1. ACOUSTIC ANALYSIS IN
KINDERGARTEN CLASSROOM
Student: Eduardo Artigas 201310871
Instructor: Poul Henning Kirkegaard
Course: Rum- og bygningsakustik
AARHUS
UNIVERSITY
DEPARTMENT OF ENGINEERING

2. Abstract
1. Introduction
2. Standard
requirements
2.1 General
acoustic
requirements
2.2 Educational
and
childcare
buildings
3. Potential
acoustic
problems
in
a
Kindergarten
4. Acoustics
of
a
room
design
for
speech
4.1 Reverberation
time
4.2 Absorption
treatment
4.3 Speech
intelligibility
4.3.1 Analytical
measure
methods
for
speech
intelligibility
5. Methodology
5.1 Room
description
and
analysis
setup
5.2 Noise
criteria
5.3 Source
and
receiver
position
5.4 Parameter
variation
5.5 Measurements
methods
6. Simulation
results
6.1 Sabine
equation
Vs.
CATT
simulation
6.1.1 Classroom
1
(single)
and
Classroom
2
(double)
6.2 Reverberation
time
(RT60)
6.2.1 Classroom
1A:
single
room
with
high
absorptive
materials
6.2.1.1 RT60
at
receiver
1:
analysis
at
frequency
level
6.2.1.2 RT60
at
receiver
1:
analysis
at
each
setup
6.2.2 Classroom
1B:
single
room
with
lower
absorptive
materials
6.2.3 Classroom
1A
and
1B:
analysis
comparison
6.2.4 Classroom
2A:
double
room
with
high
absorptive
materials
6.2.4.1 RT60
at
receiver
1:
analysis
at
frequency
level
6.2.4.2 RT60
at
receiver
1:
analysis
at
each
setup
6.2.5 Classroom
2B:
double
room
with
lower
absorptive
materials
6.2.6 Classroom
2A
and
2B:
analysis
comparison
6.3 Speech
transmission
index
(STI)
6.3.1 Classroom
1A:
single
room
with
high
absorptive
materials
6.3.2 Classroom
1A
and
1B:
analysis
comparison
6.3.3 Classroom
2A:
double
room
with
high
absorptive
materials
6.3.4 Classroom
2A
and
2B:
analysis
comparison

3. 7. Discussion
7.1 Sabine
equation
7.2 Reverberation
time
7.3 Speech
transmission
index
7.4 Reverberation
time
&
STI
8. Conclusion
9. References
Appendix
1:
Sabine
Appendix
2:
RT60
Classroom
1
Appendix
3:
STI
Classroom
1
Appendix
4:
RT60
Classroom
2
Appendix
5:
STI
Classroom
2

4.
1
1. Introduction
Acoustic
is
an
important
factor
to
achieve
a
high
indoor
climate
quality
level.
“Good
acoustic”
is
defined
as
a
combination
of
objective
and
subjective
factors,
which
can
be
divided
into
measures
that
are
related
to
the
distribution
of
sound,
the
dispersion
in
the
room
and
multiple
measures
related
to
the
noise
level
in
the
room.
Moreover,
acoustic
is
a
generic
concept
that
includes
several
interpretations
and
definitions.
Generally,
the
definition
of
acoustic
is
divided
into
concepts
[1]:
building
acoustics
or
sound
insulation
(damping
of
external
noise)
and
architectural
acoustics
or
sound
control
(damping
of
internal
noise).
In
non-­‐residential
profession
like
teaching,
noise
is
presumed
to
be
a
nuisance
than
a
risk
factor
for
noise-­‐induced
hearing
loss.
Studies
establish
that
there
are
indications
that
noise
exposure,
even
of
low
intensity,
is
associated
with
increased
sickness
absence.
In
kindergarten
classrooms,
noise
has
the
potential
to
interrupt
on-­‐
going
activities
and
to
disturb
the
perception
of
the
speech
[2].
In
educational
facilities,
the
main
mode
of
communication
are
speaking
and
listening.
Due
to
these
factors,
it
is
important
to
design
a
good
acoustic
environment
that
maximizes
the
learning
opportunities
for
the
students.
In
the
case
of
a
kindergarten,
children
become
the
major
noise
source
in
classrooms
generating
high
level
of
noise.
Then,
as
estate
in
the
previous
paragraph,
teaching
profession
might
have
a
high
noise
exposure
that
is
associated
with
increased
sickness
absence
[2].
The
paper
studies
the
architectural
acoustics
of
a
kindergarten’s
classroom
by
CATT
simulation
software.
This
program
uses
RTC-­‐II
(Randomized
Tail-­‐corrected
Cone
tracing,
second
version),
Ray-­‐tracing
(method
for
calculating
the
path
of
waves
through
a
system),
to
evaluate
the
acoustic
variables
[3].
First,
it
is
established
a
single
room
distribution
for
the
case
of
teaching-­‐learning
communication
mode.
Two-­‐design
room
configurations
are
set
up
for
the
previous
room
distribution,
one
with
better
acoustic
materials
than
the
other
room.
Then,
each
configuration
is
improved
and
evaluated
by
a
parametric
variation
study.
Three
measures
are
used
to
evaluated
the
acoustic
environment:
reverberation
time,
signal
to
noise
ratio
and
speech
transmission
index.
2. Standard
requirements
[4]
2.1 General
acoustic
requirements
The
concepts
of
reverberation
time
and
absorption
are
defined
in
DS/EN
12354-­‐
6,
Building
acoustics-­‐
Estimation
of
acoustic
performance
of
buildings
from
the
performance
of
elements
–
Part
6:
Sound
absorption
in
enclosed
spaces.
Check
measurements
of
sound
conditions
must
be
made
in
accordance
with
SBi
Guidelines
217,
Performing
building
acoustics
measurements.
2.2 Educational
and
childcare
buildings
SBi
Guideline
218,
Sound
conditions
in
educational
and
childcare
buildings
specify
the
sound
requirements
and
make
recommendations
in
respect
of
sound
conditions
in
educational
and
childcare
institutions.
o Reverberation
time,
T

