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intelligibility measured by objective and subjective methods.
The comprehensive acoustic treatment of one of the largest primary schools in Poland gave thepossibility to conduct a broader survey – in terms of number of types of rooms and situations assessed
as well as the number of the participants.

2. PROBLEMS OF RESEARCH, MEASURING METHODS
2.1 Methodology
The research puts forward the main research problem related to searching for a correlation between
the Acoustic Change Feelings Scale improvement and changes in school functioning experienced by
the students and teachers. The research problem is included in the question:
Whether and to what extent the acoustic treatment of the school interior influenced the assessmentof changes observed by the students and teachers?
The students’ and teachers' opinion surveys used the proprietary measurement scale prepared forthe needs of this study: Acoustic Change Feelings Scale for teachers and students – ACFS-T and
ACFS-S. The studies were based on statistical calculations using a Wilcoxon rank test based on rank
values. All calculations were made at the significance level Į= 0.05.
2.2 Research area
Primary school no. 340 in Warsaw with its 1200 students was (2016) the second largest primaryschool in Poland. The school building was constructed in 2012 according to a design that did not take
into account the room acoustics at all. Hard finishing of the rooms and very large number of students
meant that the building was loud enough so that the Parent Board started efforts to carry out acoustic
treatment. In 2016, the City Council of Warsaw decided to allocate some funds to this task and theworks, performed according to the design of Andrzej Kłosak (acoustics) and Weronika Nowak(architecture) was finished in August 2018. Acoustic treatment covered all classrooms, after-school
clubs, corridors, lobbies, canteen, auditorium, gymnasiums and sport hall.
2.3 Study population
378 students and 40 teachers participated in the study. The study involved students from the second
grade to the eighth grade of the primary school. The most numerous represented classes was the fourth
grade (45% of the study population) and the fifth grade (30% of the study population).

3. ACOUSTIC TREATMENT
3.1 Sound absorbing solutions applied
Acoustic treatment in school consisted in installation of sound absorbing solutions described in the
Table 1. The main objective was to fulfil the demands of PN-B-02151-4:2015-06 standard, although
it was sometimes impossible due to existing building limitations. More about that issue writes Kłosak
(2). Below are description of some particular rooms cases: applied solutions and measured effects.
Table 1 – Sound absorbing solutions used for acoustic treatment
Sol.

Description

Practical sound absorption coefficient Įp, Hz
125 Hz250 Hz500 Hz

1 kHz

2 kHz

4 kHz

A

15 mm glasswool, 200 mm air gap

0,40

0,85

1,00

0,90

1,00

1,00

B

100 mm glasswool, no air gap

0,80

1,00

1,00

1,00

1,00

0,95

C

40 mm glasswool, no air gap

0,25

0,80

1,00

1,00

1,00

0,90

D

40 mm glasswool, no air gap

0,25

0,75

1,00

1,00

1,00

1,00

E

100 mm glasswool, no air gap

0,80

1,00

1,00

1,00

1.00

0,95

3.2 Classrooms
The building has 36 classrooms with the floor surface area between 31.3 m2 and 72.3 m2 , where5897

most of these rooms (63%) have the surface area between 59.0 m2 and 67.0 m2. The height of allclassrooms before the treatment was 3.0 m. Floors finished with seamless PVC lining, masonry andplastered walls, reinforced concrete ceiling slabs floors, plastered.
The acoustic treatment consisted in the installation of sound absorbing solution B on the ceiling,around the perimeter of the rooms (coverage from 43.4% to 50.6%). Due to the building regulations
specifying the minimum height of classrooms, it was not possible to cover the more surface of theceilings. The same solution was used on two walls of each classroom (rear and one of the side walls).
Panels covering the entire available surface of these walls higher than 200 cm.
Figure 1 presents values of reverberation time (before and after acoustic treatment) measured in 6classrooms for early education located on the first floor. Despite the limitations mentioned above, thebasic requirements of the standard for classrooms (RT  0,6 s) have generally been met, subject tominor exceeds of the permissible values in few cases. These exceedances occurred mainly within the
250 Hz octave band and were usually no more than 5%, which is permitted by the standard. These
exceedances occurred in the classrooms in which the furnishing was more modest or in which there
were additional building restrictions resulting in a smaller amount of sound absorbing materials
introduced. At the same time, it should be noted that among 9 classrooms for early education andlinguistic teaching only one met the tougher recommendations of the same standard regarding thesetype of classrooms (RT  0,5 s).

