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JIPAversionModelingFinalReport
AdamS.Frankel,Ph.D.WilliamT.Ellison,Ph.D.AndrewW.White,Ph.D.
KathleenJ.Vigness‐Raposa,Ph.D.
MarineAcoustics,Inc.
MAI947
31July2016
TN16–015
2
Table of Contents
INTRODUCTION......................................................................................................................................................3
METHODS.................................................................................................................................................................4SOURCEANDPROPAGATIONMODELING.............................................................................................................................4ANIMATMODELING................................................................................................................................................................7MODELEDANIMALTYPES.....................................................................................................................................................9EVALUATIONOFMODELINGRESULTS...............................................................................................................................14
RESULTS.................................................................................................................................................................15SOURCECHARACTERISTICS.................................................................................................................................................15ACOUSTICSOUNDFIELDS(TLSLICES).............................................................................................................................16EXPOSURERESULTS..............................................................................................................................................................18
LITERATURECITED...........................................................................................................................................39
APPENDIXI:NUMBERSOFANIMALSEXPOSEDTOSOUNDLEVELSEXCEEDINGCRITERIATHRESHOLDS.......................................................................................................................................................41
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Introduction MarineAcoustics,Inc.(MAI)modeledaseismicarrayanditsunderwateracoustic
propagationduringexemplarone‐monthexplorationsurveysintheGulfofMexicotoexaminemarinemammalexposureestimatesoveraselectedcombinationofsourceandanimalmovementparameters.Fourselectedmarinemammaltypes,representingonelow(LF),twomid(MF)andonehigh(HF)frequencymembersofthehearinggroupsdefinedbySouthalletal.(2007),aswellastwosurveyconfigurations,representingnominal2Dand3Dairgunarraysurveys,aswellasastationarysourcesurvey,wereevaluatedinthisparametricstudy.TheacousticexposureandanimalresponsewereestimatedusingtheAcousticIntegrationModel©
(AIM).Foursource/animalsimulationcaseswereundertaken:
(1)stationarysourcewithstationarybutdivinganimals,(2)movingsourcewithstationarybutdivinganimals,(3)movingsourcewithmovinganddivinganimals,and(4)movingsourcewithmovinganddivinganimalswithaversivebehaviorstoreceivedsoundpressurelevels(SPL).Thesemovementswereconvolvedwiththeoutputofthesourceacousticpropagationmodeltocalculatethefull30‐dayexposurehistoriesforeachsimulatedanimalforeachsurveyconfiguration.Theseresultswerefrequencyweightedusingnoweighting,M‐weighting(Southalletal.,2007),NavyTypeIIweighting(FinneranandJenkins,2012)andproposedNOAAguidance(NOAA,2016).Theresultant30‐dayexposurehistoriesforeachanimalwereevaluatedusingbothtraditionalmetrics(unweighted160dBSPLforbehavior,180dBSPLforinjury)aswellasavarietyofTTSandPTSthresholdsfromSouthalletal.(2007),FinneranandJenkins(2012)andNOAA(2016).
ThisstudysignificantlyparallelsthemodelingassessmentpresentedinEllisonetal.(2016).Thatstudyprovidesdiscussionandevaluationtechniquesthatarecomplementarytothisreport,particularlywithregardtotheevaluationofproportionally‐scaledaversionofanimalstoreceivedsoundpressurelevels.InEllisonetal.(2016),thefull2008fallbowheadmigration(ca.10,000animals)wereindividuallyassessedduringa47‐dayperiodcoveringthepopulation’swestwardmigrationpastasimulationofnineselectedindustrynoisesourcesthatwereoperatinginthatareaandtime.ThenominalpassagetimeintheEllisonetal.(2016)studywasapproximatelyoneweekforanindividualanimal.Theunderlyingobjectiveinbothofthesestudieswastomodeleachindividualanimal(animat)continuouslyfortheentireperiodofpotentialexposure,witha‘dosimeter’recordingofexposurehistory.
