Table of Contents _________________________________________________________ 1.0 Introduction
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1.1 Aim and objective 1.2 Introduction to site
2.0 Acoustical Phenomenon 2.1 Sound Reflection 2.2 Sound Absorption 2.3 Direct & Indirect Sound Path 2.4 Reverberation Time
3.0 Acoustical Analysis
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3.1 Auditorium Design Analysis 3.2 Materials and Properties 3.3 Acoustic Wall Panelling / Wall Treatment 3.4 Sound and Noise Source 3.5 Sound Propagations and Phenomenon
4.0 Issues and Recommendations
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5.0 Conclusion
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6.0 References
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1.0 Introduction
Architectural acoustics is the science and engineering of achieving a desired sound within a building. This is the science of controlling a room's surfaces based on sound absorbing and reflecting properties. Reverberation time, which can be calculated, can determine the proper materials needed for absorption of sound. Sound reflections create standing waves that produce natural resonances that can be heard as a pleasant sensation or an annoying one. Reflective surfaces can be angled and coordinated to provide good coverage of sound for a listener in a concert hall or music recital space. 1.1 Aim & Objective The purpose of this case study is to observe the constitutions of good stage and audience acoustics. It is a study of the relationship between the auditorium’s layout, choice of exterior and interior envelope, acoustic manipulating devices such as reflective and dampening panels, and the resultant acoustic effects. The premise of good sound quality in our case would revolve around the reverberation time within our audience area. A longer reverberation means a lingering of background noise that may produce undesirable sound effects.
1.2 Introduction to Site
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PJ Live Arts Centre is a theater within Jaya One, a mixed use commercial hub located on the first floor. the theater opens weekdays 12pm-7pm. Jaya One can be reached via LDP, Sprint, Kerinchi, and Federal Highways. It is located along Jalan Universiti, Petaling Jaya. It is a 10 minutes commute from the Asia Jaya LRT station (opposite Menara Axis) by a taxi or Rapid KL Bus to Jaya One. It is also accessible by RapidKL buses, and is a 30 minute drive from KL city centre or Subang Jaya. Historical Background Opened in 2009, Selangor's first independent theatre facility, dedicated to presenting the best in family and comedy programming, PJ Live Arts is an organisation best known as a catalyst for community outreach and support, utilising arts as a platform to raise funds for charities and education; and to promote the community involvement in its theatre and audience development.
Figure 1.2.1: from stage.
Perspectives of theater
Figure 1.2.2: Perspectives of theater seats to stage.
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Drawings: Plans
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Drawings: Section
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2.0 Acoustical Phenomenon 2.1 Sound Reflection When sound travels in a given medium, it strikes the surface of another medium and bounces back in some other direction, this phenomenon is called the reflection of sound. The waves are called the incident and reflected sound waves. Hard surfaces will reflect almost all incident sound energy striking them. Convex reflecting surfaces will disperse sound while concave reflecting surfaces will concentrate the reflected sound. Reflections may be used in room acoustics to distribute and reinforcements sounds.
Figure 2.1.1: Types of sound reflection.
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Figure 2.1.2: Sound reflection on concave surface.
Focusing by concave surface
Figure 2.1.3: Sound reflection on convex surface.
Dispersion by convex surface
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2.2 Sound Absorption Sound absorption is the change in sound energy into some other form, usually heat when it passes through a material or strikes a surface. Soft, porous materials and fabrics, and people absorb a considerable amount of sound energy when it impinges on them. In Room Acoustics, the surfaces of walls, floors and ceilings, room contents including people, and the air of the space contribute to sound absorption. Sound Absorption Coefficient (α) Absorption coefficient (α) is a measure of the amount of sound absorption provided by a particular type of surface. This coefficient compares the amount of sound energy not reflected to the amount of sound energy arriving at the surface.The perfect absorber has an absorption coefficient of 1.0 and an example of such an absorber is an open window. Absorption coefficient, α = Sound Energy Absorbed Incident Sound Energy
Types of Sound Absorbers I. Porous Absorbers
Figure 2.2.1, 2.2.2: Types of porous absorber.
It consists of cellular materials such as fibreglass and mineral wool.The air in the cells provide resistance to the sound waves which then loses energy in the form of heat.