5.
2
-­‐ Occupiable
rooms
≤
0.4
s
o Absorption
area,
A
-­‐ Occupiable
rooms
with
a
ceiling
height
greater
than
4
m
and
a
room
volume
greater
than
300m3
≥
1.2
x
room
floor
area.
o Speech
Transmission
Index
(STI)
is
defined
in
DS/EN
60268-­‐16,
Sound
system
requirement
–
Part
16:
Objective
rating
of
speech
intelligibility
by
speech
transmission
index
(Danish
standards,
2003c)
and
DS/EN
ISO
14257,
Acoustics
–
Measurements
and
parametric
description
of
spatial
sound
distribution
curves
in
workrooms
for
evaluation
of
their
acoustical
performance
(Danish
Standards,
2002a).
-­‐ Within
a
teaching
group,
an
STI
in
excess
of
0.6
between
teacher
and
pupil
and
from
pupil
to
pupil
should
enable
clear
communication.
o Sound
transmission
attenuation
in
accordance
with
DS/EN
ISO
14257
(Danish
standards,
2002a).
-­‐ Recommended
sound
transmission
attenuation
should
be
greater
than
5
dB
3. Potential
acoustic
problems
in
a
Kindergarten
Noise
in
classrooms
has
the
potential
to
interrupt
on
going
activities
and
to
disturb
the
perception
of
speech.
The
annoying
noise
could
be
either
self-­‐
generated
noise
from
laughing,
chatting
or
bullying
during
lessons
or
related
to
the
physical
environment
such
as
noise
from
chairs
and
tables
or
external
noise,
such
as
from
other
classrooms.
As
it
is
mentioned
above,
either
children
or
teachers
suffer
the
consequences
from
noise
and
poor
acoustics
environments.
However,
the
effects
on
them
are
relatively
different.
From
a
teacher
view,
poor
acoustical
working
conditions
are
associated
with
increased
sickness
absence
[5].
That
absence
is
produced
by
psychological
and
physical
factors:
• Job
satisfaction;
low
satisfaction
is
associated
with
sickness
absence,
burnout,
depression,
and
anxiety
[6],
as
well
as
lower
productivity.
• Fatigue;
it
brings
negative
influence
on
task
performance,
as
well
as
it
may
lower
energy
levels
and
aggravate
voice
symptoms.
Regarding
the
world
of
the
child,
children
environment
is
becoming
much
noisier
than
fifty
years
ago
[7].
Since
they
spend
a
big
part
of
their
days
at
schools,
acoustics
conditions
there
have
a
big
influence
over
biological
(physiological
and
somatic),
psychological,
social
and
emotional
aspects.
Cognitive
effects:
• Reading:
noise
on
children's
cognition
show
negative
effects
on
acquiring
reading
skills.

6.
3
• Memory:
several
studies
of
both
chronic
and
acute
noise
have
found
adverse
effects
of
aircraft
noise
exposure
on
long-­‐term
memory
for
complex,
difficult
material.
• Motivation:
children
chronically
exposed
to
noise
are
less
motivated
when
placed
in
achievement
situations
in
which
task
performance
is
contingent
on
persistence.
• Mechanisms
and
underlying
processes:
Several
studies
suggest
that
noise
can
interfere
in
important
ways
with
speech
perception
or
language
acquisition.
Reading,
long-­‐term
memory
and
learning
in
children
are
particularly
sensitive
to
noise.
Besides
cognitive
effects,
noise
in
classrooms
can
have
further
complications
such
as:
• Higher
blood
pressure
[8]
• Higher
epinephrine
(adrenaline)
levels
• Higher
norepinephrine
levels
• Sleeping
disorders
[9]
4. Acoustics
of
a
room
design
for
speech
In
rooms
designed
for
speech
applications,
like
the
case
of
a
classroom,
many
of
the
same
criteria
used
for
any
other
room
will
still
apply.
However,
in
rooms
used
primarily
for
speech,
some
criteria
might
be
arising
in
importance
and
some
requirements
might
be
modified.
4.1 Reverberation
time
Reverberation
time
RT60
is
always
an
important
parameter
to
evaluate
the
sound
quality
for
any
room,
and
to
room
volume.
It
is
defined
as
the
time
in
seconds
required
for
sound
intensity
in
a
room
to
drop
60dB
from
its
original
level
[10].
Absorptive
qualities
and
room
dimensions
influence
reverberation
time
and
it
does
not
depend
on
the
position.
Figure
1
show
recommended
values
for
mean
reverberation
time
between
two
octave
bandwidths
500
and
1,000
Hz
when
a
room
is
occupied
between
80%
and
100%
[10]
.Two
classrooms
configurations
are
shown
in
Figure
1,
i)
Classroom
configuration
1
(red
line)
recommended
a
RT60
of
0,6
for
a
volume
of
189
m3;
and
ii)
Classroom
configuration
2
(blue
line)
recommended
a
RT60
of
0,8
for
a
volume
of
534
m3.
Figure
1:
The
recommended
mean
reverberation
time
between
500
and
1,000
Hz,
for
speech
and
music,
with
respect
to
room
volume.
(Source:
[11])

7.
4
Moreover,
it
has
to
be
considered
the
frequency
response
of
the
reverberation
field.
Figure
2
shows
the
frequency
dependent
tolerance
rages
of
reverberation
time
referenced
to
the
recommended
mean
reverberation
time
described
in
the
previous
Figure
1.
Figure
2
shows
that
reverberation
time
decrease
at
low
frequencies.
The
great
majority
of
the
speech
power
is
below
1
KHz,
and
the
maximum
speech
energy
rage
is
200
to
600
Hz.
Speech
vowels
occupy
low
frequencies,
while
consonants
occupy
higher
frequencies.
Consonants
are
more
important
in
intelligibility,
so
specially
the
frequency
range
between
2
to
4
kHz
is
the
responsible
for
the
speech
intelligibility
[10]
.
The
three
bands
at
1,2
and
4kHz
provide
the
75%
of
speech
intelligibility
content.
Figure
2:
The
frequency-­‐dependent
tolerance
range
of
reverberation
time,
as
referenced
to
recommended
reverberation
time.
Speech.
(Source:
[11])
There
are
different
ways
to
calculate
the
reverberation
time;
the
most
used
equation
is
called
Sabine
equation.
This
is
given
by
the
equation:
𝑅𝑇!" =
0.161𝑉
𝐴
where
RT60
=
reverberation
time,
sec
V=
volume
of
room,
m3
A=
total
absorption
of
room,
metric
sabins
4.2 Absorption
treatment
For
the
classroom
configuration
1
(189
m3),
it
might
be
expected
that
the
people
and
furniture
provide
the
majority
of
absorption;
therefore,
the
room
surfaces
can
be
relatively
reflective.
In
the
classroom
configuration
2
(534
m3),
it
is
a
big
space
so
relatively
greater
absorption
is
needed.
In
this
case,
strong
late
reflections
and
reverberation,
such
as
from
rear
walls,
could
produce
echoes
problems.
Two
strategies
can
be
used
to
solve
that
issue:
i)
the
implementation
of
reflective
materials
around
the
source
area
to
provide
strong
early
reflections
that
are
better
integrated
with
the
direct
sound;
and
ii)
the
use
of
absorptive
materials
in
the
seating
area
and
rear
of
the
wall
[10].
4.3 Speech
intelligibility
Speech
intelligibility
is
the
highest
design
priority
for
any
room
intended
for
speaking-­‐listening
activities
[10].
In
the
classroom
case
where
amplification
is
not
used,

