PROCEEDINGS of the
23rd International Congress on Acoustics
9 to 13 September 2019 in Aachen, Germany

Analysis of the Acoustic characteristics of a Museum of Modernist
Architecture - Art Museum of São Paulo Assis Chateaubriand
Marselle BARBO1; Eric BRANDÃO23
1,2

Universidade Federal de Santa Maria, Brasil

ABSTRACTThe architectural design involves the knowledge of variables of fundamental importance to a quality result.
Acoustically characterizing museums delivers design directives of these buildings according to the preceptsof acoustic comfort of the users. The museums have an important educational role, therefore valuing thesebuildings goes beyond the principles of museology, such as the rules for conservation of works. This work
deals with the acoustic characteristics analysis of the Assis Chateaubriand São Paulo Art Museum, located inSão Paulo city, Brazil, being the most important collection of European art in the Southern Hemisphere. The
architectural design of modernist style is authored by architect Lina Bo Bardi becoming a landmark of 20th
century architecture. The exhibition mode of the works, which instead of the traditional linear exhibition
through the installation of the works on the walls uses crystal easels in the middle of the gallery is also afeature that tells how avant-garde the design of this museum. The acoustic studies were performed throughsimulation of the three-dimensional model in computational software with comparisons between source
position and microphones and also the way of exposition of the collection. This work is part of a PhD researchthat is underway.
Keywords: Room Acoustics, Simulation, Museum

1.0 INTRODUCTION
An architecture design involves the knowledge of variables of essential importance for asatisfactory and quality result. The main activities developed in a building will demand a specificacoustic comfort program. In museums, the main activity is that of observation and introspection, sothat the interaction between people occurs between small groups.
This work deals with the needs related to museum acoustics - buildings that are of interest forroom acoustics, but which are not of critical audience. This work presents acoustic studies of the São
Paulo Art Museum, which has modernist architecture and is an icon of this movement in Brazil. The
results were obtained from acoustical simulations in a three-dimensional model. This study is an initialpart of a PhD research that is under development.
Acoustic parameters were evaluated, such as: Reverberation Time (RT), Early Decay Time (EDT),
Clarity (C80) and Definition (D50).
The Early Decay Time (EDT) analyzes the initial decay, using the first 10 dB of decay of the SPL.
This parameter has a strong relation with the reverberation perception of the listeners in the room.
The Clarity (C80) parameter analyzes the intelligibility of the articulations of the musical notes. It
is determined by the energy ratio of the impulsive response that reaches the listener in the first 80 ms
and from the 80 ms to its end (in decibel scale). In this way, clarity is a subjective term that describes
what the details of a musical performance are perceived in relation to the masking of details by thereverberant sound [1]. Although museums are not exactly places for musical performance, this activity
can happen in museums. The Definition (D50) index is the parameter that provides clues related tospeech comprehension. It is defined as the energy ratio of the impulsive response that reaches thelistener in the first 50 ms and the energy from the 0 ms to its end (in linear scale). The C80 and D50
parameters have typical values indicated at the standard ISO 3382:2009 [2], related to the average
12

