17-4-2013
LECTURE N° 5
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- Acoustical comfort -
Lecture contributions
Coordinator of the lecture:
Pavla Dvořáková, Faculty of Civil Engineering, CTU in Prague,
pavla.dvorakova@fsv.cvut.cz, http://tzb.fsv.cvut.cz/
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Contributors:
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Nathalie Geebelen, N.Geebelen@chri.nl
Pavla Dvořáková, Faculty of Civil Engineering, CTU in Prague,
pavla.dvorakova@fsv.cvut.cz, http://tzb.fsv.cvut.cz/
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Sound
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Sound is a mechanical wave that is an oscillation of pressure transmitted
through a solid, liquid, or gas, composed of frequencies within the range of
hearing and of a level sufficiently strong to be heard, or the sensation
stimulated in organs of hearing by such vibrations.
Sinusoidal waves of various frequencies; the bottom waves have
higher frequencies than those above. The horizontal axis represents
time.
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http://educypedia.karadimov.info/electronics/dataaudio.htm
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unwanted sound
environmental pollutant
a waste product
undesired physiological
or psychological effect
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Bluyssen 2009
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Noise
Sources of noise
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Sources in a building
• Sounds produced
inside -from service
equipment
(elevators, sanitary
installations, HVAC
systems), from
other users
• Sound produced
outside – traffic, ..
Bluyssen 2009
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Sound Pressure
Level
Noise =
unwanted sound
Threshold of Hearing
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Threshold of Pain
Sound at 155 decibels can
burn the skin.
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Sound at 180 decibels can kill.
http://www.abqenvironmentalst
ory.org/city/energypollution/s5noise.html
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Acoustical Comfort
ID
Room acoustical quality
-> reverberation time
-> undesirable echo’s and reflections
Sound insulation between rooms
-> air-borne sound insulation
-> structure-borne sound insulation
Background noise levels
-> technical installations
-> environmental noise
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Acoustical Comfort in relation to…
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Room acoustical quality
-> reverberation time <-> concrete core activation
-> undesirable echo’s and reflections <-> room shapes
Sound insulation between rooms
-> air-borne sound insulation <-> circulation sound
-> structure-borne sound insulation <-> floor constructions
Background noise levels
-> technical installations <-> location of technical rooms
-> environmental noise <-> building site layout
Room acoustical quality
ID
-> reverberation time
The time necessary, after switching off
the source, for the sound pressure level
to drop 60 dB.
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Room acoustical quality
-> reverberation time
Sound absorbing
space
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Sound reflecting
space
Long reverberation
time
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Short reverberation
time
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Room acoustical quality
-> reverberation time: target values
Reverberation time
Furnished room
Office space
Landscape office
Classroom
Music room
Theatre
Chamber music hall
Opera
Concerthall
Church (organ music)
T = ca. 0,5 s
T = 0,5 – 0,7 s
T = 0,7 – 0,9 s
T = 0,6 – 0,8 s
T = 0,8 – 1,2 s
T = 0,9 – 1,3 s
T = 1,2 – 1,5 s
T = 1,2 – 1,6 s
T = 1,7 – 2,3 s
T = 1,5 – 2,5 s
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Type of room
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Room acoustical quality
-> reverberation time in seconds
T= 1/6 x (V/A)
Room volume in m3
Total absorption in the room
in m2
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The larger the room, the longer the reverberation time!
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The more absorbing materials present in the room, the shorter
the reverberation time!
Room acoustical quality
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-> total absorption in m2
Surface area in m2 of the material
A = α1 x S1 + α2 x S2 + α3 x S3 + …
Absorption coefficient of the material 0 < α < 1
totally reflecting
totally absorbing
An open window has an absorption coefficient α equal to 1 (all of the sound will
disappear outside through the open window). If the surface area of the open
window equals 1 m2, then the total absorption of this window is equal to
A = 1 x 1 = 1 m2
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Room acoustical quality
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-> sound absorbing materials
= acoustically ‘soft + open’ materials or perforated materials with
an acoustically ‘soft + open’ material behind the perforations
Room acoustical quality
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-> sound absorbing materials
= acoustically ‘soft + open’ materials or perforated materials with
an acoustically ‘soft + open’ material behind the perforations
[Source: Schallschutz +
Raumakustik in der Praxis –
Planungsbeispiele und
konstruktive Lösungen, W.
