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1. INTRODUCTION
Theater Hall is that branch of the performing arts concerned with acting out stories in
front of an audience using combinations of speech, gesture, music, dance, sound and spectacle
that indeed any one or more elements of the other performing arts.
In addition to the standard narrative dialog style, theatre takes such forms as opera, ballet,
classical Indian dance, Chinese opera,mummers' plays and pantomime. The good theater halls
should have noise rating (NR), NR-25 and the Sound Pressure Level (SPL), 30dBA.
1.1 History of Architectural Acoustics in Theatres
The theatre acoustic in the world are introduce in two era which were Greek Roman
empire and Renaissance reformation era which are considered some acoustics characteristics
such as good sight lines to the stage, use of reflecting wall, low ambient noise, and rich
reverberance.
Figure 1: The architecture of acoustics theatre hall
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1.2 Greek Theatre
At that time theatre is to be defined as involving the art of acting a part on stage, that is
the dramatic impersonation of another character than themself, they begin with Thespis. A figure
of whom we know very little, he won the play competition in honor of the greek god Dionysus,
in 534 B.C. While it is uncertain whether Thespis was a playwright, an actor or a priest, it is his
name with which the dramatic arts are associated in our word "Thespian".
Greek theatre took place in large (the largest ultimately held twenty thousand people)
hillside ampitheatres. The players included a chorus and their leader, and the "lines" were more
chanted than spoken. The chorus performed in the "orchestra", not on a raised stage. The use of
masks to represent characters and high-soled boots worn to add height to the players limited the
movement of the actors. Indeed, the concept of "actors" themselves was not originally a part of
Greek theatre, but was developed as a consequence of certain playwrights of particular genius.
1.3 Roman Theatre
The decline of Greek government and society coincided with the rise of the Roman Republic
and subsequent empire. The Romans borrowed extensively from Greek theatre. Although Roman
theatre may not be held in the same high esteem as that of the Greeks, we have inherited much
from the influence of the Roman Theatre, including the word "play" itself, which derives from a
literal translation of the Latin word ludus, which means recreation or play.
Roman theatre took two forms: Fabula Palliata and Fabula Togata. Fabula Palliata were
primarily translations of Greek plays into Latin, although the term is also applied to the original
works of Roman playwrights based upon Greek plays. We are familiar with the latter from the
works of Terence (190-159 B.C.), who introduced the concept of a subplot, enabling us to
contrast the reactions of different sets of characters to the same events or circumstances.
The Fabula Togata were of native origin, and were based on more broadly farcical situations and
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humor of a physical nature. An author of some of the better examples of this type of drama is
Plautus (c.250-184 B.C.).
1.4 Renaissance and Reformation
During the 15th and 16th Centuries, European Society was influenced by the Renaissance --
a "rebirth" or rediscovery of the classical worlds of Rome and Greece -- and by a movement
toward nationalism -- the building of coherent nation-states such as England, France and Spain
(with Germany and Italy following later). The impact of these changes on the theatre went
beyond mere secularization of an artform that had been dominated for centuries by the Church.
The Renaissance, while having a major impact on the other arts, had less influence on theatre
in England than in Italy, where classic Roman plays were revived for performance. Of greater
impact was the Protestant Reformation and the movement toward nationalism which
accompanied the Reformation. The rediscovery of the classics did influence the development of
the stage - first in Italy, then in France and England and the rest of Europe. It was in Italy that the
first steps were taken toward the development of the proscenium, or "picture frame", stage with
which we are so familiar today.
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2. ACOUSTIC QUALITY CRITERIA
2.1 Reflection
In completely free space, sounds travel outwards from their source with diminishing
intensity until all the energy has been dissipated in the ever-widening wave front or lost as heat
in the air itself. By contrast, sound waves in a theatre hall are repeatedly turned back on
themselves and bounced in criss-cross patterns throughout the enclosed space. The audience
therefore hears not only the direct sound but also a mixture of later and weaker sounds.
These multiple reflections are delayed in accordance with the extra distance travelled and
they diminish in intensity through normal dissipation and absorption at each boundary reflection.
