CONTENT LIST 1 Introduction 1.1 Aim & Objective 1.2 General Information of DUMC 1.3 History of DUMC 1.4 Context & Location 1.5 Orthographic Drawings
4 4 5 6 7-8
2 Acoustic Theory 2.1 Acoustic in Architecture 2.2 Sound Pressure Level (SPL) 2.3 Sound Intensity Level (SIL) 2.4 Reverberation, Attenuation, Echoes and Sound Shadows 2.5 Acoustic Design for Auditorium
9 9 10 10-11 11
3 Methodology 3.1 Introduction 3.2 Measuring and Recording Equipment
12 12-13
4 Acoustic Analysis 4.1 Auditorium Design - Shape of Auditorium - Leveling of Seat - Sound Attenuation - Ceiling Design - Sound Shadow Area
14 14 15-17 18 19 20
4.2 Material - Material Tabulation
21-24
4.3 Acoustic Treatment & Components - Walls - Sound Reflecting Materials - Sound Absorbing Materials - Flooring - Seats - Ceiling - Stage
25 26-27 28-29 30 31 32 33-34
2
4.4 Sound Reinforcement & Noise Sources - Sound Reinforcement - Speaker Arrays - Subwoofers - Monitors - Noise and Noise Intrusion - External Noise - Internal Noise
35 36 37 38 39 40-43 44-51
4.5 Sound Propagations and Related Phenomena - Sound Reflections - Echoes and Sound Delays - Reverberation Time - Design Solution
52 53-55 56-57 58
5 Conclusion
59
6 List of Figures and Diagrams
60-62
7 Reference
63
3
1
Introduction
1.1 Aim and Objective Sound and music are fundamental to the design of auditoriums, performing arts centres, theatres, concert halls, sports arenas, lecture halls, and churches. This project aims to help students understand how acoustics and sound systems works in architectural design. By visiting a local auditorium, we are assigned to produce a case study report for showing our knowledge through the science of sound. Learning objectives: ● Know how sound waves form and how they travel through elastic mediums ● Understand how sound can be isolated and absorbed in building design ● Realize the benefits that sound masking provides for different kind of spaces.
1.2 General information of DUMC
Figure 1.2.1: Logo of Damansara Utama Methodist Church (DUMC)
FIgure 1.2.2: Damansara Utama Methodist Church (DUMC) exterior facade
Damansara Utama Methodist Church (DUMC) is one of the prominent churches in Malaysia. As name implies, the DUMC started out in Damansara Utama, one of the most rapidly growing townships in the country before expanding into larger spaces around Petaling Jaya. Known to be one of the youngest churches around, DUMC has been established for more than 30 years now. The Damansara Utama Methodist Church Auditorium is located within the DUMC Dream Centre. The auditorium is completed in the year of 2016, which has a maximum capacity of 2300 people. It functions as a multi-purpose hall, in which church services, concerts and events are frequently held. However, its main function is to serve large amount of Christians during their services.
4
1.3 History of DUMC The Damansara Utama Methodist Church or DUMC is one of the prominent Methodist church located in the Klang Valley. In its first service, there were only 80 people in the congregation in a simple setup with basic amnesties. Today, DUMC has grown to become one of the larger churches around. History Timeline 1980 The church was started in 1980 by 22 young professionals and 3 children who moved from SSMC (Sungei Way- Subang Methodist Church). 1988 From its shop lot premises in 1988, DUMC moved to Taman Mayang which could accommodate up to 500 people. 1996 In 1996, the Chinese Church of DUMC was established and a year later, there were 2 English services held every Sunday. 1998 The creation of Chinese Church of DUMC and English services has help the population to grow to a third service in 1998 where there would be about 1,000 members. 1999 A year after that, DUMC moved again and this time to the former Ruby Cinema in SEA PARK. 2001 DUMC then expanded again in 2001 where the Bahasa Malaysia ministry was established. 2007 The Dream Centre became the latest premise for DUMC. Besides the services held on Sundays, DUMC provides the platform for families and the youth in their respective ministries while cell groups are run to provide support services in smaller groups of members. 2016 The auditorium of DUMC has built to provide church service for large amount of Christians members.
5
1.4 Context and Location
Figure 1.4.1: Surrounding context of Damansara Utama Methodist Church (DUMC)
The Damansara Utama Methodist Church is located in Seksyen 13, Petaling Jaya, near to industrial and commercial zone. It also situated near to residential area which is Seksyen 14 to serve the community. Acoustic design for the auditorium is crucial due to its surrounding context. 1. 2. 3.
Industrial Area Residential Area (Seksyen 14) Commercial Area
6
1.5 Orthographic Drawings A
32770
A’ 67455
Figure 1.4: Ground Floor Plan
A
40050
A’ Figure 1.5: First Floor Plan 7
Figure 1.6: Section A-A’
8
2
Acoustic Theory
2.1 Acoustic in Architecture ●
●
●
Acoustic architecture is a field of study of how sounds are reflected and transmitted within a space. The relationship between sound produced in a space and its listeners is concerned when it comes to architectural design such as concert halls and auditoriums. Good acoustic design takes into account such issues as reverberation time; sound absorption of the finish materials; echoes; acoustic shadows; sound intimacy, texture, and blend; and external noise. Architectural acoustics can be about achieving excellence sound transmission and speech intelligibility in different kind of spaces according to its functions and requirements.