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Figure 1 – Classrooms (early education), reverberation time RT, (s), before and after acoustic treatment
Table 2 presents the results of speech transmission index STI measurements in three classrooms (one fromeach category: early education, language education and general). As a result of the acoustic treatment, asignificant improvement was achieved by increasing the averaged STI values by 0.20 – 0.23 for each room.
Thus, the requirements of the standard were met with a large margin.
Table 2 – STI values measured before and after acoustic treatment in selected classrooms
Room

Speech transmission index STI
minimum

beforeafter

averagelowestaveragelowestaveragelowestClassroom 116, Polish language

0,60

0,55

0.49

0.46

0.71

0.68

Classroom 123, English language

0,60

0,55

0.47

0.45

0.70

0.68

Classroom 137, early education

0,60

0,55

0.52

0.50

0.72

0.69

3.3 Sport hall
The sport hall has the floor surface area of 1068.0 m2 and volume of 11,072.0 m3. There are
masonry and plastered walls, sports floor on joists, a single-sided roof with a structure made of glued

5898

laminated timber and covering with sandwich panels.
Due to concerns regarding the load-bearing capacity of the roof structure, the designers decided to
introduce sound absorbing solutions only on the walls of the hall. On both gable walls and on one of
the longitudinal walls, 50 cm to 370 cm high (from the floor level), sound absorbing solution D was
installed. On all walls of the sport hall, above the height of 370 cm (from the level of the floor), soundabsorbing solution E was mounted. The total area of sound absorbing solutions is 77.3% of the total
wall surface area. The achieved reduction of the reverberation time value is presented in Figure 3.
ϴZĞǀĞƌďĞƌĂƚŝŽŶƚŝŵĞ;ƐͿ

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ZdŵĂǆ͘;WEͲͲϬϮϭϱϭͲϰͿϭϬϭϮϱ,ǌϮϱϬ,ǌϱϬϬ,ǌϭϬϬϬ,ǌϮϬϬϬ,ǌϰϬϬϬ,ǌϴϬϬϬ,ǌ&ƌĞƋƵĞŶĐǇ;,ǌͿ

Figure 2 – Sport hall, reverberation time RT, (s), before and after acoustic treatment
3.4 Corridors and halls
The layout of each floor of the building are organised around of spacious hall (670 cm wide)
converging narrower corridors (313 – 340 cm wide). The height of the corridors and halls before theacoustic treatment was 330 cm (ground floor) and 300 cm (1st and 2nd floor). Masonry and plasteredwalls, reinforced concrete ceiling slabs, plastered, floor finished with seamless PVC lining.
The acoustic treatment consisted in the installation of the sound absorbing solution A covering theentire available ceiling area (in many places it is limited by the plasterboard casing of the building
technical services). Additionally, sound absorbing solution C installed on available wall sections
above the height of 200 cm. As a result of this treatment corridors’ total equivalent absorption area
was raised 8 to 10 times by far exceeding level demanded by standard PN-B-02151-4:2015-06.
A significant increase in sound absorption of most rooms in the school led to a significant reductionin the sound level in these rooms. Before and after the modernisation, a number of random sound levelmeasurements were carried out to capture the scale of the phenomenon. Table 4 presents the results
Table 3 – LAeq values measured before and after acoustic treatment in selected rooms
LAeq (dBA)

Room

ActivitySport hall

Dodge ball: 40 students involved in the play in central
VHFWRURIWKHKDOOLQVLGHVHFWRUVWZRRWKHUJURXSVRI
students each occupied with quieter tasks

82.0

75.7 - 76.3

After-school clubFree activity: 30 students playing in groups

79.2 - 81.5

72.8 - 77.2

Hall

Break: 50-70 students, no smartphones allowed

81.4 - 86.9

73.8 - 80.0

CanteenLunch: 70-140 students

BeforeAfter85.5 - 86.0 73,4 – 76,65899

4. SURVEY RESULTS AMONG THE STUDENTS AND TEACHERS
4.1 General questions
In the first points in both questionnaires (for teachers and students) participants were asked to pointout situations and spaces where they noticed changes after acoustic treatment. The presented data
show that about 68% of children observed any sort of changes in functioning of the school and themost numerous group noticed general decrease of sound level in the building. Smaller but significant
group pointed better speech intelligibility in various situations (Table 4).
Table 4 – General changes noticed by the students after acoustic treatment
Observed changes

Number of answers

Percentage(n=378)
I can see the difference (generally).

256

67,72%

There is more quiet at school.

163

43,12%

There is more quiet in corridors

154

40,74%

Children are less running now in corridors

18

4,76%

Children are less quarreling in the corridors

19

5,03%

I understand the teacher better in the classroom

100

26,46%I understand the teacher better in the gymnasium

80

21,16%I understand the teacher better in the corridor

68

17,99%The teachers seem to be much more sensitive to the changes in acoustic environment (Table 5).
This group appreciated mostly better speech intelligibility in classrooms and corridors, lower voiceeffort and decreased level of fatigue. They also pointed out better students’ performance.
Table 5 – Changes in teachers’ working conditions and students performance noticed by the teachers after
Observed changes

Number of answers

Percentage(n=40)
improved general comfort of work

34

77,27%

in fatigue level after working day

18

40,91%

in vocal effort during the day

20

45,45%

in work comfort while on duty in corridor

19

43,18%

in students’ performance during individual work

19

43,18%

in students’ performance during team work

15

34,09%

in the level of understanding verbal instructions in classes

27

61,36%

in the students’ behaviour during breaks

15

34,09%

in communication with the students during breaks

27

61,36%

When teachers and students were asked to evaluate level of observed changes in different types ofspaces they pointed mostly for classrooms: 30% of the students and 77% of teachers answered thatchanges here were large or very large.

