Citation: Yang, Y.-N.; Zhou, J.; Song,
J.-R.; Wang, X.-P.; Xu, X.-H.; Li, Y.-X.;
Zeng, J.-C.; Sa, Y.; Jiang, W.
Architectural Physical Acoustic
Environmental Design Transformation
of Academic Lecture Halls in the
Universities—Taking the Hall of
School of Architecture and Urban
Planning of Yunnan University as an
Example. Buildings 2024,14, 1583.
https://doi.org/10.3390/
buildings14061583
Academic Editor: Antonio Caggiano
Received: 4 May 2024
Revised: 21 May 2024
Accepted: 27 May 2024
Published: 30 May 2024
Copyright: © 2024 by the authors.
Licensee MDPI, Basel, Switzerland.
This article is an open access article
distributed under the terms and
conditions of the Creative Commons
Attribution (CC BY) license (https://
creativecommons.org/licenses/by/
4.0/).
buildings
Article
Architectural Physical Acoustic Environmental Design
Transformation of Academic Lecture Halls in the
Universities—Taking the Hall of School of Architecture and
Urban Planning of Yunnan University as an Example
Yao-Ning Yang 1,2,3, Jie Zhou 1, Jing-Ran Song 1, Xin-Ping Wang 1, Xiao-Huan Xu 1, Yuan-Xi Li 1,
Jun-Cheng Zeng 4,5, Ying Sa 1,* and Wei Jiang 6,*
1School of Architecture and Urban Planning, Yunnan University, Kunming 650500, China;
[email protected] (Y.-N.Y.)
2Institute for Urban Design and Sustainable Urban Planning, Technical University of Berlin,
10623 Berlin, Germany
3Key Laboratory of New Technology for Construction of Cities in Mountain Area, Chongqing University,
Chongqing 400045, China
4College of Engineering Sciences, Hanyang University ERICA, Ansan 15588, Republic of Korea
5School of Architecture and Urban Planning, Huazhong University of Science and Technology,
Wuhan 430074, China
6School of Materials Science and Engineering, Tongji University, Shanghai 201804, China
*Correspondence: [email protected] (Y.S.); [email protected] (W.J.); Tel.: +86-139-0885-0951 (Y.S.);
+86-137-6116-6956 (W.J.)
Abstract: In recent years, multi-functional lecture halls have developed rapidly and become a symbol
of contemporary public spaces and places. This kind of spatial facility that brings together the advan-
tages of land intensiveness and multi-functional integration also faces feedback such as poor acoustic
effects. However, current research rarely involves the architectural design perspective, which is
actually the root consideration of this problem; that is, how to set up corresponding spatial layout mea-
sures to optimize acoustic performance in a relatively economical and simple way. This study uses the
academic lecture hall of the School of Architecture and Planning of Yunnan University as a case to try
to solve these problems. The research is based on holistic considerations, starting from site selection,
architectural design, aesthetic considerations, and environmental noise assessment, and combining
simulation results with actual measurement results. Using a
prediction–comparison–verification
method, key acoustic parameters such as speech intelligibility, loudness, and reverberation time were
calculated and evaluated to understand the acoustic design problems of the hall. The study found
that the out-of-control reverberation time was the main cause of poor acoustic feedback, and based
on this, optimization and transformation were carried out from an architectural perspective. Finally,
a renovation suggestion was made that the application of sound-absorbing materials on the rear
wall can achieve better acoustic effects inside the hall. Among the space combination methods, the
combination of “rear wall, central ceiling, and front ceiling” has the best effect. Practical insights are
provided for improving the acoustic performance of the multi-functional lecture halls while taking
into account the acoustic design and feasible requirements.
Keywords: multi-functional lecture halls; acoustic environment; architectural design; acoustic restoration
1. Introduction
Multi-functional lecture halls and comprehensive auditoriums have emerged as pivotal
components within contemporary infrastructural developments. Particularly in locales
characterized by land scarcity and fiscal prudence, the establishment of expansive facilities
endowed with acoustically refined attributes to accommodate large gatherings stands as a
Buildings 2024,14, 1583. https://doi.org/10.3390/buildings14061583 https://www.mdpi.com/journal/buildings
Buildings 2024,14, 1583 2 of 20
judicious choice. This architectural typology finds expression in educational institutions
and municipal entities (Liang et al., 2021) [
1
], wherein these spaces are meticulously crafted
to facilitate a myriad of activities ranging from scholarly discourse and deliberative sessions,
to the dissemination of lectures and presentations, alongside provision for multimedia
engagement and training endeavors. For instance, the Clifton Court Hall within the
precincts of the University of Cincinnati’s College of Arts and Sciences exemplifies a pivotal
nexus for scholarly dialogue and communal interaction, fostering an array of communal
and collaborative zones alongside dedicated team rooms (Bennett, 2001) [2].
Against the backdrop of burgeoning higher education pursuits in developing nations,
the exigencies placed upon academic lecture halls within university settings have witnessed
an augmenting trajectory, both in terms of functional efficacy and spatial magnitude [
3
]. In
China, in particular, it has been seen that the construction of lecture halls has peaked in
the last two decades, and much new research has been generated on how to design these
venues [
4
,
5
]. Budiaková[
6
,
7
] and Zhao Juan [
8
] proposed the optimization design strategy
of lecture halls from the perspective of ventilation, Chen Xi [
3
] proposed the design guid-
ance for academic lecture halls in universities from the perspective of environmental design,
and Huang Hui [
9
] kept eyes on the topic of the spatial design of lecture halls. However,
in recent years, the number of publications in this field in China has been decreasing year
by year and this topic is seemingly getting less attention than before (see Figure 1below).
In an era of rapidly changing materials and technologies, the reclaiming of the academic
lecture hall is an issue that needs to be emphasized by architectural researchers.
Buildings 2024, 14, x FOR PEER REVIEW 2 of 22
1. Introduction
Multi-functional lecture halls and comprehensive auditoriums have emerged as piv-
otal components within contemporary infrastructural developments. Particularly in lo-
cales characterized by land scarcity and fiscal prudence, the establishment of expansive
facilities endowed with acoustically refined attributes to accommodate large gatherings
stands as a judicious choice. This architectural typology finds expression in educational
institutions and municipal entities (Liang et al., 2021) [1], wherein these spaces are metic-
ulously crafted to facilitate a myriad of activities ranging from scholarly discourse and
deliberative sessions, to the dissemination of lectures and presentations, alongside provi-
sion for multimedia engagement and training endeavors. For instance, the Clifton Court
Hall within the precincts of the University of Cincinnati’s College of Arts and Sciences
exemplifies a pivotal nexus for scholarly dialogue and communal interaction, fostering an
array of communal and collaborative zones alongside dedicated team rooms (Bennett,
2001) [2].
Against the backdrop of burgeoning higher education pursuits in developing na-
tions, the exigencies placed upon academic lecture halls within university settings have
witnessed an augmenting trajectory, both in terms of functional efficacy and spatial mag-
nitude [3]. In China, in particular, it has been seen that the construction of lecture halls
has peaked in the last two decades, and much new research has been generated on how
to design these venues [4,5]. Budiaková [6,7] and Zhao Juan [8] proposed the optimization
design strategy of lecture halls from the perspective of ventilation, Chen Xi [3] proposed
the design guidance for academic lecture halls in universities from the perspective of en-
vironmental design, and Huang Hui [9] kept eyes on the topic of the spatial design of
lecture halls. However, in recent years, the number of publications in this field in China
has been decreasing year by year and this topic is seemingly getting less attention than
before (see Figure 1 below). In an era of rapidly changing materials and technologies, the
reclaiming of the academic lecture hall is an issue that needs to be emphasized by archi-
tectural researchers.
Figure 1. The number of studies on hall buildings in China has declined in recent years.
Meanwhile, due to the specific use of lecture halls, most countries have comprehen-
sive or specialized codes designed to guide architects in creating the best acoustical envi-
ronment in these spaces. These guidelines, such as those outlined by the World Health
Organization (WHO, 1999) [10], the Architectural Institute of Japan (Fukuchi & Ueno,
2004) [11], the Australian/New Zealand Standard [12], and the German Institute for Stand-
ardization [13], advocate for high levels of acoustic absorption and short reverberation
Figure 1. The number of studies on hall buildings in China has declined in recent years.
Meanwhile, due to the specific use of lecture halls, most countries have comprehensive
or specialized codes designed to guide architects in creating the best acoustical environment
in these spaces. These guidelines, such as those outlined by the World Health Organization
(WHO, 1999) [
10
], the Architectural Institute of Japan (Fukuchi & Ueno, 2004) [
11
], the
Australian/New Zealand Standard [
12
], and the German Institute for Standardization [
13
],
advocate for high levels of acoustic absorption and short reverberation times to enhance
speech clarity within lecture halls. China’s current reference model, GB/T50356-2005
“Code for architectural acoustical design of theater, cinema and multi-use auditorium” [
14
],
emphasizes these principles in the architectural acoustical design of theaters, cinemas, and
multi-use auditoriums.
