Rak-43.3415 Building Physics Design 2
ACOUSTICAL DESIGN
Autumn 2014
LECTURE 6, part 1
Traffic noise
Matias Remes, M.Sc. FISE A
Traffic noise and land use
”Tämän päivän melusta näyttää tulevan vaikea
yhteiskunnallinen probleema, jonka merkityksestä ei
kaikilla ihmisillä ole edes mielikuvaa. Melu ei ole
tämän päivän tuotetta, sillä jo sata vuotta sitten oli
huolestuneita ihmisiä, jotka kirjoittivat melusta ja
hälystä. Mutta heidän päiviensä rattaiden kolinasta
mukulakivikadulla on suuri askel nykypäivän
liikennekohinaan.”
Tekniikan lisensiaatti Eero Lampio 1962
Traffic noise
• Noise sources
– Road traffic
– Railway traffic
– Air traffic
• Measurement of noise
immision
• Noise modelling
Sound sources
Road traffic noise
•
Of the three noise sources road traffic constitutes the most
significant environmental problem
– In the greater Helsinki area alone the amount people subjected to noise
levels exceeding the guideline value of daytime equivalent noise level 55
dBA is over 200 000
•
•
The most significant sound sources are engine noises and tire
noise, additionally noise is caused by air friction, force transmission,
vibration of the hull and the possible noisy equipment on the vehicle
Noise mainly comprises of engine noise when speed is
– Passenger vehicles: v < 40 km/h
– Heavy vehicles: v < 60 km/h
•
•
The significance of tire noise increases with increasing speed
At high speeds (v > 120 km/h) also flow noise due to air friction
occurs
Sound sources
Road traffic noise
• Road traffic noise is by nature even; the variation in
sound level near the road is small
• Factors affecting noise attenuation (”rules of thumb”):
– Distance to road (distance 2x  SPL decreases 3 dB)
– Traffic amount (amount halves  SPL decreases 3 dB)
– Traffic speed (decrease from 100 km/h  80 km/h causes a
decrease in SPL of 2 dB)
– Terrain (in an area with soft terrain / ground surface SPL can be
several decibels lower than in, e.g., in a city where sound is
reflected from the walls of buildings and asphalt)
– Road surface (with porous ”silent” road covering materials SPL
can decrease > 3 dB)
Sound sources
Railway traffic noise
• ~30 000 people are estimated to live in an area with
daytime equivalent noise level caused by railway traffic
exceeding the guideline of 55 dBA
• Railway traffic noise is more instantaneous than road
traffic noise (disturbance caused by train pass-bys with
short duration)
• Noise is broad band and is caused mainly by the
connection of the train wheels to the tracks
• Trains also cause structure borne noise and vibration
depending on the terrain and foundation type of the
tracks
Sound sources
Spectrum of road and railway traffic noise
Sound sources
Combined effect of road and railway traffic noise
Railway traffic noise
Road traffic noise
Combined noise
Sound sources
Air traffic noise
• Air traffic noise level is stated as day-evening-night
noise level LDEN [dB]
• Sound level difference required in detail plan
(asemakaava) is based on LDEN -values
• In Finland new buildings should not be situated in areas
with LDEN > 60 dB
• The total number of people subjected to air traffic noise
in Finland has decreased due to development of more
silent aeroplanes, nevertheless air traffic noise
constitutes a problem in areas near airports
Sound sources
Air traffic noise
•
Connection between air traffic zones m1-3, corresponding LDEN
values and sound level difference in Vantaa
Noise guidelines
Council of State decree
• The Council of State decree (Valtioneuvoston päätös)
VnP 993/1992 defines the highest permitted noise levels
inside dwellings and in outdoor activity areas
• Inside dwellings:
– Day, between 7-22: LA,eq ≤ 35 dB
– Night, between 22-7: LA,eq ≤ 30 dB
• Outdoor activity areas and balconies:
– Day, between 7-22: LA,eq ≤ 55 dB
– Night, existing dwelling areas, between 22-7: LA,eq ≤ 50 dB
– Night, new areas, between 22-7: LA,eq ≤ 45 dB
Noise guidelines
Noise, health impairment and comfort
• Guidelines of equivalent noise level given in VnP
993/1992 are based on health effects of noise:
– Difficulties in falling asleep due to noise
– Waking up in the night due to noise disturbances
• In many cases single noise events are perceived as
more disturbing than average noise; e.g. pass-bys of
vehicles or trains causing a single noise peak
• Even though the guideline values (which are based on
average noise level) were fulfilled, traffic noise can be
heard and noise may cause disturbance
Control of traffic noise
Prevention
• Land use design
• Traffic arrangements
• Safety distances to noise
sources
• Positioning of building
masses
Control of traffic noise
Example of noise spreading
Control of traffic noise
Noise barriers
z