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II. Panel Absorbers
Figure 2.2.3, 2.2.4: Types of panel absorber.
Panel absorbers are typically non-rigid, non-porous materials which are placed over an airspace that vibrates in a flexural mode in response to sound pressure exerted by adjacent air molecules. III. Cavity Absorbers ( Helmholtz Resonators)
Figure 2.2.5, 2.2.6: Types of cavity absorber.
It consists of enclosed body of air contained within rigid walls and connected by a narrow opening to the surrounding. A cavity resonator can absorb maximum sound energy in a narrow region of a low frequency band. Cavity resonators can be applied as individual units, as perforated panel resonators and as slit resonators.
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2.3 Direct & Indirect Sound Path Direct sound is sound that travels straight from speakers, etc. to the ear without being affected by obstacles. Indirect sound, on the other hand, reaches the ear after reflecting off surfaces such as ceilings or walls.
Figure 2.3.1: Direct sound path.
Figure 2.3.2: The acoustical defects in an auditorium.
Reflected sound beneficially reinforces the Direct sound if the time delay between them Is relatively short, that is a maximum of 30msec. Time Delay = �1+�2 −� 0.34
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2.4 Reverberation Time Definition:- the time for the sound pressure level in a room to decrease by 60dB from its original level after the sound is stopped. Sound waves that cause reverberation loses energy as they are absorbed at each successive reflection. If the source of sound stops, then the reverberant sound level decays (loses sound pressure level over some time) The time it takes for sound pressure level to decay will affect the acoustical quality of an enclosure.
Figure 2.4.1: Reverberation time diagram.
Reverberation time, RT =0.16V A
Figure 2.4.2: Sound pressure level over time graph.
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3.0 Acoustical Analysis 3.1 Auditorium Design Analysis I. Shape and Massing The theater’s overall shape is rectilinear with several angular and parallel walls at the sides of the theater. This configuration hints to a poor acoustical design as parallel walls tend to contribute to the issue of flutter echoes which consist of a rapid succession of noticeable small echoes that affect acoustic quality of a theater. However, flutter echoes can be tackled when parallelism is being avoided. Slight tilt of the wall should be implement as it can prevent sound waves from being reflected back to the sound source.
Figure 3.1.1: Shape and massing of the theater.
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II. Arrangements of seats The seats within the theater are arranged in a fan shaped configuration to ensure a maximum number of seats are fitted, as well as to obtain an optimum view of the stage area from every seat. Most importantly, it helps to achieve the most effective acoustic quality as sound waves travel in a spherical order. In addition to this theory, it is also important to note that the angle at which the seating arrangement are fanned out. It is tested that by including a 140-degree sound projection angle from the center of the sound source on the stage. Should all seats fall within the angle of the sound projection area, the seating arrangement is well configured and effectively deemed.
Figure 3.1.2: The pattern of sound propagation in the auditorium.
III. Leveling of Seats The seats in an auditorium follow the leveling order. The seats on each row are installed higher than the seats of the row before. This ensures that sound waves projected from the stage do not face obstructions of any kind and can be transmitted smoothly across the whole
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auditorium. By doing so, even the audience being seated at the back rows of the auditorium would be able to hear the sounds as clearly as the audience being seated at the front rows.
Figure 3.1.3: The elevated seats in the auditorium.
IV. Ceiling Reflectors and Absorbers There are both reflectors and absorbers used on the ceiling of the auditorium. The ceiling absorber is used to eliminate the sound reflection to improve the speech intelligibility while the reflectors are used to reflect the sound waves toward the audience especially the audience seated at the back rows. The occupants of the balcony would also be able to hear the sounds clearly through this design, as depicted in the diagram below.
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Figure 3.1.4: The expected sound reflection from ceiling reflectors to the audience.