However, despite the existence of acoustic code guidance, numerous academic sur-
veys and reports continue to find discrepancies between expected and actual results in
terms of acoustic performance in these venues. They have emphasized that there is a gap
Buildings 2024,14, 1583 3 of 20
between the expected and actual results in these venues, particularly in terms of acoustic
performance, which often falls short of expectations. Nassiri [
15
] investigated the back-
ground noise levels in university classrooms through a study that was largely substandard,
revealing deficiencies in acoustics. Escobar [
16
] analyzed the acoustic parameters of a
university auditorium and multi-functional conference room and proposed improvements
accordingly. Pinho [
17
] examined the acoustical performance of school buildings in Portu-
gal, elucidating prevalent issues. Sala and Rantala [
18
] investigated acoustics and activity
noise in school classrooms in Finland, amplifying concerns regarding ambient noise levels.
Ricciardi and Buratti [
19
] conducted an objective and subjective assessment of acoustic
comfort in classrooms, combining perceived and actual conditions to evaluate the acoustic
effectiveness of classrooms. In addition, van den Heuij [
20
] evaluated the acoustic effective-
ness of academic classrooms through existing acoustic reference levels, pointing out where
the existing deficiencies lie. Astolfi [
21
] provides a summary of recent developments in
classroom acoustics and describes the effects of noise on students and lecturers. However,
at the same time, the researcher points out that further research is needed for this complex
communication scenario.
Many Chinese researchers have also studied these deficiencies. For example, as a
leading expert in this field, Kang Jian [
22
] has conducted a lot of research on acoustics in
Chinese venues. Xie Hui [
23
] emphasizes the importance of the acoustic environment of lec-
ture halls and puts forward the suggestion of improving the acoustic environment of lecture
halls by changing the decorative materials and design on a larger scale.
Wang Chao [24]
conducted a time-varying analysis of the acoustic effects of very large spaces, especially
public transportation spaces. Yan Xiang [
25
] specifically took the renovation of the lecture
hall of Tsinghua University as an example to explain the dilemma of multi-functional
lecture halls and proposed that architectural acoustic adaptive design should be carried out
based on more detailed acoustic functional requirements. These mainly provide guidance
for the design and remodeling of lecture halls in the institutions of higher education from
the technical level, but these high-investment optimization options are relatively difficult
to achieve in many areas, with limited referentiality. That is to say, only by the in-depth
consideration of the relationship between building renovation and the conditions and
needs of the building can we better improve the acoustic performance of the building and
promote the introduction of more applicable and reasonable specifications.
The problems that have been pointed out and still exist in the studies above show that
a large number of halls have problems with inaudibility and how to improve it in a simpler
way. To this end, the authors conducted a questionnaire survey of the academic lecture
hall of the School of Architecture and Planning at Yunnan University. It found that 131
of the 200 students surveyed (more than 65%) indicated that they were dissatisfied with
the current acoustic conditions. Only 24 students, representing 12% of the sample size,
expressed satisfaction.
Therefore, this study takes this hall as an example, which has similar problems. This
research uses a combination of experimental testing and computer software simulation to
carry out acoustic environment design research through the use of the acoustic simulation
software EASE 4.4 digital modeling of the hall. Testing with the material parameters and
environmental noise, it analyzes the data on loudness, speech intelligibility, reverberation
time, and other indicators. Later, this research studies their structural characteristics and
indicate the problems existing in the acoustic environment design of this kind of college
lecture hall. Then, the acoustic environment design transformation program is proposed
and verified by software simulation to achieve sound quality optimization so that the
academic lecture hall can meet the normal use requirements.
2. Overview and Material Test
2.1. Building Introduction
Yunnan University at college town located in Chenggong New City Area accommodates
over 20,000 students and staff, with a total construction area of about
1,029,000 square meters
.
Buildings 2024,14, 1583 4 of 20
However, the fact that most of them are located in mountainous areas means that the build-
ings have to be relatively compact. The multi-functional use of space became inevitable.
The academic lecture hall, situated within the School of Architecture and Planning at
Yunnan University, on the inside of the college building, surrounded by sloping land, was
finalized in 2010.
It was primarily serving as a venue for conferences, academic discourse, and stu-
dent engagements. It spans approximately 24 m in length, 16.8 m in width, and boasts
a net height of 8.1 m in architectural design dimensions. The hall occupies a rectangu-
lar footprint encompassing 403.2 square meters, with a volumetric capacity of around
2857.68 cubic meters
. It accommodates a total of 302 seats, averaging 9.46 cubic meters
per seat. Notably, the hall features a length of 18 m accessible to the audience (of a total
of
24 m
), with seating arranged in a tiered fashion, comprising 12 rows and 3 columns
(
13 rows
in the central column), each row accommodating 24 seats, incrementally elevated
by 0.1 m.
To mitigate potential noise disruptions, the lecture hall strategically aligns with the
eastern courtyard of the college, ensuring minimal interference with daily instructional
activities. Accessible through the ground floor main entrance of the college, a passageway
connects the hall to the college atrium, while a rear entrance facilitates ingress and egress
directly to the lecture hall (see Figure 2c).
Generally, the spatial layout of the auditorium is often in the form of theater archi-
tecture (rectangular, polygonal, fan-shaped, curved, etc.). However, the most important
prerequisite for the audience layout in the academic lecture hall is to ensure clear vision
and clear sound at the same time. Therefore, there are few balcony seats in the academic
lecture hall, and the spatial form of the auditorium has some little changes. Different from
professional opera houses, etc., due to many constraints such as land scarcity and financial
constraints, the use of a relatively simple rectangular plane is the strategy currently widely
used in such places. The sound nature of the lecture hall is mainly electro-acoustic (a
combination of microphones and speakers), and the sound propagation is optimized based
on the internal decoration and the acoustic properties of the materials.
2.2. Software Introduction
We used EASE 4.4 digital modeling software to model the lecture hall. In this software,
buildings can be constructed as a 2D surface using line elements firstly. These 2D surfaces
can then be extruded to create a 3D model. Additionally, the software allows us to match
materials from its library to the corresponding materials in the 3D model. Then, we
analyzed the building by EASE (a software developed by Ahnert Feistel Media Group,
Berlin, Germany), which is widely used in electro-acoustic simulation. The material library
of EASE is complete and can be converted with other software file formats.
The sound effect of the hall is related to the shape of the material, etc., and the basic
status quo of the hall can be simulated by EASE to obtain the relevant situation of each
acoustic parameter. The basic steps of measurement using the EASE 4.4 are as follows:
3D modeling, inputting acoustic parameters such as sound-absorbing materials, and then
outputting acoustic parameters such as speech intelligibility [26].
Before the data analysis of loudness, reverberation time, speech intelligibility, and
other indicators, according to the above design drawings and measured dimensions, first
of all, the academic lecture hall were modeled [
27
]. We set the main structure of the lecture
hall walls, columns, and other structures according to the previous CAD computer-aided
design drawings of the plan and section; then the indoor stage and seats were input in
further detail; finally, the corresponding materials were given to the lecture hall. Then,
the listening surface (bright yellow) was set—featuring blue chairs representing acoustic
simulation listening points (receivers), parallelograms delineating listening areas, and red
horn patterns symbolizing sound sources within the lecture hall (see Figure 3).
Buildings 2024,14, 1583 5 of 20
Buildings 2024, 14, x FOR PEER REVIEW 4 of 22
lecture hall. Then, the acoustic environment design transformation program is proposed
and verified by software simulation to achieve sound quality optimization so that the ac-
ademic lecture hall can meet the normal use requirements.
2. Overview and Material Test
2.1. Building Introduction
Yunnan University at college town located in Chenggong New City Area accommo-
dates over 20,000 students and staff, with a total construction area of about 1,029,000
square meters. However, the fact that most of them are located in mountainous areas
means that the buildings have to be relatively compact. The multi-functional use of space
became inevitable. The academic lecture hall, situated within the School of Architecture
and Planning at Yunnan University, on the inside of the college building, surrounded by
sloping land, was finalized in 2010.
It was primarily serving as a venue for conferences, academic discourse, and student
engagements. It spans approximately 24 m in length, 16.8 m in width, and boasts a net
height of 8.1 m in architectural design dimensions. The hall occupies a rectangular foot-
print encompassing 403.2 square meters, with a volumetric capacity of around 2857.68
cubic meters. It accommodates a total of 302 seats, averaging 9.46 cubic meters per seat.
Notably, the hall features a length of 18 m accessible to the audience (of a total of 24 m),
with seating arranged in a tiered fashion, comprising 12 rows and 3 columns (13 rows in
the central column), each row accommodating 24 seats, incrementally elevated by 0.1 m.
To mitigate potential noise disruptions, the lecture hall strategically aligns with the
eastern courtyard of the college, ensuring minimal interference with daily instructional
activities. Accessible through the ground floor main entrance of the college, a passageway
connects the hall to the college atrium, while a rear entrance facilitates ingress and egress
directly to the lecture hall (see Figure 2c).
(a) (b)
Buildings 2024, 14, x FOR PEER REVIEW 5 of 22
(c)
Figure 2. Aerial view from drone (a), architectural models formed by drone mapping and on-site
surveys (b), and basic situation map of Yunnan University School of Architecture and Planning (c).