8.
5
a
room
design
providing
high
speech
intelligibility
begins
by
recognizing
that
a
normal
voice
will
generate
a
long-­‐term
average
normal
pressure
level
of
about
65dB.
Satisfactory
speech
intelligibility
can
be
achieved
by
designing
for
an
appropriate
reverberation
time.
In
particular,
reverberation
time
at
500
Hz.
The
speech
intelligibility
is
influenced
by
two
quantities:
• Signal
to
noise
ratio
(SNR),
is
described
as
the
ratio
between
the
levels
of
the
useful
and
disturbing
signal.
SNR
is
influenced
by
several
parameters
of
the
rooms.
The
SNR
is
described
as
the
ratio
between
the
level
of
the
useful
and
disturbing
signal.
The
SNR
is
expressed
by
[12]:
𝑆𝑁𝑅 𝑟, 𝑡 = 10𝑙𝑜𝑔
𝑝!
!"#,!"#$%&
(𝑟, 𝑡)
𝑝!
!"#,!"#$%(𝑟, 𝑡)
𝑑𝐵
From
the
equation,
it
is
possible
to
see
that
the
SNR
is
a
function
of
time
and
is
influenced
by
the
distance
from
the
source
to
the
receiver.
There
is
two
measure
methods
based
on
the
SNR
to
evaluate
the
speech
intelligibility:
the
articulation
index
(AI)
and
the
speech
transmission
index
(STI).
• Direct
to
reverberant
ratio
(DRR),
is
the
ratio
between
the
direct
and
reverberant
sound
levels
and
is
expressed
by
[12]:
𝐷𝑅𝑅 𝑟 = 10𝑙𝑜𝑔
𝑝!
!"#,!"#$%&
(𝑟)
𝑝!
!"#,!"#"!$"!%&'(𝑟)
𝑑𝐵
The
distance
to
the
source,
amount
of
absorption
present
in
the
room,
the
dimensions
and
shape
of
the
room,
and
the
source
direction
influence
the
level
of
reverberated
sound.
The
level
of
direct
sound
is
determined
by
distance
from
the
source
to
the
receiver
and
the
source
directivity.
• Combined
effect
(SNR
+
DRR),
the
combined
effect
of
these
two
factors
is
bigger
than
the
sum
of
the
individual
effects.
It
means,
the
interaction
of
noise
and
reverberation
adversely
affects
speech
perception
to
a
greater
extent
than
the
sum
of
both
effects
taken
independently
[12].
4.3.1 Analytical
measure
methods
for
speech
intelligibility
Various
analytical
measures
have
been
devised
to
assess
speech
intelligibility:
• Articulation
index
(AI)
uses
acoustic
measurements
to
estimate
speech
intelligibility
and
conversely,
speech
privacy.
AI
uses
weighting
factors
in
five
octave
bands
from
25
HZ
to
4kHz.
AI
is
calculated
by
multiplying
the
signal-­‐to-­‐
noise
ratio
(SNR)
in
each
octave
band
by
the
weighting
factor
in
each
octave
band,
and
summing
the
result.
AI
ranges
from
0
to
1;
the
higher
the
value,
the
better
the
intelligibility
[10].
• Percentage
articulation
loss
of
consonants
(%Alcons),
s
focuses
on
the
perception
of
spoken
consonants.
%Alcons
can
be
approximately
measured
as:
%𝐴𝑙𝑐𝑜𝑛𝑠 ≈ 0.652
𝑟!!
𝑟!
!
𝑅𝑇!"

9.
6
%Alcons
scores
can
be
related
to
the
speech
intelligibility,
as:
i)
Ideal
(%Alcons
≤
3%);
ii)
Good
(%Alcons
3-­‐8%);
iii)
Satisfactory
(%Alcons
8-­‐11%);
iv)
Poor
(%Alcons
>11%);
and
v)
Worthless
(%Alcons
>20%).
[10]
• Speech
Transmission
Index
(STI)
predicts
the
speech
intelligibility
by
measuring
the
reduction
in
the
modulation
depth
at
the
receiver
for
seven
octave
bands
with
fourteen
modulation
frequencies.
The
modulation
might
be
reduced
by
reverberation,
background
noise,
band-­‐pass
limiting
and
non-­‐linear
distortion.
The
reduction
of
the
modulation
can
be
quantified
by
the
effective
SNR
for
a
number
of
frequency
bands.
Then,
the
SNR
is
recalculated
to
a
transmission
index
between
0
and
100%.
Table
1
shows
the
STI
in
relation
to
intelligibility
[12].
STI
(%)
0
-­‐30
30
–
45
45
-­‐60
60
–
75
75
-­‐
100
Intelligibility
Unintelligible
Poor
Fair
Good
Excellent
Table
1:
STI
in
relation
to
intelligibility
(Source:
[12])
• Rapid
acoustics
speech
transmission
index
(RASTI),
measures
the
speech
intelligibility
on
the
scale
of
0
to
1.
The
speech
intelligibility
should
be
at
least
0,6
in
ordinary
classrooms
and
should
be
more
than
0,8
before
you
talk
about
having
good
speech
intelligibility
in
a
room.
The
value
will
vary
from
seat
to
seat
and
normally
there
are
dead
areas.
It
is
correlated
to
%Alcons
by
[10]:
𝑅𝐴𝑆𝑇𝐼 = 0.9482 − 0.1845ln (%𝐴𝑙𝑐𝑜𝑛𝑠)
5. Methodology
The
objective
of
this
study
is
an
in-­‐depth
investigation
of
the
architectural
acoustics
of
a
classroom
in
a
kindergarten.
For
this,
it
is
designed
a
method
to
identify
the
acoustic
factors
which
influence
in
the
acoustic
of
the
room
in
relation
to
the
need
of
the
pupils
and
teacher.
5.1 Room
description
and
analysis
setup
The
kindergarten
has
3
blocks
of
classrooms
(each
block
is
2
classrooms),
one
canteen
with
kitchen,
the
office
area
and
an
indoor
playground.
The
office
area
is
placed
directly
to
the
main
street
(high
external
noise
sources)
while
the
classrooms
are
placed
directly
to
a
green
area
(low
external
noise
sources).
Figure
3:
Kidengarten
plan.
The
red
square
indicated
the
classroom
that
is
used
for
the
analysis