marselleb@gmail.com
eric.brandao@eac.ufsm.br3967

between 500 and 1000 Hz. For Clarity (C80), this value lies between -5 and +5 dB. For the Definition(D50), the standard consider acceptable if it lies from 30% to 70% [2]. It is known that this is apercentage value and, the closer to 100%, the better speech intelligibility condition.
The well-being of museum visitors is an important condition in these buildings. This includes theacoustic comfort, which is a qualifying and indispensable item. It is necessary to note that theexperience of visitors involves attributes that go beyond formal, geometric and aesthetic issues [3].
Jónsdóttir [4] presented the study of three Danish museums regarding Reverberation Time,
Background Noise and Speech Transmission Index (STI). The author used computer simulations andinterviews. In addition, an analysis was made of the relationship between the STI and the privacy ofspeech. It was observed that there is a need for strict concerns regarding the privacy of discourse inmuseums. The need for privacy of speech was also pointed out in studies carried out in the Serralves
Museum, Portugal [3,4], since the very concept of museum induces an intimate and private
environment. There must be balance between privacy and intelligibility, items that have opposite
acoustical needs, but which are essential for the acoustic quality of museums. There is a consensus
regarding the shortage of scientific work involving museum acoustics.
The relevance of the modeling and optimization tools in the design process, as well as the
manipulation of the architectural elements in the preliminary study phase, provides support in the
search for solutions in buildings, especially with large volumes. The process of digital manipulationand creation of surfaces is like a work of craftsman, where the professional "sculpts" the materials
with the security of obtaining the desired acoustic characteristics of the room. The parameterization
between geometry and acoustics also provides the possibility of developing solutions with shapes
adequate for an architectural style. This is especially important in works of restoration andrevitalization of buildings, integrating acoustics with architecture [7].
The development of three-dimensional modeling tools provides a more intuitive and interactive
design process, giving the ability to shape the spaces with a good understanding of the sound behavior
in the environment. The use of computational tools enriches acoustic quality of buildings. It is possible
to reconstruct scenarios of the past, in order to study the conditions of the building, and to plan,
manipulate and design buildings with the acoustic solutions already aligned with architecturalcharacteristics. For this reason, several researches on acoustic simulation of rooms were undertaken[7-11].
1.1

MASP – São Paulo Art Museum
The São Paulo Art Museum is the first museum of modernist architecture in Brazil. Its foundation
was in 1947, where it occupied a building in the center of the city for twenty years. The famous
building that marked the history of Brazilian architecture, which is being studied in this work, wasinaugurated in 1968, becoming the definitive headquarters of MASP. The building has 11.000 square
meters divided into 5 floors. Its volumetry is a suspended by a porch that sustains 74 meters of span,
where at the time was established as the largest span in the world. It is an icon in the city of São Paulo.
In 1982 it was registered by CONDEPHAAT - Defense Council for the Historical, Archaeological,
Artistic and Tourist Patrimony of the State and in 2003 by IPHAN - Institute of National Historicaland Artistic Patrimony. Figure 1 shows an external image of MASP.

Figure 1. MASP. External view from Paulista Avenue.
Source: http://museubrasil.org/es/museu/masp-museu-de-arte-de-sao-paulo
Acces in 27-03-2019.

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This work approaches a permanent exhibition hall. It is a hall of 2.100 m² and a volume of 12.600
m³. The materiality of its interior is composed of concrete floor, whole glass envelope and slab inapparent concrete. Lina Bo Bardi combines in her architecture the rough and unfinished surfaces withlightness, transparency and suspension [12]. The great difference of this museum is in its form of
exhibition of the paintings. One of the most outstanding features of MASP is the exhibition model,
where the paintings are displayed on crystal easels (glass supports to expose paintings). The museum
is the only one in the world that adopts this radical system of exposing paintings, which were also
designed by the architect Lina Bo Bardi, integrated with the architectural design of the museum on
Paulista Avenue. One of the proposals were that the works were suspended in the air, where the themeis carried by a kind of forest of pictures. There is an approach of the public with works, becoming
more accessible, since there is no sequence of visualization of the works of art established, each visitor
defines his own course within the museum, of free form, between the easels. The finishing materials
are basically composed of concrete and glass. Figure 2 shows images of the interior of the permanent
exhibition room and glass easels with two points of view.

Figure 2. MASP. Permanent exihibition hall with crystal easels with two point of view.
Source: http://museubrasil.org/es/museu/masp-museu-de-arte-de-sao-paulo
Acces in 27-03-2019.

2.0 MATERIALS AND METHODS
2.1 Model and Simulation
In order to meet the objectives of this work, the acquisition of the results began with the threedimensional modeling of the room. Commercial software was used to model the museum.
With the three-dimensional model finalized, simulations of the acoustic conditions of the roomin the Odeon (version 11.23Combined) software were started.
The simulations were performed with two configurations of the museum. The first one, with the
crystal easels according to the expository model of the place. Afterwards, studies were carried out inthe hall without glass easels. Thus, it was possible to evaluate if there is interference in the acoustic
conditions by the configuration of the expository model.
From each finalized 3D model, the simulation was started in the Odeon (version
11.23Combined) software, with the following data:Omnidirecional sound sources;
Two source positions, in the region of the main entrance of the hall;Nine microphone positions for signal reception.
In both case scenarios, the microphones positioned at the same places, so that a comparison was
possible. Figure shows an image of the simulation with and without the easels. The first image shows
the two points of source (P1 and P2 in the image were “point of source”). The blue points are thereceiver microphone points. The second imagem shows only P1 because P2 is in off for the simulation,
but the position is equal the first image.

