Applied Acoustics 140 (2018) 167–177

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Applied Acoustics
journal homepage: www.elsevier.com/locate/apacoust

Technical note

Architectural customized design for variable acoustics in a Multipurpose T

Auditorium
Maria Cairoli
Politecnico di Milano, Milano, Italy

A R T I C LE I N FO A B S T R A C T

Keywords: The use of auditoria for more than one purpose is far from new but the conscious design to accommodate more
Multipurpose Auditorium than one acoustic type of performance is relatively recent. It has become increasingly apparent that for economic
Auditorium acoustics reasons auditoria dedicated to just one single use are often unrealistic for big companies and also in large cities
Variable acoustics where a degree of flexibility in use is now becoming the norm from speech or music to theatre, performances and
fashion shows.
The possibility to find architectural solutions to control a variable acoustics within a big range is the main
interest in this discussion. Construction details are developed and their possible combinations of different cus-
tomized elements is reported, related to a specific case study: the Calzedonia Auditorium, a shoebox of
10.200 m3.
In literature there are general traditional guidelines to apply for large multipurpose rooms. Because in this
space the seats are totally removable and there are design features unique for it, some of these guidelines are
accepted and some are changed in relation with the requests of the client and considering also the possibility of a
new approach suitable for both speech and music in some special layouts and configurations.
Predicting situations are explained to create a methodological approach, according to the contemporary
multipurpose requests.
Numerous configurations, more than 12, with different combinations of the movable architectural element
positions have been recorded in the software depending on the number of seats in the room and activities to be
deployed.
Measures confirm the acoustic design, the client satisfaction the integrated Architecture.

1. Introduction The reciprocal influence among the numerous variable architectural

elements is explained to create an intriguing acoustic behavior ac-
In the case study presented, a rectangular hall designed as a multi- cording to the multipurpose requests.
purpose space, the acoustic answer control according to the single General traditional guidelines to apply for large multipurpose rooms
specific use and configuration is requested. [2], some of them are indicated below.
In traditional shoebox auditoria the predominant absorption is due
to the fixed stall. In this hall instead, seating and audience are re- 2. The head quarters Auditorium
movable, the floor becomes a reflecting surface, absorbent materials
and architectural systems with variable positions are added on the other The origins of the Auditorium of Calzedonia, the Italian-made un-
possible room surfaces. The number of seats and the volume change derwear known throughout the world, lie in precise design instructions.
significantly from a use’s configuration to the other. A space that reflects the company, one that is dynamic and sensitive to
Architectural construction details are developed and their acoustic the changes in society, a place which is capable of transmitting passion
characteristics are explained to create a methodological approach to and experience and stimulating creativity and inventiveness. Starting
find out variable acoustic architectural systems useful for multipurpose from an empty space a new interior architecture was requested, which
shoebox halls. had to be an expression of the new necessities.
The behavior described is predicted by computer simulation mod- The designer Enrico Moretti chose to interpret the outer wall as a
eling and confirmed with measurements on site. container of a dynamic space, a walled box made up of a parallelepiped

E-mail address: Maria.cairoli@polimi.it.

https://doi.org/10.1016/j.apacoust.2018.05.026
Received 25 October 2017; Received in revised form 29 May 2018; Accepted 30 May 2018
0003-682X/ © 2018 Elsevier Ltd. All rights reserved.
M. Cairoli Applied Acoustics 140 (2018) 167–177

Fig. 1. longitudinal section (the Auditorium Space is coloured green, curtains are coloured red, the foldable tent is coloured orange; the yellow area represent the
pivoting panels).

Volume 1 Volume 2

Fig. 2. first floor plan (the Auditorium Space is coloured green).

of 10.200 m3 ca. (Fig. 1), the typical shape of a shoebox, that can be stage with the speaker table)
divided into a two intercommunicating spaces (a first volume of Light can enter from the skylights on the roof, while the other ele-
5.600 m3 and a second volume of 4.600 m3) or remain a unique one ments can show differently coloured sides, which are white and black.
(Fig. 2). The pivoting panels can turn and change colour in a constructive jux-
Architectural elements and scene machinery are integrated as taposition.
acoustic solutions with which the other planning details interact. The colour transformation also encapsulates sound transformation.
The experience of a dynamic space is expressed through countless Especially in the passage from the white side to the black side, the pi-
possibilities that arise from mobile bridges and pivoting panels to au- voting panels take on different angles that influence the sound field.
tomatic curtains and a retractable wall. The Auditorium can house On the horizon of this evocative suggestion by Kandinsky, a project
maximum 1000 people, and it is characterised by a length of 60 m, which is integrated in all its parts has been developed to create a new
width of 19 m and it is 9 m height with lateral balconies on the left and idea of sound space. Losing the single focal point for the scene and the
right lateral walls at the height of 3,7 m. clear distinction between space for the speakers and audience, which is
It is an extremely flexible approach that makes this area genuinely typical in conference environments, in the Auditorium the acoustic
multipurpose (Figs. 3 and 4), and which mean it is constantly in touch quality is reached, independently of the position of the sound source
with the sometimes very varying requirements of a large company. and the audience.
In the centre of the volume there is an enormous hidden closure in Faced by the idea of the changeability of the space a new scenario of
the ceiling, a kind of foldable tent made of stiff panels. It lowers to timbre is created, which is more complex than that of a traditionally-
divide the parallelepiped into two separate rooms, thus creating two conceived space.
spaces which are independent in function and don't disturb one an- One rear wall borders with the foyer and the other with the back
other. Two main positions have been selected to house large removable stage.
stages and there is no lack of trusses, projectors and sophisticated au- At the sides of the Auditorium, other activities in other volumes take
tomated lighting systems for the show. place. They are independent in function and they don't disturb each
The green lines represent the public, the violet area represent the another. In the preliminary design concept the lateral spaces were