10.
7
The
study
is
focused
in
the
block
of
classroom
shown
in
the
Figure
3.
The
classroom
1
(see
Figure
4)
is
45
m2
where
13
m2
is
used
as
a
hall
area
(3m
height)
and
37
m2
is
used
for
teaching
functions
(4m
height).
Additionally,
the
classroom
can
be
opened
to
the
next
classroom,
giving
the
possibility
of
an
open
space
of
126
m2;
this
open
configuration
is
named
as
Classroom
2
(see
Figure
4).
Figure
4:
Description
of
both
classroom
configuration:
a)
Classroom
1-­‐Single
(left);
b)
Classroom
2
–
Double
(right)
For
each
classroom
configuration
is
setup
two
options
to
be
analysed,
as
shown
in
Figure
5.
Figure
5:
Analysis
setup
From
scenario
1,
it
is
developed
two
options:
• Option
A
–
higher
absorptive
materials:
it
has
plastered
walls,
high
quality
absorptive
ceiling
and
wooden
floor.
• Option
B
–
lower
absorptive
materials:
it
has
concrete
walls,
ceiling
and
floor.
The
main
different
between
these
two
options
lies
in
the
absorptive
materials
present
in
the
room.
Table
2
shows
the
absorptive
characteristic
of
the
material
use
for
the
simulations.
Option
Surface
and
Material
125
Hz
250
Hz
500
Hz
1
kHz
2kHZ
4kHz
A
Floor
Wood
parquet
0,04
0,04
0,07
0,06
0,06
0,07
Walls
Plaster
0,01
0,02
0,02
0,03
0,04
0,05
Ceiling
Plasterboard
(12mm
in
suspended
ceiling
grid)
0,15
0,11
0,04
0,04
0,07
0,08
B
Floor
Concrete
(sealed
or
painted)
0,01
0,01
0,02
0,02
0,02
0,02
Walls
Plaster
0,01
0,02
0,02
0,03
0,04
0,05

11.
8
A-­‐B
Window
Glass
(1,4``plate,
large
pane)
0,18
0,06
0,04
0,03
0,02
0,02
Door
Solid
wood
panels
0,1
0,07
0,05
0,04
0,04
0,04
Table
2:
Absorption
characteristics
of
the
materials
5.2 Noise
Criteria
Another
important
aspect,
which
could
lead
to
big
difference
of
the
tested
acoustic
variables,
besides
the
absorption,
is
the
amount
of
background
noise.
For
the
case
of
a
kindergarten,
it
is
advisable
to
keep
the
noise
below
Noise
Criteria
35
(NC35).
The
noise
levels
from
NC35
are
shown
in
Table
3.
Freq.
Band
[Hz]
125
Hz
250
Hz
500
Hz
1
kHz
2kHZ
4kHz
Noise
(dB)
48
40
34
30
27
25
Table
3:
Noise
Criteria
25
noise
limits
(Source:
http://www.engineeringtoolbox.com)
5.3 Source
and
Receiver
position
In
order
to
run
the
simulations
the
source
and
receiver
position
is
given
as
in
Figure
6.
Danish
standards
establish
occupancy
of
16
pupils
for
the
classroom
1
(single).
Four
tables
are
placed
in
the
room
with
four
pupils
each
and
the
teacher
is
placed
in
the
middle
of
the
classroom.
For
the
classroom
2,
the
distribution
of
the
previous
classroom
is
reflected
so
there
is
occupancy
of
32
pupils
and
the
teacher
is
placed
in
the
middle
of
the
open
room.
Figure
6:
Source
and
receiver
position
for
a)
Classroom
1
(left)
and
b)
Classroom
2
(right)
In
the
simulations
the
teacher
is
assumed
to
use
“original”
voice
at
normal
vocal
effort.
The
sound
levels
at
1-­‐meter
distance
for
normal
and
raised
efforts
are
shown
in
Table
4.
Freq.
Band
[Hz]
125
Hz
250
Hz
500
Hz
1
kHz
2kHZ
4kHz
Noise
(dB)
51,2
57,2
59,8
53,5
48,8
43,8
Table
4:
Sound
level
at
1m
in
front
of
the
speaker
for
normal
effort,
from
Catt
acoustic
simulation
program.
(Source:
[10])
5.4 Parameter
variation
Each
scenario
(four
scenarios
in
total)
is
simulated
under
five
variations:
• Empty
room
• Room
with
furniture
• Room
with
furniture
and
people
• Room
with
furniture,
people
and
rear
absorptive
wall
Source
Recievers
12
34
CLASSROOM 1 (SINGLE) CLASSROOM 2 (DOUBLE)
12
34
56
78

12.
9
• Room
with
furniture,
people
and
absorptive
ceiling
5.5 Measurements
methods
For
each
simulation
describe
previously,
it
is
obtained
data
to
evaluate
the
quality
of
the
acoustic
environment
of
the
room
in
relation
to
the
function
of
the
space.
The
main
function
of
the
room
is
the
speech
so
the
speech
intelligibility
is
the
main
factor
to
be
analysed.
The
measure
methods
uses
for
the
analysed
are:
• Reverberation
time
(RT60)
• Speech
transmission
index
(STI)
Both
measure
methods
are
described
in
section
4.1
and
section
4.3.
Moreover,
few
measure
methods
for
speech
intelligibility
area
available
in
CATT
simulation
software.
Reverberation
time
and
STI
are
the
only
one
available
to
be
measure
by
CATT
directly.
6. Simulation
Results
6.1 Sabine
Equation
Vs.
CATT
Simulation
6.1.1 Classroom
1(single)
and
Classroom2
(double)
From
CATT
software
both,
analytical
and
simulation
results
for
Reverberation
Time
(RT60)
can
be
obtained.
Results
from
both
methods
are
compared
in
order
to
see
how
much
Sabine
equation
differs
from
simulations
results
in
different
cases.
Figure
7:
Sabine
Vs.
CATT
simulation:
a)
Empty
room
1A
at
receiver
1(left);
b)
Abs
ceiling
room
1A
at
receiver
1
(right)
Figure
8:
Sabine
Vs.
CATT
simulation:
a)
Empty
room
2A
at
receiver
1(left);
b)
Abs
ceiling
room
2A
at
receiver
1
(right)
In
general,
Sabine
equation
results
are
a
bit
higher
or
almost
equal
to
simulation
values
for
“empty
room”
case
(Figure
7-­‐a,
Figure
8-­‐a,
Appendix
1).
However,
for
the
remaining
cases
(furniture,
furniture
+
people,
abs.
wall
and
abs.
ceiling)
Sabine
0"
0.5"
1"
1.5"
2"
2.5"
3"
3.5"
125" 250" 500" 1k" 2k" 4k" 8k" 16k"
RT60%&%Sabine%Eq.%
Reciever"1"
Sabine"eq."
0"
0.2"
0.4"
0.6"
0.8"
1"
1.2"
1.4"
125" 250" 500" 1k" 2k" 4k" 8k" 16k"
RT60%&%Sabine%Eq.%
Reciever"1"
Sabine"eq."
0"
0.2"
0.4"
0.6"
0.8"
1"
1.2"
1.4"
1.6"
125" 250" 500" 1k" 2k" 4k" 8k" 16k"
RT60%&%Sabine%Eq.%
Reciever"1"
Sabine"eq."
0"
0.5"
1"
1.5"
2"
2.5"
3"
3.5"
125" 250" 500" 1k" 2k" 4k" 8k" 16k"
RT60%&%Sabine%Eq.%
Reciever"1"
Sabine"eq."

