87 pages 25 figures 7 tables 30 references

Transcription

1 Deutsches Zentrum für Luft- und Raumfahrt e.v. Forschungsbericht /E EffectsofNocturnalAircraftNoise Volume1 ExecutiveSummary M.Basner H.Buess D.Elmenhorst A.Gerlich N.Luks H.Maaß L.Mawet E.-W.Müller U.Müller G.Plath J.Quehl A.Samel M.Schulze M.Vejvoda J.Wenzel InstituteofAerospaceMedicine Cologne 87pages 25figures 7tables 30references

2 Effects of Nocturnal Aircraft Noise Volume 1 Executive Summary GermanAerospaceCenter(DLR) InstituteofAerospaceMedicine FlightphysiologyDepartment LinderHoehe 51147Cologne Germany flugphysiologie@dlr.de Cologne,July2004 Directoroftheinstitute: Prof.Dr.med.R.Gerzer Headofthedepartment: Dr.A.Samel Authors: M.Basner,H.Buess,D.Elmenhorst, A.Gerlich,N.Luks,H.Maaß, L.Mawet,E.-W.Müller,U.Müller, G.Plath,J.Quehl,A.Samel, M.Schulze,M.Vejvoda,J.Wenzel

3 aircraft noise, sleep, EEG, actimetry, performance, concentration, stress, cortisol, adrenalin, noradrenalin, annoyance, logistic regression MathiasBASNERetal. InstituteofAerospaceMedicineoftheGermanAerospaceCenter(DLR),Cologne Effects of Nocturnal Aircraft Noise (Volume 1): Executive Summary DLR-Forschungsbericht /E,2004,87pages,25figures,7tables,30references From1999until2003,theDLR-InstituteofAerospaceMedicineconductedextensiveinvestigations onhumanspecificeffectsofnocturnalaircraftnoisewithintheframeworkofthehgf/dlr-project "LeiserFlugverkehr".128subjectswereinvestigatedfor13consecutivenightsinfourrepresentativelaboratorystudies.From11pmuntil7ambetween4and128aircraftnoiseeventswithmaximumsoundpressurelevelsbetween45and80dB(A)wereplayedbackinarealisticfashion.The following electrophysiological variables were continuously sampled during the night: EEG, EOG, EMG, EKG, respiratory movements, airflow, finger pulse amplitude, position and actimetry. Concentrationsofthestresshormonesadrenalin,noradrenalinandcortisolwereanalyzedinallnight urine samples. Subjective assessments of strain and annoyance were collected with standardized questionnaires.computerassistedperformancetestswereperformedeveryeveningandmorning bythesubjects.64 residents ofcologne-bonnairportwereinvestigatedintheirown homesfor nine consecutive nights with methods identical to those in the laboratory. Here, sound pressure levels outside and inside the bedroom (at the sleeper's ear) were sampled continuously. In total, 2,240studynightswerepolysomnographicallyinvestigated.Thesimultaneousrecordingofelectrophysiologicalandacousticdataallowedforaneventrelatedanalysiswitharesolutionof125ms. Theageofbothmaleandfemalesubjectswasbetween18and65years.Subjectsdidnotsuffer fromintrinsicsleepdisordersandhadnormalhearingthresholds.thisvolumegivesanoverviewof studydesignandmethodsandsummarizesthemostimportantfindings.formoredetaileddescriptionsandanalysespleaserefertotheresearchreportsdlr-fb /etodlr-fb /e. Fluglärm, Schlaf, EEG, Aktometer, Leistung, Konzentration, Stress, Cortisol, Noradrenalin, Adrenalin, Belästigung, logistische Regression (in englischer Sprache veröffentlicht) MathiasBASNERetal. InstitutfürLuft-undRaumfahrtmedizindesDLR,Köln Nachtfluglärmwirkungen (Band 1): Zusammenfassung DLR-Forschungsbericht /E,2004,87Seiten,25Bilder,7Tabellen,30Literaturstellen ImZeitraumvon1999bis2003führtedasDLR-InstitutfürLuft-undRaumfahrtmedizinimRahmen des HGF/DLR-Projekts "Leiser Flugverkehr" umfangreiche Untersuchungen zu humanspezifischen WirkungennächtlichenFluglärmsdurch.128VersuchspersonenwurdeninvierrepräsentativenLaborstudienüber13aufeinanderfolgendeNächteuntersucht.Zwischen23:00und07:00Uhrwurdenzwischen4und128FluggeräuschemitMaximalpegelnzwischen45und80dB(A)überLautsprecher realitätsnah eingespielt. Folgende elektrophysiologische Variablen wurden kontinuierlich erfasst:eeg,eog,emg,ekg,atmungsbewegungen,atemfluss,fingerpulsamplitude,positionund Aktometrie.DieStresshormoneAdrenalin,NoradrenalinundCortisolwurdenimnächtlichenSammelurinbestimmt.DiesubjektiveEinschätzungderBelastungundBelästigungwurdemitstandardisiertenFragebögenerfasst.ComputergestützteLeistungstestswurdenjeweilsabendsundmorgens durchgeführt.64anrainerdesköln-bonnerflughafenswurdenmitidentischertechnikinihrergewohnten Umgebung in neun aufeinanderfolgenden Nächten untersucht, wobei der Schallpegel außenundinnen(amohrdesschläfers)kontinuierlichgemessenwurde.indenlabor-undfeldstudienwurdensomitinsgesamt2.240probandennächtepolysomnografischuntersucht.diesimultaneaufzeichnungvonelektrophysiologischenundakustischenparameternerlaubteeineereigniskorrelierte Auswertung mit einer Auflösung von 125ms. Die Versuchspersonen beiderlei Geschlechtswarenzwischen18und65Jahrealt,altersentsprechendschlafgesundundnormalhörend. In diesem Band werden neben dem Studiendesign und der Methodik die wichtigsten Ergebnisse zusammenfassend dargestellt. Eine umfassendere Darstellung erfolgt in den Forschungsberichten DLR-FB /DbisDLR-FB /D.

