p2 presentation yvonne wattez
DESCRIPTION
P2 presentation of Yvonne Wattez on Acoustics in sports halls. TU Delft, January 25th 2012.TRANSCRIPT
ACOUSTICS IN SPORTS HALLSresearch on the acoustical behaviour of perforated panels
Presentation P225/01/2012
Graduation project of Yvonne WattezStudent nr. 1360809
Building Technology | Green Building Innovation Faculty of Architecture | TU Delft
Mentor 1: Martin TenpierikMentor 2: Peter van Swieten
ACOUSTICS IN SPORTS HALLSresearch on the acoustical behaviour of perforated panels
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Yvonne Wattez 1360809 graduation projectP2 presentation 25/01/2012
Introduction
1. Graduation so farProblem description- Legislation & standards - Parameters of acoustics in sports halls
Reverberation time - Calculations vs. measurements- Porous materials vs. perforated panels- Possible explainations for the differences
Sound absorption- Sound absorbing principles- Helmholtz resonator
2. Graduation research - Standard measuremtents- Laboratory measurements- Scale model measurements
3. Design4. Timeline
ACOUSTICS IN SPORTS HALLSresearch on the acoustical behaviour of perforated panels
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Yvonne Wattez 1360809 graduation projectP2 presentation 25/01/2012
Why?I like sports.I like acoustics.
ACOUSTICS IN SPORTS HALLSresearch on the acoustical behaviour of perforated panels
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Yvonne Wattez 1360809 graduation projectP2 presentation 25/01/2012
Problem descriptionComplaints of PE teachers: - voice problems,(- hearing problems,)- tiredness.
Mainly caused by bad acoustics of sports halls.
Teachers need to shout to make themselves heard.
Measurements show that the reverberation time is often too long.
Pictures:Protest action in Rijssen - Holten.[source: tcturbantia 27 sept 2010]
ACOUSTICS IN SPORTS HALLSresearch on the acoustical behaviour of perforated panels
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Yvonne Wattez 1360809 graduation projectP2 presentation 25/01/2012
Legislation & StandardsBased on reverberation time [RT] and backgound noise level.
Limits depend on size and volume.
[source: ISA Sport, ISA-N/A 1.1 ]
picture: sports hall in Amstelveen[source:www.sportbedrijfamstelveen.nl]
seconds, the average reverberation time will be automatically less. E.L. Nesselaar used the standard for her research, not the recommendation. In this report the newest version of the standard of ISA-Sport (NOC*NSF) will be used. Standard ISA-Sport 2005 Since 2005 the newest version of the standard: ‘Standards gymnastics and sports halls and parts of sports halls with educational use.’ is used in The Netherlands. This standard is also called: ISA-US1-BF1. The standard is still based on the reverberation time because a better option is not found yet. With the help and advice of some experts, the reverberation time is defined per volume of the hall. This is important, because a sports hall twice the size should not have twice the reverberation time. The very big sports halls may have a very long reverberation time in that case. The acoustical quality is not linear with the volume. Besides the advise to introduce the volume in the standard for reverberation time, the average absorption coefficient was advised to be at least 0,25. (Nijs 2004) The ISA-Sports standard includes: information on the location, the sports equipment, dressing rooms, and acoustics of the sports facility:
• The average absorption coefficient [α] of the materials in the sports hall has to be at least 0,25. • The reverberation time depends on volume and absorbing behaviour of the room. The average
reverberation time in frequency band of 125-4000Hz may not be higher than 1,0 seconds for a sports hall of 14 x 22 x 5.5 m.
• The reverberation time per frequency band (Tmax/fb) is calculated by Tav divided by Tmax/fb. This has to be ≥ 0,7.
• The background noise level must not be higher than 40 dB(A). This applies to external sounds like outdoor traffic and internal sound sources like installation systems.
• The noise insulation index between rooms for physical education and other residences/ classrooms should be 10 dB(A), preferably 15dB(A).