13.
10
equation
calculates
lower
RT60
values
comparing
to
simulations
by
CATT
methods
(Figure
7-­‐a,
Figure
8-­‐a,
Appendix
1).
The
same
behaviour
can
be
extrapolated
to
Option
B
(see
Figure
9),
the
Sabine
equation
calculates
RT60
a
bit
higher
or
equal
in
empty
room
case
but
when
absorptive
materials
are
added,
Sabine
equation
overestimate
the
RT60
values.
Figure
9:
Sabine
Vs.
CATT
simulation:
a)
Empty
room
1B
at
receiver
1(left);
b)
Empty
room
2B
at
receiver
1
(right)
6.2 Reverberation
Time
(RT60)
6.2.1 Classroom
1A:
single
room
with
high
absorptive
materials
Reverberation
Time
is
simulated
for
the
different
set
ups.
The
RT60
average
(from
500Hz
to
8kHz)
for
each
receiver
and
each
room
situation
(empty,
furniture…etc.)
is
plot
in
Figure
10.
Figure
10
shows
that
RT60
from
one
receiver
to
another
remains
virtually
constant.
Moreover,
it
is
easy
to
see
how
much
reverberation
time
differs
from
one
set
up
to
another.
Figure
10:
RT60
in
the
classroom
1ª
at
each
receiver
6.2.1.1 RT60
at
Receiver
1:
analysis
at
frequency
level
Since
all
receivers
get
similar
RT60
values,
receiver
1
is
selected
to
show
reverberation
times
depending
on
the
frequency.
Figure
11:
RT60
in
the
classroom
1A
at
receiver
1.
Frequency
250
Hz
to
16kHz
0.00#
0.50#
1.00#
1.50#
2.00#
2.50#
Receiver1# Receiver2# Receiver3# Receiver4#
Average'RT60'
Empty#
Furniture#
Furnit+people#
Abs.#Wall#
Abs.#Ceiling#
0"
1"
2"
3"
4"
5"
6"
125" 250" 500" 1k" 2k" 4k" 8k" 16k"
RT60%&%Sabine%Eq.%
Reciever"1"
Sabine"eq."
0"
1"
2"
3"
4"
5"
6"
125" 250" 500" 1k" 2k" 4k" 8k" 16k"
RT60%&%Sabine%Eq.%
Reciever"1"
Sabine"Eq."
0"
0.5"
1"
1.5"
2"
2.5"
3"
3.5"
125" 250" 500" 1k" 2k" 4k" 8k" 16k"
RT60%&%Reciever%1%
Empty"
Furniture"
Furniture+People"
Abs_Wall"
Abs_Ceiling"

14.
11
The
five
room’s
set
ups
are
shown
in
Figure
11.
“Empty”
and
“Furniture”
room
behave
quite
similar,
getting
lower
times
when
furniture
is
included.
On
the
hand,
once
people
is
taken
into
account,
a
big
change
in
RT60
performance
is
observed,
being
“Abs.
wall”
and
“Abs.
ceiling”
the
ones
that
get
lower
reverberation
times.
6.2.1.2 RT60
at
receiver
1:
analysis
at
each
setup
Figure
12:
RT60
in
the
classroom
1A
at
receiver
1.
RT60
value
at
each
setup
and
RT60
reduction
at
each
setup
from
the
empty
room
Figure
12
represents
how
much
RT60
decreases
when
adding
new
absorptions
in
the
room
compared
to
“empty
room”.
The
reduction
from
“empty”
to
“furniture”
is
minimum;
nevertheless,
the
difference
becomes
more
notable
when
people
are
included,
and
progressively
when
higher
absorptive
materials
are
place
on
the
wall
or
ceiling.
6.2.2 Classroom
1B:
single
room
with
lower
absorptive
materials
Due
to
the
behaviour
similarity
between
Classroom
1A
and
1B,
not
result
are
shown
in
the
report.
Appendix
2
shows
the
results
for
classroom
1B
obtained
from
the
simulations.
6.2.3 Classroom
1A
and
1B:
analysis
comparison
Figure
13:
RT60
room
average
per
each
simulation
setup
Figure
13
shows
the
reverberation
time
at
each
room
case
for
both
classroom
options
A
(high
absorptive
materials)
and
B
(low
absorptive
materials).
The
biggest
deviation
takes
place
when
the
room
is
empty
or
just
with
furniture.
Then,
reverberation
values
for
both
options
are
very
similar.
2.04% 2.04%
1.04%
0.58% 0.55%
2.64%
2.49%
1.12%
0.62% 0.57%
0.00%
0.50%
1.00%
1.50%
2.00%
2.50%
3.00%
Empty% Furniture% Furnit+people% Abs.%Wall% Abs.%Ceiling%
Average%Room%A%
Average%Room%B%
!3# !49# !72# !73#
2.05# 1.98# 1.04# 0.58# 0.54#
0#
20#
40#
60#
80#
100#
120#
Em
pty#
Furniture#
Furniture+People#
Abs_W
all#
Abs_Ceiling#
Avarage#RT60#
%#reduce#