Generally, the spatial layout of the auditorium is often in the form of theater archi-
tecture (rectangular, polygonal, fan-shaped, curved, etc.). However, the most important
prerequisite for the audience layout in the academic lecture hall is to ensure clear vision
and clear sound at the same time. Therefore, there are few balcony seats in the academic
lecture hall, and the spatial form of the auditorium has some little changes. Different from
professional opera houses, etc., due to many constraints such as land scarcity and financial
constraints, the use of a relatively simple rectangular plane is the strategy currently widely
used in such places. The sound nature of the lecture hall is mainly electro-acoustic (a com-
bination of microphones and speakers), and the sound propagation is optimized based on
the internal decoration and the acoustic properties of the materials.
Figure 2. Aerial view from drone (a), architectural models formed by drone mapping and on-site
surveys (b), and basic situation map of Yunnan University School of Architecture and Planning (c).
Buildings 2024,14, 1583 6 of 20
Buildings 2024, 14, x FOR PEER REVIEW 6 of 22
2.2. Software Introduction
We used EASE 4.4 digital modeling software to model the lecture hall. In this soft-
ware, buildings can be constructed as a 2D surface using line elements firstly. These 2D
surfaces can then be extruded to create a 3D model. Additionally, the software allows us
to match materials from its library to the corresponding materials in the 3D model. Then,
we analyzed the building by EASE (a software developed by Ahnert Feistel Media Group,
Berlin, Germany), which is widely used in electro-acoustic simulation. The material li-
brary of EASE is complete and can be converted with other software file formats.
The sound effect of the hall is related to the shape of the material, etc., and the basic
status quo of the hall can be simulated by EASE to obtain the relevant situation of each
acoustic parameter. The basic steps of measurement using the EASE 4.4 are as follows: 3D
modeling, inputting acoustic parameters such as sound-absorbing materials, and then
outputting acoustic parameters such as speech intelligibility [26].
Before the data analysis of loudness, reverberation time, speech intelligibility, and
other indicators, according to the above design drawings and measured dimensions, first
of all, the academic lecture hall were modeled [27]. We set the main structure of the lecture
hall walls, columns, and other structures according to the previous CAD computer-aided
design drawings of the plan and section; then the indoor stage and seats were input in
further detail; finally, the corresponding materials were given to the lecture hall. Then, the
listening surface (bright yellow) was set—featuring blue chairs representing acoustic sim-
ulation listening points (receivers), parallelograms delineating listening areas, and red
horn patterns symbolizing sound sources within the lecture hall (see Figure 3).
The model construction entails several other steps (flow chart in Figure 4):
(1) Importing a three-dimensional model into the EASE software 4.4 based on the actual
dimensions;
(2) Conducting inspections for sound leakage and boundary surface irregularities;
(3) Configuring interface absorption coefficients for the model (as detailed in Table 1, the
acoustic absorption index of decoration materials in the academic lecture hall);
(4) Implementing stage sound settings corresponding to the lecture theater’s actual BD-
H1086 sound usage;
(5) Generating sound simulation diagrams.
(a)
Buildings 2024, 14, x FOR PEER REVIEW 7 of 22
(b)
(c)
Figure 3. Cont.
Buildings 2024,14, 1583 7 of 20
Buildings 2024, 14, x FOR PEER REVIEW 8 of 22
(d)
Figure 3. Lecture hall drawing model in 3D (a), EASE model (b), lecture hall plan (c), and lecture
hall section (d).
Figure 4. EASE software acoustic setting flow chart (taking reverberation time test as an example).
Table 1. Acoustic absorption index of decoration materials in academic lecture hall.
Name of Material Frequency/Hz
125 250 500 1000 2000 4000
1 Hardwood flooring (WOOD FLR) 0.20 0.15 0.10 0.08 0.08 0.05
2 Smooth tile (CORTEGA) 0.31 0.32 0.51 0.72 0.74 0.77
3 Empty seats (MTSEAT FAB) 0.19 0.37 0.56 0.67 0.61 0.59
4 Audience with thick cushions (PUBLIC TKC) 0.50 0.70 0.85 0.95 0.95 0.90
5 A 12.5 mm thick plasterboard with 3 cm backspace
(GYP125MM) 0.30 0.20 0.05 0.02 0.02 0.02
Figure 3. Lecture hall drawing model in 3D (a), EASE model (b), lecture hall plan (c), and lecture hall
section (d).
The model construction entails several other steps (flow chart in Figure 4):
(1)
Importing a three-dimensional model into the EASE software 4.4 based on the
actual dimensions;
(2)
Conducting inspections for sound leakage and boundary surface irregularities;
(3)
Configuring interface absorption coefficients for the model (as detailed in Table 1, the
acoustic absorption index of decoration materials in the academic lecture hall);
(4)
Implementing stage sound settings corresponding to the lecture theater’s actual BD-
H1086 sound usage;
(5)
Generating sound simulation diagrams.
Buildings 2024, 14, x FOR PEER REVIEW 8 of 22
(d)
Figure 3. Lecture hall drawing model in 3D (a), EASE model (b), lecture hall plan (c), and lecture
hall section (d).
Figure 4. EASE software acoustic setting flow chart (taking reverberation time test as an example).
Table 1. Acoustic absorption index of decoration materials in academic lecture hall.
Name of Material Frequency/Hz
125 250 500 1000 2000 4000
1 Hardwood flooring (WOOD FLR) 0.20 0.15 0.10 0.08 0.08 0.05
2 Smooth tile (CORTEGA) 0.31 0.32 0.51 0.72 0.74 0.77
3 Empty seats (MTSEAT FAB) 0.19 0.37 0.56 0.67 0.61 0.59
4 Audience with thick cushions (PUBLIC TKC) 0.50 0.70 0.85 0.95 0.95 0.90
5 A 12.5 mm thick plasterboard with 3 cm backspace
(GYP125MM) 0.30 0.20 0.05 0.02 0.02 0.02
Figure 4. EASE software acoustic setting flow chart (taking reverberation time test as an example).
Buildings 2024,14, 1583 8 of 20
Table 1. Acoustic absorption index of decoration materials in academic lecture hall.
Name of Material Frequency/Hz
125 250 500 1000 2000 4000
1 Hardwood flooring (WOOD FLR) 0.20 0.15 0.10 0.08 0.08 0.05
2 Smooth tile (CORTEGA) 0.31 0.32 0.51 0.72 0.74 0.77
3 Empty seats (MTSEAT FAB) 0.19 0.37 0.56 0.67 0.61 0.59
4 Audience with thick cushions (PUBLIC TKC) 0.50 0.70 0.85 0.95 0.95 0.90
5
A 12.5 mm thick plasterboard with 3 cm backspace (GYP125MM)
0.30 0.20 0.05 0.02 0.02 0.02
6 A 90/15 mm wood grid with 6 cm backspace (WOOD GRID1) 0.10 0.36 0.99 0.99 0.50 0.35
7 Dual pane glass (WINDOW DP) 0.25 0.10 0.07 0.06 0.04 0.02
8 Soundproof solid wood door (DOOR HOLLOW) 0.15 0.10 0.06 0.08 0.10 0.05
9 Perforated Plate (PERFPANEL1) 0.78 0.58 0.27 0.15 0.04 0.12
2.3. Material Acoustic Performance Testing
2.3.1. Introduction to Material Distribution Location
In terms of the overall environmental material settings, the following configuration is
adopted (see Figure 5). The academic lecture hall incorporates a highly sound-absorbing
structure on both the back of the stage and the rear wall of the auditorium, effectively reduc-
ing sound focus, echo problems, and microphone feedback. This design choice also serves
to reduce reverberation time and control unwanted echoes. The use of environmentally
friendly E1 fire-rated A1 grooved wood acoustic panels for the stage back wall and rear side
walls further enhances sound absorption and propagation efficiency. Using a standardized
modular design and slot-and-keel construction, these panels facilitate optimum sound
transmission within the hall (shown as 1
in Figure 5).
Buildings 2024, 14, x FOR PEER REVIEW 9 of 22
6 A 90/15 mm wood grid with 6 cm backspace (WOOD GRID1) 0.10 0.36 0.99 0.99 0.50 0.35
7 Dual pane glass (WINDOW DP) 0.25 0.10 0.07 0.06 0.04 0.02
8 Soundproof solid wood door (DOOR HOLLOW) 0.15 0.10 0.06 0.08 0.10 0.05
9 Perforated Plate (PERFPANEL1) 0.78 0.58 0.27 0.15 0.04 0.12
2.3. Material Acoustic Performance Testing
2.3.1. Introduction to Material Distribution Location
In terms of the overall environmental material settings, the following configuration
is adopted (see Figure 5). The academic lecture hall incorporates a highly sound-absorbing
structure on both the back of the stage and the rear wall of the auditorium, effectively
reducing sound focus, echo problems, and microphone feedback. This design choice also
serves to reduce reverberation time and control unwanted echoes. The use of environmen-
tally friendly E1 fire-rated A1 grooved wood acoustic panels for the stage back wall and
rear side walls further enhances sound absorption and propagation efficiency. Using a
standardized modular design and slot-and-keel construction, these panels facilitate opti-
mum sound transmission within the hall (shown as ① in Figure 5).