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Fig. 3. two congress centre layouts (the bigger volume and the two separated ones).

though as possible reverberant chambers for the Auditorium itself but sense of clarity. Additional lateral reflections therefore, which arrive
after different analysis this solution was not appreciated in comparison early enough to enhance speech intelligibility, can be viewed as bene-
with others. ficial for both uses.
Consequently, rooms designed for unamplified music require longer
3. Multipurpose Auditorium sound design reverberation times, higher volumes, lateral rather than overhead re-
flections, and high diffusion. Rooms designed for multipurpose uses
Recent recommended methods to design multipurpose auditoria require a judicious compromise between the needs of speech and music.
indicates acoustical properties that make a space good for speech often In literature there are general traditional guidelines to apply for
make it poor for music, and vise versa. By addressing this problem, the large multipurpose rooms [2], some of them are indicated below:
solutions to less extreme problems associated with other mixes of use
have to be considered. 1. The source should be elevated above the seated audience so that
Speech Intelligibility depends on a strong early sound related to the sight lines are clear of obstruction.
late reverberant part. For music the energy balance should be shifted 2. With unamplified music the singers or musicians should be aided by
towards the later sound. It means the reverberation time has to change. nearby reflective surfaces both overhead and on either side. Musical
For good speech intelligibility, room volumes and reverberation instruments supporting the singers should be located near them, so
times should be low and the first reflections should be primarily from there is no great time difference between the two.
the ceiling, and there is little need for diffusion; for music, instead, 3. The audience should be raked.
strong overhead reflections can be undesirable. 4. The room volume and absorption should be controlled to achieve a
For music reflections that arrive from the side provide a desirable reverberation time consistent with the program. Padded seating
sense of envelopment while enhanced early reflections increase the must be used to minimize the differences between the empty and

Fig. 4. Fashion show layouts and contemporary theatre and party layouts. Violet area represent the fashion show walkway, the yellow area represent possible stages,
the green lines are referred to the public.