Kind of room Size [m] (w x l x h) Reverberation time [s] A.1 Gymnastics ≤ 14 x 22 x 5.5 ≤ 1,0 A.2 Gym 13 x 22 x 7 ≤ 1,1 A.3 1/3 sports hall /gym 14 x 24 x 7 ≤ 1,2 B.1 Gym 16 x 28 x 7 ≤ 1,3 B.2 Gym 22 x 28 ≤ 1,4 B.3 2/3 sports hall 32 x 28 ≤ 1,5 C.1 Sports hall 24 x 44 ≤ 1,6 C.2 Sports hall 28 x 48 x 7 ≤ 1,7 C.3 Sports hall 28 x 48 x 9 ≤ 1,9 D.1 Sports hall 28 x 88 x 7 ≤ 2,0 D.2 Sports hall 35 x 80 x 10 ≤ 2,3
Conclusion Legislation has been changed during the last years. There is more attention given to acoustics is sports facilities. This results in more and adapted standards. For example, the limit of the allowed background noise caused by installations is changed from 45 dB(A) to 40 dB(A).
ACOUSTICS IN SPORTS HALLSresearch on the acoustical behaviour of perforated panels
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Yvonne Wattez 1360809 graduation projectP2 presentation 25/01/2012
ParametersReverberation Time (RT):Sabine’s formula
Reverberation TimeThe reverberation time is defined as the time that expires before a sound pressure has decayed by 60 dB after the sound source has been swiched off.
T15 (blue), T20, T30 (black) Sabine 1
6
VRT
A=
with: RT= reverberation time [s] V= volume of room [m3] A= total absorption of materials in room = ( )i iSα
with: iα = absorption coefficient of element i [-]
iS = surface of element i [m2] Sabine correction of Lau Nijs This correction is made because Sabine is based on a cube. Sports halls normally have a rectangular shape. By replacing the surface factor S by a certain part of the volume V2/3, this formula becomes more realistic.
2/3
1
6 6
VRT
Vα=
⋅
with: RT= reverberation time [s] V= volume of room [m3] α = average absorption coefficient Eyring_1 This formula of Eyring works with the mean value of all absorption coefficients.
with: RT= reverberation time [s]
V= volume of room [m3] S= total surface [m2]
α = mean value of all absorption coefficients in the room = ( )i i
i
S
S
α
[-]
Eyring_2 A different formula of Eyring that works with the total absorption coefficient.
1
1
6 ln (1 )ii
VRT
S α −=
⋅ −
with: RT= reverberation time [s]
V= volume of room [m3] iS = surface of element i [m2]
iα = absorption coefficient of element i [-]
1
1
6 ln (1 )
VRT
S α−
= ⋅ −
16 4
VRTA mV
= ⋅+
4 correction for air attenuationmV =
ACOUSTICS IN SPORTS HALLSresearch on the acoustical behaviour of perforated panels
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Yvonne Wattez 1360809 graduation projectP2 presentation 25/01/2012
Parameters
absorption coefficient a= absorbed energy/incident energy
SRC diagram: Everest 2001
Absorption coefficientAbsorption coefficient a is a measure of the efficiency of a surface or material in absorbing sound.
Reflected sound (A, B, C) rTransmitted sound (D) tAbsorbed sound (E, F, G, H, I, J, K) a
r+t+a = 1Sports hall: a= 1-r
a
i
WW
α =
ACOUSTICS IN SPORTS HALLSresearch on the acoustical behaviour of perforated panels
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Yvonne Wattez 1360809 graduation projectP2 presentation 25/01/2012
ParametersSpeech IntelligibilityDepends on: - background noise- reverberation time - shape of the room
Parameters to measure speech intelligibility:- Speech Transmission Index STI- RApid Speech Transmission Index RASTI(mostly used in Europe)
Based on a comparison of the outgoing and incoming sound.Between 0 and 1. 0.8 or higher is excellent, 0.3 is the lower limit to understand sentences.
ACOUSTICS IN SPORTS HALLSresearch on the acoustical behaviour of perforated panels
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Yvonne Wattez 1360809 graduation projectP2 presentation 25/01/2012
ParametersReflecting sound in between parallel walls.