4 List of Abbreviations Abbreviation AGARD AMSAN db db(a) DIN EBF ECG EEG EMG EOG FA FAT FNL HGF khz L AS L AS,eq L AS,eq_event L AS,max LRA MDBF m min ms MST Meaning AdvisoryGroupforAerospaceResearchandDevelopment isolationfacility(arbeitsmedizinischesimulationsanlage) decibel,physicalunitofthesoundpressurelevel physicalunitofthea-weightedsoundpressure DeutschesInstitutfürNormunge.V. StrainandRecreationQuestionnaire (Erholungs-undBelastungsfragebogen) electrocardiogram electroencephalogram electromyogram electrooculogram entryquestionnaire Fatiguecheck-list AircraftNoiseQuestionnaire Helmholtz-GemeinschaftdeutscherForschungszentren kilohertz,physicalunitoffrequency A-weightedsoundpressurelevel measuredwithtime-weighting"slow" A-weightedequivalentcontinuoussoundlevel measuredwithtime-weighting"slow" A-weightedequivalentcontinuoussoundlevelfortheevent measuredwithtime-weighting"slow" A-weightedmaximumsoundpressurelevel measuredwithtime-weighting"slow" logisticregressionanalysis MultidimensionalMoodQuestionnaire (MehrdimensionalerBefindlichkeitsfragebogen) meter(s) minute(s) millisecond(s) MemorySearchTask

5 Abbreviation ng NREM-sleep REM-sleep sd sec S1,S2,S3,S4 SPT SRT STRAIN STRES TST UTT Meaning nanogram(s) sleepstages1to4 rapid-eye-movementsleep standarddeviation second(s) sleepstagess1,s2,s3,s4 sleepperiodtime SingleReactionTask StudyonHumanSpecificResponsetoAircraftNoise StandardizedTestsforResearchforEnvironmentalStressors totalsleeptime UnstableTrackingTask

6 Index 1 Introduction Study objectives Study design and methods Studydesign Samplingofstudysubjects Descriptionofthestudysample Acoustics Acousticsinthelaboratorystudies Acousticsinthefieldstudies Electrophysiologicalsignals Biochemicalmethods Performance Psychology Dataanalysis Acoustics results and discussion of the data of the field studies Sleep Influenceofnocturnalaircraftnoiseonsleep Methods Analysisoftheinfluenceofnoiseonsleepstagedistribution... 32

7 5.4 Eventcorrelatedanalysis Whatisasuitabledescriptorfornoiseinducedsleep disturbances? Methods Resultsofthelaboratorystudies Resultsofthefieldstudies Comparisonoftheresultsoflaboratoryandfieldstudies Awakeningduration Fallingasleepagain Importanceoftheresultsforthediscussionofaircraftnoise protectioncriteria TransferoftheresultstoaGermanairport Psychological effects Stress hormones Performance Summary Literature... 81

8 1 Introduction AlexanderSamel Within the framework of the HGF/DLR-Project Leiser Flugverkehr, the German Aerospace Center (DLR) developed a catalogue for the improvementoftechnical,operationalandlegalmeasuresforthereductionofaircraft noise. Within this project, the task of work package #1 "Effects of NocturnalAircraftNoiseonHumans"wastocreateinextensivestudiesa solid basis for an improved understanding of the effects of nocturnal aircraftnoiseonsleep. Anessentialreasonforthisresearchactivityisthelackofsufficientlylarge studies,inwhichsleepwaspolysomnographicallyinvestigated.sofar,this deficiency only allows a very limited and unreliable assessment of aircraft noise-inducedsleepingdisturbancesandtheiracuteeffects.althoughthere have been several proposals for limiting values, also considering principles ofpreventivemedicine,thesevaluesmainlyrelyondatafromsmallprimary studiesconductedinthepast.additionally,thesestudiespartlydrawcontradictoryconclusionsandalsoshowconsiderabledeficitsintheirmethods, execution, analysis and/or interpretation. Consequently, the proposals so fararebasedonresearchresultswhichwereattainedinsmallsamplesizes withdifferentmethodsandthereforeconsistentlyleadtofiercediscussions amongstnoise-effectsresearchersandotherinterestedgroups. Inthissituation,between1999and2003,theDLRconductedseveralstudiesinwhichidenticalmethodswithlargesamplesizeswereusedinorderto expand the scientific knowledge. As the investigations took place in the laboratoryaswellasinthefield,i.e.inthehomesofthoseaffectedbyaircraftnoise,adirectcomparisonbetweensimulatedandrealconditionswas possible. 1

9 2 Study objectives AlexanderSamel Themostimportantobjectiveoftheprojectwastodevelopcriteriaforassessing the effects of nocturnal aircraft noise on humans. A second very important goal was the establishment of a huge database of acoustical, physiologicalandpsychologicalfunctionsandpropertiesderivedfromanas muchaspossiblerepresentativesamplesurveyofpeoplewhoareaffected by nocturnal aircraft noise. By them, a broad scientific basis shall be provided for determined strategies of noise abatement by technical progress andoperationalprocedures,aswellasforplanningpurposes. increasing noise intensity?? primary during the night I II III secondary on the next day Figure 2.1: Development of assessment criteria derived from primary and secondary sleepdisturbances. 2

10 The development of criteria can be performed by the determination of dose-effectrelationshipsandthresholdlevelsforprimaryandsecondaryreactions of different dimensions, if they are existent and are detectable in properlaboratoryorfieldexperiments. Itisimportantwhetherdose-responserelationshipsandthresholdsaredetectableforprimaryorsecondarysleepdisturbances:primarydisturbances arethosewhichoccurasimmediatereactionstoaircraftnoiseduringthe night (e.g. vegetative arousals, awakenings, elevated excretion of stress hormones);secondarysleepdisturbancesarecharacterizedasreactionsvisible only on the following day as a consequence of sleep disturbances experiencedduringthepreviousnight(e.g.intensifiedfatigue,reducedperformance,enhancedannoyance).intheleastnoisyareai(seefigure2.1),it canbeexpectedthatnoisewillnotleadtomeasurablereactions,andthus, a threshold or dose-response effects will not be found. Above a certain threshold, reactions during sleep will presumably occur with interindividual variations of the threshold (primary reactions). These reactions canprobablybecompensatedandwillnotleadtoalterationsonthenext day(areaiioffigure2.1).itcanbeexpectedthatanyfurtherincrementof nightlynoise(eventrelatedorasacontinuousnoise)willproduceprimary sleep disturbances that cannot be compensated and thus, will also cause secondaryreactions.again,thresholdsanddose-effectrelationsmightdiffer inter-individually (areaiii). As secondary reactions may manifest over longlastingperiodsofmanyyears,itcannotbeexcludedthattertiaryeffectscanoccurfinally(e.g.healthimpacts),asacauseamongmanyothers accordingtoamulti-factorialetiology. Theoccurrenceofdose-effectrelationsandthresholds,respectively,ofprimaryandsecondarysleepdisturbancescanbeusedtodevelopcriteriafor theevaluationofnoiseeffectsonhumans.furthermore,itcanalsobeassumed,thattheprobabilityofhealtheffectscausedbynoise(tertiarysleep disturbances) will be extremely low, if appropriate primary and secondary sleepdisturbancesdonotoccurorcanbecompensated. 3