5900

4.2 Detailed questions
In this part of the survey respondents were asked to assess impact of the acoustic treatment on
particular aspects of school activities. Each evaluation was made in 5-level range. For each casestatistical calculations using a Wilcoxon rank test based on rank values were made. All calculations
were made at the significance level Į= 0.05. In all calculations, the hypothesis H0 was assumed thatthe average results of the assessments determined by the respondents (before and after acoustic
treatment) are significantly equal and the alternative hypothesis H1 that the average results ofassessments determined by the researched subjects (before and after acoustic treatment) aresignificantly different.
4.2.1. Students’ level of concentrationǀĞƌǇůŽǁ

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Figure 3 – Students’ level of concentration on task during individual work, assessment made by teachers(left) and students (right).
4.2.2. Students’ pace of workŵĞĚŝƵŵ

ůŽǁŚŝŐŚŵĞĚŝƵŵ

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ǀĞƌǇůŽǁ

Figure 4 – Students’ pace of work during afternoon lessons, assessment made by teachers (left) andstudents (right).
4.2.3. Students’ short term memory capacityǀĞƌǇŚŝŐŚ

ŚŝŐŚϱϱ͕Ϯϲй
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ǀĞƌǇůŽǁ

Figure 5 – Students’ short term memory capacity, assessment made by teachers and concerning new content(left) and difficult content (right).

5901

4.2.4. Students’ task fulfillmentůŽǁǀĞƌǇŚŝŐŚ

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Figure 6 – Students’ task fulfillment, assessment made by teachers for simple tasks (left) and complex ones
(right).
4.2.5. Students’ fatigueďĞĨŽƌĞ

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ŚŝŐŚ

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Figure 7 – Students’ fatigue during afternoon lessons, assessment made by teachers (left) and students(right).
4.2.6. Students’ level of aggression

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Figure 8 – Students’ level of aggression during breaks in assessment of teachers: physical aggression (left)
and mental aggression (right).

5. DISSCUSSION
Presented above data are just a part of all collected during survey answers. The whole materialshows following consequences of acoustic treatment of school premises.
Teachers asked about students’ performance and behaviour noticed positive changes in level ofconcentration and pace of work (both during individual and group work), task fulfillment, short term
memory capacity, durability of memory, level of fatigue and aggression and above all level of speech
intelligibility.

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When asked about their working conditions they can see benefits in lower fatigue, lower voiceeffort, lower prevalence of hoarse, headache and tinnitus and lower level of stress. In both groups ofquestions statistical calculations allowed for positive verification of the assumed hypotheses,
therefore the acoustic treatment at school has a positive effect on teachers’ wellbeing and students’performance and behaviour.
Students asked about their own performance noticed better concentration, speech intelligibility andpace of work. They point out lower level of aggression. Expressed levels of changes are lower thanamong teachers, however statistical calculations allowed for positive verification of the assumed
hypotheses with just one exception: students can’t see any difference in their level of fatigue.
Both groups pointed out higher students’ school achievements after acoustic renovation of thebuilding, but the teachers found stronger correlation. 76% of teachers assess that students’ school
achievements are higher and 14% said that semester grades are far better (while 86% said that changes
are small or none). Corresponding percentage for students are 29% and 26% (while 69% pointed small
or none changes and 5% reported worse grades).
Interesting observation was made concerning classrooms. In these school, like in most of others,
when discussion on “damping” started, teachers and parents were focused on corridors, sport hall,canteen and after-school clubs. Classrooms were of secondary interest. However survey proved thatthese rooms are the spaces were acoustic changes were most appreciated and where acoustic treatment
was most needed.

6. CONCLUSIONS
Data collected in the survey clearly confirms positive opinions spontaneously expressed by theusers just after school modernization. It shows how important is acoustical environment of the school
for wellbeing and performance of both, students and teachers. Thus it proves need of wide acoustic
treatments in existing buildings. Subsequent research results will be presented in later studies of theauthors

ACKNOWLEDGEMENTS
We would like to thank in particular the authorities of primary school no. 340 in Warsaw, whichgave us the opportunity to carry out extensive surveys among students and teachers. We also would
like to thank Andrzej Kłosak for sharing the measurements results.

REFERENCES
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selected primary schools, Archives of Acoustics 35 (4), 521–542, DOI: 10.2478/v10168-010-0040-2,
2010.
2. Kłosak A. From measurements, through computer modelling, design and construction, back tomeasurements: acoustical modernization of 800 pupils primary school in Warsaw, Poland, Proc I&69
7--XO\0R WUHDO&D DGD L SUL W .
3. Koszarny Z., Jankowska D., Determination of acoustic climate inside elementary schools, (in Polish)
Rocznik PZH, 1995, XLVI, Nr 3
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Climate in Selected Schools Before and After Acoustic Treatment, Archives of Acoustics 35 (4), 551-564,
DOI: 10.2478/v10168-010-0042-0, 2010.
5. Mikulski W., Radosz J., Acoustics of Classroom in Primary Schools – Results of the Reverberation Timeand the Speech Transmission Index Assessments in Selected Buildings. Archives of Acoustics 36 (4), 777793, DOI: 10.2478/v10168-011-0052-6, 2011.
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