In order to meet the requirements for floor noise insulation and vibration damping,
the academic lecture hall uses a timber floor layout—with a primary frame structure con-
sisting of 50 mm × 50 mm timber keels spaced at 400 mm intervals. In addition, a compre-
hensive application of burnt carbon slag sound insulation layer further enhances sound
transmission attenuation, thereby optimizing audience perception quality (shown as ②
in Figure 5).
Externally, the walls of the auditorium are constructed of dry-hung stone (the facing
stone is hung directly onto the external surface of the building structure, leaving a 40–50
mm cavity between the stone and the structure), which increases structural stability and
improves acoustic insulation. To ensure balanced sound dispersion, loudspeakers are
strategically positioned on either side of the stage wall and along the center of the side
walls, promoting an even distribution of sound pressure throughout the venue. This con-
figuration aims to improve the overall listening experience for the audience, providing a
comfortable and high-quality listening environment (shown as ③ in Figure 5).
Figure 5. Schematic design of acoustic environment decoration.
2.3.2. Sound Absorption Performance Experiment
We selected the decorative materials in the auditorium and determined their sound
absorption coefficients in the laboratory. This was followed by a computerized acoustic
simulation. EASE’s material editor provides a variety of materials commonly used in
rooms, and new sound-absorbing materials can be edited and added as needed. In the
simulation, we set the absorption coefficients of the materials according to the specific data
measured in the experiment.
The absorption coefficient of acoustic materials is usually determined by the rever-
beration chamber method or the standing wave tube method [28,29]. The aforementioned
method is predominantly utilized in engineering measurements; however, owing to its
substantial requirement for sample area, the practical sample area frequently falls short
Figure 5. Schematic design of acoustic environment decoration.
In order to meet the requirements for floor noise insulation and vibration damping,
the academic lecture hall uses a timber floor layout—with a primary frame structure
consisting of 50 mm
×
50 mm timber keels spaced at 400 mm intervals. In addition, a
comprehensive application of burnt carbon slag sound insulation layer further enhances
sound transmission attenuation, thereby optimizing audience perception quality (shown as
2
in Figure 5).
Externally, the walls of the auditorium are constructed of dry-hung stone (the fac-
ing stone is hung directly onto the external surface of the building structure, leaving a
40–50 mm
cavity between the stone and the structure), which increases structural stability
and improves acoustic insulation. To ensure balanced sound dispersion, loudspeakers
are strategically positioned on either side of the stage wall and along the center of the
side walls, promoting an even distribution of sound pressure throughout the venue. This
configuration aims to improve the overall listening experience for the audience, providing
a comfortable and high-quality listening environment (shown as 3
in Figure 5).
Buildings 2024,14, 1583 9 of 20
2.3.2. Sound Absorption Performance Experiment
We selected the decorative materials in the auditorium and determined their sound
absorption coefficients in the laboratory. This was followed by a computerized acoustic
simulation. EASE’s material editor provides a variety of materials commonly used in
rooms, and new sound-absorbing materials can be edited and added as needed. In the
simulation, we set the absorption coefficients of the materials according to the specific data
measured in the experiment.
The absorption coefficient of acoustic materials is usually determined by the rever-
beration chamber method or the standing wave tube method [
28
,
29
]. The aforementioned
method is predominantly utilized in engineering measurements; however, owing to its
substantial requirement for sample area, the practical sample area frequently falls short
of the necessary size, potentially resulting in significant discrepancies in test outcomes.
On the contrary, the impedance tube method simplifies the measurement process because
it requires a small sample area and the sound wave is incident perpendicularly to the
sample surface, and is more suitable for sound absorption coefficient testing in the labora-
tory [
30
]. The sound absorption coefficient tested by this method complies with the national
standard [31]
(Acoustics: Measurement of sound absorption in a reverberation room), and
is accepted by the EASE software 4.4 material parameter input terminal standard.
In order to determine the absorption coefficient of the auditorium material, we used
the AWA62902 standing wave tube equipment set (shown in Figure 6). For this material
testing, we used two sets of tubes to cover the frequency range from 125 to 4000 Hz.
Among them, the larger tube specification is
Φ
96
×
1000 (mm), and the frequency range is
90 Hz~2075 Hz
; the smaller tube specification is
Φ
30
×
350 (mm), and the frequency range
is 1500 Hz~6641 Hz.
Buildings 2024, 14, x FOR PEER REVIEW 10 of 22
of the necessary size, potentially resulting in significant discrepancies in test outcomes.
On the contrary, the impedance tube method simplifies the measurement process because
it requires a small sample area and the sound wave is incident perpendicularly to the
sample surface, and is more suitable for sound absorption coefficient testing in the labor-
atory [30]. The sound absorption coefficient tested by this method complies with the na-
tional standard [31] (Acoustics: Measurement of sound absorption in a reverberation
room), and is accepted by the EASE software 4.4 material parameter input terminal stand-
ard.
In order to determine the absorption coefficient of the auditorium material, we used
the AWA62902 standing wave tube equipment set (shown in Figure 6). For this material
testing, we used two sets of tubes to cover the frequency range from 125 to 4000 Hz.
Among them, the larger tube specification is Φ96 × 1000 (mm), and the frequency range is
90 Hz~2075 Hz; the smaller tube specification is Φ30 × 350 (mm), and the frequency range
is 1500 Hz~6641 Hz.
We first calibrated the sensitivity level using the standard material module to ensure
it reads 93.8 dB at 1k Hz. We then installed the samples of different materials (the spatial
distribution of the materials is shown in Figure 7, and the material names are shown in
Table 1) at one end of the standing wave tube, and provided different frequency sound
waves in the range of 125 to 4000 Hz to each material through a signal generator. Next,
we measured the minimum and maximum values of the sound pressure amplitude in the
system, and calculated the absorption coefficient of each material at different frequencies
based on the standing wave ratio method. The test results are shown in Table 1.
Figure 6. Standing wave tube experimental equipment for measuring sound absorption coefficient.
Figure 7. Distribution of the materials in the lecture hall.
2.4. On-Site Measurement Arrangement and Noise Testing
Environmental noise (background noise) is a physical quantity closely related to in-
door noise interference. It refers to the sum of environmental noise contributed by other
sound sources other than the measured sound source. Conducting this test can test
Figure 6. Standing wave tube experimental equipment for measuring sound absorption coefficient.
We first calibrated the sensitivity level using the standard material module to ensure
it reads 93.8 dB at 1 kHz. We then installed the samples of different materials (the spatial
distribution of the materials is shown in Figure 7, and the material names are shown in
Table 1) at one end of the standing wave tube, and provided different frequency sound
waves in the range of 125 to 4000 Hz to each material through a signal generator. Next,
we measured the minimum and maximum values of the sound pressure amplitude in the
system, and calculated the absorption coefficient of each material at different frequencies
based on the standing wave ratio method. The test results are shown in Table 1.
Buildings 2024,14, 1583 10 of 20
Buildings 2024, 14, x FOR PEER REVIEW 10 of 22
of the necessary size, potentially resulting in significant discrepancies in test outcomes.
On the contrary, the impedance tube method simplifies the measurement process because
it requires a small sample area and the sound wave is incident perpendicularly to the
sample surface, and is more suitable for sound absorption coefficient testing in the labor-
atory [30]. The sound absorption coefficient tested by this method complies with the na-
tional standard [31] (Acoustics: Measurement of sound absorption in a reverberation
room), and is accepted by the EASE software 4.4 material parameter input terminal stand-
ard.
In order to determine the absorption coefficient of the auditorium material, we used
the AWA62902 standing wave tube equipment set (shown in Figure 6). For this material
testing, we used two sets of tubes to cover the frequency range from 125 to 4000 Hz.
Among them, the larger tube specification is Φ96 × 1000 (mm), and the frequency range is
90 Hz~2075 Hz; the smaller tube specification is Φ30 × 350 (mm), and the frequency range
is 1500 Hz~6641 Hz.
We first calibrated the sensitivity level using the standard material module to ensure
it reads 93.8 dB at 1k Hz. We then installed the samples of different materials (the spatial
distribution of the materials is shown in Figure 7, and the material names are shown in
Table 1) at one end of the standing wave tube, and provided different frequency sound
waves in the range of 125 to 4000 Hz to each material through a signal generator. Next,
we measured the minimum and maximum values of the sound pressure amplitude in the
system, and calculated the absorption coefficient of each material at different frequencies
based on the standing wave ratio method. The test results are shown in Table 1.
Figure 6. Standing wave tube experimental equipment for measuring sound absorption coefficient.
Figure 7. Distribution of the materials in the lecture hall.
2.4. On-Site Measurement Arrangement and Noise Testing
Environmental noise (background noise) is a physical quantity closely related to in-
door noise interference. It refers to the sum of environmental noise contributed by other
sound sources other than the measured sound source. Conducting this test can test
Figure 7. Distribution of the materials in the lecture hall.