2.2 Sound Pressure Level (SPL)
Figure 2.2.1: Sound Pressure Level (SPL)
● ● ● ●
Sound Pressure Level (SPL) is the most commonly used indicator of acoustic wave strength and correlates well with human perception of loudness. SPL is usually calculated in decibels or db. The sound pressure level in a room depends on the strength of the sound source, the room shape and the number and quality of sound absorbing surfaces. The Sound Pressure Level (SPL) is then given by the formula:
p = the pressure of sound being measured p₀ = the pressure of the threshold of intensity taken as 20 x 10-6 Pa
9
2.3 Sound Intensity level (SIL) dB If the sound strength is considered in terms of intensity then a Sound Intensity Level (SIL) is given by the formula:
I = the intensity of the sound being measured I₀ = the intensity of the threshold of hearing
2.4 Reverberation, Attenuation, Echoes and Sound Shadows 2.4.1 Reverberation ●
●
The definition of Reverberation in enclosed space is the continuing presence of an audible sound after the source of the sound has been stopped. It is caused by rapid multiple reflections between the surfaces of a room, ie flutter echoes Reverberation Time (RT) is the time for the sound pressure level in a room to decrease by 60 dB from its original level after the sound is stopped. It is dependable upon the following variables: 1. The volume of the enclosure (Distance) 2. The total surface area 3. The absorption coefficients of the surfaces
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
2.4.2 Attenuation Nature or Energy level of sound as it propagates through mediums of different density and scatters to the surrounding environment.
10
2.4.3 Echoes Sound reflection is as ubiquitous as the cosmic radiation that surrounds us always. Echoes are defined as sound reflections that is returned to the listener with a perceptible magnitude. Multiple echoes create reverberations.
2.4.4 Sound Shadows Areas that are shielded from sound waves through mediums that either absorb or reflect such waves to a considerable degree.
2.5 Acoustic Design for Auditoriums 1. 2. 3. 4. 5. 6.
Must have a low ambient noise level from internal and external sources Provide a reasonable level of acoustic gain Provide appropriate reverberation time Avoid artifacts such as echoes. Prevent excessive vibrations Clarity in sound delivery
Figure 2.5.1 Performance happening in DUMC
Figure 2.5.2 Church and Wedding events held in DUMC
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3
Methodology
3.1 Introduction A few measuring techniques were being studied before we managed to visit DUMC. Recording and measuring equipments were prepared to facilitate our on-site measurement and recording exercise.
3.2 Measuring and Recording Equipment 3.2.1 Digital Sound Level Meter
Figure 3.2.1: Digital Sound Level Meter
● ●
A sound level meter is a measuring instrument used to assess noise or sound levels by measuring sound pressure within a space. Often referred to as a sound pressure level (SPL) meter, decibel (dB) meter, noise meter or noise dosimeter, a sound level meter uses a microphone to capture sound.
3.2.2 Measuring Tape
Figure 3.2.2: Measuring Tape
● ●
A measuring tape measure is a flexible ruler and used to measure distance. For our site visit, the measuring tape is used to measure distances between the auditorium spaces, which will benefits the generation of the drawings and calculation.
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3.2.3 Laser Distance Measure Tool
Figure 3.2.3: Laser Distance Measure Tool
â—? â—?
A laser distance measuring tool is able to measure a longer distance of space compare to measuring tape. It is used to measure the height and overall area of the auditorium which benefit the generation of drawings and calculation.
3.2.4 Digital Camera
Figure 3.2.4: Digital Camera
â—?
Digital camera is brought to the site to take photographs of important elements which will later will be used as references when further analysis of auditorium is conducted.
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4
Acoustic Analysis
4.1 Auditorium Design 4.1.1 Shape
of
Auditorium
A fan shaped designed is utilized in this auditorium. This configuration results in a more intimate space as the audiences are brought closer to the speaker. Fan shaped auditorium is suitable for a speech hall rather than a concert hall as sound is not directly reflected from the side and the degree of flutter echo is greatly reduced. However, the rear auditorium wall that forms a concave surface would produce a focused echo back to the stage. The arrangement of the auditorium, which is at 150°, exceeds the maximum limit of 130° for a wide fan arrangement. This affects the audience situated beyond the suggested limit who will have to experience a poor listening condition. Ideally, there should be no seats beyond the maximum limit for the fan shaped arrangement as it affects the listening condition of the audience.
Diagram 4.1.1: The blue area shows the region which is within the 130° limit. Note the seating on both sides which fall outside this region.
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4.1.2 Levelling of Seats There seats in the auditorium are divided into two categories, including the fixed seats and movable seats. The fixed seats are placed at level terrace on the ground floor and first floor, while the movable seats are placed at the ground floor pit.
Diagram 4.1.2: Leveling of Seats
Figure 4.1.1: Ground Floor Pit
Figure 4.1.2: Ground Floor Terrance
Figure 4.1.3: First Floor Terrance
15
In a hypothetical condition whereby the seats are not raised and the sound source is at the same level, the sound would not be able to propagate to the further-most seats at ground level as the sound wave is absorbed by the seats at the first half with majority of sound wave faded when it reaches the second. Therefore, sound intensity level will further decrease when it reaches the first floor terrace, resulting in little to no sound being heard.
Staggered ceiling aids the sound reflection to the first floor terrace
First Floor Terrace
Ground Floor
Indirect sound path Existing Poor Sound Attenuation Diagram 4.1.3: Sound propagation without a raised stage.
In this auditorium, sound attenuation issue is solved by raising the stage above the seats to ensure the sound source is projected directly to the audiences with maximum SIL and minimum delayed sound.
Audiences on first floor terrace are still unable to receive direct sound with a raised stage
First Floor Terrace Raised stage
Ground Floor
Direct sound propagation
Ground level audiences are able to receive maximum direct sound with raised stage
Diagram 4.1.4: The elevated stage reduces loss of SIL.  16
At first-floor terrace, sound attenuation is resolved by installing the sound reinforcements that aid the projection of direct sound to the audiences with minimum sound delay.
First Floor Terrace
Ground Floor
Sound amplified by speakers
Diagram 4.1.5: Installation of speakers as sound reinforcement to aid sound projection
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4.1.3 Sound Attenuation Sound propagates in a spherical wave front, and the intensity of sound will be approximate the Inverse Square Law. The sound distribution intensity is plotted out throughout the seating area and it shows that there is a distinct sound concentration zone accumulated at the stage area of the auditorium. This is obvious as the concave shaped auditorium provides a feedback where it converges sound into the center.