15.
12
6.2.4 Classroom
2A:
double
room
with
high
absorptive
materials
In
the
big
room
reverberation
time
is
also
simulated
for
the
five
different
set
ups,
although
this
time
eight
receivers
are
placed
since
room
surface
is
considerable
bigger
than
before.
The
RT
average
for
each
receiver
and
each
room
situation
(empty,
furniture…)
is
plot
in
a
Figure
14.
Figure
14
shows
that
RT60
from
one
side
of
the
room
is
lower
than
the
other.
Values
are
increasing
from
right
side
to
left
side
(receiver
1-­‐4
lower
than
5-­‐8).
Moreover,
it
is
easy
to
see
how
much
reverberation
time
differs
from
one
set
up
to
another.
Figure
14:
RT60
in
the
classroom
1A
at
each
receiver
6.2.4.1 RT60
at
Receiver
1:
analysis
at
frequency
level
Receivers
don’t
look
as
even
as
in
small
room,
therefore,
one
receiver
from
each
side
of
the
class
is
analysed
through
the
different
frequencies.
Figure
15:
RT60
in
the
classroom
2A
at
receiver
1.
Frequency
250
Hz
to
16kHz
Looking
at
the
different
set-­‐ups
in
the
room,
the
differences
among
them
seems
similar
to
small
room
(Figure
15);
empty
and
furniture
room
very
similar
and
then,
big
contrast
when
adding
people.
It
can
be
observed
a
light
increment
in
RT
from
receiver
1
to
5.
However,
it
is
not
very
drastic,
and
then,
when
making
the
average
for
each
receiver
along
the
frequencies,
values
are
pretty
similar.
6.2.4.2 RT60
at
receiver
1
and
5:
analysis
at
each
setup
Figure
16
represents
how
much
RT
decreases
when
adding
new
absorptions
to
the
room
compared
to
“empty
room”.
Even
in
Figure
16
(the
one
in
the
overview
section)
could
show
differences
between
receivers,
then,
when
looking
at
RT
in
general
through
averages,
the
reduction
from
one
set-­‐up
to
another
is
similar.
0.00#
0.50#
1.00#
1.50#
2.00#
2.50#
3.00#
Receiver1# Receiver2# Receiver3# Receiver4# Receiver5# Receiver6# Receiver7# Receiver8#
Average'RT60'(from'500Hz'to'8kHz)'
Empty#
Furniture#
Funiture+people#
Abs.wall#
Abs.ceiling#
0"
0.5"
1"
1.5"
2"
2.5"
3"
3.5"
4"
125" 250" 500" 1k" 2k" 4k" 8k" 16k"
RT60%&%Reciever%1%
Empty"
Furniture"
Furniture+People"
Abs_Wall"
Abs_Ceiling"
0"
0.5"
1"
1.5"
2"
2.5"
3"
3.5"
4"
125" 250" 500" 1k" 2k" 4k" 8k" 16k"
RT60%&%Reciever%5%
Empty"
Furniture"
Furniture+People"
Abs_Wall"
Abs_Ceiling"

16.
13
Figure
16:
a)
RT60
in
the
classroom
2A
at
receiver
1;
b)
RT60
in
the
classroom
2A
at
receiver
5
6.2.5 Classroom
2B:
double
room
with
lower
absorptive
materials
Due
to
the
behaviour
similarity
between
Classroom
2A
and
2B,
not
result
are
shown
in
the
report.
Appendix
4
shows
the
results
for
classroom
2B
obtained
from
the
simulations.
6.2.6 Classroom
2A
and
2B:
comparison
The
reverberation
time
reduction
performs
similar
as
small
room
(Figure
17).
Figure
17:
a)
RT60
in
the
classroom
2A
at
receiver
1;
b)
RT60
in
the
classroom
2A
at
receiver
5
6.3 Speech
Transmission
Index
(STI)
The
second
parameter
to
be
investigated
is
the
STI.
For
STI
in
noise
simulations
a
background
noise
level
is
used
equal
to
Noise
Criteria
(NC35).
STI
(%)
0
-­‐30
30
–
45
45
-­‐60
60
–
75
75
-­‐
100
Intelligibility
Unintelligible
Poor
Fair
Good
Excellent
Table
5:
STI
in
relation
to
intelligibility
(Source:
[10])
6.3.1 Classroom
1A:
single
room
with
high
absorptive
Figure
18:
STI
simulation
in
classroom
1A
for
different
setups.
The
STI
value
at
each
receiver
is
the
average
of
the
frequencies
from
250
Hz
to
16
kHz.
2.22# 2.26#
1.36#
1.12#
0.64#
2.85# 2.82#
1.56#
1.21#
0.65#
0.00#
0.50#
1.00#
1.50#
2.00#
2.50#
3.00#
Em
pty#
Furniture#Funiture+people#
Abs.w
all#
Abs.ceiling#
Average#Room#A#
Average#Room#B#
100# 6%#
&37%#
&51%#
&68%#
2.41# 2.55# 1.52# 1.17# 0.77#
0#
20#
40#
60#
80#
100#
120#
Em
pty#
Furniture#
Furniture+People#
Abs_W
all#
Abs_Ceiling#
Avarage#RT60#
%#reduce#
100#
107#
%41#
%49#
%73#
2.02# 2.19# 1.18# 1.03# 0.54#
0#
20#
40#
60#
80#
100#
120#
Em
pty#
Furniture#
Furniture+People#
Abs_W
all#
Abs_Ceiling#
Avarage#RT60#
%#reduce#
40#
45#
50#
55#
60#
65#
70#
Receiver#1# Receiver#2# Receiver#3# Receiver#4#
STI$in$Classroom$1A$
Empty#
Furniture#
Furniture#+#People#
Abs_Wall#
Abs_Ceiling#

17.
14
Figure
18
shows
the
STI
improvements
by
adding
elements
with
higher
absorptive
properties.
STI
keeps
similar
when
adding
furniture
respect
to
the
empty
room
(regarded
as
a
“poor”
STI).
When
furniture
+
people
is
simulated,
STI
improves
significantly
respect
to
the
previous
situations
(regarded
as
a
“fair”
STI).
Moreover,
with
the
addition
of
a
high
absorbent
wall
or
high
absorbent
ceiling
the
highest
increases
of
the
STI
are
found
(regarded
as
a
“good”
STI).
Figure19:
STI
simulation
in
classroom
1A
at
receiver
1.
Figure
19
shows
how
STI
varies
from
frequency
250
Hz
to
16k.
The
three
bands
at
1,
2
and
4kHz
provide
the
75%
of
speech
intelligibility
content.
The
band
250
Hz
and
500
Hz
might
be
rejected
due
to
the
high
divergence
between
two
calculation
methods:
impulse
response
and
energy
echogram.
It
is
detected
a
tendency
of
increase
of
the
STI
from
lower
frequencies
to
higher
frequencies.
Appendix
3
shows
the
results
of
Figure
18
and
Figure
19
but
for
the
case
of
the
classroom
1B:
single
room
with
lower
absorptive
materials.
Due
to
the
similarity
of
the
STI
results
between
classroom
1A
and
1B,
the
same
result
description
can
be
applied
for
both.
6.3.2 Classroom
1A
and
1B:
analysis
comparison
Figure
20:
STI
differences
between
single
classroom
A
(high
absorptive
materials)
and
classroom
B
(lower
absorptive
materials).
The
STI
values
for
each
setup
is
an
average
between
the
four
receiver
placed
in
the
simulation.
Figure
20
shows
how
STI
increases
for
each
classroom
when
adding
more
elements
with
high
absorptive
characteristics.
Moreover,
Figure
20
shows
how
STI
differs
from
one
classroom
to
another
in
each
setup.
The
STI
differences
are
reduced
with
the
addition
of
absorptive
elements.
30#
35#
40#
45#
50#
55#
60#
65#
70#
75#
80#
250# 500# 1k# 2k# 4k# 8k# 16k#
Classroom(1A(+(STI(at(Reciever(1(
Empty#
Furniture#
Furniture+People#
Abs_Wall#
Abs_ceiling#
5"
5"
3"
1"
2"
35"
40"
45"
50"
55"
60"
65"
70"
Empty" Furniture" Furniture"+"
People"
Abs_Wall" Abs_Ceiling"
STI$difference$between$Classroom$A$&$B$
Classroom"A"
Classroom"B"