3.2 Materials and Properties Finishing Materials
Building Component
Materials Material
Ceiling
Balcony
Surface Area
Description
Coefficient 125Hz
500Hz
2000Hz
Plywood
Hardwood veneer finishes on plywood core
31.68m² 0.15 *3= 95.03m²
0.03
0.05
Rockwool
Rockwool 30mm direct to masonry
226.75 m²
0.10
0.80
0.90
Plywood
Perforated plywood panels
37.2m²
0.30
0.70
0.30
56.09m² 0.20
0.10
0.04
Plasterboard Plasterboar d ceiling on battens with large air space
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above Wall
Rockwool
Rockwool 30mm direct to masonry
38.48m² 0.10
0.80
0.90
Fabric covered panel
Fibrous web fabric
223.18 m²
0.07
0.20
0.75
Melamine based foam 25mm
223.18 m²
0.09
0.54
0.88
Concrete
Smooth painted concrete
120.64 m²
0.01
0.02
0.02
Plasterboard Plasterboar d on cellular core partition
47.88m² 0.15
0.07
0.04
Curtain
Blackout Red main Fabric in fold act curtain (0.5kg/m²) x1 Black Grand Drape x1 Black Border x3
47.88m² 0.06 * 5= 239.4m²
0.38
0.7
Seatings
Plastic and Metal chairs
Unoccupied
0.06
0.10
0.30
0.30
0.40
0.43
Concrete
Raised 550mm
59.52m² 0.01
0.02
0.02
Plywood
Wood board on joists
51.11m²
0.15
0.10
0.10
Plywood
Hardwood veneer finishes on plywood core
226.75 0.15 m² (First floor) 56.09m² (Second Floor)
0.08
0.05
Solid timber
Painted into
0.85m² * 0.14
0.06
0.10
Floor
Door
0.37m²* 450=16 Occupied by 6.5m² Adult
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Hand Railing
door
black
2 1.5m² * 2 9.4m²
Stainless steel
-
-
0.07
0.14
0.14
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Materials Location
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Construction Materials I. Interior wall Plasterboards with cellular core are being installed on the sides of the auditorium as well the partitions between front and back stage. Plasterboard has low sound absorption, hence, sound waves will be reflected and forming echoes subsequently. On the other hand, to aid with the sound absorption, Hollow cellular core was sandwiched in between the plasterboards. The air pockets within these hollow core absorb sound wave to reduce echoes. To prevent flutter echoes,
parallelism is avoided on the sides of the auditorium.
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Figure 3.2.1: Construction materials of interior walls.
Painted concrete walls are rarely being used throughout the auditorium due to their lower sound absorption coefficient than drywalls. Concrete walls provide the mass required to effectively reduce the transmission of sound, particularly low frequency sounds such as those from audio systems.
Figure 3.2.2: Construction materials of interior walls (2).
II. Floor (Ground Floor) Plywood covered with veneer laminate floorings contribute to the sound absorption of the auditorium. Veneer laminate flooring with a layer underlayment which add a feeling of solidity to the floor and reduce the hollow percussive sound that footfalls can produce when laminate flooring is floated over a subfloor without the benefit of underlayment. Veneer laminate floor combine a long lasting resilient core with a mass loaded acoustic barrier to effectively control the hollow percussive noises associated with hard floor finishes.
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Figure 3.2.3: Construction materials of ground floor’s floor.
III. Floor (Balcony) On the other hand, plywoods are used to construct the floorings of the balcony. Plywoods are not as exceptional at providing airborne sound insulation as concrete slabs. Nonetheless, it is proficient for sound reduction with the addition of the concrete underlayment, adding a feeling of solidity to the floor and reducing the hollow percussive sound that footfalls can produce when the plywood is floated over a subfloor without the benefit of an
underlayment.
Figure 3.2.4: Construction materials of balcony’s floor.
IV. Floor (Stage)
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The materials used to construct the theater stage are similar to the materials used to construct the balcony’s floor - plywoods as decking on timber floor joists. However, to increase its stability as a performance stage, aluminium galvanized steel posts were added underneath the timber bearers.
Figure 3.2.5: Construction materials of stage.
3.3 Acoustic Wall Panelling / Wall Treatment I. Side walls
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Acoustic wall panellings are installed along the side walls of the theater in the form of fabric wrapped melamine foam. By installing porous membrane such as melamine foam, this could absorb the medium to high frequencies to reduce reverberation time subsequently. Fibrous web fabric is used for covering the foam to allow sound waves to be dissipated through the porous membrane before being trapped and dampened.