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Table 1 method proposed by Johnson, Kahle, and Essert (1997)) was in-
basic limitations on reverberation time as function of programme in a vestigated. It controls the decay characteristics of the reverberation
Multipurpose Auditorium related to max seat capacity (for some uses the seats time in concert halls, incorporating partially coupled spaces and
number is bigger than in Calzedonia). keeping a certain degree of clarity. This method includes both the
Use Maximum seat capacity Optimum reverberation time (S) variable couplings and the variability in design features, i.e., both the
width and height of the hall and the strength of the early reflections and
Popular Music – < 1.0
it is referred principally to reverberant chambers as in Meyerson-
Drama Theatre 1300 0.7–1.0
Opera and Ballet 2300 1.3–1.8
McDermott Concert Hall in Dallas and the Crouse Hinds Concert
Chamber Music 1200 1.4–1.8 Theatre in Syracuse, New York [1]. After many evaluation studies the
Orchestral Music 3000 1.8–2.2 volume changes by using reverberant chambers incorporated around
the perimeter was however excluded.
To control the reverberation time by changing the total acoustic
occupied conditions. Room reverberation must be controlled to limit absorption, the audience seating area in relation to the variable number
the loudness of large groups of seats was considered, plus additional variable absorption in the rear
5. Background noise levels should be limited to NC 25. and lateral walls and in the ceiling.
The acoustic-architectural design began with a program, listing the
Because in the Calzedonia Auditorium the seats are totally re- various uses contemplated. Program definition allowed to know whe-
movable and there are design features unique for it, some of these ther to steer the design compromise toward the different configurations
guidelines are accepted and some are changed in relation with the re- and to associate to each of them an optimum reverberation time.
quests of the client and considering also the possibility of a new ap- The main uses identified are the following: conference centre,
proach suitable for both speech and music [3] in some special layouts. concert hall for natural music (for ensemble or chamber music), fashion
Furthermore the optimum reverberation time is related to programs show hall, cinema dossier space, ballroom with flat floor arrangement,
and different uses often require different seats arrangements (Table 1). and party lounge, a space adapted to include electro acoustic system.
Because of that the basic limitations on auditorium size related to the Every configuration is characterised by a specific layout with a different
maximum seat capacity owing to visual and acoustic constraints were seat capacity. In the theatre configuration the stage can occupy 200 m2,
considered [8]. in the fashion show configuration the audience area is reduced till 50%,
in the symphonic configuration the stage has to be big enough to be
4. Sound predicted behavior of the Auditorium Calzedonia occupied by the musicians and their instruments.
It means the maximal seat capacity of 1000 seats is reached just in
In the Auditorium Calzedonia project [4], the first goal was to the conference centre configuration.
achieve the necessary reverberation time change through architectural Most of the different configurations are related to a number of seats
solutions without considering a variable acoustics through electronics. that varies from 400 to 700.
At the beginning the Ircam project was also taken in consideration [5]. Because of that, in the project the variable acoustic answer is
Starting from the basic Sabine reverberation time equation: searched especially when the space is occupied for the 40–70% and it is
α expected to be much “stable” when the hall is fully occupied by 1000
T = 0.16. V / ∑ si people, it means when the main absorption surface is represented by
i people.
It is clear that the reverberation time T is a function of the audi- From the program, the reverberation time was related per seat,
torium volume divided by the total acoustic absorption. For that reason layout and volume in a variable range due to the possible seats capa-
there were two variables to hand in the acoustic design process: the citys’ flexibility (Tables 2 and 3).
auditorium volume and the total acoustic absorption [6]. Never the less In particular the Reverberation Time T30 is considered (this
to control the acoustic answer in new project it is also important to Reverberation Time is referred to the interval of −5 dB to −35 dB and
investigate the room shape. then it is interpolated to −65 dB).
A fan shaped room, for example, brings the audience close to the The high volume with applied absorption can control well the mid-
talker more than a rectangular box allowing a better speech compre- frequency reverberation because at high frequencies the reverberation
hension. On the contrary the rectangular box is more flexible for nu- time falls off naturally due to air absorption; at low frequencies dif-
merous layouts [12]. The Calzedonia Auditorium shape was affected by ferent absorbers have to be studied separately.
the existing building (a shoebox). To reach the warmth of its sound, necessary to musicians, a wood
Changing the auditorium volume by a substantial amount to divide floor on studs is chosen. Wood floors provide both beneficial support as
the unique space in two independent rooms plus an additional reduc- a sounding board in the low registers, as well as low frequency ab-
tion excluding the upper part of the ceiling where the skylights take sorption for airborne sound. The flooring is sufficiently light that it
place, was the final decision. It was considered that the minimum vo- responds to vibrations generated by the cellos and double basses, and
lume change worth considering is at least 10 per cent. provides tactile feedback to the musicians, but not so light that it ab-
Because of the possibility to create a bigger volume from two se- sorbs significant energy [16].
parated ones (and vice versa) and to include the sides spaces, also the Normally in large auditoria the biggest absorbing surface is the

Table 2
Design Target of Reverberation Time for the Auditorium Calzedonia at middle frequencies.
Program The bigger Volume (1 + 2) The two separated volumes 1 and 2

T30 [s] Lic [dB(A)] T30 [s] Lic [dB(A)]

Congress centre 0.9 < T30 < 1.3 LAF,MAX≤25 0.9 < T30 < 1.2 LAF,MAX≤25
Natural Music hall and fashion show 1.2 < T30 < 1.6 LAF,MAX≤25 1.2 < T30 < 1.5 LAF,MAX≤25
Cinema dossier/projections 1 < T30 LAF,MAX≤25 1 < T30 LAF,MAX≤25
Ballroom 1.1 < T30 < 1.4 LAF,MAX≤25 1.1 < T30 < 1.4 LAF,MAX≤25

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Table 3
main absorption coefficients.
Surfaces Materials Absorption coefficient [Hz]

125 250 500 1000 2000 4000

Internal surfaces of the light box polyester fibreboard coated with sound- 0,12 0,25 0,68 0,94 0,94 0,94
absorption plaster, density 60 kg/m3, sp. 50 mm
Perimeter ceiling around the skylights Polyester fibreboard panels, density 60 kg/m3, sp. 0,20 0,30 0,80 0,98 0,98 0,98
60 mm
Higher part of the lateral walls, behind the pivoting panels and on the upper part of Polyester fibreboard, density 60 kg/m3, sp. 0,25 0,33 0,85 0,98 0,98 0,98
the rear wall of the back stage 70 mm
Lower part of the lateral walls, under the balconies, covered with a transparency Low absorbing material, density 60 kg/m3, sp. 0,15 0,35 0,75 0,95 0,98 0,98
wall of woven fabric with wide weave, behind a low absorbing material 30 mm
Pivoting panels Aluminum on rigid steel structure 0,04 0,04 0,05 0,05 0,06 0,06
Audience Moderately upholstered chairs, absorption 0,51 0,64 0,75 0,80 0,82 0,83
coefficient per m2
Floor Wood on studs 0,28 0,21 0,15 0,12 0,11 0,11
Curtains Low porous material, installed as as a “bass trap” 0,25 0,55 0,3 0,25 0,2 0,18