Diagram 4.1.6: Sound intensity level across the auditorium
18
4.1.4 Ceiling Design Ceiling design and reflective elements are significant for delivering the sound to every corner of the auditorium. The staggered ceiling configuration accommodates the inclusion of catwalks for easy access to the spotlight gantries and most importantly reflecting the sound towards the audiences. The front staggered ceiling reflects indirect sound to the seats at ground level and gallery whereas the rear ceiling panels further aid to reflect sound energy to the seats at the first floor terrace. Ultimately, the ceiling panels serve the function as a sound reflector to ensure that sound waves are distributed evenly throughout the auditorium.
First Floor Terrace
Diagram 4.1.7: The staggered ceiling helps to reflect and distribute the sound waves evenly to the back section seating in the gallery and ground floor. Front ceiling
Indirect Sound
Rear ceiling
Direct Sound
19
4.1.5 Sound Shadow The gallery underneath the balcony has formed a sound shadow area where sound wave failed to propagate to, resulting in a lower sound intensity level at the area. Based on the data we collected, the SIL decreases from 63dB at ground floor pit to 43dB at the gallery. Ideally, the gallery overhang depth should be less than twice the height of the gallery underside. In the case of DUMC, the height of floor to underneath the balcony is 3.5m with 5.32m depth for the galley. Hence, it’s within the ratio of 1:2 for floor to ceiling height and depth which results in shallow sound shadow area. Besides, the wooden boards reflect the sound into the shadow area.
Diagram 4.1.8: Sectional drawing indicating the dimension of sound shadow area and differences of sound intensity level.
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4.2 Material 4.2.1 Material tabulation AUDIENCE SEATING AREA COMPONENT
MATERIAL
Wall
DRY WALL
COEFFICIENT 500 HZ 0.03
Painted dry wall with plaster finish ACOUSTIC FIBREGLASS
0.8
Fiberglass core, perforated copolymer WOODEN BOARDS
0.1
Polished wooden panels Flooring
CARPET
0.50
5mm thick needle punched 21
COMPONENT
MATERIAL
Seatings
Padded Chairs
COEFFICIENT 500 HZ 0.15
Metal framed padded chairs Auditorium seats
0.59
Thick cushion Ceiling
Plasterboard and gypsum plaster Ceiling
0.06
5mm thick needle punched Others
Glass window
0.10
Used in control room and baby rooms, 4mm thick fixed window
22
COMPONENT
MATERIAL
Others
Curtains
COEFFICIENT 500 HZ 0.40
Heavy drapery, velour material Steel railings
Table 4.2.1: Tabulation of materials in DUMC auditorium, and sound absorption coefficient on 500Hz.
STAGE
AUDIENCE SEATING AREA
EXTERIOR OF AUDITORIUM
Diagram 4.2.2: Ground floor plan. Identification of areas in DUMC Auditorium.
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STAGE AREA COMPONENT
MATERIAL
Flooring
Carpeted Apron
COEFFICIENT 500 HZ 0.05
5mm thick carpet, needle punched Timber flooring
0.20
Polished timber parquet with void underneath Stage furniture
Stage curtain
0.40
Heavy velour Sound reinforment equipment
Table 4.2.3: Tabulation of materials in DUMC auditorium, and sound absorption coefficient on 500Hz. (on stage)
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4.3 ACOUSTIC TREATMENT & COMPONENTS 4.3.1 Walls Fiberglass boards
Fiberglass wall Drywall
Timber panels Figure 4.3.1: Location of reflective and absorbent walls present DUMC auditorium.
The walls of DUMC Auditorium are largely covered with sound absorbent materials to reduce overall sound reverberation. These materials help to reduce the formation of echoes by absorbing and dampening sound waves emanating from the stage. The choice and application of materials is to prevent echoes since the function of this auditorium is mainly used for preaching, the lingering of sound are not needed.
Diagram 4.3.2: Sound reflective and sound absorbing material surface
Sound reflecting materials: Plastered drywall Timber panels
Sound absorbing materials: Acoustic fiberglass walls and boards 25
4.3.1.1 Sound Reflecting Materials â–Ş
Plastered Dry Wall
Figure 4.3.3: Drywall at first floor of DUMC auditorium Diagram 4.3.3: Drywall at first floor plan
Dry walls are installed on the side of the auditorium and balcony. Hard plastered drywall have very low sound absorption and will reflect sound waves (Figure 4.3.2), forming echoes. It increases the collection of reflection sounds in the auditorium. Echoes are prevented by avoiding having parallel side walls in the auditorium. â–Ş
Timber panels
Figure 4.3.4: Timber panels in ground floor of DUMC auditorium
Diagram 4.3.4: Timber panels at ground floor plan
Timber wall panels are installed at the back wall of the ground floor of the auditorium. The panel has horizontal perforation which reflects sound waves propagated towards it. By having cavity, mineral fibre insulation and grooves (figure 4.3.5), the panels are able to absorb additional low to mid-range of frequency, such as whispering from the audiences, footsteps etc
Diagram 4.3.5: Timber wall panels cross section
26
Figure 4.3.6: Timber panels at the back wall.
Diagram 4.3.7: Sound shadow diagram
The panels are located at the sound shadow area. Sound are reflected off from the panels to the audiences at the sound shadow area. Suggestions: To maximise the effectiveness of the panels, the groove width can be increased and add thick porous absorber behind the panels. Cavity depth can be increased to trap more low frequency sound.
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4.3.1.2 Sound Absorbing Materials â–Ş
Acoustic Fiberglass Boards
Figure 4.3.8: Acoustic fiberglass boards in ground floor of DUMC auditorium
Diagram 4.3.8: Acoustic fiberglass boards at ground floor plan. Figure 4.3.9: Acoustic fiberglass boards in first floor of DUMC auditorium
Diagram 4.3.10: Sound propagation at acoustic fiberglass board
Diagram 4.3.11: Sound propagation at acoustic fiberglass board
The back wall of first floor of the auditorium are covered in acoustic fiberglass boards(figure 4.3.7) of variety of angles and sizes. They absorb the midrange sound waves coming from the stage and reduce the formation of echoes. It also helps to reduces mechanical noises from at the exterior wall. A weaved fabric is wrapped around the fiberglass panels to allow sound waves dissipate through the porous membrane before being trapped and dampened.