A near-perfect reflector such as a polished wood floor will reflect almost 100 per cent of the
incident energy, but soft furnishings, porous fibre-tiles, or pliant panels will absorb part of that
energy. In practice, the different kinds of absorber are frequency-selective, and good acoustic
design depends on careful disposition of various absorbers to control reflections evenly at bass,
middle, and treble frequencies.
2.2 Directional effects
Sound sources are described as directional or non-directional depending on whether they
are physically large or small compared with the wavelength of the musical notes being radiated.
For similar reasons, reflectors of different sizes and shapes may modify the distribution, like
diffusion, of sounds throughout a room not only by frequency-selective reflection but also by re-
radiating some bands of frequencies uniformly and others in a directional manner. If curved
surfaces are essential, a convex shape is generally preferred because it tends to scatter sounds
and help produce uniform listening conditions. Concave surfaces focus sounds back along their
axis and give rise to local echoes or dead spots.
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A domed ceiling is a classic example of the concave shape to be avoided. The Royal
Albert Hall in London is perhaps especially unfortunate in having both an oval plan and a high
domed ceiling focusing sounds on to parts of the audience area. The effects of marked echoes
were complained of for many years until arrays of flying saucers were suspended beneath the
huge dome. The underside of the saucers is convex, to scatter the upward-travelling sound
waves, and their tops carry absorbent material to capture any sounds that missed the saucers on
the way up and rebounded from the ceiling. In the same way, recesses or coffering should be of
generous proportions so that their scattering effect will be felt through most of the frequency
spectrum.
2.3 Reverberation
Although members of an audience receive the direct sound followed by a wedge or tail
of countless reflected waves, they are not normally conscious of these as separate entities or
echoes. The hearing mechanism works in such a way that sound repetitions arriving within
about1/20; of a second of each other are run together and heard as one. Note, however, that
flutter echoes can arise between parallel walls.
The prolongation effect is known as reverberation. A smooth decay is to be preferred,
secured by careful acoustic design to produce evenly diffused sounds. The time taken for sounds
to fall to inaudibility is called the reverberation time (strictly the time to fall to a millionth of its
original value, or to 60 dB). Reverberation time increases in direct proportion to the volume
(size) of the enclosurethe greater distances stretching the decay periodbut is reduced by the
introduction of absorbent materials. An audience also mops up sound energy quite effectively, so
rehearsals in an empty hall sound much more reverberant than the actual concert. To reduce this
difference, modern concert-hall seating can be designed so that each seat absorbs about the same
amount of sound whether occupied or not.
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2.4 Sound reinforcement
It is economically impossible to limit the use of most halls to musical forces of optimum
size and acoustic power. The question of amplification then arises for quiet instruments or
voices. In many hall and lecture theatres, the building shape or shortcomings in the acoustic
distribution call for augmentation of the natural sounds, either overall or selectively in particular
areas. The basic components for sound reinforcement or public address are a microphone,
amplifier, and loudspeaker.
The arrangement is inherently unstable, however, as most users can testify, since any
amplified sound from the loudspeaker that falls on the microphone is again amplified and sent to
the loudspeaker with the possibility of uncontrolled feedback. Directional microphones can ease
the problem since their less sensitive sides can be directed towards the loudspeakers and so
reduce unwanted pickup of the amplified sound. Directional loudspeaker arrays can also beam
the sound waves into specific areas to give more efficient reinforcement without feedback.
2.5 Assisted resonance
A special kind of sound reinforcement, called assisted resonance, is used in some halls to
increase the reverberation time within certain frequency bands. A classic example is the Royal
Festival Hall in London, where the original 1948 design had called for a reverberation period of
1.7 seconds, rising to 2.5 seconds at low frequencies. When the hall was built, however, the low
frequency reverberation time measured only 1.4 seconds and, while this gave excellent
definition, the hall was criticized as lacking fullness of tone. In 1964 matters were improved by
assisted resonance using 172 microphones at roof level, amplifiers tuned to narrow frequency
bands in the range 58700 Hz, and arrays of loudspeakers.
