Acoustics Of theatre . Useful in arcitecture as well as civil.

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ACOUSTICS
THEATRE DESIGN
BY : ASHUTOSH GUPTA. VTH SEM
Introduction
Theatre or theater​ ​
is a collaborative form of fine art that uses live performers, typically
actors or actresses, to present the experience of a real or imagined event before a live
audience in a specific place, often a stage. The performers may communicate this
experience to the audience through combinations of gesture, speech, song, music, and
dance. Elements of art, such as painted scenery and stagecraft such as lighting are used to
enhance the physicality, presence and immediacy of the experience.Modern theatre
includes performances of plays and musical theatre. The art forms of ballet and opera are

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also theatre and use many conventions such as acting, ​costumes and staging. They were
influential to the development of musical theatre; see those articles for more information
Problems
The elements that are most often discussed in terms of optimizing the experience had by
the audience, by contrast, revolve around audience comfort. It must be recognized,
however, that not all designers of theatres see comfort as a prime value. It is often thought
that some discomfort assists in keeping audience energy high. It is also true that comfort is
a relative term. In one culture it might mean a mud-free surface on which to stand; in
another it might suggest large soft seats with much legroom and precise temperature
control. Comfort in a theatre also has both physical and social components. Physical
comfort involves the nature of the seating or standing area, the amount of space allotted to
each audience member, and the ease of access to the space. Physical comfort also includes
the ability of all audience members to see and hear a performance in the manner that their
culture has taught them is most desirable for the proper experience of theatre. It also
includes the maintenance of a certain level of safety.The location of the theatre within a
town or city is also a factor in social comfort, as the expected audience must feel that it is
proper for them to be in the area.
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Solution
Employing stepped seating arrangements, The first row of seats was on the same
level as the stage, the second row a little higher, the third row a little higher than the
second row, and so on, all the way to the back of the theater. the sound waves
bounce off of stepped or corrugated surfaces. In such structures, low-frequency
sounds are minimized.Thus, background noise such as the breeze blowing was
minimized and the sound waves coming from the front of the theater during a
performance could be heard from the
comfort of all of the rows of the theater’s
seating. Sound waves are either
absorbed by the material that they strike
or are reflected out, bouncing off of a
material. The key to sound acoustics is
striking a balance between construction
material and layout that will allow sound
waves to be absorbed or reflected in an
optimum way for the purposes of the building that being designed. The key is to
select materials and designs that screen out the wave frequencies that are not
desired in a space while amplifying those that the space is designed for.​The amount
of space required for each auditorium depends on a number of factors but the
following guides, based on modern seating design can give you an idea of the area
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needed:
● 200 seats: 270m² | 2,900 ft2
● 150 seats: 190m² | 2,000 ft2
● 75 seats: 125 m² | 1,350 ft2
The aisle is the space for walking with rows of seats on both sides or with rows of
seats on one side and a wall on the other. In order to improve safety when the
theaters are darkened during the performance, the edges of the aisles are marked
with a row of small lights. There are usually two types of aisle arrangements:
● The multiple-aisle arrangement :
It consists of 14-16 chairs per row with access to an
aisle way at both ends. If the aisle can only be
reached from one end of a row, the seat count may
then be limited to 7 or 8.
● The continental seating plan :
If planned carefully, the continental aisle arrangement
can accommodate more seating within the same
space. Usually, it requires an average of 7,5 square
feet (2,3 square meters) per person including the
seating area and the space for aisle-ways.
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The stage is the designated space where actors and other artists perform and the focal
point for the audience. As an architectural feature, the stage may consist of a platform
(often raised) or series of platforms. In some cases, these may be temporary or adjustable
but in theaters and other buildings devoted to such productions, the stage is often a
permanent feature. There are several types of stages that vary as to the usage and the
relation of the audience to them:
● Thrust theater:
A Stage surrounded by audience on three sides. The Fourth side serves as the background.
In a typical modern arrangement: the stage is often a square or rectangular playing area,
usually raised, surrounded by raked seating. Other shapes are possible; Shakespeare’s
Globe Theatre was a five-sided thrust stage.
● End Stage:
A Thrust stage extended wall to wall, like a thrust stage with audience on just one side, i.e.
the front. “Backstage” is behind the background wall. There is no real wingspace to the
sides, although there may be entrances located there. An example of a modern end stage is
a music hall, where the background walls surround the playing space on three sides. Like a
thrust stage, scenery serves primarily as background, rather than surrounding the acting
space.
● Arena Theatre:
A central stage surrounded by audience on all sides. The stage area is often raised
to improve sightlines.