[source: Vugts, J. (2008) LBP|SIGHT via nvbv.org][source: www.ecophon.nl]
Flutter echo
13-05-2011
3
Sporthal (48 x 28 x 9 m)Ray-tracing - variant 2 t/m 4
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
125 250 500 1000 2000 4000
f [Hz]
T15
[s]
variant 2 variant 3 variant 4 Sabine norm
Wandabsorptie boven
Wandabsorptie onder
Twee wanden geheel
1 2 3
Berekende nagalmtijd ‘Aanwezige’ geluidabsorptiecoëfficiënt
Sporthal (48 x 28 x 9 m)Ray-tracing - variant 2 t/m 4
0.0
0.1
0.2
0.3
0.4
0.5
125 250 500 1000 2000 4000
f [Hz]
α [-]
variant 2 variant 3 variant 4 Sabine norm
α ‘norm’
α ‘aanwezig’
1 2 3
Sporthal (45x25x8 m) – Norm: Tgem = 1,9 s; Tmax/fb = 2,7 s
De invloed van flutterecho’s op de nagalmtijd
Sporthal (45 x 28 x 8 m)metingen
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
125 250 500 1000 2000 4000
f [Hz]
T [s
]
EDT T10 T20 T30 T15 norm
Gemeten nagalmtijd
90 m = 2 x zaallengte
Sportzaal (32x24x7,8 m) – Norm: Tgem = 1,5 s; Tmax/fb = 2,1 s
De nagalmtijd als te berekenen parameter in het ontwerp
ACOUSTICS IN SPORTS HALLSresearch on the acoustical behaviour of perforated panels
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Yvonne Wattez 1360809 graduation projectP2 presentation 25/01/2012
Reverberation TimeCalculations vs. measurements.
Formulas compared:Big differences found in comparison of different formulas, computer programmes and measurements.
sports hall Schijndel: perforated steel panels on walls
Schijndel
Method \ frequency Standard ISA Sport Standard ISA Sport max L.Nijs & Sabine Sabine Eyring Fitzroy ODEON T30 CATT ACOUSTIC T15 CATT ACOUSTIC T30 Measurement T20
0
0.5
1
1.5
2
2.5
3
average
Reve
rber
atio
n Ti
me
[s]
RT: methods vs. measurement
average 500Hz 2000Hz 1.6 1.6 1.62.3 2.3 2.3
2.22 1.62 2.241.84 1.34 1.851.62 1.09 1.621.64 1.36 1.631.79 1.83 1.661.77 1.86 1.642.01 2.2 1.772.14 2.64 1.82
500Hz 2000Hz Frequency [Hz]
RT: methods vs. measurementSchijndel
1.6 2.3
2.24 1.85 1.62 1.63 1.66 1.64 1.77 1.82
L.Nijs & Sabine
Sabine
Eyring
Fitzroy
ODEON T30
CATT ACOUSTIC T15
CATT ACOUSTIC T30
Measurement T20
Standard ISA Sport
Standard ISA Sport max
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Yvonne Wattez 1360809 graduation projectP2 presentation 25/01/2012
Reverberation TimePorous materials vs. perforated steel panels.
The reverberation is much shorter than expected at low frequencies in a sports hall constructed with perforated panels.
The perforated panels seem to behave differently than expected from laboratory results.(Especially at low frequencies.)
SRC: LBP|SIGHT
Different halls compared:
0.0
1.0
2.0
3.0
4.0
125 250 500 1000 2000 4000
T [s
]
f [Hz]
Sporthal D1 T20
S1 S2 S3 AVERAGE
Expected and measured RT; porous materials
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Yvonne Wattez 1360809 graduation projectP2 presentation 25/01/2012
So, the panels seem to behave differently in practice than in a laboratory situation.
Goal of this research:
Determine why a difference in sound absorption behaviour ofperforated steel panels exists between practical applications and lab situations.
Next, some theory...
ACOUSTICS IN SPORTS HALLSresearch on the acoustical behaviour of perforated panels
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Yvonne Wattez 1360809 graduation projectP2 presentation 25/01/2012
Sound absorbing principles
- Friction and airflow resistance through a material. Porous materials (Air) - Resonance Plate resonator Helmholtz resonator: perforated panels
friction
resonance
porous materials
sound absorptionplate resonators
Helmholtz resonators perforated panel
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Yvonne Wattez 1360809 graduation projectP2 presentation 25/01/2012
Plate resonators
A mass-spring system exists of a specific oscillation value. When the mass starts moving, it will start oscillating in a specific speed; the resonant frequency.