2.4. On-Site Measurement Arrangement and Noise Testing
Environmental noise (background noise) is a physical quantity closely related to
indoor noise interference. It refers to the sum of environmental noise contributed by other
sound sources other than the measured sound source. Conducting this test can test whether
the doors, windows, walls, floors, and partitions of the equipment room in the lecture
hall have sufficient sound insulation capabilities, and can also test the extent to which
the lecture hall is affected by external environmental noise and instrument noise. In this
regard,
Zhu Peisheng’s [32]
research shows the correlation between reverberation time,
background noise and environmental factors, and further strengthens the above view. It
is believed that before conducting on-site testing and site acoustic effect simulation, it is
necessary to test the indoor acoustic environment, and it is important to understand its
impact on the acoustic environment as an irrelevant parameter.
In this paper, the researchers used DT-859B Professional Multi-functional Environmen-
tal Test Meter as the measuring instrument, which was newly launched in 2022 to assess the
acoustical parameters in the unoccupied condition. We evenly distributed measurement
points along one side of the hall at a height of 1.2 m, as illustrated in Figure 8(bright
yellow schematic surface); the plan and section are shown in Figure 3. These points were
strategically positioned to encompass representative areas such as the front, middle, and
back of the audience area, as well as the left, middle, and right sections of the hall. The test
results revealed that the highest background noise level recorded at these measurement
points in the academic lecture hall was 34.0 dB in pressure level (see Table 2), aligning
with the background noise limits specified in GB/T50356-2005. The acoustic measurement
findings affirm compliance with design specifications and the suitability of the venue for
its intended use.
Buildings 2024, 14, x FOR PEER REVIEW 11 of 22
whether the doors, windows, walls, floors, and partitions of the equipment room in the
lecture hall have sufficient sound insulation capabilities, and can also test the extent to
which the lecture hall is affected by external environmental noise and instrument noise.
In this regard, Zhu Peishengʹs [32] research shows the correlation between reverberation
time, background noise and environmental factors, and further strengthens the above
view. It is believed that before conducting on-site testing and site acoustic effect simula-
tion, it is necessary to test the indoor acoustic environment, and it is important to under-
stand its impact on the acoustic environment as an irrelevant parameter.
In this paper, the researchers used DT-859B Professional Multi-functional Environ-
mental Test Meter as the measuring instrument, which was newly launched in 2022 to
assess the acoustical parameters in the unoccupied condition. We evenly distributed meas-
urement points along one side of the hall at a height of 1.2 m, as illustrated in Figure 8
(bright yellow schematic surface); the plan and section are shown in Figure 3. These points
were strategically positioned to encompass representative areas such as the front, middle,
and back of the audience area, as well as the left, middle, and right sections of the hall.
The test results revealed that the highest background noise level recorded at these meas-
urement points in the academic lecture hall was 34.0 dB in pressure level (see Table 2),
aligning with the background noise limits specified in GB/T50356-2005. The acoustic
measurement findings affirm compliance with design specifications and the suitability of
the venue for its intended use.
Subsequently, the measured average background noise levels were manually in-
putted into the EASE 4.4, incorporating the background noise sound pressure level for
each frequency band.
Figure 8. Distribution of the points in the lecture hall and the sound level meter DT-859B.
Table 2. Comparison of actual (hall) and normative (NR-30) values of background noise pressure
level.
Frequency/Hz 500 2000 4000
lecture hall/dB 34 28 24
NR-30/dB 34 30 26
3. Results
In the code GB/T50356-2005 of China [14], it is clearly stated that reverberation time
and loudness are important factors in judging lecture halls; at the same time, the Austral-
ian/New Zealand Standard [12] also mentions that speech intelligibility in lecture halls
can be improved by altering the reverberation time. China’s current reference model
standards [14] for the architectural acoustic design of theaters, movie theaters, and multi-
purpose auditoriums emphasize the effects of reverberation time, loudness, and speech
intelligibility on indoor sound quality. Therefore, an acoustic analysis is necessary if an
ideal lecture hall is to be built.
During the acoustic measurement and simulation process, we analyzed and com-
pared the acoustic parameters defined in the standard [14], including reverberation time
(T30), loudness, and the sound transmission index (STI) of speech intelligibility.
Figure 8. Distribution of the points in the lecture hall and the sound level meter DT-859B.
Table 2. Comparison of actual (hall) and normative (NR-30) values of background noise pressure level.
Frequency/Hz 500 2000 4000
lecture hall/dB 34 28 24
NR-30/dB 34 30 26
Buildings 2024,14, 1583 11 of 20
Subsequently, the measured average background noise levels were manually inputted
into the EASE 4.4, incorporating the background noise sound pressure level for each
frequency band.
3. Results
In the code GB/T50356-2005 of China [
14
], it is clearly stated that reverberation
time and loudness are important factors in judging lecture halls; at the same time, the
Australian/New Zealand Standard [12] also mentions that speech intelligibility in lecture
halls can be improved by altering the reverberation time. China’s current reference model
standards [
14
] for the architectural acoustic design of theaters, movie theaters, and multi-
purpose auditoriums emphasize the effects of reverberation time, loudness, and speech
intelligibility on indoor sound quality. Therefore, an acoustic analysis is necessary if an
ideal lecture hall is to be built.
During the acoustic measurement and simulation process, we analyzed and compared
the acoustic parameters defined in the standard [
14
], including reverberation time (T30),
loudness, and the sound transmission index (STI) of speech intelligibility.
3.1. Speech Intelligibility
The main purpose of using a sound reinforcement system in a lecture hall is to expand
the language sound to ensure that the auditorium has sufficient speech intelligibility
(language clarity) at some sound pressure levels. Therefore, the design of the sound
reinforcement system fundamentally revolves around optimizing speech intelligibility as
the central focus [
33
]. This entails the careful consideration of electro-acoustic properties,
maximum sound pressure levels (Max SPL), transmission frequency characteristics, sound
distribution, audio gain, system noise, and other pertinent technical indicators. The core of
solving the problem of unclear hearing reported by students (see in Section 1) is to check
whether the language intelligibility settings are reasonable. In summary, acoustic issues
based on speech intelligibility in the lecture hall still rely on further actual measurement
and analysis.
3.1.1. Speech Intelligibility Simulation
The speech intelligibility index serves as a metric to quantify the degree of the intel-
ligibility of spoken language within a given space. The indicators for evaluating indoor
speech intelligibility include definition (D50), clarity (C50), sound transmission index
(STI), etc. [34]
. Bradley [
35
] established the linear relationship between C50 and STI under
three noise-free reverberation conditions. The results show that the linear regression results
of C50 and STI are better, and the degree of fitting between the two is higher. Sato [
36
]
discussed the relationship between C50, D50, and STI—the results show that C50 and
D50 can only be a simple substitute for STI, while STI is a more comprehensive indicator.
Therefore, this simulation uses STI to evaluate indoor speech intelligibility.
In the EASE 4.4, the Speech Transmission Index (STI) method is used to calculate
the speech intelligibility, which computes the expected value index based on architectural
acoustics through resembling the reverberation time frequency response curve, and ensures
that all loudspeakers are operating under normal conditions. The STI method is a rapid
approach for objectively evaluating speech intelligibility in halls, contingent upon meeting
the following prerequisites:
(1)
Essentially linear speech transmission, devoid of clipping or distortion.
(2)
Broadband speech transmission spanning typical frequencies of 125–4000 Hz, as this
method assumes an unrestricted speech spectrum.
(3)
Background noise devoid of pure tones and lacking distinct peaks or valleys in the
octave band spectrum.
(4)
The absence of impulse characteristics in the background noise.
(5)
Consistency in reverberation time across different frequencies.
Buildings 2024,14, 1583 12 of 20
The rating criteria for the speech intelligibility index (STI) are outlined in the
following Table 3.
Table 3. Criteria for rating the speech intelligibility index (STI).
STI Value Categorization Generic Type of Information Typical Application Cases
STI > 0.76 A+ Recording room
0.74 ≤STI < 0.76 A
Complex information,
unfamiliar words
Theatre, drama theatre, courtroom,
parliament, and hearing aids
0.70 ≤STI < 0.74 B
0.66 ≤STI < 0.70 C Theatre, drama theatre, courtroom,
parliament, and teleconferencing system
0.62 ≤STI < 0.66 D
Complex information, familiar
words
Lecture halls, classrooms, and concert halls
0.58 ≤STI < 0.62 E
Complex information, familiar
context
Concert halls and modern classrooms
0.54 ≤STI < 0.58 F Shopping center, open office space, and
cathedral
0.50 ≤STI < 0.54 G Shopping center and open office space
As depicted in the figure below, the academic lecture hall has a low level of speech
intelligibility, and the average STI index value for it was determined to be 0.549. As shown
on the right side of Figure 9, the maximum value of STI does not exceed 0.578 and the
minimum value is only 0.530. The abscissa of the right figure in Figure 9is the STI value,
and the ordinate is the weight. For example, nearly 30% of the test points have an STI
assignment of about 0.54, while the corresponding maximum value point (0.578) only has
less than 3% of the area. The entire curve is plump in the middle, and the maximum and
minimum values account for a small proportion. It shows that the test results have strong
universality and uniform performance.
