The study centred on the “school as a workplace” and as such the workplace of teachers and pupils. The study shows the link between a reduction in noise and the reduction in teachers stress levels. It also demonstrates that sound level reduction in the occupied room is more dramatic with multi conversation activities such as groupwork.

1. Modern School Acoustics
On teaching styles, room acoustics, teachers'
health and pupil behaviour

2. Modern School Acoustics on teaching styles,
room acoustics, teachers’ health and pupil
behaviour
By Dr. Markus Oberdörster, Ecophon Germany and Dr. Gerhart Tiesler, Institut für Interdisziplinäre Schulforschung
der Universität Bremen (Institute for interdisciplinary school research of the University of Bremen, Germany)
1. Noise in schools – current by pupil noise. One year later, the Of course, the sound pressure level performance and/or teachers' work
status of school research Bundesanstalt für Arbeitsschutz und measured in the classroom does stress? And, not least, what are
Schools have become much noisier Arbeitsmedizin (German Federal not only consist of unwanted noise, teachers really talking about when
in recent years, with the number Institute of Occupational Health) since the teacher's voice and a they complain about noise in the
of complaints about this steadily was commissioned to carry out necessary contribution of pupil classroom – the measurable SPL
increasing. In 1999, a study by the most extensive research project voices are also involved. Thus, or, rather, the way in which their
the ISF (Institute for Interdisciplinary to date on "Noise in educational overall classroom noise is generated teaching is disturbed?
School Research) of the University establishments". Observations from by the two-way teaching process All these issues resulted in the
of Bremen, with about 1,200 more than 570 lessons showed as well as by other factors. Even most recent ISF study in 2005
teachers participating, gave a very an average classroom SPL (sound if this overall level were generated on the "Acoustic ergonomics of
clear picture of the stress factors that pressure level) of approximately exclusively by the teacher, this schools". Based on 175 lessons,
arise in schools. When questioned, 65 dB(A). Levels that are this would mean - at the very least - that the first stage involved researching
more than 80% of those taking part high mean that communication he or she would have to speak in the effects of different teaching
admitted experiencing stress caused can be extremely difficult or even a raised voice throughout the entire methods (direct teaching vs.
impossible. lesson. student-centred teaching) on the
The question of noise in schools basic* and working** SPL in
"I am stressed Answers (%)
is therefore extremely complex. the classroom. The second stage
by the noise 50 How, for instance, does the general involved an investigation into
that pupils noise level in the classroom affect how changing room acoustics
make." 40 the communication processes (reverberation time and speech
that take place there? How it is intelligibility) affects this level for
30 possible to differentiate between each respective teaching method.
disturbing noise on the one hand It was possible not only to analyse
20 and useful noise (sound) on the average values for lessons but
other hand, when carrying out a also to gain insight into actual
ISF study, 1999: 80%
of teachers complain 10 scientific teaching analysis? How teaching phases that showed clear,
about the noise made do SPL and poor understanding pedagogical characteristics.
by pupils 0
of communication affect pupil
do not agree tend not to agree totally agree
at all agree slightly *The Basic SPL: the general basic noise level in a fully occupied class over a defined time period.
** The Working SPL: the noise level parameter describing a working situation.
2