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Methods
Source and Propagation Modeling
Acoustic Source Model
ThecurrentstudyusedacombinationofmethodstoevaluatethesourcecharacteristicsoftheairgunarraydescribedinTable1.ThefirststepwastoinputafulldescriptionoftheairgunintotheGundalfmodel(Hatton,2008)thatpredictedthearraysourcespectrumusedtocalculatethe1/3‐octaveSELsourcelevelsforthearrayfrom10Hzto1kHz.
ThedirectivitypatternofthearraywascalculatedusingthevolumetricbeampatterngeneratormoduleintheCASS‐GRABpackage(Burdic,1984;Weinberg,2004).Theinputstothemodulewerethex,y,andzlocationofeachgunandtherelativeamplitudeofeachgun,representedasthecuberootofitsvolume.Thedirectivitypatternwasgeneratedforeverytwodegreesofdeclination(verticaldirection)from+90to‐90,every10degreesinazimuth(horizontaldirection)andforeach1/3‐octavebandcenterfrequencyfrom10Hzto1kHz.
Acoustic Propagation Modeling
Thesoundfieldcreatedbytheproposedairgunarraywasmodeledusingtherange‐dependentacousticmodel(RAM).RAMisaPE‐basedmodelthatincorporatesageoacousticoceanbottommodelthataccountsforbottomlossduetoshearwavepropagation(Collins,1993).
Physical Environmental Inputs
TheOAMLGeneralizedDigitalEnvironmentalModel(GDEM)Version3.0database(NavalOceanographicOffice,2003)wasaccessedforsoundvelocityprofiles.ThesoundvelocityprofilesforJulythroughDecemberareshownbelow(Figure1).TheOctoberprofileswereusedforpropagationmodeling.
GeoacousticmodelparameterswereextractedfromtheGulfofMexicoG&GActivitiesDraftProgrammaticEIS,AppendixD,Table53(Zeddiesetal.,2015).TheseareshowninTable2.
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Table 1: Detailed specifications of the 5,110 in3 airgun array
String Element Pressure
(psi) Volume (cu. In.)
X (m) Y (m) Z (m)
1 1 2000 90 0 8 10 1 2 2000 155 3 8.5 10 1 3 2000 155 3 7.5 10 1 4 2000 175 6 8.5 10 1 5 2000 175 6 7.5 10 1 6 2000 230 9 8.5 10 1 7 2000 230 9 7.5 10 1 8 2000 155 12 8.5 10 1 9 2000 155 12 7.5 10 1 10 2000 140 15 8 10 2 1 2000 90 0 0.5 10 2 2 2000 90 0 -0.5 10 2 3 2000 120 3 0.5 10 2 4 2000 120 3 -0.5 10 2 5 2000 200 6 0.5 10 2 6 2000 200 6 -0.5 10 2 7 2000 250 9 0.5 10 2 8 2000 250 9 -0.5 10 2 9 2000 120 12 0.5 10 2 10 2000 120 12 -0.5 10 2 11 2000 90 15 0.5 10 2 12 2000 90 15 -0.5 10 3 1 2000 140 0 -8 10 3 2 2000 155 3 -8.5 10 3 3 2000 155 3 -7.5 10 3 4 2000 200 6 -8.5 10 3 5 2000 200 6 -7.5 10 3 6 2000 230 9 -8.5 10 3 7 2000 230 9 -7.5 10 3 8 2000 155 12 -8.5 10 3 9 2000 155 12 -7.5 10 3 10 2000 90 15 -8 10
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Figure 1: Sound velocity profiles for July through December for the modeling location in the Gulf of Mexico. More detailed structure of the upper portion of the water column is presented in the
right panel.
Table 2: Geoacoustic parameters used for acoustic propagation modeling
Depth below
seafloor (m) Material
Density P-wave speed
P-wave attenuation
S-wave speed
S-wave attenuation
(g/cm3) (m/s) (dB/λ) (m/s) (dB/λ)
0–20 Silt 1.44 1515 0.33
150 0.22
20–50 φ=6 1.7 1670 0.82
50–200 1.7 1750 1.07
200–600 1.87 1970 1.48
> 600 2.04 2260 1.82
N x 2‐D Volume Approximation
TheRAMacousticpropagationmodelisatwo‐dimensionalmodel;itreturnsasoundfieldforasinglebearingwithvaluesasafunctionofrangeandwaterdepth.Thisrepresentationissometimesreferredtoasasliceorazimuth.Becauseacousticpropagationisdependentonrange‐varyingbathymetryandsoundvelocityprofiles,36azimuthsat10intervalstoamaximumrangeof50kilometersfromthemodelinglocation(50‐meterincrements)werecalculatedforthisstudy.