Fasold / E. Veres, Verlag für
Bauwesen – Berlin, 1998]
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Room acoustical quality
-> calculation of reverberation time
3.0m
3.0m
S [m2]
0<α<1
α x S [m2]
Ceiling
Floor
Window
Door
Walls
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2
33
0,79
0,04
0,03
0,08
0,02
7,11
0,36
0,03
0,16
0,66
Total
A [m2]
8,32
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3.0m
Surface
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A = a1 x S1 + a2 x S2 + a3 x S3+…. [m2]
T= 1/6 x (V/A) = 0,167 x (27/8,32) = 0,54 s
Room acoustical quality
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-> problem:
classroom 15 x 8 x 3 m3, door 2 m2, window 12 m2
target value reverberation time T = 0,7 seconds
Surface
0<α<1
Floor
Window
Door
Walls
0,04
0,03
0,08
0,02
[Source: Schallschutz +
Raumakustik in der Praxis –
Planungsbeispiele und
konstruktive Lösungen, W.
Fasold / E. Veres, Verlag für
Bauwesen – Berlin, 1998]
Which absorption coefficient is necessary for the ceiling to achieve
a reverberation time equal to 0,7 seconds?
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Room acoustical quality
-> solution: T= 1/6 x (V/A)
A = 1/6 x (V/T)
= 0,167 x (360/0,7) = 86 m2
S [m2]
0<α<1
α x S [m2]
Ceiling
Floor
Window
Door
Walls
120
120
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124
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0,04
0,03
0,08
0,02
?
4,8
0,36
0,16
2,48
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Total
A [m2]
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Surface
α = A/S = 78,2/120 = 0,65
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86 – 7,8 = 78,2 m2
Room acoustical quality
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-> Regular office room with concrete core activition
target value reverberation time T < 0,8 s
Solution: Add sound absorbing materials to the upper
part of the walls
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Room acoustical quality
-> Landscape office with concrete core activition
target value reverberation time T < 0,5 s (furnished room)
upper part of the walls = not sufficient
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Ceiling islands or baffles
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Alternative solutions
Room acoustical quality
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-> undesirable echo’s and reflections -> reflectogram!
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Room acoustical quality
-> undesirable echo’s and reflections -> reflectogram!
- direct sound: source
receiver
+ pseudo-direct sound: reflections within 20 ms
=> speech intelligibility and localisation of the source
- reverberation: after 100 ms
positive effect speech intelligibilty
negative effect speech intelligibilty
positive effect music
negative effect speech intelligibilty
effect music depends on music type
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- reflections: within 50 ms
50 ms – 80 ms
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- flutterecho: back-to-back refelctions on opposite (parallel) acoustically hard walls
- focussing: cocentrated sound through bundling of reflected sound rays
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Room acoustical quality
ID
-> undesirable echo’s and reflections -> effected by room shape and
location of sound absorbing materials
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Sound insulation between rooms
structure-borne
sound insulation
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air-borne
sound insulation
Sound insulation between rooms
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-> air-borne sound insulation
Sound transmission
-1 direct
-2 flanking
-3 circulation
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Sound insulation between rooms
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-> circulation sound = sound that reaches the destination room
through an adjacent space or room, for example a plenum
Solution? Sound barriers
Sound insulation between rooms
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-> flanking sound = sound that reaches the destination room
through adjacent constructions
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Sound insulation between rooms
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-> sound leaks, for example with pore seam sealing, through cable
trays, duct transits, etc.
Sound insulation between rooms
-> structure-borne sound insulation
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• sliding chairs
• walking sounds
• falling objects
•…
Direct <<excitation>>
of the building
Lots of energy injected into
the buidling structure!
FLOOR MASS = UNSUFFICIENT
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Sound insulation between rooms
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-> improving structure-borne sound insulation
floating floors structures!