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Figure 3. Three-dimensional simulation with and without the easels

3.0 RESULTS AND DISCUSSION
The analyzes were performed from comparisons between source-receiver pairs and scenario
configuration (with and without easels). For each acoustical parameter there are three graphs. The
first graph is valid for the configuration without the easels and shows the results for the nearest
receiver microphone (RM1) and the farthest receiver microphone (RM9) for each of the sound sources.
The secong graph is the same as the first, but for the scenario with the easels. The third graph shows
the average results of the receivers ensemble for each point sound source (P1 and P2) with the tworoom exposure settings. The analyses from the farthest point to the nearest point of the source isjustified to check how much of the criteria is lost when moving away from the source. In addition, it
is also valid for the study of the influence of the easels in relation to the distance of the listener to thesource.
3.1 -Early Decay Time (EDT)The results of EDT are presented in the graphs of Figure . It is observed that at 63 Hz is where
the greatest results are presented, so that it is with the room without the easels that occur the largest,
reaching EDT around 7,5 seconds. Up to 1 kHz, there is a decrease of the EDT values in the room
without the easels. A secondary peak is found at 2 kHz band. When analyzing the result of the roomwith the easels, it is possible to detect nearer values between 125 Hz and 1 kHz frequency bands. The
secondary peak is also found in 2 kHz, but with a smaller value. The room without the glass easels
presents a harmonious relationship of results both in the microphone closest to the source and in thefarthest. This can be related to the diffraction of sound waves promoted by the easels, which tend to
make the sound field in the room more diffuse in that scenario. The diffraction is taken into account,at least, in part by Odeon. When the room is studied with the crystal supports, the most distant pointof the S2 source is that it presents the greatest results.
Early Decay Time without easel
RM1P1

RM9P1

7

RM1P2

RM9P2

8
7
6

5

5

EDT (s)EDT (s)

6
4

RM1P1

RM9P1

RM1P2

RM9P2

Early Decay Time_average
87

P1 with easel
P2 with easel
P1 without easel

6
EDT (s)8

Early Decay Time with easel

4

5
4

3

3

3

2

2

2

1

1

1

0

0
63 125 250 500 1000 2000 4000 8000

63 125 250 500 1000 2000 4000 8000

Frequency (Hz)Frequency (Hz)063 125 250 500 1000 2000 4000 8000
Frequency(Hz)Figure 4. Results of EDT. The first graphic is the exhibition hall without easel with two source
configurations. The second graphic is the exhibition hall with easel and with two source configurations. The
thirt graphic is the medium results with both sources and room settings.

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It is possible to observe that the configuration without the glass easels inside the enclosure is thatit presents the highest results up to the frequency of 2 kHz. For higher frequencies the EDT values are
more similar.
3.2 –Reverberation Time (RT)
The results of RT are contained in the graphs of Figure 5. It is possible to observe behavior similar
to the EDT, in which the 63 Hz Hz has the highest peaks, around 6,8 seconds. The Brazilian legislation
does not present an ideal RT for museums, because it is not a room of the critical audience. In a casestudy [5] at the Serralves museum, in the city of Porto (Portugal), with modernist architecture,designed by the architect Álvaro Siza, it was reported the difficulty of finding bibliography with RT
indicators ideal for museums. In this research mean values of RT (500, 1 kHz, 2 kHz), between 1,0
and 1,4 seconds were used as a guideline. These values were chosen according to a survey carried out
during the study but there is no standardization. However, the values used in this work may serve asa valid reference.
Higher RT values are found in the configuration of the room without the easels. In the frequencyof 500 Hz, slightly higher values were observed without the easels, around 3,9 seconds, while withthe supports these values were around 3,1 seconds. At 1 kHz the values are very close, around 3,4 s
without easels and 3,2 s with them. This greater proximity of values is also observed in 2 kHz, where
RT is observed between 4,8 and 5 seconds with and without easels, respectively. The distance ratio of
the microphone to the source is repeated as observed in the EDT responses, but in the case of the RT
it is possible to verify a greater proximity of the results. The closer results for RT are explained by
the fact that RT is found from the decay between -5 dB and -25 dB. On the other hand, the EDT is
obtained from decays between 0 dB and -10 dB. The initial decays tend to be more irregular than latedecays. For this reason, the EDT values tend to be more irregular than the RT values.