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â–Ş
Acoustic Fiberglass Wall
Figure 4.3.12: Acoustic fiberglass walls in ground floor of DUMC auditorium
Diagram 4.3.12: Acoustic fiberglass walls at ground floor plan.
The fiberglass wall includes an air gap space. This gap has a mechanism similar to a cavity absorber. It works well with low frequency range which is appropriate for the auditorium, as bass reliant music are played every weekend in the hall. The incident sound energy are dampened by the first absorption of the panel entering the air gap, then sound waves are reflected and trapped in the panels before reaching to the listener. It reduces the reverberation time of sound waves. Diagram 4.3.13: Acoustic Fiberglass wall cross sectional detail
29
4.3.2 Flooring â–Ş
Needle punched carpet
Figure 4.3.14: carpeted area in ground floor of DUMC auditorium
Diagram 4.3.14: carpeted area in ground floor plan
Figure 4.3.15: carpeted area in first floor of DUMC auditorium
Diagram 4.3.15: carpeted area in first floor plan
Majority of the areas in DUMC auditorium is covered in needle punched carpet. It is created by having barbed needles punched into a matted layer of fibre that form a mat of surface fibre. It is porous and able to absorb sound energy and reduces reflections and echoes. It is a good sound absorbent, preventing the transmission of floor vibration, hence it dampens unwanted noises such as footsteps.
Diagram 4.3.16: Carpet has high sound absorption, hard floor has low sound absorption
Diagram 4.3.17: carpet cross section
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4.3.3 Seats
Figure 4.3.18 moveable padded seats in ground floor of DUMC auditorium
Figure 4.3.19 fixed theatre seats in first floor of DUMC auditorium
The auditorium has 2 types of seatings – fixed folding theatre seats, and moveable padded seats. The seatings are padded with cushions and fabrics. They help with acoustical absorption of empty auditorium and allow the space to achieve similar quality of sound, whether it is partially filled or fully occupied.
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4.3.4 Ceiling Ceiling design is important where it must be able to break impact noise vibrations, reflect sound waves and absorb airborne noises entering from each ceiling wall connection. The materials choice also can influence the acoustical properties of ceiling. The ceiling in DUMC auditorium is made of plaster, and tiled gypsum plaster. Plaster can absorb low frequencies of sound, and reflect sound at other frequencies.
Figure 4.3.20 Tiled gypsum plaster ceiling
Figure 4.3.21 Plasterboard ceilings
Figure 4.3.22 Location of different ceiling materials
The seamless surface of plaster ceiling creates a better reflection of sound waves, ensuring the coverage of sound propagation where the audience at different areas are able to hear the sound produced. However, the rigid ceiling system has greater area of direct contact between the finish material and the structure above.
Figure 4.3.23 Rigid ceiling system with sound batt insulation and closed cell foam
Suggestions: To improve the acoustical qualities, resilient channels with sound clips should be attached to the structure system. Another way is to add sound batt insulation between the joist to help on the absorption of the airborne and flanking transmission. Adding another layer of gypsum board can help to increase the mass and damping ratings.
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4.3.5 Stage â–Ş
Flooring
Figure 4.3.24 timber parquet flooring on stage of DUMC auditorium
Timber parquet flooring Timber parquet flooring is used as the finishing surface for the stage as it is able to withstand foot traffic. It creates long reverberation time as it is a hard and acoustically reflective surface. The timber flooring is layered over concrete slabs where it proves enough airborne sound insulation between the two spaces. Sound reduction can be achieved with the addition of concrete underlayment to increase the solidity of stage floor and reduce hollow percussive sound produced from footfalls. â–Ş
Figure 4.3.25 timber parquet flooring sectional detail
Stage apron
The main stage apron has a layer of carpet finish. It helps to absorbs reflected sound from the auditorium. However, it does not have any major impact towards sound absorption because the area of stage apron is insignificance compared to carpeted floors. The apron are more functional for aesthetic and decorative purposes.
Figure 4.3.26 stage apron side view
Figure 4.3.27 carpeted stage apron close look
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â–Ş
Stage curtain
stage curtain
canvas background
Figure 4.3.28 stage curtain
The curtains located at the stage helps to control the reverberation by absorbing excess sound and eliminate acoustical reflections. Behind the stage curtain is a layer of canvas background followed by a concrete wall. There is an air gap between the curtain and the wall to isolate noise while the curtain is used to absorb sound which enables the reduction of reverberation time and to prevent echoes. The concrete wall on the sides of the backstage help to reflect sound waves of noises from the back of the stage, so that the sound is not transferring into the auditorium.
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4.4 Sound Reinforcement & Noise Sources 4.4.1 Sound Reinforcement Due to the nature of a large auditorium, reinforcement by loudspeaker system is used in Damansara Utama Methodist Church. Sound reinforcement system is used for the following purpose: ● ● ● ●
To reinforce the sound level when the sound source is too weak to be heard. To provide amplified sound for overflow audience. To minimize the sound reverberation. To provide artificial reverberation in rooms which are too dead for satisfactory listening.
An auditorium’s built in sound reinforcement system is comprising input and output components which amplified the internal sounds. The input components in Damansara Utama Methodist Church include dynamic microphones, condenser microphones, direct input from keyboards and electric pickups for guitars and bass. Output components include amplifiers, array speakers and stage monitors.
Array Speakers and Subwoofers
Dynamic Microphones Stage Monitors Diagram 4.4.1 Position of input component (dynamic microphones) and output components (array speakers, subwoofers, stage monitors).