seated audience. Because in this Auditorium the seats are removable reflecting big surface.
since some Auditorium uses don’t require them, many other absorbent The fix absorbing surfaces were distributed symmetrically on the
surfaces were searched. Anyhow it was decided to choose chairs with other surfaces.
thick padding whose absorption characteristics closely resemble that of The lower part of the lateral walls, under the balconies, were cov-
a seated occupant to not introduce another process variable as also ered with low absorbing material (αw = 0.35), the same solution was
suggested by Beranek [9]. utilized for the lower part of both the two rear walls. In that one con-
nected to the foyer the upper part was completed by a succession of
inclined windows for technical rooms while on rear wall connected
4.1. Architectural movable elements design for a variable acoustics with the backstage, pivoting panels with absorbing material behind
were installed.
In order to influence the reverberation time, the area of adjustable The surfaces of the ceiling between the light boxes are made of
absorption is very large, in fact comparable in size of the floor, con- inclined gypsum boards (reflecting panels). On the contrary the internal
sidering the removable seats. This made the variable absorption a surfaces of the light box are covered by absorbing material (αw = 0.65),
progressively more extravagant option in the design of the archi- windows excluded. The perimeter ceiling around the skylights and the
tectural-acoustic solutions. inclined panels is made of absorbing acoustic panels (αw = 0.80).
Before discussing the position choice of the different absorbing
materials, the physical realization of such architectural-acoustic solu-
tions are discussed. In fact it was difficult to locate both the fixed ab- 5. Prediction from computer simulations and results
sorbent materials and the movable elements to optimise the different
acoustic answers (see the “Prediction from computer simulations” In large halls, as in this case study, a longer reverberation time
paragraph). becomes necessary for music but it creates risks for speech it means
Motorized pivoting panels (Fig. 5) were located over absorber ma- high intelligibility is no more possible [2].
terials (αw=0.85 according to UNI EN ISO 11654) in the upper part of Introducing acoustic absorbing material is necessary, but this has
the lateral walls and on the upper part of the rear wall which is con- the additional effect of reducing sound level, which may be un-
nected with the back stage. acceptable for the lower reverberation time configuration (electro
The motorized panels can rotate: they can be vertical or reach an acoustic amplification excluded). Furthermore porous materials is
horizontal position. They can also stop at any intermediate positions to usually effective at mid frequencies but not at low frequencies.
provide different lateral reflections in intensity and direction. Another problem with variable absorption is the possible suppres-
They are made of curved steel plates with 30 cm depth and 3 m sion of early reflections.
high, there are distributed on 18 columns and 9 rows for each lateral Because of the possible radical reverberation time changes, the
wall. Every column of panels can be moved separately. areas of movable elements for variable acoustics required are con-
The most common technique in modern halls for variable absorp- siderable and comparable to the total area of 1000 seating.
tion to use acoustic curtains was here applied just on the ceiling under The lateral pivoting elements were located so that they influence
the skylight boxes but not in a traditional way. The curtains can be late reverberant sound and not early reflections. Curtains were installed
retracted from the auditorium and folded into boxes when not required to control the sound intensity of the overhead reflections.
(Fig. 6). Their application is unusual because the texture is heavy and Their location in the hall is symmetrical to make possible to change
made of plastic material (αw = 0.20). They are significantly less ab- the source position for different layout avoiding echoes and flutters and
sorbing in comparison to the upper part of the ceiling they mask. It is such that the effects of the movable elements on the acoustic filed
means the reverberation time increases when they are used, even if they remain the same in the unique space or the two separated ones.
reduce the active volume of the space. They are in number of 12 each at For the congress center use a specific layout for the source and the
2 m ca. of distance from the other. Each one cover a surface of 41 m2. seats is proposed, the one that optimize the STI values. The reflecting
They can be moved singularly. surfaces of the fordable tent is proposed behind the source to create first
To reduce the volume an enormous hidden closure is hidden In the order reflections. For other uses different source positions are possible.
centre of the ceiling, a kind of foldable tent made of stiff reflecting Computer simulation modeling was conducted using CATT-
panels. It lowers to divide the parallelepiped into two separate rooms, Acoustic.
thus creating two spaces which are independent in function and don't The absorption coefficients were known accurately.
disturb one another (volume 1 and 2 in Fig. 7). Most of absorbing materials’ coefficients are the measured values in
When lowered, the foldable tent made of stiff panels introduces a the reverberant room following the UNI EN ISO 354, in particular for

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Fig. 5. rotating panels on the balcony: drawing and preliminary render.

Fig. 6. curtains on the ceiling to hidden the skylight: transverse and longitudinal section.