Frequency Dependence: Summing Over 1/3 Octave Bands
Airgunsourcesareimpulsiveandproducebroadbandsignals.BecauseRAMisasinglefrequencyacousticpropagationmodel,thetransmissionlosswascalculatedforeach
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1/3‐octavebandcenterfrequencyfrom10Hzto1kHz.Eachtransmissionlossslicewassubtractedfromitscorrespondingsourcelevelvaluetoproduceasliceofreceivedsoundexposurelevels.Theseseparate1/3‐octavebandsoundlevelfieldswerethencombinedasintensitiestoproduceabroadband,three‐dimensionalacousticfieldforthemodelinglocation.Thisprocesswasrepeatedwithsourcelevelvaluesthathadbeenadjustedwithauditoryweightingfunctions,sothatthefinaloutputincludedmultipleSELacousticfields:a‘flat’orunweightedacousticfield,aswellasnineweightedacousticfieldsthatincorporatedtheM‐weighting,NavyTypeIIandNOAA(2016)auditoryweightingfunctionsforlow‐,mid‐,andhigh‐frequencycetaceans.
ThesourcelevelcalculatedfromthearraysignatureisaSoundExposureLevel(SEL)measure.However,RMSvaluesarealsoneededforbehavioralresponseevaluation.TheformulasdescribedintheFinalProgrammaticEnvironmentalImpactStatement(EIS)fortheAtlanticOuterContinentalShelfProposedGeologicalandGeophysicalActivities:Mid‐AtlanticandSouthAtlanticPlanningAreas(http://www.boem.gov/Atlantic‐G‐G‐PEIS/#Final%20PEIS)wereappliedtotheSELversionsoftheacousticfieldstocreatetheirRMSpressureequivalents.
Animat Modeling
TheAcousticIntegrationModel©(AIM)isanindividual‐based,MonteCarlostatisticalmodeldesignedtopredicttheexposureofreceiverstoanystimuluspropagatingthroughspaceandtime,whichinthisanalysisisacousticenergy(Frankeletal.,2002).ThecentralcomponentofAIMistheanimatmovementengine,whereparameterscontrolthespeedanddirectionofmovementof“animats”inthree‐dimensionalspaceatspecifiedtimeintervalstocreateafullfour‐dimensionalsimulationoftheproposedsurvey.AIMhasbeenusedformanyenvironmentalcompliancedocumentsandwasapprovedbyexternalCenterforIndependentExperts(CIE)review(Cordue,2006).
Threedifferentsourcemovementpatternswereused:1)Stationary,2)2‐Dsurvey(Figure2),and3)3‐Dsurvey(Figure3).
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Figure 2: The track lines of the 2-D survey (large spatial area) are shown. Nominal spacing
between tracks was 10 km.
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Figure 3: The tracklines of the 3-D survey (small spatial area) are shown. Nominal track spacing
was 500 m.
Aseparatesimulationwascreatedandrunforeachcombinationofmarinemammaltypes(n=4),animalmovementpattern(n=3),andsourcegeometry(n=2).Anadditionalfoursimulationswererunwiththestationarysourceandanimaltypesmodeledasstationarybutdiving,resultinginatotalof28exposurescenarios.Eachsimulationwasrunfor30daysusingatimestepof30seconds.Thenominalfiringtimeoftheairgunarraywas10seconds.Thereforeitwasassumedthatthereceivedlevelateach30‐secondintervalrepresentedthreeairgunshots.