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4.4.1.a Speaker Arrays There are 3 speaker arrays suspended from the ceiling directly in front of the stage. To ensure a balanced transmission of sound to the entire hall, the 3 speaker arrays are directed to the centre, the left and the right sides of the hall . The speakers are configured in a 9-8-9 configuration whereby there are 9 speakers for each left and right array and 8 speakers in the centre array. The speakers are installed in such a manner to avoid reflection from the flat floor which can produce inconsistent amplification should the speakers be on ground level.
Figure 4.4.1 Suspended array speakers.
Diagram 4.4.2 Arrangement and propagation of suspended array speakers.
Figure 4.4.2 Suspended array speakers in DUMC.
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4.4.1.b Subwoofers The subwoofers in Damansara Utama Methodist Church are placing alternate in between the 3 speaker arrays which boosts the lower frequency range of sound, typically below 100Hz. There is total of 4 subwoofers which are also suspended from the ceiling of the stage. Instead of being configures in an array similar to the speakers, the 4 subwoofers are installed as single units as lower frequencies have slower attenuation and can easily reach the audiences. However, to overcome the shortcoming of suspended subwoofers which the energy of direct vibration might attenuate in the air, a parallel hard concrete wall is designed facing the output source of the subwoofers.
Figure 4.4.3 Subwoofer.
Diagram 4.4.3 Arrangement and propagation of subwoofers.
Figure 4.4.4 Subwoofers in DUMC. 37
4.4.1.c Monitors Monitors speakers use to provide feedback to the performers on stage which are situated in the blind spot area of the speakers. It is placed on the stage floor facing the performers to ensure that they can hear their owns sound to help with synchronization between different instruments during performances.
Figure 4.4.5 Monitor.
Diagram 4.4.4 Arrangement and propagation of monitors.
Figure 4.4.6 Monitors in DUMC.
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4.4.2 Noise and Noise Intrusion Introduction The DUMC auditorium experiences noise intrusions, which is characterized by recipients as undesirable and unwanted sound. As a multipurposed auditorium which serves to host a series of activities such as church sermons, concerts as well as talks, a desirable acoustical environment is essential for all these activities to take place. However, the noise intrusions are unavoidable. These are few disadvantages of the noise intrusions: ● ●
Hindering concentration and knowledge retention Creating distractions, which will eventually lead to inefficiency and inattention when a particular work is conducted Causing interference with desirable sounds such as music or speech, which delays productivity due to the annoyance created.
ROOM CRITERIA: BACKGROUND NOISE Room criteria measured have been developed to evaluate existing background noise levels in enclosed areas, such as rooms as well as to specify required background levels for enclosed area to be constructed. The simplest noise criteria are determined by measuring or specifying a maximum A-scale weighted level (dBA) Occupancy
Max dBA
Small auditoriums (≤500 seats)
35 -39
Large auditoriums, theaters and churches ( >500 seats )
30 - 35
Table 4.4.7: weighted criteria of auditoriums.
On-site measurement: 1streading: 36dB 2ndreading: 40 dB Average reading: 38 dB
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4.4.2.a Acoustic Analysis of Noise - External Noise sources 1. ACTIVITIES SURROUNDING THE HALL
Diagram 4.4.8 Ground floor plan of auditorium that showing the possible external noise source.
Diagram 4.4.9 First floor plan of auditorium that showing the possible external noise source.
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Most of the external noise comes from the hallway surrounding the hall where including the cafeteria and the entrance foyer. The noise is approximately at -46dB. However, the external noise from the outside is reduced to an approximately at -38dB when the door is completely shut.
Diagram 4.4.10 Photo of the exit of the auditorium
The event that taking place in the auditorium also affect the noise level. For example, during Sunday services, some of the door are left partially opened to welcome the visitors and more congregants are around in the hallway. Hence, there is significant increase in external noises compared to the other days.
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4.4.2.a Acoustic Analysis of Noise - External Noise sources 2. NATURAL WEATHER CONDITION
Some noised that are created by natural weather conditions can be identified within the auditorium. For example, thunder. They are under the categories of external noise sources, as their sources originate outside of the building. The noise created by natural weather conditions are transmitted from above the auditorium.
Diagram 4.4.11 Diagram shows that how the natural weather conditions became the external noise sources.
However, noise from the exterior environment is able to enter the auditorium through the exit doors at the galleries as the door are lack of sound proofing treatments.
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4.4.2.a Acoustic Analysis of Noise - External Noise sources 3. LACKING OF SOUND LOCKS TREATMENT
The auditorium does not apply sound lock treatment at the entry/exit points. Thus, The external noise may penetrate from time to time depending on the intensity of the noise. However, some of the heavy curtains on the doors can be found to suppress external noise which may be adequate for a multi-purpose hall. The curtains also act as sound absorbers to prevent sounds from the inside of the hall to leak to the exterior hallways, vice versa.
Diagram 4.4.12 Curtains located at the exit to act as sound absorbers to prevent sound leaking.
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4.4.2.b Acoustic Analysis of Noise - Internal Noise sources The sounds produced by the electrical equipment such as HVAC system, server, AV deck and minor static noise from fluorescent lighting contributed most of the internal noises while using the auditorium.
1. HVAC SYSTEM NOISE SOURCE
Diagram 4.4.13 Diagrams showing the noise path from HVAC system.
The source of noise produced by the HVAC system can be easily identified however, the actual system component which contribute to the noise itself remain unknown as they are concealed by walls near the backstage. Nonetheless, there are few types of sound path which allow the noise to transmitted to the receiver through the medium such as airborne sound-transmission, structure-borne transmission and breakout sound.