Sound insulation between rooms
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-> floating floors structures = very sensitive to construction details on site
- levelling ducts
- border strips
- flexibel layer
- covering foil
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Background noise levels
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-> Installation noise = background noise coming from the operation of
all the necessary technical installations in a building such as airconditioning units, elevators, sanitary installations, etc.
Background noise levels
-> technical installations
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Energy efficiency / Comfort
Ventilation system (incl. cooling)
Technical installations larger and larger
Project enough technical rooms
Where??
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Background noise levels
-> building design
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• Technical rooms not directly adjacent to work or living
spaces
• Installations not on the roof, noise disturbance for the
environment
• Sanitary blocks, elevators, traffic zones not
directly adjacent to work or living spaces
• Installation noise can also be useful for
preserving speech privacy in a landscape office
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Background noise levels
-> building design
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Office or
living space
Office or Office or
living space living space
Office or Office or Office or
living space living space living space
Office or
living space
Target value
background noise
max. 30 à 35 dB(A)
[Source: Bouwakoestiek, G.
Vermeir, Uitgeverij Acco Leuven,
1999]
Target value
background noise
max. 30 à 35 dB(A)
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Noise radiation
-> air-conditioning unit on roof top: - 3 dB with doubling of the
distance
Sound pressure
level
80 à 100 dB(A)
40 à 60 dB(A)
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Sound power level
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30 m
Mesures necessary!! Enclosures, silencers, …
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Background noise levels
ID
-> Environmental noise = background noise coming from sound
sources outside such as traffic (cars, trains, airplanes), industry,
bars, etc.
[Source: Bouwakoestiek, G.
Vermeir, Uitgeverij Acco Leuven,
1999]
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Background noise levels
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-> High environmental noise levels
solutions through building site layout
Background noise levels
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-> High environmental noise levels
solutions through building design
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Background noise levels
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-> High environmental noise levels
solutions through facade design
Background noise levels
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-> Facade sound insulation = composed sound insulation
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Background noise levels
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-> Weak link in facade sound insulation = seam sealing
- ‘deaf’ facade = completely ‘closed’ facade -> windows cannot be
opened -> to be used with high sound pressure levels from
environmental noise
- ventilation through facade
openings not possible
Background noise levels
ID
-> Weak link in facade sound insulation = ventilation openings
- mechanical balanced ventilation system
- ventilation through sound muffled ventilation unit
sound absorbing
material
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Standards on acoustics
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EN 12354 Building acoustics: estimation of acoustic performance of
buildings from the performance of elements
EN ISO 14257 Acoustics: measurements and parametric description of
spatial sound distribution curves in workrooms for evaluating acoustical
performance
EN ISO 140 Acoustics. Measurement of sound insulation in buildings and
of building elements
EN ISO 10052 Acoustics: field measurement of airborne and impact
sound insulation and of service equipment noise; survey method
ISO 9921 Ergonomics. Assesment of speech comunication
EN ISO 18233 Acoustics: application of new measurement methods in
building and room acoustics
ISO 6897, ISO 2631-1, ISO 2631-2
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Literature
L. CREMER, M. HECKL, E. UNGAR, Structure-Borne Sound, Springer Verlag, 1973
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L. CREMER, H. MÜLLER, T. SCHULTZ, Principles and Applications of Room
Acoustics, Volume 1, Volume 2, Applied Science Publishers, 1982
L.L. Beranek (ed.), Noise and vibration control, Institute of Noise Control
Engineering, 1988
W. Fasold, H. Winkler, Bau- und raumakustik, Verlag für Bauwesen, VEB, Berlin,
1987
Bluyssen Philomena M.: The Indoor Environment Handbook, How to Make Buildings
Healthy and Comfortable, Earthscan Ltd (United Kingdom), 2009, ISBN-13:
9781844077878
http://educypedia.karadimov.info/electronics/dataaudio.htm
http://www.abqenvironmentalstory.org/city/energy-pollution/s5noise.html
http://www.freewebs.com/soundwaves-/introduction.htm
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