The absorption coefficient can be calculated with the use of acoustical impedance.
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Yvonne Wattez 1360809 graduation projectP2 presentation 25/01/2012
Acoustical impedance
Acoustical impedance is the ratio of the sound pressure at a boundary surface to the sound flux (flow velocity of the particles or volume velocity, times area) through the surface.
Specific acoustical impedance is the ratio of the sound pressure at a point to the sound flux through that point.
( )( )( )( )
a
s
p tZv t Sp tZv t
=⋅
=
ACOUSTICS IN SPORTS HALLSresearch on the acoustical behaviour of perforated panels
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Yvonne Wattez 1360809 graduation projectP2 presentation 25/01/2012
Helmholtz resonators, perforated panel
'1 0
' 2 ''20 1
4( )
Z ZZ Z Z
α =+ +
Absorption coefficient
For Helmholtz resonators can be calculated from: Z
0= the characteristic impedance of air
Z1= the impedance of the resonator in total = Z
R/h
ZR= Z
V+Z
M
h= the percentage perforations
ZV
= impedance of the air cavity Z
M = impedance of the air in the perforation
Z’ =Z’M+ Z’
V = the real component of the complex number of Z
R
Z1’’ =Z’’
M+ Z’’
V = the imaginary component of the complex
number of ZR
Z= impedance, a complex number (z)Z’= the real component of the impedance (a)Z’’= the imaginary component of the impedance (i*b)z= a+i*b or Z=Z’+Z’’
ZV
ZM
Z0air
Z1total
h
Z1 = ZR/hZR = ZM/ZV
ACOUSTICS IN SPORTS HALLSresearch on the acoustical behaviour of perforated panels
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Yvonne Wattez 1360809 graduation projectP2 presentation 25/01/2012
Helmholtz resonators, important factors Percentage perforation The more perforations, the higher the resonance frequency.
Thickness of facing The thicker, the higher the frequency of the maximal absorption peak.
83
Chapter 12
Fig,2. Absorption coefficient versus frequency graphs for a perforated faced sound absorber system for different percentage perforations of the facing. (Davern 1977)
Fig,3. Absorption coefficient versus frequency graphs for a perforated faced sound absorber system using different thickness of facing with the same percentage perforations. (Davern 1977)
ACOUSTICS IN SPORTS HALLSresearch on the acoustical behaviour of perforated panels
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Yvonne Wattez 1360809 graduation projectP2 presentation 25/01/2012
Helmholtz resonators, important factors Density of the porous backing material The denser, the broader the tuning of the system.
Air space between the facing and backing material Gives an overall decrease of absorbing properties of the system.
85
Chapter 12
Fig,4. Absorption coefficient versus frequency graphs for a perforated faced sound absorber system using porous backing materials of different densities. (Davern 1977)
Fig,5. Absorption coefficient versus frequency graphs for a perforated faced sound absorber system with and without an air space between facing and porous backing with the same facing perforations but different facing thickness. (Davern 1977)
ACOUSTICS IN SPORTS HALLSresearch on the acoustical behaviour of perforated panels
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Yvonne Wattez 1360809 graduation projectP2 presentation 25/01/2012
Helmholtz resonators, important factors Impervious layer between the facing and backing material Gives a huge overall decrease of absorbing properties of the system.
87
Chapter 12
Fig,6. Absorption coefficient versus frequency graphs for a perforated faced sound absorber system with and without an impervious layer between facing and porous backing with the same facing perforations but different facing thickness. (Davern 1977)
Fig,7. As in figure 13. but with different facing perforations and the same facing thickness. (Davern 1977)
ACOUSTICS IN SPORTS HALLSresearch on the acoustical behaviour of perforated panels
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Yvonne Wattez 1360809 graduation projectP2 presentation 25/01/2012
Research to do
Test method: scale model
Test method: laboratory measurement
Fundamental data: standard measurements in sports halls: RT and background noise.