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4.4.2.b Acoustic Analysis of Noise - Internal Noise sources
Main HVAC noise sources i. Fans – air circulation system Axial Centrifugal Propeller ii. Compressors – compress gas to liquid Piston Rotary Scroll Centrifugal iii. Pumps – to circulate liquid iv. Diffusers and ductwork – distribution of air Turbulent aerodynamic noise “break-out” noise
Sound paths of the HVAC system i. Airborne sound transmission sound which travel through the air from the source able to travel with or against the direction of airflow sound which travels through supply ductworks, return ductworks, or an open plenum ii. Structure-borne sound transmission Sound which travels through the vibration of solid parts of the building’s structure, such as walls, floors or ceilings. iii. Breakout sound Sound that breaks out through the walls of the supply or return ductwork
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4.4.2.b Acoustic Analysis of Noise - Internal Noise sources Noise control approaches for HVAC systems To effectively control noise problems caused by HVAC systems, a few strategies can be applied, such as: -
Resilient mounting & connected services Planning location of HVAC systems at a certain distance from the receivers Flexible connections to equipment to lower fluid velocities Internal duct lining and attenuators Routing of ductwork and piping Enclosing ductwork and piping
Noise of HVAC system in DUMC auditorium As an auditorium, DUMC has a very large space. Hence, conditioning the air throughout the space become a major issue. To solve this issue, usually the space will be coupled with diffusers to maintain the temperature in the auditorium. However, high amount of noise will be produced when high velocity blowers supply air into the space. However, different types of diffusers can be found in this auditorium:
1. Louvered Bladed Diffuser -
4.4.14 Photo of Louvered Bladed Diffuser
To supply air Usually installed where the ceiling is lower such as the area below the upper tier Blades deflect in all four directions to spread the supply of air evenly Produced noticeable noise but at a much lower level relative to the jet diffuser.
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4.4.2.b Acoustic Analysis of Noise - Internal Noise sources 2. Jet Diffuser -
-
To supply air Usually installed at the perimeter of upper tier pointed towards the center of the auditorium. Produces loud noise during operation.
4.4.15 Photo of Jet Diffuser
3. Return Air Grill -
To return / intake air Single deflection return diffuser.Z
4.4.16 Photo of Return air grill
Besides the diffusers, the noise produced from HVAC system also can be identified at the left side of the auditorium stage. It is categories as internal noise due to it occurs within the building itself. It is caused by the ventilation system machineries.
47 4.4.17 Ground floor plan of auditorium that showing the HVAC system noise source on ground level.
4.4.2.b Acoustic Analysis of Noise - Internal Noise sources 2.
LIGHTING LAYOUT, TYPES OF LIGHTING FIXTURES, FUNCTION in DUMC AUDITORIUM
All electrical equipment produces some noise. However, this statement includes lighting fixtures. Hence, care must be taken to select a ballast with the sound rating for a particular lighting installation. It is the degree of noise or hum which determines the existence of a problem. Ballast sound usually will be noticeable when it exceeds the ambient sound level. The presence of objectionable ballast hum depends upon various factors: - The ambient sound level of the area to be lighted - The selection of properly sound-rated ballasts - Fixture design and construction - Method of mounting ballast to fixture - Type and purpose of room - Acoustic of room - Number of ballasts in a given area - Excessive ballast operating temperatures Such a common nuisance, the industry does publishes “sound ratings” for ballasts and then recommends in which settings different ratings are appropriate. (see “sound rating” chart below) Rating
Areas
Ambient sound level
A
Private offices recording studios, study halls, libraries
20 – 24 decibels
B
Offices, residential use
25 – 30 decibels
C
Large office areas, commercial use, stores
31 – 36 decibels
D
Manufacturing facilities, large stores, office which much equipment in use
37 – 42 decibels
Table 4.4.18 Sound Rating table.
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4.4.2.b Acoustic Analysis of Noise - Internal Noise sources 2.
LIGHTING LAYOUT, TYPES OF LIGHTING FIXTURES, FUNCTION in DUMC AUDITORIUM
There are several types of lighting fixtures were installed all over the auditorium. Most of them are recessed lighting using fluorescent energy saving light bulbs that are embedded In the high ceiling of the center atrium. Also strips pf fluorescent tubes installed as up lights that are suspended used to light up the ceiling of the upper tier seating area. However, the noise produced from the lighting fixtures are often dwarfed by the noise of the HVAC system. Different types of lighting fixture can be found in this auditorium: 1. Recessed light
Diagram 4.4.19 Photo showing the recessed light in DUMC
2. Spot Light
Diagram 4.4.20 Photo showing the spot light in DUMC
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4.4.2.b Acoustic Analysis of Noise - Internal Noise sources 3. Suspended linear fluorescent light
Diagram 4.4.21 Photo showing the suspended linear fluorescent light In DUMC
Reflected Ceiling Plan
Diagram 4.4.22 Ground floor ceiling plan of auditorium that showing the Lighting fixtures
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4.4.2.b Acoustic Analysis of Noise - Internal Noise sources
Diagram 4.4.23 First floor ceiling plan of auditorium that showing the Lighting fixtures
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4.5 Sound Propagations and Related Phenomena 4.5.1 Sound Reflections Reflection is often used in room acoustics to efficiently distribute and reinforce the sound waves heard by the audience. Normally, only 10% of what is heard in a room is from direct sound; the other 90% is aided by reflective surfaces to redirect more sound waves to the audience.
d
t Soun
Indirec
ound
ect S Indir
Direct
d
oun
Sound
Ind
tS irec
d Direct Soun
ou tS c e dir
nd
In
Absorbers Reflectors Diagram 4.5.1: Sound Propagation of Auditorium
These reflections should be kept under control so as not to bombard audience members with too much The auditorium of DUMC, incorporates reflectors all around the stage area and also the back of the auditorium which serve to reflect sound effectively back to the audience. While the rest of the auditorium then must be covered with absorbent materials which can minimize the resultant reflected sound.
The extensive use of absorbent materials reduces the reverberation time of the auditorium to counter its large volume. It is also to comply with the function of a speech auditorium.