Buildings 2024, 14, x FOR PEER REVIEW 13 of 22
0.54 ≤ STI < 0.58 F Complex infor-
mation, familiar
context
Shopping center, open office space, and
cathedral
0.50 ≤ STI < 0.54 G Shopping center and open office space
As depicted in the figure below, the academic lecture hall has a low level of speech
intelligibility, and the average STI index value for it was determined to be 0.549. As shown
on the right side of Figure 9, the maximum value of STI does not exceed 0.578 and the
minimum value is only 0.530. The abscissa of the right figure in Figure 9 is the STI value,
and the ordinate is the weight. For example, nearly 30% of the test points have an STI
assignment of about 0.54, while the corresponding maximum value point (0.578) only has
less than 3% of the area. The entire curve is plump in the middle, and the maximum and
minimum values account for a small proportion. It shows that the test results have strong
universality and uniform performance.
Corresponding to a sound quality grade of F, this finding deviates somewhat from
the standard STI value (supposed to be D at least for the lecture hall in Table 3).
Figure 9. Analysis of the STI speech intelligibility calculations for the academic lecture hall.
3.1.2. Speech Intelligibility Measurement
Student volunteers were mobilized to execute speech intelligibility experiments
within the lecture hall. Before each experiment, the volunteers were positioned in desig-
nated test areas and instructed to utilize standardized pronunciation. Subsequently, syl-
lable articulation within the room was evaluated by analyzing feedback from the volun-
teers. The calculation formula for this assessment is outlined as follows:
𝑆𝑦𝑙𝑙𝑎𝑏𝑙𝑒
𝐴
𝑟𝑡𝑖𝑐𝑢𝑙𝑎𝑡𝑖𝑜𝑛 = 𝑁𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑛𝑜𝑟𝑚𝑎𝑙 𝑠𝑦𝑙𝑙𝑎𝑏𝑙𝑒𝑠
ℎ
𝑒𝑎𝑟𝑑 𝑏𝑦 𝑣𝑜𝑙𝑢𝑛𝑡𝑒𝑒𝑟𝑠
𝑁𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑎𝑙𝑙 𝑠𝑦𝑙𝑙𝑎𝑏𝑙𝑒𝑠 𝑖𝑛 𝑇𝑒𝑠𝑡 𝑃𝑜𝑖𝑛𝑡 × 100%
A total of 37 student volunteers participated in the test (9 for each time), during which
50 syllables were pronounced at the designated test site. Subsequently, 37 test lists were
issued, all of which were duly recovered, rendering 37 valid lists for analysis. The syllable
articulation was then averaged and compared against the reference table. The results re-
vealed that the syllable articulation within the lecture hall averaged at 72%, indicating a
listening experience that is barely acceptable (Table 4). Consequently, at the subjective as-
sessment level, the hall’s performance essentially meets the requirements for normal lan-
guage usage. However, it aligns with the general information obtained from simulations,
corresponding to a level of “complex information, familiar context (E/F/G)”.
Therefore, there is still a lot of room for improvement, and we hope to explore the
possibility of improvement through the two most direct influencing quantities, loudness
and reverberation time.
Table 4. Relationship between syllable articulation and listening perception.
Syllable Articula-
tion % Listening Perception Syllable Articula-
tion % Listening Perception
<65 unsatisfactory 75–85 favorable
65–75 barely >85 first-rate
Figure 9. Analysis of the STI speech intelligibility calculations for the academic lecture hall.
Corresponding to a sound quality grade of F, this finding deviates somewhat from the
standard STI value (supposed to be D at least for the lecture hall in Table 3).
3.1.2. Speech Intelligibility Measurement
Student volunteers were mobilized to execute speech intelligibility experiments within
the lecture hall. Before each experiment, the volunteers were positioned in designated
test areas and instructed to utilize standardized pronunciation. Subsequently, syllable
articulation within the room was evaluated by analyzing feedback from the volunteers.
The calculation formula for this assessment is outlined as follows:
Syllable Articulation =Number o f normal syllables heard by volunteers
Number o f all syllables in Test Point ×100%
Buildings 2024,14, 1583 13 of 20
A total of 37 student volunteers participated in the test (9 for each time), during which
50 syllables were pronounced at the designated test site. Subsequently, 37 test lists were
issued, all of which were duly recovered, rendering 37 valid lists for analysis. The syllable
articulation was then averaged and compared against the reference table. The results
revealed that the syllable articulation within the lecture hall averaged at 72%, indicating
a listening experience that is barely acceptable (Table 4). Consequently, at the subjective
assessment level, the hall’s performance essentially meets the requirements for normal
language usage. However, it aligns with the general information obtained from simulations,
corresponding to a level of “complex information, familiar context (E/F/G)”.
Table 4. Relationship between syllable articulation and listening perception.
Syllable Articulation % Listening Perception Syllable Articulation % Listening Perception
<65 unsatisfactory 75–85 favorable
65–75 barely >85 first-rate
Therefore, there is still a lot of room for improvement, and we hope to explore the
possibility of improvement through the two most direct influencing quantities, loudness
and reverberation time.
3.2. Loudness
W. Sabine, a pioneer in the field of architectural acoustics, underscored in his book
“Reverberation” the significance of achieving sufficient loudness in a hall for optimal sound
quality. In the context of a lecture hall, ensuring adequate loudness during normal use is a
primary objective of sound quality design [
37
]. Consequently, loudness emerges as a pivotal
indicator for assessing the sound quality of the hall and warrants careful consideration in
the evaluation process.
3.2.1. Loudness Simulation
In an academic lecture hall, it is imperative that the volume is sufficiently large and the
sound field is evenly distributed. Typically, a sound level from the speakers that exceeds
the surrounding noise by 5 to 10 dB is deemed adequate for meeting the hall’s requirements.
Utilizing the EASE software 4.4, the maximum sound pressure level (Max SPL) of the
reverberation sound in the academic lecture hall was calculated, with the results illustrated
in Figure 10 below.
Buildings 2024, 14, x FOR PEER REVIEW 14 of 22
3.2. Loudness
W. Sabine, a pioneer in the field of architectural acoustics, underscored in his book
“Reverberation” the significance of achieving sufficient loudness in a hall for optimal sound
quality. In the context of a lecture hall, ensuring adequate loudness during normal use is
a primary objective of sound quality design [37]. Consequently, loudness emerges as a
pivotal indicator for assessing the sound quality of the hall and warrants careful consid-
eration in the evaluation process.
3.2.1. Loudness Simulation
In an academic lecture hall, it is imperative that the volume is sufficiently large and
the sound field is evenly distributed. Typically, a sound level from the speakers that ex-
ceeds the surrounding noise by 5 to 10 dB is deemed adequate for meeting the hall’s re-
quirements. Utilizing the EASE software 4.4, the maximum sound pressure level (Max
SPL) of the reverberation sound in the academic lecture hall was calculated, with the re-
sults illustrated in Figure 10 below.
Figure 10. Illustration of the sound pressure level of the measured surface under different frequen-
cies.
The sound field uniformity analysis table is obtained from Figure 10 as shown in the
Table 5 below:
Table 5. Sound field uniformity analysis table.
Frequency/Hz SPL/dB Unevenness/dB
Greatest Minimal
125–4000 101.63 100.8 0.83
125 90.38 89.7 0.68
500 90.22 89.51 0.71
1000 88.74 87.7 1.04
2000 88.1 86.89 1.21
4000 87.42 85.98 1.44
Obviously, the sound field distribution in this academic lecture hall is relatively uni-
form under all frequency conditions (the unevenness is very small < 2 dB). Therefore,
when the sound pressure levels from 125 to 4000 Hz are mixed and superimposed, the
full-band modal distribution of the academic lecture hall shows a change of less than 8 dB
(unevenness), and the minimum total sound pressure level is 100.8 dB. This performance
Figure 10. Illustration of the sound pressure level of the measured surface under different frequencies.
The sound field uniformity analysis table is obtained from Figure 10 as shown in the
Table 5below:
Buildings 2024,14, 1583 14 of 20
Table 5. Sound field uniformity analysis table.
Frequency/Hz SPL/dB Unevenness/dB
Greatest Minimal
125–4000 101.63 100.8 0.83
125 90.38 89.7 0.68
500 90.22 89.51 0.71
1000 88.74 87.7 1.04
2000 88.1 86.89 1.21
4000 87.42 85.98 1.44
Obviously, the sound field distribution in this academic lecture hall is relatively uni-
form under all frequency conditions (the unevenness is very small < 2 dB). Therefore, when
the sound pressure levels from 125 to 4000 Hz are mixed and superimposed, the full-band
modal distribution of the academic lecture hall shows a change of less than 8 dB (uneven-
ness), and the minimum total sound pressure level is 100.8 dB. This performance exceeds
the acoustic characteristic indicators specified in the national standards for conference-level
sound reinforcement systems—the rated passband maximum sound pressure level (Max
SPL) requirement of more than 98 dB and the stable sound field distribution standard of
less than 8 dB at 1000 and 4000 Hz were exceeded.
3.2.2. Loudness Measurement
To validate the accuracy of the computer software simulation results, loudness field
measurements were conducted at nine selected points within the academic lecture hall, as
depicted in Figure 3. Utilizing stage-independent speakers and the AUDIO BASIK sound
system, the hall’s empty-field loudness was assessed. The test results in Table 6indicate
a strong consistency between the field measurement data and the simulation analysis,
affirming a uniform distribution (uniformity) of the sound field within the hall.