3. The third stage then addressed how 2. Teaching past and
noise, in terms of natural, working present - schooling reflected
sounds, affects teachers during in educational trends
lessons. How do room acoustics The education system in most
affect teachers' measurable industrialised countries is changing
physiological stress in relation to faster than ever before, not just
actual teaching events? since recent OECD-Reports1).
These kinds of ergonomic The organisation of schooling in
questions, linked with actual general, and teaching methods in
educational trends, may be particular, have changed a lot in School with predominantly student-centred teaching method.
surprising at first glance. However, recent years.
they give an interesting insight into Is noise in schools a new
the concept of noise in schools, problem, one that did not exist
its causes and effects, and into previously? This question is certainly
other acoustic factors such as justified, since complaints by
reverberation time and speech teachers about noise do not occur
intelligibility. in the literature from the beginning
of the 1900s. The "modern",
"student-centred" and "non teacher-
centred" teaching methods (e. g.
partner, group or project work)
that are promoted by educational
experts do certainly produce totally
different communication scenarios
1) OECD (Organisation for Economic Co-operation and Development)/PISA (Programme for International Student
Assessment, Learning for Tomorrow's World, First Results from PISA 2003, OECD Publishing, Dec 2004, 478 p,
ISBN: 9264007245. (Available in English, German, French, Portuguese and Spanish)
OECD/Centre for Educational Research and Innovation (CERI), Schooling for Tomorrow: Think Scenarios, Rethink
Education, OECD Publishing, April 2006, 200 p, ISBN: 926402364X (Available in English and French) School with predominantly direct teaching method.
3

4. in the classroom in comparison The methods chosen are generally
with those produced by traditional, dependent on the personal
direct teaching. The image of the preferences of the teaching staff
teacher as a distributor of material, and on the prevailing teaching
a channel of knowledge, is fading. style at the school in question.
The presence of technology was only unfamiliar for a short time. After just a few
Pupils now have to independently The layout of the classroom and hours, children saw the measuring instruments and loudspeakers as just another
investigate, weigh up, discuss the arrangement of the desks are part of normal classroom equipment.
and acquire the knowledge and sometimes relevant, since these
skills to solve the problems they indicate the teaching methods
are presented with. Modern that are used to determine what
teaching relies much more on happens in the classroom. 3. The peculiarities of noise around 65 dB(A) must be rated as
shared learning, and deliberately Shortsighted analyses, which in schools a useful or wanted signal, general
permits several people to talk in have attributed the much higher When discussing noise in relation pupil murmur of around 55 dB(A)
the classroom at the same time. noise levels in recent decades to education and schools, its quality during a quiet working period might
Even in a disciplined discussion exclusively to social or educational and quantity are very different be rated as noise interference. A
environment, however, higher noise trends, fall far short of the truth. from that of the noise occurring in straightforward increase in the noise
levels than before occur, when Even early investigations proved commercial workplaces, be it an level in a classroom, without taking
teachers used to lecture the class the relationship between a room's industrial or an office environment. the actual teaching situation into
as a whole. This is particularly the acoustic working environment, While the noise produced by consideration, is only a small part
case when the teacher exercises a the quality of communication and machinery is generally felt to be of the noise in schools concept.
high level of discipline. the development of noise in the noise interference, the noise level A first, decisive criterion for
Nowadays we tend to find a classroom. It is therefore important in educational environments should appraising noise in schools
mix of direct and student-centred to ask: What are the determining be regarded as a useful signal is the ratio of “useful signal”
teaching styles in the classroom (key factors for teaching in respect of with a widely varying degree of to “interference signal” in the
phrase "frontal teaching discussion"). modern, educational methods? interference factor. Its differentiation classroom, taking into account the
and evaluation depend on the communication processes in the
teaching method being used in lesson. For an adult, the useful
the case in question. For example, signal must generally be around
while text being read out in a 9 dB higher than the interference
voice with a speech volume of signal if error-free speech
4

5. intelligibility is to be achieved. the teacher's voice is transmitted
Since an adult voice is designed for from only one point and –
a normal speech volume of around depending on the size of the room
50 to 55 dB(A), this means that and the position of the teacher
the noise interference level must be - may need to travel over a distance In more than 570 lessons, as well as the SPL being measured, the activities in
less than 40 dB(A). Even in quiet of up to 6 m to reach pupils sitting the classroom such as teaching methods or proportion of speech were recorded
work periods, however, the SPL in at the back. If the basic noise is every second.
schools seldom measured under 50 unchanged, this involves either
dB(A), i.e. teachers usually have to a distinct additional strain on the
raise their voices in order to pass teacher's voice, leading to long
information on to the pupils. In term health consequences, or an will compensate for the poorer
addition, specialist literature points interrupted flow of information to speech intelligibility in their groups
out that primary-school children pupils sitting further away, resulting by raising their voices, which in
need to specifically learn how to in negative effects on their learning. turn increases the noise interference
listen and understand before they There is another aspect to level for the others, and so on.
can develop their as yet untrained consider in relation to modern, The noise level in the classroom
acoustic memory. Young hearers student-centred teaching methods. If therefore gradually increases even
therefore need a useful signal level there are several groups speaking if the number of people actually
that is about 15 dB louder than in the room at the same time, the communicating remains the same.
the ambient noise interference. An signal from one group becomes This is known in acoustic circles as
added difficulty is the fact that the noise interference for the other the Lombard effect.
noise interference in a classroom is groups. This results in a negative
relatively evenly distributed, while chain reaction. The other groups
5