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4.5 Sound Propagations and Related Phenomena 4.5.2 Sound Delay and Echo Echo, the repetition of a sound caused by reflection of sound waves will occur when the Audience hears the reflected sound from a source with a notable delay time after hearing the direct sound.
Diagram 4.5.2: Formula for the time delay calculation
R1 = Incident distance R2 = Reflection distance D = Direct sound distance T = Delay time V = Speed of sound (0.34)
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4.5 Sound Propagations and Related Phenomena 4.5.2 Sound Delay and Echo As a multipurpose hall, DUMC held both speech and music. So, it is important that the sound Transmission in DUMC should not be exceed the time delay for both speech and music. A time delay of 40 msec for speech and 100 msec for music is deemed as an echo, a sound distinct from that travelling directly from sources to listener will be perceived.
At different position, the time delay will be different.
1.
Position A
Diagram 4.5.3: Sound delay at position A
Time Delay =
12.30+10.56-7.21 0.34
The time delay at position A is 46.03msec. Echo will be heard during a speech. Due to the high ceiling which Elongates the travel path of the sound, the sound delay happened.
= 46.03msec
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4.5.2 Sound Delay and echo 2. Position B
Diagram 4.5.4: Sound delay at position B
Time Delay =
26.78+3.34-26.33 0.34
The time delay at position B is 3.79msec. The direct sound is reinforced by the reflected sound, so there is no Echo to be heard.
= 3.79msec
3. Position C
Diagram 4.5.5 Sound delay at position C
Time Delay =
12.66+16.57-18.34 0.34
= 32.03msec
The time delay at position B is 32.03msec. The direct sound is reinforced by the reflected sound, so there is no Echo to be heard. 55
4.5.3 Reverberation Time DUMC is a large auditorium with a volume of 28116mÂł, the auditorium function as a multipurpose hall for the church. The ideal reverberation time for such a large multipurpose hall auditorium will be 1.6-1.8.
Diagram 4.5.6: Reverberation Time for Different Spaces
Due to the large volume of the auditorium, the reverberation time of the auditorium will be high according to Sabine’s Formula. This situation has led to a heavy use of sound absorption materials in the auditorium, yet the reverberation time is still approximately 1.8s which considered high for a multipurpose hall. It will affect the experience of the audience during a speech.
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Sabine’s Formula : RT = 0.16V / A Where, RT : Reverberation Time (sec) V : Volume of the Room A : Total Absorption of Room Surfaces
EFFECTIVE SURFACE AREA m²
Note, A : Area ⍺ : Absorption Coefficient A⍺ : Absorption Surface 500Hz SOUND ABSORPTION COEFFICIENT
ABSORPTION UNITS (m²sabins)
1211.72
0.03
36.35
Acoustic Fibreglass
731.34
0.80
585.07
Wooden Boards
344.58
0.10
34.46
Brick Wall
561.70
0.01
5.62
2129.89
0.50
1064.95
Timber Parquet
220.61
0.20
44.12
Gympsum Plaster Ceiling Panel
241.77
0.06
14.5
2381.34
0.06
142.88
45.36
0.06
2.72
Padded Chair
230.75
0.15
34.61
Auditorium Seats
763.65
0.59
450.56
Curtain
179.69
0.40
71.88
24.7
0.10
2.47
MATERIALS
Drywall
Carpet
Plaster Ceiling Solid Timber Double Door
Glass Window
TOTAL ABSOPRTION (A)
2490.19
Table 4.5: Calculation of Sound Absorption Unit in DUMC
According to Sabine’s Formula, RT= 0.16 x V A
Reverberation time for the auditorium is , RT = 0.16 x 28116 2490.19 = 1.81s
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4.5.4 Design Solution 1.
Introducing double entrances
Double entrances to create a buffer zone area which prevents the sound transmission from outside to the auditorium as the sound is trapped within the door to door space as well as absorbed by the sound absorption material at both side of walls. 2.
Sound absorbing material for doors and walls.
Material of doors and walls at the buffer zone could affect the sound intrusion into the auditorium depending on its absorption coefficient. Acoustic wood door is utilized across the entrances as it has a better sound proofing quality and proper intumescent seal should be installed at the bottom of doors to further prevent the diffraction of noise. 3.
Installing higher absorption coefficient acoustic panels
Though the extensive use of acoustic panels in the auditorium, the reverberation time still indicates a high degree of time required for the sound to decay. The acoustic fiberglass panels with the absorption coefficient of 0.8 should be replaced with a higher coefficient value material to create a better acoustical environment for the users.
Diagram 4.5.7: Buffer zone added to prevents sound transmission.
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Conclusion
In summary, DUMC serves as an auditorium ideally for speech delivering rather than musical and instrumental performances as they highly depend on electronic audio reinforcements to deliver the sound across the auditorium.Although it was designed to function as a speech delivering auditorium with the extensive use of absorption material, it still possesses several acoustical defects. Through our accumulated findings and analysis, the auditorium is still acceptable for speech delivering based on its acoustical design with the reverberation time of 1.8s which is considered slightly higher. Besides, the noise intrusion has become the major problem faced by the auditorium. Therefore, the acoustical design of DUMC could modified based on the proposed suggestions to achieve a better listening environment with the ideal range of reverberation time and noise insulation. Finally, this project has given us an insight on the application of different acoustical design to suit the various functions of the auditorium. We have a better understanding on how different components such as walls, floors, furniture and materials work together to provide a decent acoustical environment for the audiences.