11 3 Study design and methods MathiasBasner 3.1 Study design DatasamplingforthestudycommencedinSeptember1999andendedin June2003.Table3.1showsnames,timeperiodsandtypesofthedifferent studyparts. Name Study period Type of study STRAINI SeptemberuntilNovember1999 Laboratory STRAINII MayuntilJuly2000 Laboratory STRAINIII FebruaryuntilApril2001 Laboratory STRAINV September2001untilMay2002 Field STRAINVI May2002untilNovember2002 Field STRAINIV MarchuntilJune2003 Laboratory Table3.1:StudyperiodsofthedifferentpartsofthestudySTRAIN(STudiesonhuman specificresponsetoaircraftnoise). Inthelaboratorystudies,128subjectswereinvestigatedfor13consecutive nights, whereas in the field studies 64 volunteers were observed for nine consecutive nights. For comparative reasons, both the laboratory and the fieldstudiescommencedonamondayevening. Inthelaboratorystudies,thesimulationfacilityoftheDLR-InstituteofAerospace Medicine allowed for the simultaneous investigation of eight subjects.thefirstofthe13observationnightsservedasadaptation,thesecondasbaselineandnights12and13asrecovery.allofthesenightswere noise-free.acontrolgroupof16subjectswasusedtoinvestigatetheinflu- 4

12 enceofthelaboratorysituationonotherwiseundisturbedsleepandtherefore the subjects did not receive any noise at all. The experimental group consistingoftheremaining112subjectsreceivedbetween4and128aircraftnoiseevents(anes)pernightwithdifferingmaximumsoundpressure levels (SPL) during nine consecutive nights (nights 3 to 11). Lights were turnedoffat11pmandonagainat7am,whichallowedforamaximum sleepperiodtimeof8hours.intotal,1072nightscontainingaircraftnoise and592nightswithoutaircraftnoise(adaptation,baseline,recovery,control)wereinvestigated. In the field studies, the homes of residents living in the vicinity of Cologne/Bonn Airport were selected in a way that the exposure to aircraft noise was high on one hand, but the exposure to other kinds of traffic noise, especially road traffic noise, was as low as possible on the other hand. Because flight paths change due to alternating weather conditions, andthefrequencyofplanestakingoffandlandingdependsontheweekday,thestudyperiodconsistedofnineconsecutivenights,includingweekends.besidenoiselevelsoutsideandinsidethebedroom,exactlythesame dataasinthelaboratorystudies(seebelow)werecollectedinthefield.in contrasttothelaboratorystudies,subjectsparticipatinginthefieldstudies were allowed to individually choose sleep period times with the requirement that sleep period times included the time period between midnight and6am.intotal,64subjectswereinvestigatedin576nightsduringthe fieldstudies. Intotal,2,240subjectnightswereinvestigatedinbothlaboratoryandfield studies together. 20 volunteers participated in both, laboratory and field studies. ThestudyprotocolwasapprovedbytheethicscommissionoftheMedical AssociationofthedistrictNorthRhine.Subjectswereinstructedaccording tothehelsinkideclaration,participatedvoluntarilyandwerefreetodiscontinuetheirparticipationatanytimewithoutexplanation. 5

13 3.2 Sampling of study subjects Studysubjectsreceivedanallowanceamountingto 75,-(field)and 55,- (laboratory) per observation night. Training of computer-assisted performancetestspriortothestartofthestudywasreimbursedwithupto 350,-. Studysubjectsweresampledinamulti-stageselectionprocess.Eachapplicanthadtopassthefollowingstepsoftheselectionprocess: FilloutandreturnentryquestionnaireFA participate in a detailed presentation of the study and fill out the FPIquestionnaire[9] participate in the medical check-up (medical history, medical examination,ecg,bloodandurinesamples,hearingthresholdtest) constant performance by the end of 40 training sessions of the computer-assistedperformancetests(seechapter8) Adetaileddescriptionofthemulti-stageselectionprocesscanbefoundin the report DLR-FB /E:"Effects of Nocturnal Aircraft Noise Volume 2:StudyDesignandMethods,Acoustics". Theapplicantshadtofulfillcertaincriteriaforstudyeligibility.Theexclusion ofcertainapplicantswasintendedtoincreasethevalidityoftheresultsfor thestudysample(internalvalidity).additionally,thestudygroupwasaimed tobeasrepresentativeaspossibleinordertobeabletoextendthefindings ofthestudytoalargerpopulation(externalvalidity). Themostimportanteligibilitycriteriawillbedescribedandexplainedindetailbelow.Theselectionofsubjectswasperformedinsuchawaythatrecommendationsbasedonthestudyresultswereinfavorofairportresidents affected by nocturnal aircraft noise, i.e. the selection process guaranteed 6

14 thattheeffectsofnocturnalaircraftnoisewereratheroverestimatedthan underestimated. The age of the study subjects was restricted to the range from 18 to 65 years. An investigation of children for nine or 13 consecutive nights was ethically not passable. Applicants older than 65 would not have to be excludedinevitably.butwithalimitednumberofstudysubjectsawiderage rangewouldhavecausedadecreaseinprecisionforsingleagecategories becauseofthesmallernumberofsubjectspercategory.asidefromthis,it isnotexpectedthatthesensitivitytoaircraftnoiseofsubjectsolderthan65 increasessuddenlyanddisproportionately,whichiswhytrendsfoundupto theageof65canbeextrapolateduntilnewevidenceisavailable. Studysubjectshadtohaveahealthy sleep according to age.thegoalof the study was to investigate the influence of nocturnal aircraft noise on sleep.ifasubjectsuffersfromanintrinsicsleepdisorder,itisimpossibleto differentiate whether secondary sleep disorders (tiredness, performance decrements,etc.)observedonthenextdayarecausedbyaircraftnoiseor by the intrinsic sleep disorder itself, especially as the severity of intrinsic sleep disorders may fluctuate unsystematically over several observation nights. Frequent spontaneous awakenings caused by an intrinsic sleep disorder leadtoasystematicunderestimationofthefractionofawakeningsinduced by aircraft noise. Aircraft noise induced awakenings are defined as the amountofawakeningssolelyattributabletoaircraftnoise.theyarecalculatedasthedifferenceof"awakeningsoccurringundertheinfluenceofaircraft noise" minus "spontaneous awakenings" (see chapter5). The sleep pressureofpatientswithanintrinsicsleepdisorderisfrequentlyincreased because of the perpetual disruption of normal sleep structure. Thus, the probabilityofreactionsinducedbyaircraftnoisemybereducedcompared tosubjectswithhealthysleepaccordingtoage.thereisnodoubtthattrafficnoiserepresentsanadditionalstrainforpatientswithintrinsicsleepdis- 7