Modeled Animal Types
FouranimaltypeswerechosentoproviderepresentativevariationsinbehavioraldiveandmovementpatternsaswellastherespectivehearinggroupsofmarinemammalsintheGulfofMexico.LF(low‐frequencyhearing)whaleswerebasedonBryde’swhalesastheonlymysticetenormallyfoundintheGulfofMexico.Shallowanddeep‐divingMF(mid‐frequencyhearing)animalswerebasedonbottlenosedolphinsandspermwhalesrespectively.FinallyHF(highfrequency)animalswerebasedKogiaspecies,theonlyhigh‐frequency(HF)hearinganimalfoundintheGulfofMexico.
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Animal movement cases:
Threeanimalmovementpatternswereinvestigated.Thesimplestwashorizontallystationarybutdivinganimals.Thiswasexaminedwithastationarysourceandthe2Dand3Dsurveys.Next,fullymovingfourdimensional(spaceandtime)animatswereassessedforexposurefromthearrayperforming2Dand3Dsurveypatterns.Finally,fullymovinganimalswithaversionweremodeledwiththearrayperforming2Dand3Dsurveysourcepatterns.AnimatswereprogrammedinAIMwithbehavioralvaluesdescribingdivedepth,surfacinganddivedurations,swimmingspeed,andcoursechange.Aminimumandmaximumvalueforeachoftheseparametersisspecified.Theresultisastochasticallygeneratedpathovertime.ThebehavioralparametersusedtoprogramtheseanimatsweretakenfromtheliteratureandareshowninTable3.Figure4providesanexampleofthefull30‐daytrackforanindividualanimatrepresentingeachofthefouranimaltypes.
Table 3: Animat Behavioral Parameters
Animal type
Behavioral State
Top Depth
(m)
Bottom Depth
(m)
Time min/ max
(min.)
Heading Variance
(deg)
Speed min / max
(km/h)
Heading Variance
Turn Time (sec)
Percentage of Time in Behavioral
State
Min Water Depth
(m)
LF
Surface 0 -5 1/1 30 2/10 300 50 20 Dive 1 -50 -267 2/11 90 2/20 90 10 20 Dive 2 -50 -267 2/11 30 2/20 300 10 20 Dive 3 -10 -40 1/10 30 2/20 300 40 20 Dive 4 -10 -40 1/10 90 2/20 300 40 20
Shallow MF
Surface 0 -6 1/1 30 2/16 300 45 20 Dive 1 -6 -50 1/2 300 2/16 300 40 20 Dive 2 -6 -50 1/2 90 2/16 90 40 20 Dive 3 -50 -100 2/3 30 2/16 300 5 20 Dive 4 -100 -250 3/4 90 2/16 300 5 20 Dive 5 -250 -500 4/6 90 2/16 300 10 20
Deep MF
Surface 0 -10 5/9 10 1/3 300 50 100 Dive 1 -600 -1000 35/65 30 1/8 300 50 100 Dive 2 -600 -1000 35/65 90 1/8 300 50 100
HF Surface 0 -5 1/2 30 1/11 300 50 500 Dive 1 -200 -1000 5/12 90 1/11 300 50 500 Dive 2 -200 -1000 5/12 30 1/11 300 50 500
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Figure 4: One example of the movement track for each animal type of animat is shown. The
white lines represent the 30-day tracks for each animal type.
Theresidencypatternforanyanimaltypeisoneofthekeyfeaturesthatwouldcontributesignificantlytotheaccuracyoflong‐termmodeledassessmentsinagivenregion.Onecanvisualizetheneedforresidencyassessment(e.g.,fromlong‐termtagdata)byexaminingthetracksshowninFigure4,wherethedifferencesinthespatialextentofthemonth‐longtracksofthedifferentanimaltypecanbeeasilyseen.TheHFandshallowMFcetaceanshaveahigherproportionoflong,mostly‘linear’travel,whereastheLFanddeepMFcetaceanshavemorecircuitousandtwistingmovementpatterns.Acandidatemetrictodescribesuchanoverallmovementpatternisthelinearityindex(BakerandHerman,1989).Thisissimplytheratioofthenetmovement(i.e.,astraight‐linedistancebetweenthefirstandlastpointofthetrack)dividedbythetotaldistanceswum.Alowlinearityscoremeansthepathoftheanimalwasfairlycircuitous,whichwouldrepresentafairlyresidentanimal.Ahighlinearityscoremeansthepathoftheanimalisfairlystraight,whichwouldrepresentananimaltravelingacrossagreaterspatialextent.ThemeanandstandarddeviationsofthelinearityscoresforthefouranimaltypesareshowninTable4.