7

RM1P1

RM9P1

RM1P2

RM9P2

8

6
RT (s)

RT (s)

5
4

RM1P1

RM9P1

RM1P2

RM9P2

8

7

7

6

6
RT (s)

8

Reverberation Time_average

Reverberation Time with easel

Reverberation Time without
easel

5
4

P2 without easel

4

3

3

2

2

2

1

1

1

0

0

Frequency (Hz)P2 with easel

P1 without easel

5

3

63 125 250 500 1000 2000 4000 8000

P1 with easel

0
63 125 250 500 1000 2000 4000 8000
Frequency (Hz)63 125 250 500 1000 2000 4000 8000
Frequency(Hz)Figure 5. Results of RT. The first graphic is the exhibition hall without easel with two source configurations.
The second graphic is the exhibition hall with easel and with two source configurations. The thirt graphic is
the medium results with both sources and room settings.
When analyzing the averages, again the high similarity of the behavior of the curves with EDT
is observed, with the highest values presented in the situation of the room without the glass easels.
The frequencies of 500 Hz and 1 kHz present close values and both room and source settings, between
3,5 and 3,9 seconds. There is also the peak at 2 kHz, around 5 seconds and decreasing again at 4 and
8 kHz.
It is observed that the values are considerably above the indices taken as reference for this work,
which is between 1,0 and 1,4 seconds in the frequencies of 500 Hz, 1 kHz and 2 kHz. On the other
hand, this study did not reach the experimental phase yet, and model adjustment may be necessary.
Only the experimental part will determine if these parameters are higher than the recommendations.
3.2 –Definition (D50)
The results of D50 are shown in the graphs of Figure 6. It is observed that in the situation of theroom without the easels the results of D50 are larger for the closest microphones, not reaching 0,4 of3971

Definition (40%) up to the frequency of 4 kHz. The receivers closer to the source are more exposedto the direct sound and stronger first reflections. This feature will make the D50 increase much morethan for the most distant points. In the situation of the room with the easels, the results do not diverge
so much in relation to the position of the microphone, observing similar results in both the closest andthe most distant points, except for RM9 with P2. This can be again attributed to the diffraction ofsound by the easels, which tend to even out the sound in the room. In this configuration, the D50 does
not reach 0,3 (30%) between the frequencies of 250 Hz and 4 kHz. The mean results shows that theD50 only exceeding 0,3 at the 8 kHz frequency and high standard deviation, which is natural due tothe characteristic of this parameter.
Definition (D50) without easel
RM1P1

RM9P1

RM1P2

RM9P2

D50 (s)

1
0,9
0,8
0,7
0,6
0,5
0,4
0,3
0,2
0,1
0

Definition (D50) with easel
1
0,9
0,8
0,7
0,6
0,5
0,4
0,3
0,2
0,1
0

63 125 250 500 1000 2000 4000 8000

RM1P1

RM9P1

RM1P2

RM9P2

63 125 250 500 1000 2000 4000 8000

Frequency (Hz)Definition (D50)_average
1,0
0,9
0,8
0,7
0,6
0,5
0,4
0,3
0,2
0,1
0,0