15 orders.nonetheless,recommendationsbasedonsamplescontainingthese patients would underestimate the influence of nocturnal aircraft noise on sleep,beanti-conservativeandnotinfavorofairportresidentsaffectedby nocturnalaircraftnoise. Loudlysnoringparticipantswereexcludedfromthelaboratorystudies,as therewasthepossibilitythatthesleepofsubjectsinneighboringsleepcabinswasdisturbedbythesesnoringsounds.intotal,twoparticipantshadto be exchanged for so called backups because of snoring and sleep related breathing disorders in the laboratory studies. In order to prevent interferenceofsnoringsoundswithaircraftnoiseeventsrecordedinthefieldstudies,soundlevelandnoiseeventswererecordedforonenightpriortothe selectionofparticipantsforthefieldstudiesandloudlysnoringapplicants wereexcluded. Thereweresomerequirementsaccordingtothesleep habitsoftheapplicants.applicantsshouldnotnapregularlyduringthedaybecausedaytime napswerenotallowedduringthelaboratorystudies.usualpersonalsleep periodtimesshouldatleastbesixandnolongerthantenhours,because otherwisehabituationtothestrictsleepperiodtimefrom11pmuntil7am inthelaboratorystudieswouldhavebeendifficult.regularlygoingtobed before9pmorafter1amaswellasshiftworkduringthenightleadtoexclusion from the application process. Additionally, applicants should not regularly need to go to the restroom for more than two times during the night,becauseeachvisittotherestroomrepresentsapotentialinterference of the other subjects' sleep, aside from the disturbance of the subject's ownsleep. All participants of the study needed to have normal hearing thresholds. Depending on age the hearing loss on the weaker ear was restricted to 10%(18to33years),15%(34to49years)and20%(50to65years). 8

16 Applicants with arrhythmias were excluded because the analysis of parameters related to heart frequency or pulse amplitude would have been toocomplicatedorevenimpossible. Theconsumptionofdrugswithdepressanteffectsonthecentralnervous systemwerenotallowed,asthesedrugsmayelevateawakeningthresholds andinfluencetheresultsofthecomputer-assistedperformancetests. TheFreiburgerPersönlichkeitsinventar(FPI,seebelow)wasusedtotestfor psychological eligibility,animportantfeatureforgroupintegrityduring thelaboratorystudies.thecriteriawereevaluatedaccordingtotheprognosisofsocialcompatibilityaswellastothepsychologicalandphysicalstability.applicantswiththetendencytoanswerintermsof"socialdesirability" were excluded, because otherwise interpretation of questionnaire results wouldhavebeendoubtful. ApplicantshadtobeabletofluentlyspeakandwriteGerman.Contagious diseaseswerenotallowed.applicantswithalcoholordrugaddictionswere excluded. As sleep cabins in the underground sleep facility are relatively small,subjectswithclaustrophobiawereexcludedfromthelaboratorystudies. Itisemphasizedthatotherdiseasesthantheonesdescribedabovedidnot leadtoanexclusionfromthestudy,aslongasthosediseasesdidnotinterferewiththeexperiment. 3.3 Description of the study sample Bothinthelaboratoryandinthefieldstudiesafewmorewomenthanmen wereinvestigated(seetable3.2),thoughthereweremoremaleapplicants (52,1%)inthelaboratoryandmorefemaleapplicants(50,6%)inthefield studies. 9

17 Gender Laboratory subjects (n=128) Field subjects (n=64) Male 41.4% 45.3% Female 58.6% 54.7% Table3.2:Genderdistributioninlaboratoryandfieldstudies. Table3.3showstheagedistributionsofparticipantsofbothlaboratoryand fieldstudies. Age range (years) Age M(SD) Laboratory subjects (n=128) Field subjects (n=64) 19.5% 27.3% 14.1% 14.8% 13.3% 10.9% 38(13) 25.0% 14.1% 20.3% 23.4% 9.4% 7.8% 37(13) Table3.3:Agedistributionoversixcategorieswithacategorywidthofeightyearsin laboratoryandfieldstudies(m=mean,sd=standarddeviation). Originally,auniformagedistributionforallcategorieswasplannedinorder toreceivepreciseestimatesforthewholeagerangeinvestigated.forauniformdistributioneachcategoryshouldhaveconsistedofabout17%ofthe participants.table3.3showsthatthegoalofuniformitywasnotreached completely,yetsufficiently. Aircraft noise annoyance represents an important control variable. Therefore,itwasaccountedforintheselectionprocess.Itisemphasizedatthis pointthatthesubjectiveevaluationofaircraftnoiseannoyancemustnotbe equatedwiththeactualphysicalexposuretoaircraftnoise.infact,psychologicalresearchwasabletoshowthatonlyaboutonethirdofaircraftnoise 10

18 annoyanceiscausedbytheactualaircraftnoiseload.hence,itispossible thatsomeonefeelsstronglyannoyedbyaircraftnoisealthoughtheactual exposuretoaircraftnoiseislowandviceversa. Table 3.4 compares annoyance ratings of participants in laboratory and field studies, applicants for laboratory studies STRAINI to III, and a crosssectionrepresentativeforthegermanpopulationin2000[18].bothinthe last laboratory study and in the field studies subjective annoyance ratings werecollectedonlyaftertheendofthestudyperiodwiththefa-2questionnaire.therefore,dataonannoyanceratingsareonlyavailableforapplicantstostrainitoiii. Aircraft noise annoyance not little medium quite very Germany 2000 OrtscheidundWende[18] STRAIN I to III Applicants (n=763) Laboratory Subjects (n=128) Field Subjects (n=64) 67.5% 17.7% 9.1% 3.7% 2.0% 43.4% 33.2% 13.1% 7.5% 2.9% 29.7% 38.3% 19.5% 8.6% 3.9% 3.1% 21.9% 39.1% 28.1% 7.8% Table3.4:Aircraftnoiseannoyance acomparison. The cross-section of the German population is not uniformly distributed overthefiveannoyancecategories.onereasonforthismightbethatmany people were interviewed in areas not influenced by aircraft noise. More thantwothirdsoftheintervieweesdidnotfeelannoyedbyaircraftnoiseat all.asmanyoftheapplicantsforthelaboratorystudiesstrainitoiiiwere living in the vicinity of Airport Cologne/Bonn, which is also situated near 11