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2.6 Sound insulation
A requirement in every type of theatre hall is for the lowest practical level of extraneous
noise, whether airborne or transmitted through the structure of the building. A first step in
planning is to choose a quiet site not very practicable in a large city and to design the building
with as many layers or shells as possible on the side nearest to railway lines or other identifiable
sources of noise. Aircraft noise is an increasing problem requiring the use of massive roofs on
insulating supports, with suspended ceilings, floating floors, and multi-layered exterior walls.
The Bridgewater Hall in Manchester has achieved almost total exclusion of external noise. Its
massive 22,500-tonne weight is suspended on some 300 isolation spring bearings, and its three-
layer roof has an outer sheet of steel lined with acoustic panels.
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3. SOUNDS IN THE THEATER HALL
Who travelled many times to various theaters, that it is well known that in the sense of
hearing rooms come with good acoustics and bad acoustics and in some areas voices of artists
and sounds of musical instruments clearly audible at a distance, in others sounds even close to
the perceived vague.
Any sound produced in the building long enough to hear the end of sound source, due to
multiple reflections several times he avoids the terms of the building in the meantime, other
sounds are heard, and listeners are often unable to catch them in a proper manner and understand
them. For example, if the sound lasts about 3 seconds and he said at a rate of three syllables per
second, the sound waves corresponding to the nine syllables, will move around the room all
together and create total confusion and noise, due to which the listener can not understand the
speaker. Caught in such circumstances, the speaker is speaking very clearly and not too loud. But
usually the speakers, just the opposite, try to speak loudly and this only increases noise.
The construction of the theater with good acoustics was considered a matter of luck.
Currently found successful ways to combat unwanted sound duration which spoils the hearing.
The struggle with poor acoustics is to create surfaces that absorb unwanted sounds. The best
sound absorber is an open. The visitors absorb the sounds of the theater and if the correct
observation of one physicist, that the audience absorbs the speech the speaker in the truest sense
of the word; it is equally true that the empty room is unpleasant for the speaker in the direct
sense of the word.
If the sound absorption is too large, it also creates a degraded hearing. First, the excessive
absorption of sound and mutes, and secondly, reduce the reverb so that the sounds are heard as it
were broken, and the impression of a certain dryness. Therefore, if we want to avoid too long
reverb, then and too short reverb is also undesirable. Best value for different reverberation room
is not the same and must be installed in the design of each room.
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In the theater, there is also another subject, interesting from the standpoint of physics:
prompt-box. A set of booths is a concave acoustic mirror, which has a dual purpose to delay the
sound waves coming from the mouth breather towards the public. Plus, it purposes to reflect the
waves toward the stage.
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4. FACTORS OF THEATRE DESIGN
Theatre acoustics is key factor in creating memorable entertainment experiences.
Acoustical design directly affects the quality of the performing arts events, musical theatre, and
opera from the theatre stage. The general factors of theatre design are:
4.1 Room Volume
Reverberation time is directly proportional to room volume. Reverberation time (RT) is the
time it takes for sound intensity to decay by one millionth of its steady state value after the sound
source has been terminated. Reverberation times for Various Activities at 500 Hertz is shown in
Figure 2. If the volume per seat is small, the sound energy available to each listener is greater. As
the volume per seat increases in a speech hall, the need to use sound absorption on room surfaces
increases to obtain the required reverberation time. A gross area of 0.55 to 0.7 meter square is
recommended per seat.
Figure 2: Reverberation times for Various Activities at 500 Hertz
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4.2 Seating Layout
Audiences should be able to comfortably and clearly see and hear the performance in
order to fully experience the events intended effects. Unobstructed sight lines from all seats to
the front of the stage allow full view of performers and scenic elements, as well as unobstructed
and direct sound propagation. Floor and balcony slopes are designed so there are no obstructions
of view to the seated audience as shown in Figure 3.