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M. Cairoli Applied Acoustics 140 (2018) 167–177

Volume 1 Volume 2

Fig. 7. the foldable tent made of stiff reflecting panels in two different positions: lowered and stored.

the polyester fiberboard’s absorption coefficients and for the same pa- model the curved surfaces took place without any discretizing process.
nelcoated with sound-absorbing plaster. Many possible problems caused by side wall reflections [13] were
The internal surfaces of the light box are covered by the absorbing studied.
material polyester fibreboard coated with sound-absorbing plaster. Next to the reverberation time, other subjective and objective Room
The perimeter ceiling around the skylights and the inclined panels is acoustic Parameters were investigated but just the main ones are ex-
made of black polyester fibreboard panels. plained. From the configurations with the highest reverberation time
In the higher part of the lateral walls polyester fibreboard behind the configuration with the shorter reverberation time is studied trough
the pivoting panels and on the upper part of the rear wall of the back configurations that include different% of seating occupations and dif-
stage takes place. ferent positions for the movable architectural elements (pivoting pa-
The lower part of the lateral walls, under the balconies, are covered nels, curtains and the foldable tent made of stiff panels) studying the
with a transparency wall of woven fabric with wide weave and where effects of the single effects and the coupled ones.
behind there is a low absorbing material. The T30 values for different configurations are shown in the fol-
The pivoting panels are made of aluminum. Because of their rigid lowing table (Table 4).
internal structure, they don’t vibrate at low frequencies, it is supposed In the much more reverberate configuration (T30 – max) the pivoting
they reflect the sound in a large range of frequencies [17]. panels are vertical and all the curtains are under the skylight. In the less
Audience is on moderately upholstered chairs, data from the lit- reverberate configuration (T30 – min) the pivoting panel are horizontal
erature [15]. The floor is made of wood on studs [7]. and the curtains are stored to make active le absorbing surfaces of the
Curtains are made of a low porous material. They are considered as skylights.
membrane absorbers providing a sound absorptive resonant system. Those configurations are studied with different% of public. Other
They are mounted on a suitable frame anchored to a rigid wall. The T30 values for possible intermediate configurations are reported. The
sealed volume formed at its back offers an air spring compliance. less reverberate configurations are suggested for electroacoustic am-
Additional damping to that provided by the losses in the membrane and plification even if also intermediate configurations can be included
the losses due to the air pumping, where the membrane is attached to The variation of the reverberation time according to the position of
the battens, are given by adding the porous material at the top of the the pivoting panels and the curtains (the “bass traps”)is very wide in the
enclosed air space (the internal surfaces of the light box described empty room configurations in which the widest surface is represented
above). At middle and high frequencies the estimated absorption by the reflecting floor, while it tends to decrease gradually as the pre-
coefficient is that one measured in the reverberant room, at low fre- sence of the audience increases (Figs. 8 and 9).
quencies it is estimated considering the membrane acoustic behavior When the audience is 100%, in fact, the largest sound-absorbing
[18]. surface is represented by the spectators and the other areas influence
Curved surfaces discretization of the pivoting panels and scattering the parameter in a less significant way.
coefficient evaluation as Catt acoustic input were evaluated according In the configuration in which the auditorium is subdivided by the
to Vorlander [10] i.e. relevant scattering appear for frequencies re- fordable tent, the pivoting panels' potion and curtains’ position, it
ferred to a wave length that is around two times the dicertization means their sound absorption, become factors that most influence the
segment length (corrugation profile). Given the simplicity of the other reverberation time in both the two new environments, even in the
model surfaces the simulations are accurate and a scale modeling was presence of audience is equal to 100%, since the area occupied by pi-
considered not necessary [11]. The auditorium in fact is similar to a voting panels and curtains remains larger than the area occupied by the
shoe box and the only curved surfaces are represented by the pivoting public.
panels. It is useful to use scale model when many curved surfaces have Because porous material takes place behind the pivoting panels and
to be modeled. Their discretisation in fact introduce a sensitivity in the behind the curtains at the top of the enclosed air space, their influence
software: a different standard to model the curved surfaces can in- on the reverberation time can be partially erased one with the other in
troduce a significant output variation. On the contrary in the scale relation to their configuration. In the two separated volumes, the

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Table 4
predicted reverberation time for the Auditorium Calzedonia considering the max and min absorption on the surfaces in relation with the seats number.
Unoccupied configuration

T30-min (max absorbion in the hall) T30-max (min absorbion in the hall)
Layout Horizontal pivoting panels ( − −), hidden curtains(Ø) Vertical pivoting panels (||), horizontal curtains (E)
125 Hz 250 Hz 500 Hz 1 kHz 2 kHz 4 kHz 125 Hz 250 Hz 500 Hz 1 kHz 2 kHz 4 kHz
The bigger Volume (1 + 2) 1,87 2,22 1,81 1,54 1,42 1,02 2,04 2,51 2,05 1,84 1,7 1,28
Volume 1 1,58 1,95 1,71 1,41 1,3 1,03 1,86 2,35 1,97 1,71 1,63 1,24
Volume 2 1,52 1,89 1,62 1,35 1,3 1,03 1,8 2,1 1,83 1,6 1,53 1,2

