Openairtheatre 141218040606 Conversion Gate02

8/17/2019 Openairtheatre 141218040606 Conversion Gate02

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Open Air Theatre


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• The defnition o the rows on thecavea horizontal reections betweencavea and proscenium. The soundwill in this case bounce back andorth between the vertical seat risesand the proscenium wall. These

reections will arrive at a listenerposition with a large delay andattenuation but will nevertheless

contribute to a long reverberation


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• When the cavea o the theatre is modeled as sloped suracesthe theatre will resemble the shape o an inverse cone. Thisshape will tend to direct most o the reections towards theopen sky and thereore the energy will dissipate uicklyleaving ew late reections.

• The di!raction and scattering e!ect rom the empty seats isnot usually considered important in computer simulations orooed theatres.

• "any strong reections rom the roo and side walls mask themuch lower energy coming rom scattering and di!raction.

• #ut in the case o the open$air theatres ewer strongreections are present and the gaps between strongreections in the impulse response have to be flled in with

scattered energy in order to get a smoother decay curve.• An abrupt decay curve with a ew strong reections makes it

very di%cult to estimate any acoustic parameter and can bemisleading .


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&esign details '

•

(election o site is is a critical point. topographical)meteorological and acoustical properties should betaken into consideration.

•(lope o seating should not be less than *+ degrees)or better audibility n visibility

•,oise level should not e-ceed / decibel.0.

(eating arrangement

speaker

(oundreection


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1ong term acoustic studies conducted in outdoor spaceshave shown that the basic principles o design include'

• minimisation o e-ternal noise 2noise protection3)

• harmonic development o the unctional elements o

the theatrical space within the limits o human vocaland acoustical scale)

• su%cient emergence o directly propagated sound andits reinorcement through early positive sound

reections 2rom the amphitheatre gradient andnatural loudspeaker response o the space3)

• control o late sound reections 2limitations o thereverberation time) eliminations o echoes3


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• The design o the new open air theatres goesback to the positive models o similarmonuments that have been preserved in the

contemporary urban plan. 4n order tooptimise advantages o acoustic design) theusual cases involving adverse sound

environments reuire the combined

e-ploitation o the advantageso open spaceplan and the limitation o the boundaries othe theatre space based on the model o5reco$roman theatre.


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6istoric Overview

Greek Theatre

• Open air

• Direct sound path

• No sound reinforcement

• Minimal reverberation

S: p. 78! ".#8.#7a


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overhang

(ound reecting

suraceActing arena

Orchestraarea

seating


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W67 T68 5988:( ;O


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• The key is the arrangement o the steppedrows o seats.

• "ost o the noise produced in and aroundthe theatre was probably low$reuencynoise) the rustling trees and murmuringtheatre$goers) or instance. (o fltering out

the low reuencies improves the audibilityo the perormers voices) which are rich inhigher reuencies) at the e-pense o thenoise. The cut$o! reuency is right where

you would want it i you wanted to removenoise coming rom sources that were therein ancient times.


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ArchitectBs 9ole

Source $ath %eceiver

sli&ht ma'or desi&n primaril( interest

in)uence


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Acoustical &esign

9elationshipsSite

*ocationOrientation

$lannin&

+nternal *a(out


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(ite

"actor(:

• ,lose to %%-/(

• Seismic


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1ocation

Take advanta&e of distance-barriers

Distance


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1ocation


Natural or Man0made 1erm


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1ocation


1uildin&


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Orientation

Orient 1uildin& for 2coustical2dvanta&e

$arkin& *ot "actor(

O3ce

Note: Sound is 40dimensional!check overhead for

)i&ht paths


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Mechanical vibration! ph(sical /ave orseries of pressure vibrations in anelastic medium

Described in ert5 6c(cles per second

%an&e of hearin&: 909!999 h5

(ound


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• An e%ciently designed orchestral shell is mandatory) oruniorm distribution o average sound level and the shellenables on stage audibility o a perormer .

• (ound amplifcation system should be provided or anaudience over ?//.

(ound 4ntensit


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(ound 4ntensity

ound po/er distributed over

an area

+$-2

+: sound 6po/er intensit(!;-cm

$: acoustic po/er! /atts

2: area 6cm


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9eector wall.


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9eection Caths o (ound

• The sound will in the case o the cavea horizontalreections between cavea proscenium bounce backand orth between the vertical seat rises and theproscenium wall. These reections will arrive at a

listener position with a large delay and attenuation butwill nevertheless contribute to a long reverberationtime.

• When the cavea o the theatre is modeled as slopedsuraces the theatre will resemble the shape o an

inverse cone. This shape will tend to direct most o thereections towards the open sky and thereore theenergy will dissipate uickly leaving ew late reections


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• "any strong reections rom the roo and sidewalls mask the much lower energy coming romscattering and di!raction. #ut in the case o theopen$air theatres ewer strong reections arepresent and the gaps between strongreections in the impulse response have to beflled in with scattered energy in order to get asmoother decay curve. An abrupt decay curve

with a ew strong reections makes it verydi%cult to estimate any acoustic parameterand can be misleading.


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• The unction o an open air theatre must ulflthe dual goal o ma-imising the advantageso acoustic design and minimising the e!ects

o noise pollution on the environment) anobDective that can be described with thesignal to noise ratio (E,. on the basis o apractical method or applying this acoustic

evaluation criterion) we shouldevaluate thespatial distribution o the revelant derivativevalues o FemergenceB and spectral density


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Openairtheatre 141218040606 Conversion Gate02

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