Testing hypothese:A perforated steel panel behaves differently in practice than in a laboratorysituation on absorption coefficient because the shape of the panels causes a better sound absorption of parallel striking sound than on sound with a normal incidence, based on a phase shift principle. This principle increases the absorption coefficient results of the measurement in practice since there is more specific parallel striking sound than in a reverberation room (like the laboratory).
A perforated steel panel behaves differently in practice than in a laboratory situation on absorption coefficient because the different placement of the panel in the laboratory than in practice has influence on the result.
S R
S R
S R
a
b
ACOUSTICS IN SPORTS HALLSresearch on the acoustical behaviour of perforated panels
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Yvonne Wattez 1360809 graduation projectP2 presentation 25/01/2012
Research to do
Test method: scale model
Test method: laboratory measurement
Results and design:When the shape of the panels and so the phase shift seems to have good influence on the sound absorbing behaviour, the design could adapt on this result by using panels with other dimensions.
When the height / different placement of the panels in the laboratory gives different sound absorbing results, the design of the backing construction could be adapted in a way that the sound absorbing behaviour is optimized. S R
S R
S R
a
b
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Yvonne Wattez 1360809 graduation projectP2 presentation 25/01/2012
Timeline:Week 50 51 52 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27Presentaons P2 P3 P4 P5Date 12-Dec 19-Dec 26-Dec 02-Jan 09-Jan 16-Dec 23-Dec 30-Jan 06-Feb 13-Feb 20-Feb 27-Feb 05-Mar 12-Mar 19-Mar 26-Mar 02-Apr 09-Apr 16-Apr 23-Apr 30-Apr 07-May 14-May 21-May 28-May 04-Jun 11-Jun 18-Jun 25-Jun 02-Jul
geen onderwijs afwezigMondayTuesdayWednesdayThursdayFriday aanvraag P4 aanvraag P5Weekend
Acvity Liter
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Liter
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e, th
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, org
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Liter
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Prep
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test
s, p
repa
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2
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test
s, p
repa
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Prep
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test
s, p
repa
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2
Repo
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ot a
lot)
Test
s sca
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Test
s sca
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s sca
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Test
s spo
rts h
all
Test
s spo
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Test
s lab
orat
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Test
s lab
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Repo
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Desig
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rt, P
repa
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Prep
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pres
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Prep
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pres
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on
Deadline Thur
sday
: Zal
en b
eken
d (m
ater
iaal
bek
end)
fabr
ikan
t ben
ader
en
Seco
nd m
ento
r kno
wn
Mar
teria
l ava
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Test
s spo
rts h
alls
done
Test
s lab
orat
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done
In si
tu m
easu
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don
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Mos
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Timeline version 19-01-2012
ACOUSTICS IN SPORTS HALLSresearch on the acoustical behaviour of perforated panels
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Yvonne Wattez 1360809 graduation projectP2 presentation 25/01/2012
Questions?
ACOUSTICS IN SPORTS HALLSresearch on the acoustical behaviour of perforated panels
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Yvonne Wattez 1360809 graduation projectP2 presentation 25/01/2012
13-05-2011
2
Achtergrond huidige norm (2) • Goede
spraakverstaanbaarheid
• Signaal-ruisverhouding: – Direct geluid (nuttig) – Diffuus geluid (storend)
• De verhouding tussen ‘signaal’ en ‘ruis’ wordt bepaald door de hoeveelheid
geluidabsorptie
Sporthal (48 x 28 x 9 m)Afname geluidniveau
-20
-10
0
10
20
30
1 2 4 8 16 32
afstand bron-ontvanger [m]
G [d
B]
Totaal Direct Diffuus S/N
diffuusdir
tot
mfpr
GGNSAr
QG
/
)1(44
log1031/
2
S/N = 0
Achtergrond huidige norm (3) • De hoeveelheid geluidabsorptie in een sportzaal is bepalend
voor het ‘akoestisch comfort’ • Uitgedrukt in de gemiddelde absorptiecoëfficiëntα.