Table 6. Measured loudness at points.
Point 123456789
Loudness/dB 87.5 87.2 87.6 88.1 87.4 87.9 87.4 87.0 87.6
Its sound pressure level (SPL) and unevenness (or uniformity) meet the requirements.
Within this consideration range, the loudness index is qualified. The main reason the
volunteers could not hear clearly was not the loudness factor in this case.
3.3. Reverberation Time
Reverberation time stands as a fundamental attribute of the indoor sound field, wield-
ing considerable influence over the quality of indoor acoustics. The factor of reverberation
time is mentioned in the World Health Organization (WHO, 1999) [
10
] and the Archi-
tectural Institute of Japan (Fukuchi & Ueno, 2004) [
11
]. Meanwhile, Mike Barron [
33
],
Brunskog [
37
], Alibaba [
38
] and Adekalu [
39
] found that the unreasonable reverberation
time of lecture halls would have a certain adverse effect on the sound quality of the room.
Reasonable reverberation time can help lecture halls achieve more excellent acoustic effects.
Given its significance, reverberation time assessment assumes paramount importance in
the endeavor to construct an optimal lecture hall environment [40].
Determination of Reverberation Time and Measured Values
The decay of sound within a room following the cessation of sound emission by the
source is termed the reverberation process [
41
]. This duration significantly impacts the
audience’s auditory experience. To calculate the reverberation time of the academic lecture
hall, factors such as the room’s function, volume, interior surface absorption, relative
Buildings 2024,14, 1583 15 of 20
humidity of the air, temperature, and other influencing parameters are considered. Eyring’s
formula is frequently employed for this purpose, providing a comprehensive framework
for reverberation time estimation.
T=KV
−Sln(1−a)
where Vis the room volume, m3;
Kis a constant related to the speed of sound, generally taken as 0.161;
Sis the total surface area of the room, m2;
ais the average room sound absorption coefficient, calculated as:
a=a1S1+a2S2+. . . +anSn
S1+S2+. . . +Sn
where S
1
,S
2
, and S
3
are the surface areas of different interfacial materials in the room (m
3
).
a
1
,a
2
, and a
3
are the sound absorption coefficients of different materials (details see Table 1).
We employed the AIWA AWA6290 Building Acoustic Measuring Instrument (a mea-
surement system that can support reverberation time measurement, sound absorption
coefficient measurement, airborne acoustic isolation measurement, floor impact sound
measurement, and the sound quality measurement of the hall) to conduct the reverberation
time test and evaluate the academic lecture hall (Figure 11).
Buildings 2024, 14, x FOR PEER REVIEW 16 of 22
We employed the AIWA AWA6290 Building Acoustic Measuring Instrument (a meas-
urement system that can support reverberation time measurement, sound absorption co-
efficient measurement, airborne acoustic isolation measurement, floor impact sound
measurement, and the sound quality measurement of the hall) to conduct the reverbera-
tion time test and evaluate the academic lecture hall (Figure 11).
During the measurement of reverberation time, the auditorium was unoccupied, and
an acoustic pulse was detected at the speaker’s position (where the speaker would sit dur-
ing the conference) using a microphone placed at a height of 1.50 m. Receivers (at a height
of 1.2 m) were positioned at various locations throughout the hall, evenly distributed
across nine different spots. The positions of the sound source and receivers are illustrated
in Figures 3 and 11.
Figure 11. On-site test equipment layout.
The theoretical and actual reverberation times for the lecture hall are shown in Figure
12. The calculation of the theoretical reverberation time for each frequency using EASE 4.4
revealed that the reverberation time in each frequency band exceeds the standard value,
indicating a lack of acoustic treatment in this academic lecture hall.
The actual results of the measurement indicated that the average reverberation time
of the measurement points did not meet the requirements set out in the “Theatre, Cinema
and Multi-purpose Hall Architectural Acoustic Design Code (GB/T50356-2005)” [14] for
an academic lecture hall. This indicates that there is an urgent need to improve the acous-
tic absorption problems.
Figure 11. On-site test equipment layout.
During the measurement of reverberation time, the auditorium was unoccupied, and
an acoustic pulse was detected at the speaker’s position (where the speaker would sit
during the conference) using a microphone placed at a height of 1.50 m. Receivers (at a
height of 1.2 m) were positioned at various locations throughout the hall, evenly distributed
across nine different spots. The positions of the sound source and receivers are illustrated
in Figures 3and 11.
The theoretical and actual reverberation times for the lecture hall are shown in
Figure 12.
The calculation of the theoretical reverberation time for each frequency us-
ing EASE 4.4 revealed that the reverberation time in each frequency band exceeds the
standard value, indicating a lack of acoustic treatment in this academic lecture hall.
Buildings 2024,14, 1583 16 of 20
Buildings 2024, 14, x FOR PEER REVIEW 17 of 22
Figure 12. Differences between theoretical value simulation, field test results, and value in
GB/T50356-2005 [14] of reverberation time.
Through the simulation and measurement of the speech intelligibility, loudness, and
reverberation time of this hall, combined with the calculation of the specification, it is
found that it meets the requirements of loudness, but there are problems of low speech
intelligibility and the non-compliance of reverberation time. Based on the formula pro-
posed by Rao Yu’an [42],
𝑆% = 98.7 − 21.7lg 𝑇𝑅
where T is the reverberation time;
S is speech intelligibility;
R is the different acoustic ratios (room constant);
From the above, it can be concluded that the speech intelligibility (S) in the reverber-
ation field is inversely proportional to the logarithm of the (TR) product; that is, reducing
the reverberation time in the lecture hall can effectively improve the speech intelligibility
inside the lecture hall. Therefore, this article mainly proposes relevant acoustic modifica-
tion plans for the reverberation time problem in the lecture hall.
4. Results and Retrofit Solution
Due to the problem that different types of sound-absorbing materials have different
sound absorption coefficients and the update speed of sound-absorbing materials changes
with each passing day, this study did not compare the different types of sound-absorbing
materials. Instead, computer simulation methods are used to predict the appropriate lo-
cations for using sound-absorbing materials and imported into the architectural acoustics
software EASE. The acoustic performances are then calculated based on different acoustic
parameters such as material and location, to predict the impact on speech metrics where
sound-absorbing materials should be placed in the room. From the aspect of reducing the
quantity of sound-absorbing materials and thus the proper placing of building materials,
a feasible renovation plan is proposed for the indoor acoustic environment of the existing
lecture hall.
Kawata [43] suggested that acoustic materials should be distributed over at least two
surfaces of a room to achieve acceptable acoustic conditions for speech intelligibility.
Based on previous studies [44], this experiment applied acoustic materials to the acoustic
Figure 12. Differences between theoretical value simulation, field test results, and value in
GB/T50356-2005 [14] of reverberation time.
The actual results of the measurement indicated that the average reverberation time
of the measurement points did not meet the requirements set out in the “Theatre, Cinema
and Multi-purpose Hall Architectural Acoustic Design Code (GB/T50356-2005)” [
14
] for
an academic lecture hall. This indicates that there is an urgent need to improve the acoustic
absorption problems.
Through the simulation and measurement of the speech intelligibility, loudness, and
reverberation time of this hall, combined with the calculation of the specification, it is
found that it meets the requirements of loudness, but there are problems of low speech
intelligibility and the non-compliance of reverberation time. Based on the formula proposed
by Rao Yu’an [42],
S%=98.7 −21.7lg(TR)
where Tis the reverberation time;
Sis speech intelligibility;
Ris the different acoustic ratios (room constant);
From the above, it can be concluded that the speech intelligibility (S) in the reverbera-
tion field is inversely proportional to the logarithm of the (TR) product; that is, reducing the
reverberation time in the lecture hall can effectively improve the speech intelligibility inside
the lecture hall. Therefore, this article mainly proposes relevant acoustic modification plans
for the reverberation time problem in the lecture hall.
4. Results and Retrofit Solution
Due to the problem that different types of sound-absorbing materials have different
sound absorption coefficients and the update speed of sound-absorbing materials changes
with each passing day, this study did not compare the different types of sound-absorbing
materials. Instead, computer simulation methods are used to predict the appropriate
locations for using sound-absorbing materials and imported into the architectural acoustics
software EASE. The acoustic performances are then calculated based on different acoustic
parameters such as material and location, to predict the impact on speech metrics where
sound-absorbing materials should be placed in the room. From the aspect of reducing the
quantity of sound-absorbing materials and thus the proper placing of building materials, a
feasible renovation plan is proposed for the indoor acoustic environment of the existing
lecture hall.
Buildings 2024,14, 1583 17 of 20
Kawata [
43
] suggested that acoustic materials should be distributed over at least
two surfaces of a room to achieve acceptable acoustic conditions for speech intelligibility.
Based on previous studies [
44
], this experiment applied acoustic materials to the acoustic
performance of the rear wall, front ceiling, and rear ceiling. The acoustic absorbing materials
were placed and tested in three steps as shown in the following figure (Figure 13).
Buildings 2024, 14, x FOR PEER REVIEW 18 of 22
performance of the rear wall, front ceiling, and rear ceiling. The acoustic absorbing mate-
rials were placed and tested in three steps as shown in the following figure (Figure 13).