Figure 3: Seat of audience
4.3 Sound Fields
There are two types of sound fields which are direct and reverberant. Direct Sound is a sound
field in which all sound comes directly of a source (With complete absence of any reflected
sound) while reverberant sound is a sound field in which all sound consists of reflected sound.
The reverberant sounds are dividing to three parts which are echoes, creep, and reflections.
Echo is a sound that has been reflected with sufficient time delay, and is of a sufficiently high
level to be heard as distinct from the original sound. Creep is useless sound reflections
concentrated near and along smooth concave surfaces (whispering gallery effect). Reflected
sounds arrive at the listener with different delay times and levels. There are two types of
reflection which are specular reflections (focus the sound generally produced by concave
surfaces) and diffuse reflections (scatter the sound, generally produced by convex surfaces).
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Figure 4: The Sound Fields
4.4 Lighting
Lighting for the theatre involves planning lighting of both interior and exterior spaces.
The design should, allow for a wide range of productions. The typical small theatre may range
from 200 to 1000 seats and use between 50 and 250 lighting fixtures. A theatrical lighting system
must be designed to provide proper illumination of the space, with attention given to lighting
efficiency and lighting safety.
The primary function of stage lighting is to provide selective visibility. Stage lighting
should illuminate the performers so their gestures, movements and expressions can be seen by
every member of the audience, but should also deemphasize the elements on stage that should
not be seen. The lighting should help compose and color the stage picture, establish the setting,
mood, and tone, and reinforce the rhythm and style of the production.
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Figure 5: Theatre lighting
4.5 Stage Rigging and Machinery
Stage rigging and machinery is used to move and support the lighting, scenic, and audio
systems for a production or performance. Rigging system design involves the expert application
of equipment, structural loading analysis, and operational considerations to create a safe and
maintainable system. A typical stage rigging system is housed in a tall fly tower which allows
the scenery to be flown up and out of view of the audience.
A walking grid at the top of the fly tower is used to gain access to the overhead rigging
equipment and for temporary or spot block rigging. Fly galleries and cross-over catwalks at mid-
height in the fly tower allow for additional lighting positions on the stage, as well as access to
spot block rigging lines. A loading gallery catwalk is used to load or un-load weights from the
counterweight arbors while technicians below install or remove scenery or lighting elements
from the rigged batten.
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5. ACOUSTIC TREATMENT
There are four primary goals of acoustic treatment:
- To prevent standing waves and acoustic interference from affecting the frequency response
of recording studios and listening rooms.
- To reduce modal ringing in small rooms and lower the reverb time in larger studios, churches,
and auditoriums.
- To absorb or diffuse sound in the room to avoid ringing and flutter echoes, and improve stereo
imaging.
- To keep sound from leaking into or out of a room. That is to prevent your music from
disturbing the neighbours, and to keep the sound of passing trucks from getting into your
microphones.
An acoustic treatment as described here is designed to control the sound quality within a
room. It is not intended to prevent sound propagation between rooms. Sound transmission and
leakage are reduced via construction - using thick massive walls, and isolating the building
structures - generally by floating the walls and floors, and hanging the ceilings with shock
mounts.
Proper acoustic treatment can transform a muddy sounding room, having poor midrange
definition and erratic bass response, into one that sounds clear and tight, and is a pleasure to
work and listen in. Without effective acoustic treatment, it is difficult to hear what you're doing,
making you work much harder to create a good mix. In a home theatre, poor acoustics can make
the sound less clear, harder to localize, and with an uneven frequency response. Even if you
spent many thousands of dollars on the most accurate loudspeakers and other equipment
available, the frequency response you actually realize in an untreated room is likely to vary by 30
dB or even more.
There are two basic types of acoustic treatment - absorbers and diffusors. There are also
two types of absorbers. One type controls midrange and high frequency reflections; the other, a
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bass trap, is mainly for low frequencies. All three types of treatment are usually required before a
room is suitable for making mixing decisions and for serious listening.