50% occupied configuration

T30-min (max absorbion in the hall) T30-max (min absorbion in the hall)
Layout Horizontal pivoting panels ( − −), hidden curtains(Ø) Vertical pivoting panels (||), horizontal curtains (E)
125Hz 250Hz 500Hz 1kHz 2kHz 4kHz 125Hz 250Hz 500Hz 1kHz 2kHz 4kHz
The bigger Volume (1+2) 1,48 1,79 1,42 1,15 1,1 0,84 1,63 1,86 1,65 1,38 1,21 0,95
Volume 1 1,37 1,57 1,33 1,13 1,01 0,85 1,48 1,64 1,4 1,23 1,1 0,89
Volume 2 1,27 1,58 1,32 1,11 1,02 0,83 1,49 1,7 1,45 1,24 1,12 0,95

100% occupied configuration

T30-min (max absorption in the hall) T30-max (min absorption in the hall)
Layout Horizontal pivoting panels ( − −), hidden curtains(Ø) Vertical pivoting panels (||), horizontal curtains (E)
125Hz 250Hz 500Hz 1kHz 2kHz 4kHz 125Hz 250Hz 500Hz 1kHz 2kHz 4kHz
The bigger Volume (1+2) 1,47 1,59 1,27 1,12 1,07 0,84 1,61 1,85 1,6 1,35 1,14 0,91
Volume 1 1,32 1,48 1,26 1,08 0,99 0,81 1,42 1,58 1,41 1,2 1,13 0,88
Volume 2 1,25 1,41 1,17 1,05 1 0,82 1,44 1,56 1,37 1,22 1,11 0,91

greatest increase of the reverberation time it is due to the position of the correspondence with the simulated sceneries.
curtains, when they are horizontal. Because of their membrane beha- The measurements include three source locations for every config-
vior, they can increase the reverberation time without increasing to uration, two positions 6 m far from the two rear walls and one near the
much the Bass Ratio BR (Table 5). centre (1 m far from the longitudinal symmetric axis). The receivers are
in number of 14 homogenously redistributed (on the left side only) for
6. Measures the bigger volume and 7 for the volume 1 and 2. The microphone is
placed at a height of 1.2 m above the floor level.
During the realization process and before inauguration acoustic The reverberation time T30 and other Room Acoustics descriptors
tests were executed. [16–18] are detected. Measurements are carried out in the absence of
The main reference from which the measurement methodology and public at a temperature of 19 °C, 45% humidity. Omnidirectional sound
procedures were taken is the UNI EN ISO 3382 [14] standard, in- source (dodecahedron). The measurement technique used is the classic
tegrating some aspects to best define the environment in terms of both impulse response produced by sine sweep signal, generated with three
its main uses (speech and music)and secondary ones (fashion shows and different software. For comparative purposes.
contemporary performances). For summary purposes only the average values of the T30 in octave
In the measures here shown, the hall is empty and the floor free bands are reported.
from seats (no chairs installed) to better test the acoustic behavior of Curtains, when spread under the skylights, contribute to the re-
the customized principal architectural element with variable acoustic verberation field from 250 Hz. At all the lower frequencies they behave
answer, it means the pivoting panels and the curtains and to check their as “bass traps”, since they are not rigidly fixed to the side edges and

Fig. 8. Bigger Volume (Vol tot): predicted Reverberation Time T30 exponential tendency (related to the max and min absorption surfaces and an increasing per-
centage% of seats occupation).

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M. Cairoli Applied Acoustics 140 (2018) 167–177

Fig. 9. Sources positions. Blu sources: sources for volume 1 and for the bigger volume 1 + 2; Orange source: source for volume 1; Green source: source for the bigger
volume 1 + 2; Yellow source: source for volume 2; red source: source for volume 2 and for the bigger volume 1 + 2, white rectangular figures: receivers positions.

T30 volume 1+ 2 they can vibrate dissipating energy.

3 Pivoting panels affect the reverberation field from 500 Hz. The
measurements confirm the simulations trend: when the pivoting panels
2.5 is are in a horizontal position, their sound absorbing contribution is
Expon. (T2 (n°7)) maximum, while it is minimal when positioned vertically. Its bent
2
Expon. (T1 (n°8)) shape also introduces a diffused field that contributes to the homo-
1.5 geneity of the acoustic response throughout the environment. Usually,
s

Expon. (Tmax (n°9))

in fact, the spherical wave front from a point source tend to become
1 Expon. (T3 (n°10)) plane waves at greater distance from the source. Reflections of plane
wave front of sound from a solid convex surface tends to scatter the
0.5
sound energy in many directions. This amounts a diffusion of the im-
0 pinging sound.
125 Hz 250 Hz 500 Hz1000 Hz2000 Hz4000 Hz Other different inclinations of the pivoting panels also give sig-
nificant changes in the reverberation time, more than 1 JND as shown
T30 volume 1 in the table below.
2.5 Unfortunately there was no possibility to make measurements with
the public inside and/or with installed scenography.
2 From tab. 6 and Fig. 10 it is possible to understand better how the
Expon. (T2 (n°6)) movable acoustic elements (pivoting panels and curtains) “play their
1.5 rule” in relation with the different configurations and the curtains po-
Expon. (Tmin (n°6b))
s