6. 4. "Acoustic Ergonomics" – contrary, under optimum conditions Share of "quiet" teaching phases (overall) in classrooms with
noise in schools and the noise level measured during good/poor acoustics.
teachers' health student-centred teaching phases Share of time (%)
Room acoustics are particularly was even lower than during direct
80
significant with regard to modern teaching.
70
teaching. For instance, short Overall, the basic SPL in
reverberation times result in a classrooms with reverberation times 60
precise speech signal (especially of less than 0.5 seconds were 8 50
in respect of consonants), and dB lower than in classrooms with
40
people can communicate with a reverberation times of between 0.6
lower signal-to-noise ratio. The study and 0.8 seconds. 30
Acoustic Ergonomics in Schools 20
(2005) showed that the build-up
10
of noise is considerably less, or
does not occur at all, in classrooms 0
Reverberation time > 0.5 sec. Reverberation time < 0.5 sec.
that have good acoustics. On the
Under better acoustic conditions, the proportion of "quiet" teaching units was
more than 80% compared to approximately 67% under poorer conditions (in
relation to the average speech volume of an adult - approx. 62 dB(A) - taken
as normal teaching speech).
6

7. Pupil-centred teaching phases are frequently quieter under The rise of the basic SPL over the morning is much less in
good acoustic conditions. rooms with short reverberation times.
Share of time (%) LA95 [dB(A)]
80
70
70
60 65
50
60
40
30
55
20
10 50
0
Reverberation time > 0.5 sec. Reverberation time < 0.5 sec. 45
Even more obvious is the change in classroom conditions during student-centred
40
teaching phases. In this case the proportion of quiet time units doubles! This
clearly indicates an absence of the Lombard effect during partner, group or
project work. The difference in levels between rooms with good acoustics and 35
those with poor acoustics while these teaching methods were used was more
than 13 dB! 30
1 2 3 4 5
Lessons
An additional, important aspect was revealed by this comparison of teaching
situations. The normal increase in the basic noise level over the course of the
school day did not occur in the classrooms with short reverberation times (< 0.5
seconds). This has a significant effect on the teaching process and provides an
initial indication of the physiological reactions that take place as a result of the
acoustic working environment.
7