• De in de norm gestelde eis aan de nagalmtijd is dus een indirecte eis aan de hoeveelheid geluidabsorptie!
totAVT
6
ii
n
itot SA
1
tot
tot
SA
Gymzaal (21x12x6 m) – Norm: Tgem = 1,0 s; Tmax/fb = 1,4 s
De nagalmtijd als indicator voor de hoeveelheid geluidabsorptie
Gymzaal (21 x 12 x 6 m)Meting vs berekening
0.0
0.5
1.0
1.5
2.0
2.5
125 250 500 1000 2000 4000
f [Hz]
RT [s
]
T20-meting T-Sabine norm
Tgem = 1,0 s
Tgem = 1,6 s
Tgem = 0,8 s
Nagalmtijd
Gymzaal (21 x 12 x 6 m)Meting vs berekening
0.0
0.1
0.2
0.3
0.4
0.5
0.6
125 250 500 1000 2000 4000
f [Hz]
α [-]
T20-meting T-Sabine norm
α ‘norm’
α ‘aanwezig’
α ‘gemeten’
‘Berekende’ geluidabsorptiecoëfficiënt De nagalmtijd in relatie tot de verdeling van de geluidabsorptie Sporthal (48x28x9 m) - Norm: Tgem = 1,9 s; Tmax/fb = 2,7 s
3 varianten met gelijke hoeveelheid geluidabsorptie • Variant 1: Wandabsorptie rondom bovenste vlakken • Variant 2: Wandabsorptie rondom onderste vlakken • Variant 3: Wandabsorptie twee hele wanden
13-05-2011
2
Achtergrond huidige norm (2) • Goede
spraakverstaanbaarheid
• Signaal-ruisverhouding: – Direct geluid (nuttig) – Diffuus geluid (storend)
• De verhouding tussen ‘signaal’ en ‘ruis’ wordt bepaald door de hoeveelheid
geluidabsorptie
Sporthal (48 x 28 x 9 m)Afname geluidniveau
-20
-10
0
10
20
30
1 2 4 8 16 32
afstand bron-ontvanger [m]
G [d
B]
Totaal Direct Diffuus S/N
diffuusdir
tot
mfpr
GGNSAr
QG
/
)1(44
log1031/
2
S/N = 0
Achtergrond huidige norm (3) • De hoeveelheid geluidabsorptie in een sportzaal is bepalend
voor het ‘akoestisch comfort’ • Uitgedrukt in de gemiddelde absorptiecoëfficiëntα.
• De in de norm gestelde eis aan de nagalmtijd is dus een indirecte eis aan de hoeveelheid geluidabsorptie!
totAVT
6
ii
n
itot SA
1
tot
tot
SA
Gymzaal (21x12x6 m) – Norm: Tgem = 1,0 s; Tmax/fb = 1,4 s
De nagalmtijd als indicator voor de hoeveelheid geluidabsorptie
Gymzaal (21 x 12 x 6 m)Meting vs berekening
0.0
0.5
1.0
1.5
2.0
2.5
125 250 500 1000 2000 4000
f [Hz]
RT [s
]
T20-meting T-Sabine norm
Tgem = 1,0 s
Tgem = 1,6 s
Tgem = 0,8 s
Nagalmtijd
Gymzaal (21 x 12 x 6 m)Meting vs berekening
0.0
0.1
0.2
0.3
0.4
0.5
0.6
125 250 500 1000 2000 4000
f [Hz]
α [-]
T20-meting T-Sabine norm
α ‘norm’
α ‘aanwezig’
α ‘gemeten’
‘Berekende’ geluidabsorptiecoëfficiënt De nagalmtijd in relatie tot de verdeling van de geluidabsorptie Sporthal (48x28x9 m) - Norm: Tgem = 1,9 s; Tmax/fb = 2,7 s
3 varianten met gelijke hoeveelheid geluidabsorptie • Variant 1: Wandabsorptie rondom bovenste vlakken • Variant 2: Wandabsorptie rondom onderste vlakken • Variant 3: Wandabsorptie twee hele wanden
Example RT to a
ACOUSTICS IN SPORTS HALLSresearch on the acoustical behaviour of perforated panels
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Yvonne Wattez 1360809 graduation projectP2 presentation 25/01/2012
ZV
ZM
Z0air
Z1total
h
Z1 = ZR/hZR = ZM/ZV
( )( )
0 ,2
0 ,
1 /1
1 /s material
s material
Z Z
Z Zα
−= −
+
absorption coefficient calculation porous materialsZs,material= specific impedance of the material