19 the German Aerospace Center(DLR) and the sleep lab, in this group only 43.4%didnotfeelannoyedbyaircraftnoise. Takingintoaccounttheaircraftnoiseannoyancedistributionoftheapplicants,here,incontrasttoageandgender,itwasimpossibletoachievea uniform annoyance distribution in the subjects participating in the study: Only 7.5% of the applicants felt quite annoyed, and only 2.9% felt very annoyed.duetotheselectionprocessinthelaboratorystudies,moreparticipants than applicants fell in the categories "medium", "quite" and "very",attheexpenseofthecategories"not"and"little".afterall,two thirds of the participants of the laboratory study felt annoyed by aircraft noisetosomeextent.inthefieldstudies,onethirdoftheparticipantsfelt "quite"or"very"annoyed.here,only3.1%(2subjects)werenotannoyed by aircraft noise at all as opposed to 67.5% of the cross-section of the Germanpopulation. 3.4 Acoustics Thefollowingsectionsdescribehowaircraftnoiseeventswererecordedfor and played back in the laboratory studies and how aircraft noise events weresampledinthefieldstudies Acousticsinthelaboratorystudies Duringnights3to11between4and128noiseeventsofstartingorlandingplaneswithmaximumsoundpressurelevels(SPL)from50to80dB(A) were played back between 11pm and 7am. In the last laboratory study STRAINIVaircraftnoiseevents(ANEs)withmaximumSPLsof45dB(A)were additionally played back. With a constant difference of 5dB(A) between events,14differentaircraftnoiseeventswereappliedintotal. The combinations of maximum SPL and number of ANEs per night that wereusedduringthelaboratorystudiesisshownintable3.5.thecombi- 12

20 nationsthatthesubjectsreceivedduringastudyperiodwererandomlyassigned.asthereweremorecombinationsthanexposurenightspersubject, the study design may be described as an incomplete block cross-over design. Number of Noise Events starting Number of Noise Events landing Maximum SPL LAS,max in db Table3.5:CombinationsofmaximumSPLatthesleeper'searandnumberofaircraft noiseeventspernightinthelaboratorystudiesstrainitoiv(e.g.24subjectnights with4x60db(a)atthesleeper'sear).frequenciesotherthan16arehighlightedinred color. Thecombinations4x50dB(A)and8x50dB(A)werenotusedbecauserelevantreactionsarenotexpectedatthislowlevelofexposure.Ontheother hand, the combinations 128x60 up to 128x80dB(A), 64x70 up to 64x80dB(A), 32x75dB(A), 32x80dB(A) and 16x80dB(A) were not played back because such exposures are unrealistically high and might not have been tolerated by the subjects, or might have caused subjects to discontinuestudyparticipationaheadofschedule. Each category was planned to consist of at least 16 subject nights, which wasaccomplishedforallcategoriesbut8x80db(a)landing.theincreased numberofnightswithcombinations64x45db(a)landingand64x65db(a) landing resulted from a special sub-experiment, in which both combina- 13

21 tionswerecompared(seebelow).thenumberofnightswiththecombinations4x55db(a)und4x60db(a)wereincreasedbecausetheywerejustbelowthesocalledjansen criterion,andthusshouldbecoveredmoreintensively. The ANEs played back during the night were recorded with class-1 sound levelmeters(nc-10,cortexindustries)inthevicinityofdüsseldorfairport withclosedortiltedwindows.themicrophonewaspositionednearpillow positionor"atthesleeper'sear". During a single study night always the same ANE was played back (e.g. 50dB(A) starting only), i.e. there was no mixing of different ANE in one singlenight.alleightsubjectsofonestudyperiodreceivedthesamenoise pattern,i.e.thesameanewasplayedbackinallsleepcabinsatthesame time.assoundinsulationinthesleepcabinswasnottotal,atemporaloffsetofplaybackofanesmighthaveleadtotheperceptionofanesfrom neighboringsleepcabins. Fromfourto128ANEswereequidistantlyplayedbackbetween11:15pm and 6:45am. The distance between two ANEs was 120 minutes at four eventspernight,60minutesateighteventspernight,30minutesat16 eventspernight,15minutesat32eventspernight,sevenoreightminutes at 64 events per night and 3 or 4 minutes at 128 events per night (see Figure3.1) AstheparticipantsdidnotknowoftheequaldistancesbetweenANEs,an anticipation of the time of occurrence of the next ANE was impossible. Watchesandalarmclockswerenotallowedinthesleepcabins. 14

22 Number 4x 20 8x 16x 15 32x 10 64x 128x 5 64x real :00 0:00 1:00 2:00 3:00 4:00 5:00 6:00 7:00 Time Figure3.1:PlaybackpatternofANEsdependingonthenumberofANEspernight.At thebottomarealisticpatternderivedfromthefieldstudies,whichwasusedin night12ofstrainivwithmaximumsplof65db(a),isshown. PlaybackofANEswasrealizedwithanAcousticWorkstationCF85(Cortex Industries). Before each study period, every sleep cabin was acoustically calibrated with class-1 sound level meters in order to guarantee realistic playbackofanes. The SPL in each sleep cabin was recorded continuously during each study nightandallowedforthecontrolofthecorrectplaybackofeveryane.additionally,itwaspossibletoidentifyloudlysnoringsubjects. Atthe beginningoftheplaybackofeachaneadigitaltriggersignal was putoutandsimultaneouslysampledwiththeelectrophysiologicalsignalsat a sampling rate of 8Hz. Thus, all signals were available on a single time axis,whichallowedforaneventcorrelatedanalysiswithamaximumresolutionof125ms. 15

23 Thesubjectswereonlyinformedthatthefirsttwostudynightswerenoisefree.Theywereotherwiseblindedwithrespecttonoiseexposure,i.e.they didnotknowwhen,howmanyandwhatkindofaneswereplayedback after the second night. In order to avoid subconscious manipulations, the investigators were also blinded for the noise pattern of the specific night. Onlyafterthebeginningofdatasampling,i.e.after11pm,theywereinformedaboutthenoisepatternofthespecificnight,andthuswereableto monitorthecorrectplaybackofanes. Altogether, 34,688 ANEs were played back in the laboratory studies. The equivalent continuous sound level [DIN1] depending on the combinations of maximum SPL and number of ANEs per night are shown in Table 3.6. Therewasaconstantbackgroundnoiseofabout30dB(A)inthelaboratory studiescausedbytheairconditionsystem. Number of Noise Events Starting Number of Noise Events Landing ,5 31,0 Maximum SPL LAS,max in db Table3.6:EquivalentcontinuoussoundlevelL AS,eq (3)dependingonthecombinations ofmaximumsplandnumberofanespernight(topandbold:aircraftnoiseonly, bottom:aircraftnoiseplusconstantbackgroundnoiselevelofabout30db(a)). 16