D  10 log10 1  20 


Control of traffic noise
Noise barriers
Note: noise barrier only has effect near the ground surface!
Sound insulation of envelope (ulkokuori)
Determination of the detail plan regulation
70 dB
Without reflection
from the facade
Permitted sound
level inside 35 dB
70 dB
Equivalent noise level outside without facade reflection
– Permitted equivalent noise level inside
= Detail plan regulation (asemakaavamääräys) ∆LA,vaad
70 dB
35 dB
35 dB
Sound insulation of the envelope
Detail plan regulation
• Regulations given in the detail plan are based on the
permitted noise levels inside a dwelling given in VnP
993/1992
• Fulfilling the guideline values does not necessary
guarantee dwelling comfort because the values are
based on average noise level
• Standard SFS 5907 enables better acoustical conditions
than required by VnP 993/1992
– Class C: same values as in VnP 993/1992
– Class B: 5 dB lower equivalent noise level inside dwelling than
required in VnP 993/1992
– Class A: 10 dB lower ”
Sound insulation of the envelope
Calculation methods
• Requirement concerning the sound insulation of the
envelope is stated in the detail plan as a sound level
difference LA
• Weighted sound reduction index of a facade or roof
structure cannot be directly compared to the planning
regulation, because the sound level difference is not the
same thing as sound reduction index!
 A method is needed to calculate the sound insulation
of the envelope
– There are no official regulations of what method should be used
– Two methods are used in Finland
• Environment guide 108/2003 method
• Sound level difference method (äänitasoeromenetelmä)
Sound insulation of the envelope
Environment guide method
• The sound insulation requirement of the envelope of the
investigated room is given by:
Rtr ,vaad  LA  K1  7
where ∆LA is the planning regulation and K1 is a
correction factor depending the surface areas of the
envelope and the floor area of the investigated room:
Sound insulation of the envelope
Environment guide method
• The method uses only weighted sound reduction
indexes agains traffic noise (RA,tr = Rw+Ctr) no matter
what the noise source is
• Requirements for different parts of the envelope are
given by:
– Exterior wall:
RA,tr ,US  Rtr ,vaad  3
– Roof:
RA,tr ,YP  Rtr ,vaad  5
– Doors and windows:
RA,tr  Rtr ,vaad  K 2
Sound insulation of the envelope
Sound level difference method
• Sound level transmitted inside the room through a single
building element of the envelope, Ls, depends on the
noise level outside (LU), the sound reduction index of the
element and the relation of the area of the element Si to
floor area SH:
 Si
LS  LU  Rw  Ctr   7  10 lg
 SH



• ... from which the sound level difference corresponding
to a single building element can be solved:
LA,i
 Si
 LU  LS  Rw  Ctr   7  10 lg
 SH



Sound insulation of the envelope
Sound level difference method
• Sound level difference is calculated separately for each
building element, LA,i
• The total sound level difference of the envelope is given by:




1

LA,kok  10 lg n

 L A ,i / 10 
 10

 i 1

• In buildings the sound insulation of windows and doors which
can be opened is not as good as in the laboratory (where the
values have been measured); this is taken into account by
decreasing the laboratory values in the calculation by 3 dB
Sound insulation of the envelope
Method comparison
•
•
Both methods take account of the areas of building element in the
envelope, floor area of the investigated room and the sound
insulation values of all structures (exterior wall, roof, windos, doors,
fresh-air vents), but…
Environment guide 108/2003 method
– Does not allow investigation of how the sound insulation of different
building elements affects the sound level difference of the envelope
– Can lead to sound insulation requirements for windows and doors which
are not possible to fulfill with any commonly available products on the
market
•
Sound level difference method
– Enables investigation of the sound level transmitted inside the room
through a single building element
– Building element with weak sound insulation (e.g. window) can be
compensated with a better sound insulating exterior wall, compensation is
possible within a few decibels which can be significant to the total sound
level difference of the envelope
Sound insulation of the envelope
Measurement
• Measurement methods presented in standard ISO 140-5
• The are no regulations on which method should be used
• The main issue is that the method should produce a value
which can be directly compared to the sound level difference
given in the detail plan
• A measurement method in which this is the case is the
measurement of the normalised level difference of the
facade:
Dls , 2 m ,n  L1, 2 m  L2  10 lg
A
A0
where L1,2m is SPL produced by a loudspeaker measured at
an 2m distance from the facade, L2 is the SPL measured
inside the receiving room, A is the absorption area of the
receiving room and the normalising factor is A0 = 10 m2
Sound insulation of the envelope
Measurement
•
•
Dls,2m,n is measured in one-third octave bands; the corresponding single-number
value is Dls,2m,n,w
Sound hitting the facade is reflected from it, causing the sound level in front of
the facade to increase by about 3 dB
–
–
•
•
The reflection is directed away from the building
This must be taken into account by subtracting 3 dB from the measurement result
The sum of sound level difference Dls,2m,n and spectrum adaptation term Ctr
subtracted by 3 dB corresponds to the sound level difference of the planning
regulation
The measured sound level difference must, thus, be equal to or higher than the
planning regulation:
LA,mit  Dls , 2 m ,n , w  Ctr  3dB  LA
•
If the planning regulation applies to railway of air traffic noise, the spectrum
adaptation term C is used
Sound insulation of the envelope
Combined effect of building elements
US: 60 dB
10 m2
I: 40 dB
2 m2
US: 45 dB
10 m2
I: 40 dB
2 m2
• Through exterior wall 5 % • Through exterior wall 60 %
• Through window 95 %
• Through window 40 %
Sound insulation of the envelope
Effect of exterior wall on windows
•
•
•
•
Floor area of room 12 m2
Area of exterior wall 10 m2
Area of window 2 m2
Sound level difference required in detail plan 35 dB
Exterior wall
Rw + Ctr
Requirement for window
Rw + Ctr
42
45
50
39
60
37
Sound insulation of exterior walls
Concrete sandwich elements
80
70
Ilmaääneneristävyys R [dB]
60
50
40
30
20
Exterior envelope 60 mm: Rw+Ctr = 49 dB
4000
2000
1000
500
250
Exterior envelope 40 mm: Rw+Ctr = 49 dB
0
125
Exterior envelope 20 mm: Rw+Ctr = 48 dB
10
63
70
Keskitaajuus [Hz]
Ulkokuori 20 mm
Ulkokuori 40 mm
Ulkokuori 60 mm
Sound insulation of exterior walls
Inner envelope and thin rendering
80
70
Ilmaääneneristävyys R [dB]
60
50
40
30
20
70
10
Isover FL 200mm: Rw+Ctr = 40 dB
Keskitaajuus [Hz]
Jäykkä mineraalivilla ja ohutrappaus 10 mm
4000
2000
1000
500
250
125
Paroc FAS4 160mm: Rw+Ctr = 41 dB
0
63
Paroc FAL1 150mm: Rw+Ctr = 39 dB
Sound insulation of exterior walls
Inner envelope and thin rendering
Betonien sisäkuori
[mm]
eriste
paksuus + tyyppi
Rappaus [mm]
Rw (C, Ctr) [dB]
150 mm
160 mm EPS
10 mm
52 (-3,-7) dB
150 mm
160 mm EPS
25 mm
54 (-4,-9) dB
150 mm
160 mm FAL1
10 mm
53 (-2,-5) dB
150 mm
160 mm FAS4
25 mm
56 (0,-4) dB
150 mm
250 mm EPS
10 mm
52 (-3,-8) dB
150 mm
250 mm EPS
25 mm
54 (-4,-9) dB
150 mm
250 mm FAL1
10 mm
53 (-2,-6) dB
150 mm
250 mm FAS4
25 mm
58 (-1,-5) dB
150 mm
450 mm EPS
10 mm
53 (-3,-8) dB
150 mm
450 mm EPS
25 mm
56 (-1,-5) dB
150 mm
450 mm FAL1
10 mm
54 (-3,-8) dB
150 mm
450 mm FAS4
25 mm
59 (-1,-4) dB
Sound insulation of exterior walls
Inner envelope, studding, plate
80
70
Ilmaääneneristävyys R [dB]
60
50
40
30
20
10
Keskitaajuus [Hz]
Rankarakenne ja tuulensuojakipsilevy 9 mm
4000
2000
1000
500
250
Rw+Ctr > 50 dB
125
0
63
70
Exterior walls with thin rendering
Effect on sound insulation of the envelope
• Example: requirement ∆LA = 35 dB
US: 55 dB
10 m2
US: 42 dB
10 m2
I: 37 dB
2 m2
I: 37 dB
2 m2
Before renovation:
After renovation:
•
US = concrete sandwich element
•
•
∆LA = 35 dB
US = concrete inner envelope +
insulation + thin rendering
•
∆LA = 32 dB
Window renovations
Effect on sound insulation of the envelope
• In window renovations:
– Windows are changed
– Often air conditioning is improved by installing freshair vents (korvausilmaventtiili) into the windows
• In noise sensitive areas, where there is a regulation for
the sound insulation of the envelope, the effect of the
renovations must be checked
• Fresh-air vents can deteriorate sound insulation
 Choosing the right type of vent
 Choosing the right type of window
Window renovations
Effect on sound insulation of the envelope
• Example: requirement ∆LA = 35 dB
US: 55 dB
10 m2
I: 37 dB
2 m2
Before renovation:
• US = concrete sandwich element
• No fresh-air vents
• ∆LA = 35 dB
V:37 dB
1 m2
US: 55 dB
10 m2
I: 37 dB
2 m2
After renovation:
• US = concrete sandwich element
• Fresh-air vent added
• ∆LA = 33 dB
Ventilation of the roof
Effect on sound insulation of the envelope
In air traffic noise
areas the ventilation
of the roof structure
must be done so
that sound leak via
the ventilation
channel does not
deteriorate sound
insulation
 Sound
attenuating
ventilation channel

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