Many studio owners and audiophiles install acoustic foam all over their walls, mistakenly
believing that is sufficient. After all, if you clap your hands in a room treated with foam (or
fiberglass, blankets, or egg crates), you won't hear any reverb or echoes. But thin treatments do
nothing to control low frequency reverb or reflections, and hand claps won't reveal that.
Basement studios and living rooms having walls made of brick or concrete are especially prone
to this problem - the more rigid the walls, the more reflective they are at low frequencies. Indeed,
simply building a new sheet rock wall a few inches inside an outer cement wall helps to reduce
reflections at the lowest frequencies because a sheet rock wall that flexes also absorbs a little.
Why we need acoustic treatment at all, since few people listening to your music will be in
a room that is acoustically treated. The reason is simple: All rooms sound differently, both in
their amount of liveness and their frequency response. If create a mix that sounds good in your
room, which has its own particular frequency response, it is likely to sound very different in
other rooms. For example, if room has a severe lack of deep bass, we mixes will probably
contain too much bass as you incorrectly compensate based on what you are hearing. And if
someone else plays your music in a room that has too much deep bass, the error will be
exaggerated, and they will hear way too much deep bass. Therefore, the only practical solution is
to make your room as accurate as possible so any variation others experience is due solely to the
response of their room.
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6. CONSIDERATION IN DESIGNING THEATHER HALL
We must control the reverberation time on the stage. The reverberation time in the stage
area should be the same as in the house. Since the stage area might have a higher ceiling than the
rest of the theater, more absorptive materials might be required in this area. Frequently, the back
wall of the stage, and possibly one or both of the side walls, is treated with an acoustically
absorptive material, typically black in color. Recommended reverberation time is 1.0-1.3 seconds
(might be higher for some theaters, particularly for music performances). Although the seating
area will provide absorption, thereby reducing the reverberation time, we will most likely need to
add absorptive materials to the other surfaces within the space.
It is vital to control the reflections from the back wall. If we don't control them, the
presentation could reflect off the back wall and reflect back to the presenters. This won't
necessarily impact the audience, but could be disastrous and distracting for the people on stage.
Because of this, it's usually necessary to treat the back wall with an absorptive material. A
concave back wall could compound this problem. If you can't avoid a concave back wall, it's
imperative that it be treated with absorptive material.
Remember the space will be less absorptive when only half full, since the audience itself
is absorptive. By using absorptive seating areas, the reverberation time will remain more
consistent regardless of the audience size.
Splay or use irregular surfaces on the walls to avoid flutter echoes. Parallel reflective
surfaces can allow sound to "ricochet" back and forth between the surfaces. This potentially
annoying condition is referred to as standing wave or flutter echo. It is avoided by constructing
non-parallel surfaces or by adding absorptive materials to the surfaces. Plus, consider faceting
the ceiling to help with sound dispersion.
If there is a balcony, consider adding an acoustic treatment to its face to avoid slap back.
Persons seated deep under a balcony might experience auditory distortion. To avoid this, the
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balcony should be no deeper than twice its height. Ideally, the balcony should not be any deeper
than its height.
Even if everything else is controlled perfectly, the space might not be usable if the
background noise (e.g. HVAC system) is too loud. To help protect design, the NC level should
not exceed 20 to 35. When specifying NC, specify an actual rating, such as NC 20, rather than a
range, such as NC 20-30. Although specifying a lower number will ensure minimal background
noise, it might be cost prohibitive to achieve. Be realistic about the amount of acceptable noise
and the project's budget when specifying an NC level.
Beware of potential outdoor noise impacting your space. To do effectively, we must
address not only the STC or isolation quality of the exterior wall, but also for the possibly
weaker building elements, such as the windows, doors and HVAC systems. Noise from the lobby
area also can be disruptive. Be sure openings such as doorways are properly sealed. Consider a
vestibule door system.
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7. EXAMPLES OF THEATRE HALLS
There are many types of theatres requiring many different functions. There are theatres
for drama or speech, theatres for specific types of music such as opera or concert halls and
multipurpose theatre halls.