24 3.4.2 Acousticsinthefieldstudies 2meters Bedroom Trigger Both field studies STRAINV and VI were conducted in the vicinity of Cologne/BonnAirport.Thischapterdescribestheacousticalsetupinthefield studies.resultsoftheanalysisoftheacousticalsignalssampledduringthe fieldstudiescanbefoundinchapter4. Inthefieldstudies,solelythenoisegeneratedbyairtrafficattheAirport Cologne/Bonn was sampled, i.e. no additional ANEs were presented via loudspeakers,aswassometimesdoneinfieldstudiesbyotherinvestigators. AsketchoftheacousticalsetupisshowninFigure3.2. Auto- Trigger Laptop Figure3.2:AcousticalsetupofthefieldstudiesSTRAINVundVI(schematically). Threeclass-1soundlevelmeters(NC10,CortexInstruments)weresimultaneouslyused.Onesoundlevelmeter(#1)recordednoiseeventsoutsidethe bedroom with a distance of two meters to the windows, while two more 17

25 soundlevelmeters(#2and#3)recordednoiseeventsinsidethebedroom atthesleeper'sear. The SPLs L AS and L lin were continuously sampled and stored during the whole night. Once a certain background noise level (L90) was exceeded (usually by at least 4dB),#1 recorded the actual noise event with a samplingrateof24khzuntilthedifferencetothebackgroundnoiselevelfell againbelow4db,butatleastfor30s.thesinglenoiseeventswerestored as wav-files. Hence, the identification of the noise source (e.g. aircraft, road, rail) was possible. Simultaneously, with the beginning of the recording of the noise event outside, #2 was triggered and recorded the noise event synchronously with #1, but now inside the bedroom. As recordsofthesamenoiseeventexistedbothoutsideandinside,conclusions about dampening properties of windows and masonry were possible (see chapter4). Asinthelaboratorystudies,thetriggersignalwassynchronouslyrecorded withtheelectrophysiologicalsignalsatasamplerateof8hz.inthatway, an event correlated analysis of acoustical and electrophysiological signals witharesolutionofupto125mswaspossibleinthefieldstudiesaswell. Athirdsoundlevelmeter(#3)recordednoiseeventsinsidethebedroomas soonasacertainbackgroundnoiselevelwasexceeded(usuallybyatleast 4dB).Inthatway,itwaspossibletoadditionallyidentifynoiseeventsoriginatinginsidethebedroomorhouse(e.g.snoring)andthatotherwisemight havebeenmissed,assoundlevelmeter#2wastriggeredfromtheoutside soundlevelmeter. 3.5 Electrophysiological signals All electrophysiological signals were synchronously sampled during the night,electronicallyamplified,convertedfromanalogtodigitalsignalsand sent via optical fibers to a personal computer(laboratory) or laptop(field) 18

26 where they were reproduced on a computer screen for monitoring purposes,andstoredforsubsequentanalyses.theacousticalsignalsweresynchronouslystored. Scoringofsleepstageswasperformedaccordingtotheacceptedstandard of Rechtschaffen and Kales [21] making use of the polysomnographic recordsofeachnight.theelectroencephalogram(eeg)wasderivedwithsilver/silverchlorideelectrodesinthepositionsa1,a2,c3undc4,theelectrooculogram(eog)withelectrodesplacedneartheedgeoftherightand lefteyeandtheelectromyogram(emg)withelectrodesplacedontheskin abovethemusclesofthechin. ECGandfingerpulseamplitudeweresampledcontinuouslyaswellinorder to be able to detect vegetative arousals during sleep. Respiratory movementsofthethoraxweremeasuredwithpiezzotechniquebuiltintoathoracic strap. Air flow at mouth and nose were sampled with a thermistor. Both signals were used to diagnose sleep related breathing disorders. The thoracic strap also contained a position sensor in order to detect body movementsduringsleep. Thesimultaneousrecordingofelectrophysiologicalandacousticalsignalsallowed for the differentiation of spontaneous and noise induced reactions duringsleep. Additionally, study participants wore actimeters 24 hours a day, i.e., also duringthedaytime. 3.6 Biochemical methods Duringthelaboratorystudies,excretionratesofthestresshormonescortisol,adrenalin,andnoradrenalinandelectrolytes(potassium,sodium,magnesium,calcium)weredeterminedfromurinesamplescollectedwithintwo defined periods daily: between 7pm and 11pm (evening urine), and between11pmand7am(nighturine). 19

27 Duringthefieldstudies,however,onlynighturineswerecollectedbetween the time of going to bed in the evening and the waking-up time in the morning. The urine samples for adrenalin and noradrenalin were analyzed by high performance liquid chromatography (HPLC) and electrochemical detector. Unconjured cortisol concentrations in urine were determined by immuno assays,samplesfrom164subjectsbyaradioimmunoassay(ria),andfrom 32 subjects by a solid phase chemo luminescence enzyme immunoassay (LEIA).Bothmethodsarenotimmediatelycomparable.Therefore,herestatistical analyses on relative changes were applied too, i.e. against night2, thebaselinenight.thedeterminationofpotassiumandsodiumconcentrations was by ion selective electrodes that of magnesium and calcium by photometry of their colored complex compounds in standard clinical routinemethods. 3.7 Performance Computer-assisted performance tests represent a very important method forthedetectionofsecondaryeffectsofnocturnalaircraftnoiseonmental performance. ThetestsusedfortheevaluationofchangesinmentalperformancecapacitiesweretakenfromthesocalledAGARD-STRES-battery[8]andcontained: Singlereactiontime SRT Memorysearchtaskwith4letters MS4 Memorysearchtaskwith6letters MS6 Unstabletrackingtask UTT In order to attain a stable performance, both in the laboratory and in the fieldstudiessubjectshadtoperform40trainingsessionsofalltestspriorto 20

28 thebeginningofthestudy.allperformancetests(totalprocesstimeabout 25min)wereconductedintheevening(abouttwohoursbeforegoingto bed) and in the morning(after getting up) to be able to detect effects of sleepdisturbancesinducedbyaircraftnoise. 3.8 Psychology The investigation of psychological effects contained the measurement of subjectivechangesofsleepsensation,annoyance,mood,strainandrecreation depending on the nocturnal aircraft noise exposure. Hence, in both laboratoryandfieldstudiesthefollowingquestionnaireswereused: FatigueChecklistFAT[26] AircraftNoiseQuestionnaireFNL[5] MultidimensionalMoodQuestionnaire(MehrdimensionalerBefindlichkeitsfragebogenMDBF)[29] StrainandRecreationQuestionnaire(Erholungs-undBelastungsfragebogenEBF)[13] All variables were analyzed in connection with physical parameters (maximumspll AS,max,continuousequivalentsoundlevelL AS,eq,numberofANE) as well as psychological moderators in order to derive dose-responserelationships. 3.9 Data analysis Data analysis was performed with the software packages SPSS(SPSS Inc., version11.5.1) und EGRET(Cytel, version ). Chapters 4 to 8 inform about the individual statistical methods used for data analysis of special topics(sleep,performance,etc.). 21