8. After acoustic refurbishment, the teacher works with a 5. Consequences and schools. The relationships were
relaxed heart rate for more than 80% of the time compared outlook easily identifiable. Only the schools
to just 60% before refurbishment. With a change in educational where the staff followed a common,
Share of time (%) approaches, a steady increase in accepted educational concept were
student-centred teaching methods really quiet. In schools where the
100 and a corresponding reduction in same rules apply in all classrooms,
direct teaching, it may be necessary during all lessons and in all the
90 to re-evaluate school buildings that different areas of the school, and
have functioned well for many where the children can expect the
80 years. New teaching methods same teacher reaction if they do not
place new demands on the basic comply with those rules, the noise
70 ergonomic conditions. levels measured over a long period
It would be absurd to claim were lower. The recipe is therefore
60 that teachers themselves have as simple as it is effective. The only
no influence on noise in their requirement is that staff work as a
50 classrooms. They do, of course team and are consistent.
Reverberation time > 0.5 sec. Reverberation time < 0.5 sec. – and it is important that they The school organisation and
The positive effects of good room acoustics also reduce the teacher's stress level. exert this influence. This issue is the personal contributions of
After an acoustic refurbishment, the same teacher was subject to comparatively addressed in depth in the research individual teachers are essential
little work stress for a much greater part of the lesson. Further investigations also report of the study "Noise in factors in effectively reducing
showed that the teacher was less sensitive to the stress-inducing noise, with educational establishments" (2004). noise in schools. The ergonomic
work thus becoming much more relaxed. It is undoubtedly true that there is an This study also showed the level conditions provide the necessary
ergonomic dimension to the acoustic design of classrooms. It directly affects the reductions that can be expected foundation for the teaching activities
levels of work stress, activation and fatigue of the people who teach (and learn) after fairly immediate intervention by of the school day. Neither of the
in these premises.
individual teachers: approximately two aspects can be replaced
2 dB. At the same time, however, nor offset by the other. They are
in rooms with resembling acoustic mutually interdependent and need
conditions and a comparable pupil to interact if the teaching process
social structure, there was evidence in context of modern pedagogical
of similar differences (5 to 6 dB) communication is to function
in the noise levels of different properly.
8

9. The proud team of "scientific staff" after successfully measuring the acoustics of their classroom.
9

10. Classroom solution
Recommendation for normal sized classrooms
(area: <100m², volume: <200m³, length: <9m)
Acoustic ceiling of sound absorption
1.1 - Classroom Solution class A (Ecophon Master) Wall absorber from 0.8 to 2.0 metres
above the floor (Ecophon Wall Panel)
1.1 Classroom solution
Reflector over the teacher's desk
area if enhanced speech comfort is
needed (Ecophon Master/gamma)
Additional wall absorber from 0.8 to 2.0
above the floor if there is a risk for flutter
echo or if increased sound level reduction
1.2 Classroom solution with low
1.2 - Classroom Solution is needed (Ecophon Wall Panel)
with low frequency absorber
frequency absorber Low frequency absorber
(Ecophon Master Extra Bass)
10

11. Glossary
Acoustics
The study of sound. In everyday language also refers to how sound is
perceived in particular premises.
Reverberation time, (T or RT)
The time it takes for the sound pressure level to fall by 60 dB after the
sound has been turned off. Measuring the reverberation time allows us
to calculate the total sound absorption. The reverberation time varies
according to the frequency.
Sound pressure level (dB)
The variations caused by sound waves in air are called sound pressure.
The lowest sound pressure level which can be heard is 0 dB, known as
the hearing threshold. The highest level which can be tolerated is called
the pain threshold and is around 120 dB.
Speech intelligibility
Speech intelligibility is directly dependent on the level of background
noise, reverberation time and the shape of the room. Different methods
are used to evaluate speech intelligibility, the most common ones are
RASTI, STI and %ALcons.
Lombard effect
The Lombard effect is the tendency to increase one's vocal intensity in
noise.
© Ecophon Group 2006 11
Idea and layout: Saint-Gobain Ecophon AB, Printer: Skånetryck AB, Photo: Saint-Gobain Ecophon GmbH, Illustrations: Condesign Infocom AB, Dr Gerhard Tiesler and Saint-Gobain Ecophon GmbH

12. Complaints about noise pollution in educational premises were the
reason to cast a light on causes and consequences of “school noise”.
This interdisciplinary study investigated various kinds of teaching/
learning styles and sound pressure levels in the classroom, and
moreover, how improved room acoustic conditions affect sound levels
together with teachers' workload and fatigue.
This publication is a complement to the book “Don't limit your senses” Sound and the Learning Environment,
Saint-Gobain Ecophon, ISBN 91-974193-2-X published in 2002.
06.11 5000, Art no: 929050
Saint-Gobain Ecophon AB, Box 500, S-260 61 Hyllinge, Sweden, phone +46 42 17 99 00, fax +46 42 22 59 29,
e-mail: ecophon.export@ecophon.se, www.ecophon-international.com