Figure 3.2.6, 3.2.7: Wall panelling on the side walls of the theater.
II. Rear walls The rear walls of the theater are treated with a layer of rockwool, which also functions as sound absorption element. The rockwool is being used to absorb the sound waves after it has passed over the audience and prevents a second wave, as known as echo from occurring.
Figure 3.2.8: Wall treatment on the rear wall of the theater.
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3.4 Sound and Noise Source Technically similar in definition, noise and sound differ based on the user’s perception. Noise is simply undesirable sound that emanates from a variety of sources. Sound on the other hand, is almost always intentional and directed towards its audience. Sound Source Sound Surround System The PJ Live Arts using the 5.1 surround sound system since August 2009. Most auditorium had used this surround sound system as to reinforce the basic stereo sound. With this system, it provides a high standard quality of sound for the audience who is watching the performance in a large space of auditorium. The speaker consists of 5 speakers with installed on each location differently and a subwoofer which is an ideal solution to increase audio clarity and intelligibility in a large auditorium space. The placement of speakers need to be considered where mostly installed on high level and mounted on the sidewall to deliver enough of the sound to the audience. Equipment Location
Figure 3.4.1: Placement of the sound sources.
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Figure 3.4.2: Placement of the speaker.
There are two different location of speakers that are installed in this auditorium. 8 speakers with divided into two group are mounted on top of the ceiling level and two portable speakers on the stage which to cover up the whole space that can available to receive the sound clearly whether is on the balcony or the floor level. The 4 subwoofer are installed on the ceiling of the auditorium which produce low frequencies of bass sound to balance the music or speech on the equalization for the audience the perfect sound.
Figure 3.4.3: Sound source diagram.
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Equipment Specification Specification (A) Product Brand
VRX932 LAP Loudspeaker System
Dimensions (H x W x D)
349mm x 597mm x 444mm
Frequency Range
57 Hz - 20 kHz (-10dB)
Weight
24 kg
Power Rating
1750W Peak / 875W Continuous
Placement (colour)
Ceiling level (Red) Specification (B)
Product Brand
VRX915S Bass Reflex Subwoofer
Dimensions (H x W x D)
495mm x 420mm x 597mm
Frequency Range
35 Hz - 250 Hz (-10dB)
Weight
26.3 kg
Power Rating
800W / 1600W / 3200W
Placement (colour)
Ceiling level (Orange)
Specification (C) Product Brand
EON 206P P.A. System
Dimensions (H x W x D)
530mm x 705mm x 340mm
Frequency Range
64Hz - 22kHz (-10dB)
Weight
11.38 kg
Power Rating
160 W
Placement (colour)
Stage (Red)
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Noise Source I. External Sources There are multiple noise sources from the external environment of PJ Live Arts. These include the walking and talking noises from the restaurants and bars and the background hum from the mall nearby. Noise is undesirable sound so steps to control the penetration of noise into the auditorium are necessary. The auditorium utilises methods of wall acoustic treatments covered in section 3.3. The diagram below indicates the ground floor plan and the potential external noise sources.
Figure 3.4.4: Jaya One block layout.
Jaya One being a commercial hub for small and large retail stores attracts a steady flow of patrons. Located away from the main road, the most prominent noise comes from chatter from the bars and restaurants near the auditorium.
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Figure 3.4.5: Jaya One bars and restaurants.
Even though these are not evident in our case study, further suggestions can be made to append the degree of insulation from external noises if need be. For instance, the installation of a drywall with an air channel and connected using resilient clips. To further insulate from external noise, the addition of mass to the drywall will reduce the noise energy transfer thereby losing the energy as heat within the wall. II. Internal Sources Internal sound and noise sources include the overhead speakers adjacent to the stage, HVAC systems such as ceiling air vents and air conditioning vents installed at the lower floor ceiling. The overhead speakers and ceiling light produce a dim static noise when operating. More background noises include the thudding produced by footsteps on the auditorium floor and stage and noises from backstage. Air cond and diffuser Japan Ventech Air diffuser round shape
ceiling diffuser Aluminum air vent jet nozzle CB series Linear slot diffuser
Fluorescent light (purple Neon) Leyton lighting 13w T15 slimline
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Ceiling Light Watt Frosted Round LED Ceiling Light
Figure 3.4.5: Internal sounds produced by existing sound system.