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LIST OF FIGURES AND DIAGRAMS
Chapter 1 Figure 1.2.1 Logo of Damansara Utama Methodist Church (DUMC) Figure 1.2.2 Damansara Utama Methodist Church (DUMC) exterior facade Figure 1.4.1 Surrounding Context of Damansara Utama Methodist Church (DUMC) Figure 1.5.1 Ground Floor Plan Figure 1.5.2 First Floor Plan Figure 1.5.3 Section A-A’
Chapter 2 Figure 2.2.1 Sound Pressure Level (SPL) Figure 2.5.1 Performance happening in DUMC Figure 2.5.2 Church and Wedding events held in DUMC
Chapter 3 Figure 3.2.1 Digital Sound Level Meter Figure 3.2.2 Measuring Tape Figure 3.2.3 Laser Distance Measuring Tool Figure 3.2.4 Digital Camera
Chapter 4 Diagram 4.1.1: The blue area shows the region which is within the 130° limit. Note the seating on both sides which fall outside this region. Diagram 4.1.2: Leveling of Seats Diagram 4.1.3: Sound propagation without a raised stage. Diagram 4.1.4: The elevated stage reduces SIL loss. Diagram 4.1.5: Installation of speakers as sound reinforcement to aid sound projection Figure 4.1.1: Ground Floor Pit Figure 4.1.2: Ground Floor Terrance Figure 4.1.3: First Floor Terrance Diagram 4.1.3: Sound propagation without a raised stage. Diagram 4.1.4: The elevated stage reduces loss of SIL. Diagram 4.1.5: Installation of speakers as sound reinforcement to aid sound projection Diagram 4.1.6: Sound intensity level across the auditorium Diagram 4.1.7: The staggered ceiling helps to reflect and distribute the sound waves evenly to the back section seating in the gallery and ground floor. Diagram 4.1.8: Sectional drawing indicating the dimension of sound shadow area and differences of sound intensity level.
Table 4.2.1 Tabulation of materials in DUMC auditorium, and sound absorption coefficient on 500Hz Table 4.2.3 Tabulation of materials in DUMC auditorium, and sound absorption coefficient on 500Hz. (on stage) Figure 4.2.2 Ground floor plan. Identification of areas in DUMC Auditorium. Figure 4.3.1 Location of reflective and absorbent walls present DUMC auditorium Figure 4.3.2 Diagrams of sound reflective and sound absorbing material surface Figure 4.3.3 Drywall in first floor of DUMC auditorium Figure 4.3.4 Timber panels in ground floor of DUMC auditorium 60
Figure 4.3.6 Timber panels at the back wall. Figure 4.3.7 Sound shadow diagram Figure 4.3.8 Acoustic fiberglass boards in ground floor of DUMC auditorium Figure 4.3.9 Acoustic fiberglass boards in first floor of DUMC auditorium Figure 4.3.10 Sound propagation at acoustic fiberglass board Figure 4.3.11 Sound propagation at acoustic fiberglass board Figure 4.3.12 Acoustic fiberglass walls in ground floor of DUMC auditorium Figure 4.3.13 Acoustic Fiberglass wall cross sectional detail Figure 4.3.14 carpeted area in ground floor of DUMC auditorium Figure 4.3.15 carpeted area in first floor of DUMC auditorium Figure 4.3.16 Carpet has high sound absorption, hard floor has low sound absorption Figure 4.3.17 carpet cross section Figure 4.3.18 moveable padded seats in ground floor of DUMC auditorium Figure 4.3.19 fixed theatre seats in first floor of DUMC auditorium Figure 4.3.20 Tiled gypsum plaster ceiling Figure 4.3.21 Plasterboard ceilings Figure 4.3.22 Location of different ceiling materials Figure 4.3.23 Rigid ceiling system with sound batt insulation and closed cell foam Figure 4.3.24 timber parquet flooring on stage of DUMC auditorium Figure 4.3.25 timber parquet flooring sectional detial Figure 4.3.26 stage apron side view Figure 4.3.27 carpeted stage apron close look Figure 4.3.28 stage curtain Figure 4.4.1 Suspended array speakers. Figure 4.4.2 Suspended array speakers in DUMC. Figure 4.4.3 Subwoofer. Figure 4.4.4 Subwoofers in DUMC Figure 4.4.5 Monitor. Figure 4.4.6 Monitors in DUMC. Diagram 4.4.1 Position of input component (dynamic microphones) and output components (array speakers, subwoofers, stage monitors). Diagram 4.4.2 Arrangement and propagation of suspended array speakers. Diagram 4.4.3 Arrangement and propagation of subwoofers. Diagram 4.4.4 Arrangement and propagation of monitors. Table 4.4.7 Weighted criteria of auditoriums. Diagram 4.4.8 Ground floor plan of auditorium that showing the possible external noise source. Diagram 4.4.9 FIrst floor plan of auditorium that showing the possible external noise source. DIagram 4.4.10 Photo of exit in the auditorium. Diagram 4.4.11 Diagram shows that how the natural weather conditions became the external noise sources Diagram 4.4.12 Photo of curtains located at the exit to act as sound absorbers to prevent sound leaking. Diagram 4.4.13 Diagrams showing the noise path from HVAC system. Diagram 4.4.14 Photo of Louvered Bladed Diffuser in DUMC. Diagram 4.4.15 Photo of Jet Diffuser in DUMC. Diagram 4.4.16 Photo of return air grill in DUMC. Diagram 4.4.17 Ground floor plan of auditorium that showing the HVAC system noise source on ground level. Table 4.4.18 Sound rating table. Diagram 4.4.19 Photo of recessed light in DUMC. Diagram 4.4.20 Photo of spot light in DUMC Diagram 4.4.21 Photo of suspended linear fluorescent light. Diagram 4.4.22 Ground floor ceiling plan of auditorium that showing the lighting fixtures in DUMC. DIagram 4.4.23 First floor ceiling plan of auditorium that showing the lighting fixtures in DUMC. Table 4.5 Calculation of Sound Absorption Unit 61
Diagram 4.5.1 Sound Propagation of Auditorium Diagram 4.5.2 Formula for the time delay calculation Diagram 4.5.3 Sound delay at position A Diagram 4.5.4 Sound delay at position B Diagram 4.5.5 Sound delay at position C Diagram 4.5.6: Reverberation Time for Different Spaces Table 4.5: Calculation of Sound Absorption Unit in DUMC Diagram 4.5.7: Buffer zone added to prevents sound transmission.
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References
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