18.
15
6.3.3 Classroom
2A:
double
room
with
high
absorptive
materials
Figure
21:
STI
simulation
in
classroom
2A
for
different
setups.
The
STI
value
at
each
receiver
is
the
average
of
the
frequencies
from
250
Hz
to
16
kHz.
Figure
21
shows
the
STI
improvements
by
adding
elements
with
higher
absorptive
properties.
STI
keeps
almost
similar
when
adding
furniture
respect
to
the
empty
room
(regarded
as
a
“poor”
STI).
When
furniture
+
people
is
simulated,
STI
improves
significantly
respect
to
the
previous
situations
(regarded
as
a
“fair”
STI).
Moreover,
the
addition
of
a
high
absorbent
wall
or
high
absorbent
ceiling
increases
the
STI
(regarded
as
a
“good”
STI).
Due
to
the
distribution
of
the
source
and
receivers
(see
Figure
6),
it
is
detected
a
“symmetry”
between
receivers
1-­‐4
with
receivers
5-­‐8.
These
two
groups
of
receivers
follow
the
same
patron
but
the
receiver
5-­‐8
have
lower
STI
values
respect
to
the
other
ones.
Figure
22:
STI
simulation
in
classroom
1A
at
receiver
1.
Figure
22
shows
how
STI
varies
from
frequency
250
Hz
to
16k.
The
three
bands
at
1,2
and
4kHz
provide
the
75%
of
speech
intelligibility
content.
The
band
250
Hz
and
500
Hz
might
be
rejected
due
to
the
high
divergence
between
two
calculation
methods:
impulse
response
and
energy
echogram.
It
is
detected
a
tendency
of
increase
of
the
STI
from
lower
frequencies
to
higher
frequencies.
The
addition
of
an
absorbent
ceiling
increase
significantly
the
STI
respect
to
the
rest
of
the
variations.
Appendix
5
shows
the
results
of
Figure
21
and
Figure
22
but
for
the
case
of
the
classroom
2B:
double
room
with
lower
absorptive
materials.
Due
to
the
similarity
of
the
STI
results
between
classroom
2A
and
2B,
the
same
result
description
can
be
applied
for
both.
35#
40#
45#
50#
55#
60#
65#
70#
Receiver#1# Receiver#2# Receiver#3# Receiver#4# Receiver#5# Receiver#6# Receiver#7# Receiver#8#
STI$in$Classroom$2A$
Empty#
Furniture#
Furniture#+#People#
Abs_Wall#
Abs_Ceiling#
25#
30#
35#
40#
45#
50#
55#
60#
65#
70#
75#
250# 500# 1k# 2k# 4k# 8k# 16k#
Classroom(2A(+(STI(at(reciever(1(
Empty#
Furniture#
Furniture+People#
Abs_Wall#
Abs_ceiling#

19.
16
6.3.4 Classroom
2A
and
2B:
analysis
comparison
Figure
23:
STI
differences
between
classroom
2A
(high
absorptive
materials)
and
classroom
2B
(lower
absorptive
materials).
The
STI
values
for
each
setup
is
an
average
between
the
four
receiver
placed
in
the
simulation.
Figure
23
shows
how
STI
increases
for
each
classroom
when
adding
more
elements
with
high
absorptive
characteristics.
Moreover,
Figure
23
shows
how
STI
differs
from
one
classroom
to
another
in
each
setup.
The
STI
differences
are
reduced
with
the
addition
of
absorptive
elements.
7. Discussion
7.1 Sabine
equation
The
reliable
of
the
Sabine
equation
seems
very
sensible
to
absorption
values.
Sabine
equation
looks
quite
accurate
when
it
is
applied
for
simple
setups.
When
reverberation
time
is
simulated
for
the
“empty”
room
case,
CATT
simulation
and
Sabine
equation
don’t
produce
high
divergences
between
both
of
them.
By
contrast,
when
multiple
materials
and
elements
are
added
to
the
room,
the
reverberation
time
results
diverge
from
CATT
simulations
to
Sabine
equation.
Sabine
equation
is
not
very
accurate
for
complex
models.
In
those
cases,
Sabine
equation
calculates
better
reverberation
conditions
times
when
comparing
to
the
CATT
simulations.
It
could
result
in
a
wrong
perception
of
the
acoustic
environment
and
thereby,
in
a
wrong
acoustic
design.
7.2 Reverberation
time
As
it
is
mentioned
in
section
4,
the
addition
of
people
in
the
simulation
has
a
huge
effect
in
RT60
results.
Reverberation
Time
decrease
around
50%
when
people
is
included,
consequentiality,
it
is
possible
to
say
that
the
occupancy
rate
of
room
has
a
huge
influence
in
the
acoustic
environment.
The
other
most
influent
factor
that
contribute
to
the
benefit
of
the
reverberation
time,
it
is
the
addition
of
high
absorptive
surface.
Two
simulation
setups
(abs.
ceiling
and
abs.
wall)
show
the
positive
effects
in
reverberation
time
when
adding
high
absorptive
materials
to
the
room.
If
the
results
between
both
cases
are
compared,
some
significant
issues
are
found.
In
classroom
1
(single),
similar
reverberation
time
results
are
obtained
from
both
cases.
In
classroom
2
(double),
the
application
of
a
high
absorptive
ceiling
produce
better
reverberation
time
values
than
the
high
absorptive
wall.
The
reason
might
be
the
ratio
between
areas
(high
absorptive
area
to
room
floor).
In
the
classroom
1
(single),
the
ratio
between
areas
is
similar
for
both
cases.
In
contrast,
6"
5"
3"
2"
0"
35"
40"
45"
50"
55"
60"
Empty" Furniture" Furniture"+"
People"
Abs_Wall" Abs_Ceiling"
STI$differences$between$Classroom$A6B$
Classroom"A"
Classroom"B"