Note that the sound path travelling towards the stage is dimmed. This is because sound refracts upwards at night due to temperature differences and is subsequently absorbed by the panels immediately behind the speakers.
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Figure 3.4.6: Absorbent panel.
Figure 3.4.7: HVAC vents on the lower ceiling.
Any noise from people or objects using the walkways are highly legible to the existing audience due to a lack of carpeting. However, the use of a timber laminate flooring finish on top of plywood decking are inherently sound absorbent materials due to their elasticity. This property allows vibrations to filter through a little better than hard rigid materials like concrete.
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Figure 3.4.8, 3.4.9: Stage and Seating Area Floor Cut Section.
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Figure 3.4.10: Background noises from HVAC system.
3.5 Sound Propagations and Phenomenon I. Sound shadow The diagram highlighted the deep balcony as a potential acoustic shadow area , the application of absorption wall possibly reflect to lose the energy , received low intensity of those
reflected sound towards the area below forming a sound shadow area.
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Figure 3.5.1: Sound shadow diagram in section. The result shows the low sound intensity at the acoustic shadow area by sound clapping
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Figure 3.5.2: Potential sound shadow area.
II. Sound Concentration The diagram shows the sound intensity levels of the sound source with the distinct sound at the concentrate zone which located at centre of auditorium , has the highest intensity level.
Figure 3.5.3: Sound intensity level diagram
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Figure 3.5.4: Sound reflection diagram.
The diagram shows that the sound concentration zone has been formed because of the rectangular shape of the auditorium. This rectangular design of the auditorium will fit well into
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many conventional new buildings. This form is only well suited for lecture, film or speech type theatre. However, this design does not facilitate a close relationship between performer and the audience which the PJ Live Arts Center is striving for. On the other hand, a fan shaped massing of the auditorium with a 130 degrees wide spread from a central focal point will be able to pull the attention of the audience towards to the performers. III. Sound Reflection To make better use of the sound, the reflected sound has to be controlled properly to avoid echoes. Therefore, reflectors have to be used so that maximum amount of sound in the auditorium can be reflected to the audiences.
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Figure 3.5.5: Sound reflection towards audience at row 6.
Figure 3.5.6: Sound reflection towards audience at row 11.
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Figure 3.5.7: Sound reflection towards audience at the balcony area.
The sound is effectively reflected back to the audience by the ceiling reflector. However, the flooring of the auditorium should be covered with more absorbent material to minimize the reflection of sound. IV. Echoes and Sound Delay An echo is distinctly different from a reverberation as it is a constant repetition of the original sound. The nature of the programme influences the desired sound delay period and hence, the definition of its echo. In this analysis, only reflective surfaces will be treated as effective sources of sound delay. Generally, in a theater designed for performances, any sound delay above 100ms will be considered as an echo.
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Figure 3.5.8: 5.49ms of sound delay is acceptable for a performance theater.
Echo =[(8.0+7.9)-7.7]*0.34 =5.40ms
Figure 3.5.9: 2.24ms of sound delay is acceptable for a performance theater.
Echo =[(11.4+8.1)-12.9]*0.34 =2.24ms
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Figure
3.5.10: 0.82ms of sound delay is acceptable for a performance theater.
Echo =[(15.1+2.8)-15.5]*0.34 =0.82ms The sound delay present in PJ Live Arts is very minimal that it is close to impossible to discern. Therefore, this theater will not suffer from any intelligible sound caused by echoes. V. Reverberation Time Calculation *Absorption of surface at 500Hz Ceiling a. Rockwool : 0.80 x 226.75m² = 181.4 m²sabins
b. Perforated plywood panels : 0.70 x 37.2m² = 26.04 m²sabins Balcony
a. Plasterboard : 0.10 x 56.09m² = 5.61 m²sabins Wall
a. b. c. d.
