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RumsakustikErling Nilsson, AkustikerECOPHON Saint-Gobain
Community school no 15, Gdynia, Poland. Architect: Adam Drochomiercki. Photo: Szymon Polanski.System: Ecophon Master A/alpha
Hospital Spital św. Zofii, Warsaw, Poland. System: Ecophon Hygiene A dvance
Axel Springer AG, Hamburg, Germany. Photo: Eric Sha mbroom. System: Ecophon Light coffer with Focus E .
Restaurang Restaurangen, Stockholm. Architect: Matt ias Ljunggren. Photo: Åke E:son Lindman. System: Focus D with Connect Shadow channel trim
• SWIMMINGPOOL
Miejska Sala Widowiskowo-Sportowo, Community Sports Hall. Architect: Przedsibiorstwo Projektowo-Wykona wcze pro-Art KONOPKA. Photo: Szymon Polanski. System: Ec ophon Focus DG
Sultan Ahmad State Mosque, Kuantan, Malaysia. Syste m: Ecophon Gedina.
Örat
Hörselsnäckan
Hair cells in cochlea: a) In healthy conditions
b) With ongoing damage by noise, gluing together.
c) With ongoing damage by noise, loss of stiffness.
d) Complete degeneration, hair cells broken off.
Skador på hårcellerna i örat
Hörseltest
Did you .eethe .portmaga.inelast .aturday?
Audiogram
Normal hörsel
Hörselskada
Kerstin Persson Waye, Occupational and Environmental Medicine, Gothenburg University
Gränsvärden för att undvika hörselskador• 75 dB LAeq 8 timmar – anses som en riskfri nivå
• 85 dB LAeq 8 timmar, riktvärde i många länder
• 130-150 dB peak – ökad risk för hörselskada
Kerstin Persson Waye, Occupational and Environmental MedicineGothenburg University
� annoyance, disturbance
Effects in the occupational environment due to noise
� performance and learning
� speech interference
� tiredness
� lower job satisfaction
� social interaction
� hearing impairment, tinnitus
Wallace Clement Sabine(June 13, 1868 – January 10, 1919)
American physicist who founded the field of architectural acoustics
Definition: Reverberation time
Sound pressure level, dB
Time, seconds
60 dB
T60
His formula
where
T=the reverberation time (s)V=the room volume (m3)A=the total equivalent absorption area (m2 sabin)
where
=A
VT 16.0
=TV
A 16.0or
The equivalent absorption area A for a surface with area S m2
is equal to α x S where α is the absorption coefficient for the surface
Standards and regulations
Absorption coefficient at normal incidence
AbsorberIncident sound energy
Reflected sound energy
Absorbed sound energy
������������ ����� � = �������������������
�������������������
Impedance tube (Kundt’s tube)
Lmax (dB)
Lmin (dB)
� = 10(#$%&'#$())/,-
� =4�
(1 + �),
Absorber
Absorption coefficient
AbsorberIncident sound energy at angle θ
θ
θ
Reflected sound energy at angle θ
Absorbed sound energy at angle θ
������������ ����� �(0) = �������������������1�1��2�3
�������������������1�1��2�3
Reflected sound
0,30 – 0,55 (class D) 1-4 dB0,60 – 0,75 (class C) 4-7 dB0,80 – 0,85 (class B) 7-10 dB0,90 – 0,99 (class A) 10-20 dB
The reflected sound is reduced by
Absorption coefficient
)1log(10 α−⋅=∆ L
LincidenceLreflected ∆L = Lincidence- Lreflected (dB)
Glass wool
Open and closed structures
Closed cell Open cell Simple model of porous absorber
Microscopic structure
Friction
Acoustic design with Sabine formula
� A(before treatment)=0,161xV/T= 0,161x200/2,5=12,9 m2 sabin
� A(needed to fulfil 0,40 s)= 0,161xV/T=0,161x200/0,40=80,5 m2 sabin
� A( to be added to fulfil 0,40 s)=A(needed)-A(before)=80,5-12,9=67,6 m2 sabin
