Comparing measurements and simulations for acoustics in open-plan office spaces

119 Pages·2017·11.32 MB·English

by  Hogne Opsahl Olufsen

Comparing measurements and
simulations for acoustics in open-plan
office spaces
Hogne Opsahl Olufsen
Master of Science in Electronics
Submission date: July 2017
Supervisor: Peter Svensson, IES
Norwegian University of Science and Technology
Department of Electronic Systems

Dedication
Thisthesishasgivenmevaluableexperience,ithasallowedmetofamiliarizemyself
withoneofthemostcommonsimulationtoolsforacoustics,Odeon. Ihavealsohadthe
opportunitytolearnCATTacoustics,andthemeasurementprogramWinMLS.Ithasalso
givenmetheopportunitytocloselyrelatemyselftotheparametersoftheISO3382-3.
IwouldliketothankmysupervisorPeterSvenssonforsteeringmeontherightpathand
hisengagementintheproject.
Iwouldalsoliketothankmyco-supervisorDanielaToledoHelboefromCOWIOslofor
valuableinputandgreatfacilitationinOsloduringthemeasuringperiod. Alsothanksto
ChristopherGeheandEirikTuftinforhelpwithWinMLSandinformationaboutthe
materialsintheoffice.
ThankstoBa˚rdStøfringsdal,COWIFørdforvaluablesupportandexperiencesharing.
IwouldalsoliketothankCOWITrondheim,forlettingmeuseOdeonandprovidinga
deskformeinanopen-planoffice. Thatallowedmetoexperienceprosandconsrelated
tomythesiswork.