20.
17
the
ratio
of
areas
is
not
keep
equal
for
the
classroom
2;
the
ceiling
surface
is
much
bigger
while
the
wall
surface
is
kept
as
in
the
classroom
1
case.
That’s
why
ceiling
simulation
setup
produce
a
higher
positive
impact
in
the
classroom
2,
resulting
in
a
reverberation
time
between
0.5
and
1
while
the
wall
simulation
setup
results
in
a
reverberation
time
between
1
and
1.5.
Another
important
aspect
to
be
mentioned,
it
is
how
the
location
of
the
high
absorptive
material
can
influence
in
the
room.
For
the
case
of
the
kindergarten,
a
flexible
space
is
demanded
where
multiple
classroom
configurations
are
allowed.
A
flexible
space
means
high
variation
in
the
source
positions,
as
well
as,
in
the
position
of
the
receivers.
The
use
of
absorptive
wall
simulation
setup
might
not
contribute
to
the
flexibility
of
the
space,
so
the
teacher
(source)
might
have
sometime
the
absorptive
element
in
front
and
other
on
the
back.
For
that
reason,
it
might
be
more
optimum
to
place
the
high
absorptive
element
in
the
ceiling
so
their
influence
is
equally
distributed
along
the
room.
Comparing
option
A
(room
with
higher
absorptive
materials)
and
option
B
(room
with
lower
materials),
it
is
observed
that
when
high
absorptive
materials
are
included
in
the
simulations,
both
options
perform
similar.
The
only
difference
between
both
options
is
the
floor
material,
option
A
has
a
wood
floor
while
option
B
has
concrete
floor.
When
comparing
the
first
simulation
setups
(empty
and
furniture),
option
A
performs
better;
even
it
performs
better,
it
still
does
not
fulfil
the
requirements.
When
absorptive
elements
are
included,
the
differenced
between
both
options
is
reduced.
It
seems
that
materials
established
on
the
design
basis
may
reduce
their
influence
on
RT60
if
high
absorptive
materials
are
added
in
the
design.
In
classroom
2,
it
was
expected
symmetry
of
the
results
between
the
receivers
1-­‐
4
and
5-­‐8
but
the
receivers
behave
in
different
way.
The
reason
might
be
due
to
an
issue
in
CATT
simulation
software
regarding
the
vector
normal
of
the
surface.
In
the
model,
there
is
an
open
partition
wall
that
limits
the
space
between
both
classes.
When
adding
the
material
properties
to
this
wall,
it
seems
to
be
added
to
one
face
instead
of
both
surfaces.
This
might
be
the
reason
that
breaks
somehow
room
model
symmetry.
7.3 Speech
Transmission
Index
The
highest
increase
of
STI
is
produced
when
the
people
or
high
absorptive
materials
are
implemented
in
the
simulations.
When
the
STI
is
evaluated
at
frequency
level,
it
is
possible
to
see
how
it
is
improved
from
lower
to
higher
frequencies.
This
improvement
might
have
special
influence
in
the
speech
intelligibility
because
the
three
bands
at
1,2
and
4kHz
provide
the
75%
of
speech
intelligibility
content.
When
looking
to
the
classroom
1,
not
huge
differences
between
the
absorptive
ceiling
and
wall
ceiling
are
found.
In
the
other
hand,
when
looking
to
the
classroom
2,
it
is
possible
to
say
that
the
use
of
an
absorptive
ceiling
produce
higher
benefits
in
the
STI
than
the
wall
absorptive
setup.
It
might
be
due
to
the
areas
ratio
between
the
absorptive
material
area
and
room
floor.
When
comparing
option
A
and
B,
it
is
possible
to
see
that
the
application
of
high
absorptive
materials
reduce
the
influence
of
the
materials
establish
as
a
base
for
the
room.

21.
18
7.4 Reverberation
time
&
STI
As
it
is
known,
STI
is
affected
by
background
noise
and
reverberation
time.
In
the
simulations
it
is
possible
to
observe
the
direct
relations
between
STI
and
RT0.
For
all
the
simulations
when
reverberation
time
is
reduced
in
the
same
way
STI
is
increased.
8. Conclusion
The
report
analysis
the
speech
intelligibility
in
a
kindergarten
by
two
measures:
reverberation
time
and
speech
transmission
index.
It
is
found
a
high
relation
between
the
occupancy
rate
of
the
room
and
the
quality
of
the
acoustic
environment.
Moreover,
the
use
of
high
absorptive
materials
is
a
good
strategy
to
achieve
a
good
acoustic
environment.
It
is
found
that
is
crucial
to
optimize
the
relation
between
the
absorptive
material
area
and
the
room
volume.
In
addition,
it
is
important
the
location
of
the
absorptive
materials
in
relation
to
the
function
of
the
space.
In
the
case
of
this
kindergarten,
a
flexible
space
is
demanded.
Then,
it
is
recommended
to
place
the
absorptive
elements
in
somehow
that
their
influence
is
equally
distributed
along
the
entire
room,
e.g.
absorbent
elements
in
the
ceiling.
To
achieve
the
standard
requirements,
the
use
of
high
absorbent
materials
is
required.
When
high
absorptive
elements
are
included,
the
materials
established
on
the
design
basis
reduce
their
influence
to
improve
the
acoustic
environment.
Then,
from
a
budget
perspective,
it
is
more
profitable
to
use
lower
absorptive
material
on
the
design
bases
and
include
high
absorptive
materials
in
specific
place
to
achieve
standard
requirements.
9. References
1
Kirkergaard,
P.H.
(2004).
Building
and
Room
acoustics.
Structural
dynamics,
vol
10.
Aalborg
University.
2
Mealings,
K.T.,
Buchholz,
J.M.,
Denuth,
K.,
&
Dillon,
H.
(2014).
An
investigation
into
the
acoustics
of
a
open
plan
compared
to
enclosed
kindergarten
classroom.
Macquarie
University,
Australia.
3
CATT-­‐Acoustic
v9.0.
Introduction
manual.
4
SBi
230.
Guidelines
on
building
regulation
2010.
Danish
building
research
institute.
Aalborg
University.
5
Clausen T, Christensen KB, Lund T, Kristiansen J (2009) Self- reported noise exposure as a
risk factor for long-term sickness absence. Noise Health 11(43):93–97
6
Faragher,
E.
B.,
Cass,
M.,
&
Cooper,
C.
L.
(2005).
The
relationship
between
job
satisfaction
and
health:
A
meta-­‐analysis.
Occupational and Environmental Medicine, 62,
112.
7
Marie
Louise
Bistrup,
Health
effects
of
noise
on
children
and
perception
of
the
risk
of
noise,
coordinated
by
the
National
Institute
of
Public
Health
Denmark,
2001.
8
Evans,
G.W.,
Bullinger,
M.,
Hygge,
S.,
Chronic
noise
exposure
and
psychological
response
a
prospective
study
of
children
living
under
environmental
stress.
9
Noise
from
Civilian
Aircraft
in
the
Vicinity
of
Airports
–
Implications
for
Human
Health,
Healt
Canada.
10
Everest,
F.A.,
&
Pohlmann,
K.C.
(2009).
Master
handbook
of
acoustics.
5th
Edition.
Ed.
Mc
Graw
Hill.
11
Anhert,
W.
&
Tennhardt,
H.P.
(2008).
acoustic
for
auditoriums
and
concert
halls,
in
Handbook
for
sound
engineers,
ed.
G.M.
12
Zeilstra,
G.J.
(2009).
Speech
intelligibility
in
classrooms.
A
new
mwasurement
method.
Master
thesis
Project.
Delft
University.