Example: The reverberation time in a room with a volume of 200 m3
is 2,5 s at 1000 Hz. Target value for the reverberation time is 0,40 s at 1000 Hz
If e.g. the absorption coefficient for a ceiling absorber is 0,90 at 1000 Hzwe will need S= A/α=67,6/0,90=75 m2
Sabine formula: How it works in theory
Absorption coefficients (500 Hz):
Walls=0,15Ceiling=0,80Floor=0,10
Absorption data from EN 12354-6
Absorption data from EN 12354-6
Sabine formula: How it works in theory
Absorption coefficients (500 Hz):
Walls=0,15Ceiling=0,80Floor=0,10
A=∑αi x Si = 0,10x6x7,5+2x0,15x7,5x2,5+2x0,15x6x2,5+0,80x6x7,5=51 m2 sabin
T60=0,161x(V/A)=0,161x112,5/51≈0,36 s
Not a typical classroom
Reverberation decay in rooms with suspended absorbent ceiling
T20
Increased diffusivity
On the use of practical absorption coefficients
On the use of practical absorption coefficients
S,
VA=equivalent absorption area, m2 sabine
V= room volyme, m3
T= reverberation time, s
absorption coefficient
α = ∆A/S
Measurement of absorption coefficients according to EN ISO 354
α
withoutTV
withTVAAA
withoutwith⋅−⋅=−=∆ 16.016.0
FHU - Acoustic specification
S
A=α
Equivalent absorption area (ISO 354)
A (m2)
Absorption factor (ISO 354)
S ?
Absorbent ceiling FHU – free hanging unit
V
Reverberation chamber
)11(16.0withoutTwithT
VA −=
AFHU =A/6
Free hanging units “Solo”
Typical classroom
Effect of furniture
absorption
scattering
No boxes
Boxes on the wall
Sabine
Scattering – why is it important?
Glass wool
Reflection from a surface
Specular reflection
–Angle of reflection equals
angle of incidenceθ
θ
Incident sound energy, Iinc
Reflected sound energy, Irefl
Absorption coefficient:
� = 4��� − 4��62
4���=
41��
4���
Reflection from a surface
Specular reflection
–Angle of reflection equals
angle of incidence
Diffuse reflection
–Scattered in many
directions
Reflection from a surface
Scattering coefficient, s
• Fraction of energy which is scattered
• Always between 0 and 1
Absorption and scattering
� + 1 − � ∙ 1 − � + 1 − � ∙ � = 1
absorbed specularly reflected diffusely reflected
Simulation of sound fields
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Room Acoustic Comfort
Assessment of sound in rooms
Room types
Reverberant room
(Sabine room)
Open-plan spaces
Corridors
Room with absorbent
ceiling
An approach to create room acoustic comfort
Sensation of soundSeveral room acoustical descriptors
Characterisation of room types
Room acoustic requirements adapted for the activity
People Room
Activity
Reverberance: EDT, T20, T30
Speech inelligibility: C50, STI
Strength of sound: G, SPL
Sound propagation: DL2, DLf
Reverberant rooms
industrial spaces,
central stations,
cathedrals
Ordinary rooms with absorbent ceilings
class rooms,
offices,
health care premises
dining rooms,
conference rooms,
day-care centres
Rooms with extended forms
open-plan offices,
corridors
Education
Machinery noise
Noisy activities
Office sounds
Music
Room acoustic quality aspects• Reverberation• Speech clarity• Auditory strength• Spatial decay
Efterklang
• Relaterar till hur snabbt ljudenergin försvinner i ett rum
Lång efterklang
Kort efterklang
Taltydlighet
• Relaterar till hur tydligt tal uppfattas
Otydligt
Tydligt
Ljudstyrka
• Upplevelsen av ljudets styrka
Hög ljudnivå
Låg ljudnivå
Ljudets avståndsdämpning
• Ljudnivån avtar med avståndet från ljudkällan.