29 4 Acoustics results and discussion of the data of the field studies UweMüller Inthefieldstudiesthesoundpressurelevelwasrecordedcontinuouslyduring the entire night outside and inside the bedroom at the sleeper's ear. Additionally, all those noises were recorded with 24kHz sample rate, whose sound pressure level was at least 4dB(A) above the background level(seealsochapter3.4.2). This permitted an unambiguous identification of each noise event during theentirenight.foreverystudynighteachnoiseeventwasmarkedatthe beginningandtheendandidentifiedwithacomment.foreachevent,the analysisprogramcomputedtheoveralllength,thet 10 -time,themaximum level, the time of occurrence of the maximum level, the level rise, theenergy equivalent continuous noise level L eq_event (e.g. forairplanes, cars,all trafficnoiseetc.),andthebackgroundleveloneminutepriortothestartof eachevent.fortheevaluationofnoiseeffectsthesoundpressurelevelat the top of the bed was relevant in order to allow for an event correlated analysis of acoustical data (measured at the sleeper's ear) and electrophysiological signals. However, the above-mentioned values were calculatedbothforinsideandoutsidethebedroom. Inthe14monthsofthefieldstudies,46locationscontainingatotalof64 subjectswereexaminedfornineconsecutivenights.theinvestigationstook placeatninemeasuringpointsinthespring,ateleveninthesummer,at19 intheautumnandatseveninthewinter.394nights,inwhichacoustical dataofbothinsideandoutsidemeasurementswereavailable,wereconsideredinthefollowinganalyses. 22

30 freq. of occurence / night freq. of occurence / night outside median: 64.0 db(a) maximum sound pressure level [db(a)] at the sleeper's ear median: 44.0 db(a) average total noise length: 78.0 [s] maximum sound pressure level [db(a)] Figure4.1:Frequencydistributionofthemaximumsoundpressurelevelsofaircraft noiseevents2metersinfrontofthewindowsandinsidethebedroom(atthesleeper s ear)in1db(a)-steps,averagedover394nights.forthisevaluationonlyaircraftnoise eventsnotdisturbedbyothernoisesourceswereconsidered. Inthese394nights,altogether16,102airplaneswerecounted(thatcorrespondsto40.9pernight,averagedovertheentireweek).14,247aircraft noiseeventswerenotdisturbedbyothernoiseeventsatthesleeper'sear and will be designated"undisturbed"from now on. Furthermore, 12,256 cars (11,653 undisturbed), 239 motorcycles (217 undisturbed) and 127 trucks(120undisturbed)wereidentified.thislistindicatesthatthemeasuring points were predominantly selected in residential areas strongly affectedbyaircraftnoisebutcalmintermsofothertrafficnoise.figure4.1 showsthefrequencydistributionofthemaximumsoundpressurelevelsof theaircraftnoiseevents,averagedoverall394nightsandthusnotdifferentiatedbytheweekday. 23

31 Subjects of the field studies were asked not to change their usual sleep habits during the investigation, with the restriction that a minimum bed timewasgivenfrommidnightto6.00am.hence,subjectswerealsofree tochosethewindowpositiontheywantedtosleepwith. The difference of the sound pressure levels measured inside (at the sleeper's ear) and outside the bedroom is particularly determined by the sizeofthewindowgapandthedistanceofthemicrophoneinsidethebedroomtothewindow,additionallyalsobythewindowsize,itssoundreduction index, the frequency distribution of the aircraft noise event and the weatherconditions.inordertoconsidertheseadditional,non-constantparametersforthecalculationofanaveragesoundpressureleveldifference, thel eq_event ofeachundisturbedaircraftnoiseeventwascalculatedforeach night.fromthesevalues(36pernightonaverage)themedianwascalculated. Thus, for each of the nine study nights at each measuring point a medianwasreceived,fromwhichthetotalmedianforthemeasuringpoint wasthendetermined.atthreemeasuringpointsthewindowpositionwas changedforatleastoneoftheninestudynights.thesemeasuringpoints contributed twice to the calculation, however with a smaller number of nights representing the total median of the according window position at thatmeasuringpoint. Figure4.2showstheresultsfortheaveragedifferencesinsoundpressure levelmeasuredoutsideandinside(atthesleeper'sear)thebedroom.since no standardized acoustical measuring conditions were present (since the goal of the study was the determination of the sound pressure level and theidentificationofthenoiseeventattheearofthesubjects,whichpermittedaneventcorrelatedanalysis),thesoundpressureleveldifferencesof the different window positions scatter relatively strong. Although thedistance of the interior microphone to the window was not measured, this strongdispersionisduetothedifferentdistancesofthebedstothewindows,sincewithtiltedwindowstheexactgapopeningwidthandtheexact windowareaandwithclosedwindowsthesoundreductionindexandthe 24

32 window size contribute only little to the sound pressure level difference comparedtostandardvaluesfortiltedandclosedwindows[14].themedian values of 28.4dB(A) for closed, 18.4dB(A) for tilted and 13.5dB(A) foropenwindows(onlythreemeasuringpoints)indeedgiveagoodrepresentationofthedifferencesinsoundpressurelevelsforaircraftnoiseevents inpractice closed window, Med: 28.4 db(a), N=12 tilted window, Med: 18.4 db(a), N=34 open window, Med: 13.5 db(a), N=3 frequency of occurence difference of sound pressure level [db(a)] Figure4.2:Averagedifferenceinsoundpressurelevelsmeasuredinside(atthe sleeper'sear)andoutsidethebedroom.themedianwastakenfromnineobservation nights,wherebythesmallestandlargestvaluedidnotenterthecalculation.atthree measuringpointsthewindowpositionchangedduringtheexperiment.foradetailled descriptionofthecalculationsofthedifferencesseetext. Incontrasttothedeterminationoftheenergyequivalentcontinuoussound level L AS,eq(3) for the controlled acoustic conditions in the sleep laboratory, thel AS,eq(3) inthefielddoesnotexclusivelydependonaircraftnoiseevents, but also on contributions from other traffic and the respective weather situation. 25

33 Averaged over all measuring points for the time between midnight and 6aminspringanaverageL AS,eq(3) of54.8db(a)foroutsideand34.3db(a) forinsidewascalculated,insummer52.8db(a)outsideand37.3db(a)inside, in autumn 53.5dB(A) outside and 36.0dB(A) inside and in winter 55.0dB(A)outsideand36.8dB(A)inside.Consideringthefactthattheaveragenumberofaircraftmovementsbetweenmidnightand6.00aminthe annual average amount to 21.1% during spring, to 30.0% during the summer,to22.9%duringautumnandto25.9%duringwinter,thenone recognizesthatthel AS,eq(3) -calculationsarealsostronglyaffectedbythedifferentweathersituations(windandrainleadtohighersoundpressurelevels)andthewindowpositionsvaryingwiththeseasons. 26