sition. In the configurations with the highest Reverberation Time trend,

1 Expon. (Tmax (n°1))
it means with horizontal curtains (columns 1–4 and 9–10 in Table 5),
Expon. (T3 (n°2)) the different pivoting panel positions influence the T30 values especially
0.5
at middle and high frequencies see (Tables 6 and 7).
When curtains are in hidden position, the auditorium ceiling is very
0
absorbent at middle and high frequencies and the absorption variation
125 Hz 250 Hz 500 Hz 1000 2000 4000
Hz Hz Hz referred to different pivoting panels positions are less effective, espe-
cially in the bigger volume (1 + 2).
Fig. 10. measured Reverberation Time T30 related to the Table 6. When the pivoting panels are in horizontal positions, the absorbing
material is visible in the room form the gap between two sequential

Table 5
The T30 according to the seats number referred to different possible uses of the hall.
Possible uses according to Table 2 Fully occupied bigger Volume1 + 2 50% Occupied bigger volume1 + 2 Unoccupied bigger volume1 + 2

T30 min Average T30 max Average T30 min Average T30 max Average T30 min Average T30 max Average
500–1000 Hz 500–1000 Hz 500–1000 Hz 500–1000 Hz 500–1000 Hz 500–1000 Hz

1,18 1,47 1,28 1,52 1,65 1,95

Fashion show (1.2 < T30 < 1.6) x x x x x
Congress (0.9 < T30 < 1.3) x x
Natural Music(1.2 < T30 < 1.6) x x x x x
Ballrooms (1.1 < T30 < 1.4) x x x
Cinema 1 < T30 *with a x*
supplementary absorbing
curtains

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M. Cairoli Applied Acoustics 140 (2018) 167–177

Table 6
measured T30 in different configurations (Pivoting panel position: vertical II, Horizontal –, 45° ⧹ /, 135°/ ⧹).
Unoccupied configuration

Hidden curtains Horizontal curtains

N° 125 250 500 1000 2000 4000 N° 125 250 500 1000 2000 4000
Vol.1 5 /⧹ 1,9 2,03 1,38 1,18 1,15 0,99 4 /⧹ 1,83 2,16 1,43 1,63 1,58 1,28
6 II 1,95 2,15 1,43 1,24 1,22 1,12 1 II 1,73 2,27 1,46 1,79 1,67 1,39
6b – 1,9 2,1 1,31 1,1 1,02 0,98 2 – 1,69 2,1 1,44 1,61 1,62 1,32
– 3 ⧹/ 1,81 2,21 1,44 1,65 1,59 1,3
biggerV.1 + 2 7 II 1,82 1,75 1,34 1,25 1,22 1,09 9 II 1,96 2,4 2,1 1,87 1,69 1,28
8 __ 2,03 2,07 1,36 1,23 1,22 1,05 10 __ 1,98 2,07 1,69 1,58 1,47 1,15