Rockwool : 0.80 x 38.48m² = 30.78 m²sabins Fibrous web fabric : 0.20 x 223.18m² = 44.64 m²sabins Melamine based foam : 0.54 x 223.18m² = 102.72 m²sabins Concrete : 0.02 x 120.64m² = 2.41 m²sabins
Curtain
a. Blackout fabric : 0.38 x 239.4 m² = 90.97 m²sabins
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Seating
a. Unoccupied : 0.1 x 6.5m² = 0.65 m²sabins Floor
a. Veneer finishes : 0.08 x 282.84m² = 22.67 m²sabins b. Plywood : 0.1 x 51.11m² = 5.11m²sabins c. Concrete : 0.02 x 59.52 m² = 1.19 m²sabins Total absorption areas : 181.4 + 26.04 + 5.61 + 30.78 + 44.64 + 102.72 + 2.41 + 90.97 + 0.65 + 22.67 + 5.11 + 1.19 = 514.19 m²sabins
Reverberation Time = (0.16 x Volume of the room) / Total absorption area RT = (0.16 x 3473.25) / 514.19 = 1.08 s According to the calculation, the reverberation time of the theatre is 1.08s which is within the recommended range of 1.00s - 1.25s for a medium sized multipurpose room. This shows that the materials used is good absorbers and causes less echoes are heard. Sounds within the halls does not linger around for a long period. However, it does not suitable for music performances as the sound diminished too quickly.
4.0 Issues and Recommendations Issue 1 : Finishing materials of floor
Figure 4.0.1: Addition of pile carpet to floor materials.
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The present floor in PJ Live Arts Theatre consist of concrete, plywood with veneer finishing acts as a form of noise source. This is mainly due to the low absorption coefficient of the finishing material which contributes the most to sound absorption. Recommendation : The thickness of hardwood veneer finishing can be increased to improve the efficiency of sound absorption. 6 mm pile carpet bonded to open-cell foam underlay which has 0.2 absorption coefficient also can be added to help reduce noise from both the reflection and also the impact sound of between shoes and floor.
Issue 2 : Wall Reflective Panel
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Figure 4.0.2: Application as reflector.
of acoustic timber panel
Recommendation: Timber side wall panel can be applied to the first â…“ portion of the auditorium in order to supply additional sound energy which ensure the uniform distribution of sound wave in the theater.
5.0 Conclusion
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Through this project, we understand that a successful design of theater depends on different acoustics design such as theater layout, types of absorption materials and also type of acoustics features used. Acoustic plays a role in enhancing the quality of sound and to eliminate noise and undesired sound. After visiting and doing research on our chosen theater, we learnt about material absorption coefficient and how to identify existing acoustic and sound sources. Through understanding all the information, we learnt how to calculate and analyze the data we collected from site. Thus, enabling us to learn about sound reflection, sound intensity level and reverberation time.
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5.0 References Sound Transmission and Flooring Types. (2010, March 26). Retrieved September 30, 2017, from https://www.builddirect.com/learning-center/home-improvement-info/soundtransmission/ Ovation Reflector Panels. (n.d.). Retrieved September 30, 2017, from http://www.kineticsnoise.com/interiors/ovation.html Absorption Coefficients. (n.d.). Retrieved September 20, 2017, from http://www.akustik.ua/ Material data. (n.d.). Retrieved September 20, 2017, from https://cds.cern.ch/record/1251519/files/978-3-540-48830-9_BookBackMatter.pdf Sound Insulation Properties of Concrete Walls and Floors (2009, March). Retrieved September 18 2017, from http://59.167.233.142/publications/pdf/SoundInsulation.pdf Acoustic Reflectors. (n.d.). Retrieved September 25, 2017, from http://www.totalvibrationsolutions.com/page/289/Acoustic-Reflectors.htm Inc., T. S., Says, J., Says, N., Says, R. C., Says, E., Says, H. S., & Says, S. (2017, June 30). Auditorium Seating Layout & Dimensions Guide. Retrieved September 30, 2017, from http://www.theatresolutions.net/auditorium-seating-layout/ Roode, L. D. (2016, November 14). 5 Sound levels in decibels: What is a decibel? Retrieved October 02, 2017, from https://www.alpinehearingprotection.com/wiki/5-sound-levels-indecibels/
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