S1 with easel
P1 without easel

S2 with easel
P2 without easel

63 125 250 500 1000 2000 4000 8000

Frequency (Hz)Frequency (Hz)Figure 6. Results of D50. The first graphic is the exhibition hall without easel with two source configurations.
The second graphic is the exhibition hall with easel and with two source configurations. The thirt graphic is
the medium results with both sources and room settings.
3.4 –Clarity (C80)
The results of C80 are shown in the graphs of Figure . It is noted that with the exception of 8
kHz, all results are negative, with averages ranging from -2,5 dB to -8 dB across all frequency bands.
The negative results means that there is less energy in the direct sound and first reflections than in thereverberant tail. Like the D50, the C80 is influenced by the source-receiver relationship. The
microphones farthest from the source have the greatest negative results in both positions. When
analyzing the results of the hall with the glass easels, there is a greater similarity of responses between
RM1P1, RM9P1 and RM1P2, so that RM9P2 presents a trigger of negatives values for C80.
Clarity (C80) without easel
RM1P1

RM9P1

RM1P2

RM9P2

4

RM1P1

RM9P1

RM1P2

RM9P2

Clarity (C80)_average

2,0

2

2

0

0

0,0

C80 (dB)

4

Clarity (C80) with easel

-2

-2

-2,0

-4

-4

-4,0

-6

-6

-6,0

-8

-8

-8,0

-10

-10

-10,0

-12

-12

63 125 250 500 1000 2000 4000 8000
Frequency (Hz)63 125 250 500 1000 2000 4000 8000
Frequency (Hz)P1 with easel

P2 with easel

P1 without easel

P2 without easel-12,0
63 125 250 500 1000 2000 4000 8000
Frequency (Hz)Figure 7. Results of C80. The first graphic is the exhibition hall without easel with two source configurations.
The second graphic is the exhibition hall with easel and with two source configurations. The third graphic is
the medium results with both sources and room settings.

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The average responses of C80 show predominantly negative results, considering that the room ishighly reverberant this is a result consistent with the other parameters.

3.0 CONCLUSIONSThis work approached the acoustic simulation in a three - dimensional model of a museum withmodernist architecture.
The results of Early Decay Time (EDT) and Reverberation Time (RT) were very similar, showingthat the room is highly reverberant. In both parameters, the simulations of the room with the glass
easels showed slightly lower values, indicating that the configuration with these elements allows asmall reduction in the results. RT ranged from 3,2 to 5,5 seconds at the frequencies of 500, 1 kHz and
2 kHz, well above values between 1,0 and 1,4 seconds for this frequency range [5]. In the experimental
phase, these results must be revisited and the model adjusted accordingly. On the other hand, it is afact that the architectural characteristics of the place, composed of concrete and glass, besides thelarge volume and the geometric shape contribute to these high values.
The results of D50 show a room with extremely low Definition factor, hardly exceeding 0,3 (30%)
of D50. Naturally, the results of the microphones closest to the fonts are superior to the more distantmicrophones. In the situation of the room with the easels, it is observed that the farthest microphone(RM9) with the source in the corner of the room (P2) is that it presented smaller D50 than the others.
This point is exposed to the highly reverberant field, which justifies this result. The Definition of thepermanent exhibition hall is low, however, it should be noted that museums are places of short-range
dialogues. On the other hand, it is important that there is at least an average room definition so that
audible warnings, especially in case of emergencies, are perfectly understood. This is a security issue.
The results of Clarity (C80) presented predominantly negative results, varying from -2,5 to -8 in
all frequencies, except for the frequency of 8 kHz. These results are in agreement with the high RT
found. It is not usual musical activities in this specific room of the MASP, therefore it is a parameterthat influences less in the comfort of the regulars of the place.
Finally, it can be affirmed that the simulations provided coherent answers to the situation of thebuilding, made of highly reflective materials and expressive volume.
It is also possible to observe that the simulations do not present a great difference in the acoustic
performance of the place with and without the glass easels. In addition, there is no other way of
studying how MASP glass easels can influence acoustic behavior other than with simulations, since
it is a permanent exhibit room, these elements do not leave the room. It is possible to understand thatthe building may present some acoustic problems due to the high RT, which may impair speech
intelligibility, privacy and comfort in general. Museums are not places for critical audience, so
conversations occur with people close to each other, but it is important to note that better D50 results
are important especially when audible warnings happen to the public.
This work is part of a doctoral research that is under development. These were the first results
about the simulations of this museum. Other studies are in continuation for detailed investigations of
the problematic that involves museum acoustics and experiments will be carried out in the near future.

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