Table 7 7. Conclusions
comparison between predicted and measured T30 values (yellow cells indicate a
variation bigger than 1 JND). Numerous configurations, different from each other for the in-
The bigger volume (1 + 2) clination of the panels and for openings in different numbers of ceiling
curtains, have been recorded in the software for the management of the
Configuration 1: Horizontal pivoting panels ( − −), hidden curtains(Ø) mobile architectural elements, depending on the number of seats in the
room and activities to be deployed.
Simulated values 1,87 2,22 1,81 1,54 1,42 1,02
Misured values 2,03 2,07 1,36 1,23 1,22 1,05 In total more than 12 configurations were automated. It is believed
JND 1.5 1 6 5 3 0 that such a large number of scenarios can hardly be achieved without
Configuration 2: Vertical pivoting panels (||), horizontal curtains (E)
introducing customized elements with both aesthetic and acoustic
Simulated values 2,04 2,51 2,05 1,84 1,7 1,28 function.
Misured values 1,96 2,4 2,1 1,87 1,69 1,28 Simulations, made on a simple model (which is very close to a shoe
JND 1 1 0,4 0,4 0 0 box with two balconies and pivoting panels spread to the top of the side
Volume 1
walls, as well as a ceiling with a subsequent pattern of broken lines
Configuration 1: Horizontal pivoting panels ( − −), hidden curtains(Ø) among the horizontal curtains) are consistent with the measurements,
Simulated values 1,58 1,95 1,71 1,41 1,3 1,03
and the T30 trend is confirmed. At 125 and 250 Hz where measurements
Misured values 1,9 2,1 1,31 1,1 1,02 0,98
JND 3 1 −6 5 5 1 show a little greater absorption of the curtains in comparison with the
predicted values trough the simulation, because of their “bass trap”
Configuration 2: Vertical pivoting panels (||), horizontal curtains (E)
Simulated values 1,86 2,35 1,87 1,71 1,63 1,24
behavior that is much more evident in the measured values.
Misured values 1,73 2,27 1,46 1,79 1,67 1,39 When curtains are in hidden position, the auditorium ceiling is very
JND 1.5 1 5 1 0 2 absorbent at middle and high frequencies and the absorption variation
referred to different pivoting panels positions are less effective, espe-
cially in the bigger volume (1 + 2).
panels. It means, a percentage of sound is also still reflected by the The importance of inserting several mobile elements allows, in any
panel surfaces. Because of that the absorption efficacy for the pivoting case, to manage different layouts by controlling, for each configuration,
panels variable system is less than that one of the curtains variable the entire frequencies range (from 125 to 4000 Hz).
system in which the absorption material can be totally efficient. Installing porous materials behind rotating pivoting panels and
In comparison with the predicted values in the simulation analysis, behind translating curtains, that means high absorption materials be-
in the reality the T30 range in the unoccupied hall is much more spread: hind reflecting ones, give in fact the possibility to combine their ab-
.1.9 < T30 < 1.3 ca sec. This result is an advantage for activities in sorption effects in relation to the movable elements’ position.
which the speech comprehension is important (cinema, congress) and This customized Design of Acoustic and Architectural Solutions
also for configurations in which electroacoustic equipment is required. generates the opportunity to increase or reduce seamless the sound-
In configurations in which the natural music is requested, it is suggested absorbing properties of the auditorium surfaces within a preset range
to hidden some curtains, (increasing of the public it increases the (when the variable acoustic elements are in the total reflecting position
number of hidden curtains) starting from that ones that are much more or in the totally absorbing position).
far from the source. For example, with the presence of 50% public an The big advantage is that it is possible, every time, to find the most
automated configuration require two hidden curtains. suitable acoustic response of the Auditorium Room depending on the
For completeness of the analysis, the comparison between the si- event is played inside in a very simple way.
mulated and the measured values is shown in the following table and The integrated design, where architectural elements can handle
expressed trough the JND (just noticeable difference) (tab. 7). The acoustics, should not be experienced as a limit to acoustic design, but as
variation of 1 JND is equal to a 5% of variation of the T30 parameter a positive and enriching challenge for new possibilities and to achieve
value. more satisfying goals linked to new dynamic requests of the society, as
It follows that, although some measured absolute values of T30 are this case study testifies.
different from the simulated ones, the TR trend related to the different
variable acoustic elements is confirmed both by simulations and mea-
sures. Acknowledgements
The bigger differences of the trend between the simulated and
measured values are found in the configurations in which the pivoting Considerable thanks to Enrico Moretti who gave the big opportunity
panels are in horizontal position. to follow the project and its realization. Thanks also to Andrea Pozzi
It means the simulation model with horizontal panels could be who conducted the computer simulations.
improved.

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M. Cairoli Applied Acoustics 140 (2018) 167–177

References [9] Leo Beranek -Concert Halls and Opera Houses – Springer.
[10] Auralization – Vorlander M. (2008) RWTH p. 45.
[11] Rindel JH, Modelling in auditorium acoustics – from ripple tank and scale models to
[1] Architectural Acoustics. Blending Sound Sources, Sound Fields, and Listeners – computer simulations, in: Jordan NV, Rindel JH, Gade AC. (eds.) Revista de
Ando Y. (1998) Springer p. 193. Acústica 2002, Vol. XXXIIl No 3–4, p 31–35.
[2] Architectural Acoustics – Long M. (2014) 2nd Ed. Academic Press p. 697. [12] Springer Handbook of Acoustics: Chapter 9 – CCRMA.
[3] Barron Mike. Sven Kissner “a possible acoustic approach for multi-purpose auditoria [13] Jeona Jin Yong, Kim Jae Ho, Ryu Jong Kwan. The effects of stage absorption on
suitable for both speech and music”. Appl Acoust 2017;115:42–9. reverberation times in opera house seating areas. J Acoust Soc Am 2015;137:1099.
[4] Maria Cairoli, Daniele Stefanoni, Lo spazio del suono – Moretti e Vitali (2017) [14] UNI – Acoustics – Measurement of room acoustic parameters - Part 1: Performance
section II. spaces (ISO 3382–1:2009).
[5] Ergan M.D.J – Architectural Acoustics (2007) Ross Publishing p. 135. [15] Kuttruff H. – Room Acoustics – (2009) 5th Ed. Spon Press p. 192.
[6] Michel Hans, Myers Joseph. Increasing liveness and clarity in a multipurpose civic [16] Long M. Architectural Acoustics. Elsevier Academic Press p. 724.
center. J Acoust Soc Am 2016;140:3294. [17] Absorption coefficients www.akustik.ua.
[7] Ermann M.A. – Architectural Acoustics Illustrated – (2015) Wiley p. 38. [18] Kleiner M, Tichy J, Acoustics of Small Rooms CRC Press. 2014. p. 151.
[8] Auditorium Acoustics and Architectural Design – Barron M. (2009) 2nd Ed. Spon
Press cap. p. 10.

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