34 5 Sleep MathiasBasner Sleepisaconditionwitharestrictedperceptionoftheindividualtowards himselfandtheenvironment.humansspendaboutonethirdoftheirlives sleeping.withthesamplingofcertainbiologicsignals,thesocalledpolysomnography, an awake human with closed eyes can be differentiated fromasleepinghuman.additionally,makinguseofpolysomnographicsignals,sleepcanbedividedintosixdistinctandfunctionallydifferentstates: Firstly,beingawakecanbedistinguishedfrombeingasleep.Then,sleepitselfcanbeclassifiedintoREM-sleep(seebelow)andnon-REM-sleep,while non-rem-sleep can be subdivided again into sleep stages S1, S2, S3 and S4.SleepstagesS1andS2arealsocalledlight sleepandstagess3ands4 deep sleep. These terms are based upon the fact that humans are more easily awakened from light than from deep sleep. For the classification, a nightissplitinto30secepochs,andeachoftheseintervalsiscategorized inoneofthefivedifferentsleepstagesor"awake".followinganinternationalstandard[21]oneofthesleepstagesisassignedtoeach30secepoch. Currently, there is no reliable automated sleep stage analysis, and hencesleepstageshavetobeclassifiedbyanexperiencedhumananalyzer. Thisprocessistimeconsumingandthereforeexpensive,whichiswhypolysomnographyhasbeenappliedonlyinsmallernoiseeffectsresearchstudieswithonlyafewsubjectsinthepast. Polysomnographyconsistsofthefollowingelectrophysiologicalsignals: Electrodesattachedtothescalpareusedtoderivetheelectroencephalogram (EEG). Besides EEG-frequency and -amplitude special EEG-patterns (e.g.k-complexesandspindles)playanimportantroleforsleepstageclassification.slowwaveswithhighamplitudearecharacteristicfordeepsleep, e.g.,andhencedeepsleepisalsocalledslow wave sleep (SWS). 27

35 Eye movements (electrooculogram EOG)arederivedfromtwoelectrodesusuallyattachedclosetotheeyes.Sloweyemovementscanbeobservedwhilefallingasleep(S1),whereasrapideyemovementsarecharacteristic for REM-sleep. These eye movements are the reason for the term "REM-sleep"(rapid eye movement sleep). Muscle tension (electromyogram EMG)isderivedfromtwoelectrodes attachedtotheskinabovethechinmuscles.muscletensiondecreaseswith increasingdepthofsleepfromstages1tos4,butshowsthelowestvalues duringrem-sleep. Sleep stages are not uniformly distributed over the sleep period. In 128 baselinenightsofthelaboratorystudiesthedifferentsleepstagesweredistributed as follows: S2~52%, REM~22%, SWS~16%, Awake~8% unds1~2%.theproportionofsleepstages2ishighest,whereass1,representingaspecialtransitionalstatefrombeingawaketofallingasleep,can onlyseldombeobservedinundisturbednights.furthermore,thefractions ofthedifferentsleepstagesintotalsleeptimeareagedependent.areductionofsws-fractions,especiallyinfavorofs2canbeseeninolderpeople. Often,noSWSatallcanbefoundinsubjectsveryadvancedinyears. Alternatingepisodesofnon-REM-sleepandREM-sleeparealsocalledsleep cycles.eachnormalnightconsistsofseveralcycleslastingbetween60and 120mineach.Thecompositionofthesleepcycleschangesinthecourseof the night: SWS dominates the first third of the night, whereas REM-sleep prevailsinthelastthirdofthenight.asocalledhypnogramisobtainedby plottingthedifferentsleepstagesagainsttheelapsedsleeptimeandvisualizesthestructureofsleep.figure5.1showsthehypnogramsoftwoparticipantsofthelaboratorystudies. 28

36 Awake REM S1 S2 S3 S4 B Awake REM S1 S2 S3 S4 A 23:00 0:00 1:00 2:00 3:00 4:00 5:00 6:00 7:00 Time Figure5.1:Hypnogramsoftwoparticipantsofthelaboratorystudies.Inbothnights 64aircraftnoiseeventswithamaximumSPLof65dB(A)atthesleeper'searwere playedback. Both subjects received 64 aircraft noise events with a maximum SPL of 65dB(A) at the sleeper's ear during the night shown in Figure 5.1. The group of all participants who were exposed to the combination 64x65dB(A)wokeupwithameanprobabilityof23.3%whilebeingexposedtoaircraftnoise.SubjectAwokeupwithaprobabilityofonly3.3%, thelowestpercentageobservedinthegroup.subjectb,ontheotherhand, woke up with a probability of 88% and therefore expressed the highest sensitivitytoaircraftnoise. BothextremesofthepercentagebeingawakenedareshowninFigure5.1 onpurpose,topointoutthestrongdifferencesinenvironmentalnoisesensitivitybetweensubjects.hence,investigationswithsmallsamplesizes,e.g. 16subjects,areinsufficient,as16veryinsensitiveor16verysensitivesubjects may be sampled by chance, which would mean that the results are 29

37 strongly influenced by chance as well. This bias can be minimized by the use of larger sample sizes and a suitable selection process of study applicants. Therestorativepowerofsleepisnotonlyinfluencedbysleepdurationbut also by sleep structure. Present scientific knowledge assumes that the six sleepstagesdifferintheirrecuperativevalue,althoughthefunctionsofthe different sleep stages and the mechanisms of these functions are still not exactlyknown.deeporslowwavesleep(sws)isconsideredtobeparticularlyimportantfortherestorativepowerofsleepbecauseofthefollowing reasons[7]: itsproximitytosleeponset itsimmediatereboundaftersleepdeprivation itsassociationwithhighsensorythresholdsandtheexcretionofgrowth hormones ResultsoftherecentpastindicatethatSWSisinvolvedintheconsolidation ofexplicitmemorycontents,whereasrem-sleepseemstobeimportantfor the consolidation of implicit memory contents[22]. Stages Awake and S1 do notcontribute to the recuperative value of sleep or only very little respectively,whereassleepstages2takesanintermediateposition. 5.1 Influence of nocturnal aircraft noise on sleep Theregenerationofmentalandphysicalpowersprimarilytakesplaceduringsleep.Undisturbedsleepisaprerequisiteforthisrecuperativeprocess. The human organism recognizes, evaluates and reacts to environmental soundsevenwhileasleep.thesereactionsarepartofanintegralactivation process of the organism and express themselves e.g. as changes in sleep structureorincreasesinheartfrequency.environmentalnoisemaydecrease therestorativepowerofsleepbymeansofrepeatedlyoccurringactivations, 30