7.1 Istana Budaya (Drama Theatre Halls)
The most important requirement of a drama theatre is intimacy. It is essential for the
audience to see gestures and facial expressions of the performers. The distance from the stage to
the farthest seat should not exceed 65 feet. Where a larger audience is to be accommodated,
balconies and a fan shaped floor plan can be utilized. Another requirement is balcony depth
which the depth should not exceed twice the height of the opening. Shallow side balconies are
useful in providing diffusion and intimacy and for the room volume should be limited to 200
cubic feet per person.
For ceiling of theatre hall, it should be reflective and profiled to direct reflected sound to rear
parts of the hall and for the rear wall, it should use absorption to avoid delayed reflections.
Whereas for seating must use fabric covered seats which provide generally the same absorption
with or without the audience. The orchestra pit as shown in Figure 6 is another requirement of a
drama theatre.
Figure 6: An Orchestra Pit
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Figure 7: Istana Budaya
7.2 Royal Albert Hall (Music Theatre Halls)
Parameters that control Acceptability of Music Theatre Halls are Early Decay Time and
Clarity. Measurements in actual halls have revealed that 60dB decay may not be uniform. It is
the subjective sensation of reverberation that we call reverberance. It is the initial part of the
decay that correlates best with this subjective sensation of reverberance. Short EDT provides
clarity, and a long RT provides liveliness.
Clarity is the sound energy received at the listener in the first 80 ms while the late
reverberant energy is all energy arriving after 80 ms. Figure 5 shows the early decay time (ETD)
where it is the time associated with the early part of the decay process.
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Figure 8: Early decay time
7.2.1 Intimacy
Intimacy is the subjective impression of the size of the hall. The acoustical measure of
intimacy is the initial time delay gap (ITDG). It is the difference in milliseconds between the
arrival of the direct sound and the first reflection at the listener. The smaller this interval, the
more intimate the hall, or the more involved the listener feels with the performance.
7.2.2 Warmth
Warmth is a slight increase in low frequency (bass) reverberation has been identified as an
important requirement for music halls to provide warmth to music. Warmth is determined by
comparing low and high frequency reverberations, called the bass ratio (BR).
7.2.3 Loudness
Acoustically, loudness (G) is defined as the difference in sound pressure level at the center of
the hall due to a source minus the sound pressure level due to the same source in an anechoic
chamber 10 meters away from the source. Desirable G lies between 4.0 and 5.5 dB.
Uniform Decay Rapid Initial Decay/
Slow Later Decay
Slow initial Decay/Rapid Later Decay
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Figure 9: Royal Albert Hall
7.3 Multipurpose Theatre Halls
Most assembly halls designed today, are designed as multipurpose theatres. In such a theatre
that requires a concert hall on one occasion, a drama theatre, or a lecture hall on another, a great
deal of compromise is called for in the acoustical design criteria.
The designer must determine the foremost function of the hall, design the hall for that use,
and allow adjustments to be made in the hall to serve other uses. A multifunction hall should be
designed for a change in its reverberation characteristics by varying the absorption in the hall.
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REFERENCES
1. James Cowan.Architectural Acoustics Design Guide. Acentech.
2. Kleppe, J. (1989). Engineering applications of acoustics. Sparks, Nevada: Artech House.
3. Kinsler, L., Frey, A., Coppens, A., & Sanders, J. (Eds.). (2000). Fundamentals of acoustics
(4th ed.). New York: John Wiley and Sons.
4. Cyril M. Harris. "Noise Control in Buildings: A Practical Guide for Architects and Engineers",
1994.
5. L.L. Beranek, Concert Halls and Opera Houses:Music, Acoustics, and Architecture. New
York:Springer, 2004.
6. L.L. Beranek, Seeking Concert Halls Acoustic:IEEE Signal Processing Magazine:September
2007.
7. R.A Metkemeijer, The Acoustic of The Auditorium of the Royal Albert HAll Before and After
Redevelopment,May 2002.
8. Pompoli, Roberto; Prodi, Nicola (April 2000). "Guidelines for Acoustical Measurements
inside Historical Opera Houses: Procedures and Validation".