Summary
ThisreportistheresultofamasterthesisattheNorwegianUniversityofScienceand
Technology(NTNU).TheISO3382-3[2]describesthemeasurementprocedureofroom
acoustical parameters in an open-plan office. The aim was to investigate how well these
parameterscouldbesimulated, bycomparingmeasuredandsimulatedvalues. Aspecial
study of diffraction has also been conducted, indicating that Odeon strongly underesti-
matesdiffraction.
Measurementsandsimulationsofthereverberationtime,RT,andtheISO3382-3pa-
rameters have been done in two Zones of the COWI main office in Oslo. The parame-
tersarethetheA-weightedSPLbasedparameters(D ,L ,L )andtheSTI
2,s p,A,S,4m p,A,B
based parameters (STI in nearest workstation, r , r ). The absorption and scattering
d p
coefficientofthematerialsinthesimulationmodelwereadjustedsuchthatthesimulated
RTwassimilartothemeasuredRT.ThentheISO3382-3parameterswereestimatedfrom
thesimulation.
ThemeasuredandsimulatedISO3382-3parameterswerequitesimilarforoneZone
intheoffice,butnotfortheotherZone.
i
Preface
Open-planofficesspaceshavesomecontradictingrequirements. Theemployeesneed
tobeabletoheareachotherwhenworkingasteams,butnotbedistractedbyotherswhen
working alone, especially when solving concentrations demanding tasks. The noise in
open-planofficesconsistsofmanydifferentsounds,suchasspeech,laughter,ringtones,
impactnoise,trafficandotheroutdoornoise,ventilationandair-conditioningnoise,print-
ers and copy machines. The most annoying factor for concentration and cognitively de-
mandingtasksisspeech. AlargeSTIcanleadtodistractedemployeesandalossinpro-
ductivityuptoasmuchas7%,Hongisto[19]. Hence,investmenttoimprovetheacoustics
inanopen-planofficespacecanleadtopositivelongtermeffects,suchasmoresatisfied
employeesandhigherproductivity.
The goal is to simulate and measure the ISO 3382-3 [2] parameters in an open-plan
office,usingthegeometricalacousticsoftwareOdeon. Theobjectiveistocomparemea-
suredparametervaluestosimulatedparametervalues,andtooevaluateiftheparameters
correlate with one another for the measurements and for the simulations. A sub task is
to verify if simulation tools like CATT and Odeon are suitable for looking at nuances in
theISO3382-3parameters. Thisshouldbedonebyimplementingaspecialstudyofedge
diffraction.
Simulationisanimportanttoolwhendesigningopen-planoffices,butwhatisthequal-
ityofthesimulations? Thequalitycanbeconsideredbasedontheresultingvaluesofthe
ISO3382-3:2012parameters. Theparameterscanbeseparatedintotwocategories;
-TheA-weightedSPLbasedparameters(D ,L ,L )
2,s p,A,S,4m p,A,B
-TheSTIbasedparameters(STI innearestworkstation,r ,r )
d p
Open-planofficesareusuallyquitelargeandmanyhaverelativelylowceilings,there
arealsooftenscreenand/orotherobjectobscuringthepathbetweentheemployees.Open-
planofficesareseldomadiffusefiledcase. Therefore,twowidelydiscussedissueswhen
itcomestosimulationingeneralandofopen-planofficesinparticular,aretheaccuracyof
theedgediffractionandtheangledependentabsorption.Notallacousticalsimulationtools
includeangledependentabsorption,butratherassumediffuseincomingwaves. Therehas
notbeenconductedastudyontheangledependentabsorption,butthiswouldbeanatural
nextstep.
ii
Table of Contents
Summary i
Preface ii
TableofContents v
ListofTables viii
ListofFigures xi
Abbreviations xii
1 Introduction 1
2 LiteratureReview 3
3 Theory 5
3.1 A-weightedsoundpressurelevelbasedparameters . . . . . . . . . . . . 5
3.1.1 A-weightandSoundpressurelevelofnormalspeech . . . . . . . 5
3.1.2 Distanceattenuationofspeech,D . . . . . . . . . . . . . . . 6
2,S
3.1.3 A-weightedsoundpressurelevelofspeechat4mdistance,L 6
p,A,S,4m
3.1.4 Backgroundnoiselevel,L andL . . . . . . . . . . . . . 7
p,B p,B,n
3.2 Speechtransmissionindex,STI . . . . . . . . . . . . . . . . . . . . . . 7
3.2.1 Distractiondistance,r . . . . . . . . . . . . . . . . . . . . . . . 7
d
3.2.2 Privacydistance,r . . . . . . . . . . . . . . . . . . . . . . . . . 7
p
3.3 Linearregression . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
3.3.1 Diffraction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
3.4 Scatteringcoefficient . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
3.5 NS8175 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
3.6 Correlation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
3.7 Applicationoftheory . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
iii
4 Method 15
4.1 Theofficelayout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
4.2 Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
4.2.1 Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
4.3 Simulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
4.3.1 Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
4.3.2 STIestimation . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
5 Results 31
5.1 Backgroundnoiselevel . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
5.2 Reverberationtime . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
5.3 A-weightedSPLbasedparameters . . . . . . . . . . . . . . . . . . . . . 34
5.4 STIbasedparameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
5.5 Correlation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
6 SpecialstudyonDiffraction 47
6.1 Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
6.1.1 CATTandOdeonanalysis . . . . . . . . . . . . . . . . . . . . . 48
6.1.2 Matlabanalysis . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
6.2 ComparingresultsfromEDB1andESIE . . . . . . . . . . . . . . . . . . 52
6.3 1. and2. orderdiffractionresultswithOdeon,CATTandEDB. . . . . . . 54
6.4 CompletediffractionestimationwithCATTandEDB1. . . . . . . . . . . 57
6.5 Comparing CATT and EDB1 results with complete diffraction versus 1.
and2. orderdiffraction . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
6.6 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
7 Discussion 63
8 Conclusion 67
Bibliography 69
Appendix 73
A Matlabcodes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
A.1 STIfunction . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
A.2 Distanceattenuationfunction . . . . . . . . . . . . . . . . . . . 75
A.3 Octavebandfilterfunction . . . . . . . . . . . . . . . . . . . . . 76
B Diffractionanalysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
B.1 1. and 2. order diffraction results with Odeon, CATT and EDB,
usingS andthickscreen. . . . . . . . . . . . . . . . . . . . . . 77
1
B.2 1. and 2. order diffraction results with Odeon, CATT and EDB,
usingS andthickscreen. . . . . . . . . . . . . . . . . . . . . . 79
2
C MeasuredandsimulatedRT . . . . . . . . . . . . . . . . . . . . . . . . 80
C.1 RTmeasured . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80
C.2 RTsimulationmodel1 . . . . . . . . . . . . . . . . . . . . . . . 81
C.3 RTsimulationmodel2 . . . . . . . . . . . . . . . . . . . . . . . 81
iv
D Materialproperties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83
D.1 Tropic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83
D.2 Krios . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87
D.3 Suspendedceiling . . . . . . . . . . . . . . . . . . . . . . . . . 91
D.4 EpocaStructure . . . . . . . . . . . . . . . . . . . . . . . . . . . 93
D.5 Screens . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97
D.6 Measurementuncertainties . . . . . . . . . . . . . . . . . . . . . 103
v
vi