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● The Proscenium Stage or End Stage :
It is the most common type of stage and it is also called ​picture frame stage. ​Its
primary feature is a large opening, the ​proscenium arch​ through which the audience
views the performance. The audience directly faces the stage and views only one
side of the scene. Often, a stage may extend in front of the proscenium arch which
offers additional playing area to the actors. This area is a referred to as the ​apron​.
Underneath and in front of the apron is sometimes an ​orchestra pit​ which is used by
musicians during musicals and operas.
In the Theater in the round or the Arena Stage Theater, the stage is located in the
center of the audience, with the audience members facing it from all sides. The
audience is placed close to the action, which provides a feeling of intimacy and
involvement. However, this type puts major restrictions on the amount and kind of
visual spectacle that can be provided for a
performance, because scenery more than
a few feet tall will block the audience view
of the action taking place onstage.
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A thrust stage is one that extends into the audience
on three sides and is connected to the backstage
area by its upstage end. A thrust has the benefit of
greater intimacy between the audience and
performers than a proscenium while retaining the
utility of a backstage area. The audience in a thrust
stage theater may view the stage from three or more
sides.
Flexible stage theaters are those that do not establish a fixed relationship between the
stage and the house. They can be put into any of the
standard theater forms or any of the variations of
those. Usually, there is no physical distinction
between the stage and the auditorium and the
audience is either standing, intermingling with the
performance or sitting on the main floor.
Although theater performances are a visual medium, poor sound quality will ruin even the
better plays. The sound is an area often overlooked but, just as you need good sightlines,
you also need good sound-lines.
Apart from the obvious comfort and
size considerations, it is imperative
that the auditoria are designed with
the following in mind:
● Internal sound insulation – this
is particularly important with
multiple screens where a loud
soundtrack can leak into the adjoining auditorium
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● Services and equipment noise control – noises such as air conditioning, lifts, toilets
and projection equipment need to be controlled.
● Acoustics – acoustic design in theaters should be considered from feasibility stage –
location, auditorium planning etc. through to final commissioning.
ABSTRACT :
The application of impulse response theory with architectural design principles provides a
foundation for the acoustical design of drama theaters, linking the perceptions of the
audience, acoustical measurements made in completed rooms, and acoustical modeling
and simulations of rooms being designed.
● Provide a quiet environment free from exterior and equipment noise;
● Design each interior surface of the room to be acoustically productive by having it
contribute essential elements to the idealized impulse response of a drama theater;
● Use layered architectural/acoustic systems that accomplish multiple functions
within one assembly that at once provides for sound reflection and diffusion of
sounds to the audience on its interior face, reduces sounds from outside the
building with its exterior skin, includes space for inlet and attenuation of return air
systems within wall cavities,allows transit of HVAC and building structural systems
within it, and has a variable layer at its outermost surface that can adjust the interior
acoustical response of the room for varying performance types. The construction of
the room impulse response element by element as the design of the theater
emerges allows a vehicle for the integration of architecture, acoustics, and
engineering systems to occur during design.
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CASE STUDY
TAGORE THEATRE, CHANDIGARH.
While the exterior presented a blank brick-walled, cuboidal structure, the interior of the
theatre, made in consultation with actors Prithviraj KapOor and Zul Vellani, was primarily
based on first of all a careful study of design issues like acoustics, sight-lines, size of stage in
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relation to the size of auditorium, optimal distance for un-aided facial recognition.
Secondarily, in its aesthetics, the origin yellow and red tapestries, the processional routes
entering the theatre were based on a Le Corbusier inspired "lexicon of cubism". Some
structural features, such as the massive steel trusses on the interior, were initially left
visible.
DETAILS :
The auditorium capacity of the Tagore Theatre is 600. Its plan consists of two square forms:
the larger one accommodating the auditorium,
foyer, booking office, etc., and the smaller,
stage, green rooms (there are eight dressing
rooms and two retiring rooms), properties,
reversal area, workshop, electrical installation,
air-conditioning etc. the acting area of the stage
is located at the meeting place of the two
squares. The entrance, foyer and booking, etc.,
are on the ground floor. Three flights of stairs
lead directly from the foyer into the auditorium
which is located right on top of it. The acoustics are designed to achieve the maximum
through reflected sound. The flanking walls on two sides of the stage reflect sound and so
also does the specially designed canopy, and
the two long side walls of the auditorium. Only
on the three areas wall surfaces has a novel
sound absorbing device been tried out: they are
lined with earthenware pots of various shapes
with necks and mouths of varying sizes opening
towards the auditorium. These pots absorb
sound by resonance, and this treatment, it is
stated, works out fairly cheap.
There is a lighting booth located inside the
auditorium as also equipment in front and
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around the stage to enable any quality of lighting to be provided, as required by a
particular performance. All the lights are on a dimmer-stat control.
Instead of the usual picture frame proscenium opening, there is an acoustic canopy which
provides design interest as well as reflects sound to the audience.
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