 26.867) + (5.25 x 14 x 26.867) + (6.75 x 26.867) = 6985 + 1975 + 725 = 9685 m3
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7.2 Absorption of Surface, As = Surface area (m2 ) x Absorption coefficient of surface at 500 Hz As (Ceiling) = 879.7m2 x 0.8 = 703.76m2 sabins As (Carpet Flooring) = 631.6m2 x 0.14 = 88.4m2 sabins As (Stage Flooring)= 248m2 x 0.015 = 3.72m2 sabins As (Wall W) = 268m2 x 0.02 = 5.36m2 sabins As (Wall W1) = 100.5m2 x 0.015 = 1.5m2 sabins As (Wall W2) = 100.5m2 x 0.015 = 1.5m2 sabins As (Wall W3) = [(268m2 -158.4m2 ) x 0.015] - (2 x 26.8m2 ) = 55.24m2 sabins As (Wall X) = 260m2 x 0.02 = 5.2m2 sabins As (Wall Y) = (47m2 x 1.0) + (170.4m2 x 0.015) + (42.6m2 x 0.31) =62.75m2 sabins As (Wall Z) = 217.08m2 x 1.2 =260.5m2 sabins As (Curtains) = 279.4m2 x 0.4 = 111.7m2 sabins As (Seating) =604.6 x 0.015 = 9.07m2 sabins Total Absoroption, At = 703.76m2 + 88.4m2 + 3.72m2 + 5.36 m2 + 1.5 +1.5 + 55.24 + 5.2 +62.75m2 + 260.5m2 + 111.7m2 + 9.07m2 = 1308.7m2 sabins
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7.2 Reverberation Time = 0.16 x Volume of the room (m3) รท Total Absorption RT = 0.16 x 9685m3 รท 1308.7 RT = 1.18s
Conclusion The reverberation time calculated falls under the recommended reverberation time for theatres which is 1.0-1.5 seconds.This shows a proper balance of absorption and reflection to provide a favorable acoustical environment. One must address both the needs to hear and understand speech, and the desire to have a pleasant space for music.
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8.0 RECOMMENDATION Issue 01
Figure 1.1.1 Areas where users experience the least sound quality
Solution 01
Figure 1.1.1 Proposed allocation of new smaller speakers
Shadow of the speaker range In Pentas 1, different seats provide a different sound quality to the audience. Based on figure 1.1.1 , it highlights the region where audience experience the least sound quality due to the location and direction of the speakers creating an imbalance sound frequency. Hence, adding several small speakers are suggested to provide equal sound quality to the audience as shown in figure 1.1.2.
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Issue 02
Figure 1.1.1 Current ceiling shape of Pentas 1
Solution 02
Figure 1.1.1 Proposed new concave shaped ceiling
Sound path
Shape of ceiling
Concave Ceiling The current surface of the ceiling structure in Pentas 1 is flat and it doesn't reflect significant sound frequency equally. Therefore, creating a concave ceiling surface is suggested as the geometry of the surface will force the energy to concentrate.
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Issue 03
Figure 1.1.1 Single layer brick wall
Solution 03
Figure 1.1.1 Proposed double layer brick wall
Brickwall Currently, the single layer brick wall enclosing the auditorium does not block external noise and it creates distraction to the audience. External noise interrupts the performance. Hence. By using double layer brick wall it gives minimum distraction to the audience. The thickness and mass of the brick work to reflect sound back at the source with minimal vibration occurring, even at lower frequencies. Double brick walls prevent sound from travelling through by virtue of sheer weight and mass.
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REFERENCES (APA STYLE) Kuala Lumpur Performing Arts Centre. (2017, August 24). Retrieved September 25, 2017, from https://en.wikipedia.org/wiki/Kuala_Lumpur_Performing_Arts_Centre Mominzaki Follow. (2014, April 07). Auditorium Acoustics. Retrieved October 02, 2017, from https://www.slideshare.net/mominzaki/auditorium-acoustics-33230112 Http://ljournal.ru/wp-content/uploads/2016/08/d-2016-154.pdf. (2016). doi:10.18411/d-2016-154 Sound Diffusers 101: Free Designs for DIY Diffuser Panels. (2015, September 08). Retrieved October 02, 2017, from http://arqen.com/sound-diffusers/ Partners, S. (2017, June 19). How to Build an Acoustic Diffuser - And Why You Need Diffusion – Soundfly. Retrieved October 02, 2017, from http://flypaper.soundfly.com/produce/how-to-build-an-acoustic-diffuser/
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