Tal på 1 meters avstånd
Tal på 4 meters avstånd
Tal på 8 meters avstånd
Reverberation
Speech Clarity
Auditory Strength
Spatial decay
Early Decay Time (EDT), T20, T30 (ISO 3382-1/2)
C50 , U50, STI (ISO 3382-1, IEC 60268-16)
Sound Strength G (ISO 3382-1)
D2,S , Lp,A,S,4m , STI (ISO 3382-3)
Human qualities – objective descriptors
Useful reflections
Detrimental reflections
)end)Energy(50
50ms)Energy(0log(10C50 −
−×= , dB
Definition of room acoustic measures: Speech Clarity C50 (dB)
Room acoustic measures: Sound strength G (dB)
G = LpRoom – Lp10m =Lp – Lw + 31 dB (omni-directional sound source)
10 m
Subjective listener aspect
Room acoustic quantity
Just noticeable difference
Subjective level of sound
Sound Strength G in dB 1 dB
Perceived reverberance
Reverberation time T20 in seconds
5%
Perceived clarity of sound
Speech Clarity C50 in dB 1 dB
Just noticeable difference of room acoustic quantities according to ISO 3382-1
Microphone
Loudspeaker
Reverberation time, T20
Speech clarity, C50
Sound Strength, G
Impulse response
time, s
Room acoustic measurements
Dining/meeting room at a hospital in Landskrona, Sweden.
• It echoes a lot.• If you sit in the middle of the room you
can’t participate in any conversation at all.
• I just take shorts breaks and avoid having lunch together with others.
• Sometimes you have to ask people to repeat what they said.
• There is an incredible din that prevents you from talking, even with the person sitting next to you, when there are a lot of people here.
• I leave the room as fast as possible.
Dining/meeting room at a hospital in Landskrona, Sweden.
Room dimension
Volume = 68 m3
Floor area = 25 m2
Acoustic refurbishment
• Ceiling: Master B
• Wall: Wall Panel C/Texona (2700 x 1200)
0
0,2
0,4
0,6
0,8
1
1,2
125 250 500 1000 2000 4000
Frequency Hz
Pra
ctic
al s
ound
abs
orpt
ion
coef
ficie
nt
Acoustic treatment of dining/meeting room
Room acoustic measurements
1. before acoustic treatment
2. for the room with ceiling treatment only and
3. for the ceiling treatment in combination with the wall panel
Table 2. Result of measurements at Landskrona Hospi tal
Parameter Before acoustic treatment
Only acoustic ceiling
Acoustic ceiling and wall panel
Average 500 and 1000 Hz
Average 500 and 1000 Hz
Average 500 and 1000 Hz
T20 [s] 0.76 0.37 0.27
∆L [dB]* - -8 -8
C50 [dB] 1.8 8.6 12.0
D [%] 60 88 94
RASTI ** 0.66 0.82 0.87
* * ∆L is the reduction of sound levels in the room compared to the untreated room.**Room Acoustic Speech Transmission Index according to IEC 60268-16
Some comments from the staff after the refurbishment
• Much more subdued environment. I feel more relaxed in the room.• It’s easier to talk to each other.• There’s less din when a lot of people are in the same room.• There are less echoes in the room.• A lot of people can talk simultaneously in different parts of the room without a
problem.
Acoustics extremes
Anechoic chamber
Reverberation chamber
Equaliser: Balanced sound for optimal room acoustics
T20 (s) (250 – 4000 Hz) G (dB)
0,200,30
0,80
0,500,600,70
1,001,101,201,30
0,90
78
13
9101112
15161718
14
D50 (%)
5056
80
61677276
86899193
83
Reverberation Sound strength Speech clarity
T20 (s) (125 Hz)
0,200,30
0,80
0,400,500,600,70
1,001,101,201,30
0,90
Example: Classroom, traditional education
1,401,501,501,40 19
20
44
94
0,40
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