Figure 13. Sound-absorbing material layout plan at different locations.
Step 1: Sound-absorbing materials with an area of 88.2 m2 were applied to the rear
wall (RW), front ceiling (FC), middle ceiling (CC), and rear ceiling (RC) to compare their
acoustic performance.
Step 2: Based on the results of step 1, we set the sound-absorbing material on the RW.
And 88.2 m2 of sound-absorbing material was applied to FC, CC, and RC, respectively,
and the acoustic performance of the three spatial combinations of RW + FC, RW + CC, and
RW + RC was compared.
Step 3: Based on the results of step B, we applied sound-absorbing material to RW
and CC. Then, we set 88.2 m2 of sound-absorbing material on FC and RC, respectively. We
compared the acoustic performance of RW + CC + FC, RW + CC + RC, and the ceiling part
(AC = FC + CC + RC).
Through calculation, we found that in step 1, the shortest reverberation time was ob-
tained at RW. In step 2, the method RW + CC obtained the shortest reverberation time. In
step 3, the method RW + CC + FC obtained the shortest reverberation time. The current
measured values on-site (MEAS) are also shown in Figure 14.
Figure 13. Sound-absorbing material layout plan at different locations.
Step 1: Sound-absorbing materials with an area of 88.2 m
2
were applied to the rear
wall (RW), front ceiling (FC), middle ceiling (CC), and rear ceiling (RC) to compare their
acoustic performance.
Step 2: Based on the results of step 1, we set the sound-absorbing material on the RW.
And 88.2 m
2
of sound-absorbing material was applied to FC, CC, and RC, respectively,
and the acoustic performance of the three spatial combinations of
RW + FC, RW + CC
, and
RW + RC was compared.
Step 3: Based on the results of step B, we applied sound-absorbing material to RW
and CC. Then, we set 88.2 m
2
of sound-absorbing material on FC and RC, respectively.
We compared the acoustic performance of RW + CC + FC, RW + CC + RC, and the ceiling
part (AC = FC + CC + RC).
Through calculation, we found that in step 1, the shortest reverberation time was
obtained at RW. In step 2, the method RW + CC obtained the shortest reverberation time.
In step 3, the method RW + CC + FC obtained the shortest reverberation time. The current
measured values on-site (MEAS) are also shown in Figure 14.
Buildings 2024,14, 1583 18 of 20
Buildings 2024, 14, x FOR PEER REVIEW 19 of 22
Figure 14. The influence of the setting position of sound-absorbing materials on the reverberation
time.
In summary, we found that the best sound absorption effect is obtained when the
sound-absorbing material is applied to the rear wall, followed by the center, front, and
rear of the ceiling. Therefore, when limited material updates are being made, the lecture
hall should prioritize the use of sound-absorbing materials on the back wall to obtain
higher clarity. In terms of multi-position combination arrangements, the combination of
rear wall + ceiling center + ceiling front (RW + CC + FC) is the most efficient, exceeding the
traditional combination of full ceiling (AC) and full rear (RW + CC + RC). This idea de-
serves more trials and field research.
5. Conclusions and Discussion
A multi-purpose lecture hall known for its space-saving features faced a flood of
feedback about poor acoustic performance. This study takes the lecture hall of the School
of Architecture and Planning of Yunnan University as an example to explore the possibil-
ity of improving the acoustic environment performance through spatial layout optimiza-
tion from the perspective of architectural design. Through a combination of experimental
testing and computer software simulation, the research deeply explored three key objec-
tive parameters for evaluating the sound quality of academic lecture halls: speech intelli-
gibility, loudness, and reverberation time, and summarized the acoustic environment of
the academic lecture hall in design problems. According to this, it was found that the main
obstacle to the unclear hearing problem reported by students lies in the design and control
of reverberation time. Software simulation is then used to determine the optimal location
for sound-absorbing material placement, and the reverberation time can be controlled
within the range required by the specification while using the better spatial distribution
of sound-absorbing materials. At the same time, in conjunction with other optimization
methods, strategies to optimize the acoustic environment of the academic lecture hall are
proposed to better meet the needs of use.
Nonetheless, there are still several domains that necessitate further refinement.
Firstly, despite numerous studies indicating that computer simulations can precisely un-
dertake architectural acoustic investigations, an on-site comparative experiment would
constitute a valuable adjunct. However, the implementation of the upgrade project, based
on the findings of this study, will require a considerable duration to finalize, thus post-
poning the before–after comparison until its completion, which constitutes a significant
limitation of this research.
Secondly, the activation of numerous electronic devices (e.g., air conditioning and
lighting systems) complicates the actual conditions of the venue beyond the ideal scenario.
The human body, acting as a sound absorber, and the low murmur of crowds have the
potential to skew the actual audience effects derived from the research. It is noteworthy
Figure 14. The influence of the setting position of sound-absorbing materials on the
reverberation time.
In summary, we found that the best sound absorption effect is obtained when the
sound-absorbing material is applied to the rear wall, followed by the center, front, and
rear of the ceiling. Therefore, when limited material updates are being made, the lecture
hall should prioritize the use of sound-absorbing materials on the back wall to obtain
higher clarity. In terms of multi-position combination arrangements, the combination of
rear wall + ceiling center + ceiling front
(RW + CC + FC) is the most efficient, exceeding
the traditional combination of full ceiling (AC) and full rear (RW + CC + RC). This idea
deserves more trials and field research.
5. Conclusions and Discussion
A multi-purpose lecture hall known for its space-saving features faced a flood of
feedback about poor acoustic performance. This study takes the lecture hall of the School of
Architecture and Planning of Yunnan University as an example to explore the possibility of
improving the acoustic environment performance through spatial layout optimization from
the perspective of architectural design. Through a combination of experimental testing and
computer software simulation, the research deeply explored three key objective parameters
for evaluating the sound quality of academic lecture halls: speech intelligibility, loudness,
and reverberation time, and summarized the acoustic environment of the academic lecture
hall in design problems. According to this, it was found that the main obstacle to the unclear
hearing problem reported by students lies in the design and control of reverberation time.
Software simulation is then used to determine the optimal location for sound-absorbing
material placement, and the reverberation time can be controlled within the range required
by the specification while using the better spatial distribution of sound-absorbing materials.
At the same time, in conjunction with other optimization methods, strategies to optimize
the acoustic environment of the academic lecture hall are proposed to better meet the needs
of use.
Nonetheless, there are still several domains that necessitate further refinement. Firstly,
despite numerous studies indicating that computer simulations can precisely undertake
architectural acoustic investigations, an on-site comparative experiment would constitute
a valuable adjunct. However, the implementation of the upgrade project, based on the
findings of this study, will require a considerable duration to finalize, thus postponing the
before–after comparison until its completion, which constitutes a significant limitation of
this research.
Secondly, the activation of numerous electronic devices (e.g., air conditioning and
lighting systems) complicates the actual conditions of the venue beyond the ideal scenario.
The human body, acting as a sound absorber, and the low murmur of crowds have the
potential to skew the actual audience effects derived from the research. It is noteworthy that
the volunteers engaged in this study were young students, possibly introducing variations
in auditory perception across different demographic groups.
Buildings 2024,14, 1583 19 of 20
In conclusion, the findings of this study, alongside the results of future investiga-
tions conducted within these constraints, are anticipated to serve as a reference for the
establishment of regional standards in campus hall acoustic environment design.
Author Contributions: Conceptualization, Y.-N.Y. and J.Z.; methodology, X.-H.X. and J.-R.S.; software,
X.-H.X. and J.Z.; validation, Y.-N.Y., W.J. and Y.S.; formal analysis, J.-R.S. and J.Z.; investigation, Y.-X.L.
and J.-C.Z.; resources, Y.-N.Y., J.Z. and X.-P.W.; data curation, Y.-N.Y., W.J. and Y.S.;
writing—original
draft preparation, Y.-N.Y., J.Z. and X.-H.X.; writing—review and editing, Y.-N.Y., J.Z. and Y.S.;
visualization, W.J.; supervision, Y.-N.Y., W.J. and Y.S.; project administration, Y.-N.Y., W.J. and Y.S.;
funding acquisition, Y.S. All authors have read and agreed to the published version of the manuscript.
Funding: This research was funded by the National Natural Science Foundation of China, grant
number 51668066; Key Laboratory of New Technology for Construction of Cities in Mountain Area:
LNTCCMA, grant number 20230103; Yunnan University, grant number 2023Y43; Yunnan University,
grant number 202301138; and Yunnan University, grant number 202307058.
Data Availability Statement: Data provided in this article are supported by experimental results and
by the mentioned references.
Acknowledgments: The authors wish to express their sincere gratitude to Yunnan University, Tech-
nical University of Berlin, Huazhong University of Science and Technology, Korea University, and
Hanyang Institute for their invaluable theoretical and technical support provided for this article.
Additionally, we would like to express our heartfelt appreciation to Cui Lei from the Mathematics
Department of Beijing Normal University for his invaluable technical support throughout this project
and Johannes Reinders from TU Berlin for the proofreading.
Conflicts of Interest: The authors declare no conflicts of interest.
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