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Table 4: The linearity indices (mean and standard deviation) of the four modeled animal types. The modal speed and shallow water limits are also listed for each, as defined in AIM. There was
no deep-water limit for any animal type.
AnimalTypeLinearity ModalSpeed
(km/h)Shallowwaterlimit(m)Mean S.D.
ShallowLFCetacean 0.83 0.160 9 20
HFCetacean 0.94 0.088 5.5 500DeepMFCetacean 0.68 0.211
4.5100
LFCetacean 0.54 0.215 4.0 20
Animat Spatial Distribution
Inatypicalenvironmentalassessment,themodeledanimalseasonaldistributionswouldbeinformedbythemostcurrentanimaldistributiondatabases,e.g.Robertsetal.(2016).However,forthisparametricevaluation,weelectedtouniformlypopulateeachanimaltypethroughouttheentireGulfregion,constrainedonlybylimitingwaterdepthandboundarylimitations.Thisallowedustofullyevaluatethekeyparametersofhearingtypeandshallowvs.deepdiversacrossthevariouscombinationsofsourceconfigurationsandhearingweightingfunctions.Thus,animatsweredistributedovertheentirenorthernGulfofMexicousingamodeldensityof0.01animatspersquarekilometer.Thisproducedsimulationswith8,000–12,000animatspersimulation.Distributiontothenorthandwestwasconstrainedbyland.Thesouthernboundarywasthe22Nlatitudeline.TheeasternboundarywasFloridaandthe80.5WlongitudelinebetweenFloridaandCuba.Theshallow‐waterdepthlimitations(i.e.,aversiontowaterdepthsetinAIMtopreventanimalsfrommovingintoshallowwaters)areprovidedinTable4andillustratedinFigure5forshallowMFandHFcetaceans.
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Figure 5: Exemplar distributions of shallow MF cetaceans (red) and HF cetaceans (yellow). The
displayed animal distributions have lower densities than the actual simulations to allow the bathymetry to be seen.
WithregardtoLFcetaceans,Bryde’swhalesareknowntobeconcentratedneartheDeSotoCanyonoffnorthwestFlorida.However,iftheLFcetaceanswereconstrainedtothatarea,thennomeaningfulexposureresultswouldhavebeenobtained.Therefore,LFcetaceansweredistributedthroughouttheGulfofMexico.Again,thiswasdoneonlyforthepurposeofthisstudyanddoesnotrepresenttheactualdistributionofLFcetaceansintheGulfofMexico.Thus,theLFresultsprovidedherecanbeviewedtosomedegreeasaproxyforexposureassessmentinregionswheremysticetesaremorewidelydistributed.
Auditory Weighting Functions
Akeycomponentofthestudyistocomparetheeffectsofdifferentfrequencyweightingsonthelevelofexposurepredictedforeachsourceandanimalmovementcombination.Fourfrequencyweightingswereemployed.Thesewere1)unweighted,2)M‐weighting(Southalletal.,2007),3)NavyTypeII(FinneranandJenkins,2012),and4)NOAA(2016)proposedacousticguidance,asdepictedinFigure6.
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Figure 6: The weighting functions for low, mid and high frequency cetaceans. Three weighting
functions are presented, the M-weighting (Southall et al. 2007), Navy Type II (Finneran and Jenkins, 2012) and NOAA draft acoustic guidance (NOAA 2016).
Aversion Parameters
AnominalsetofaversionparametersforreceivedsoundpressurelevelwasdevelopedinEllisonetal.(2016)andacomplementaryversionwasusedforthisstudy.Thesecanbesummarizedasanincreasingprobabilityofaversionasthereceivedsoundlevelincreases.Specifically,theprobabilityofaversiongoesfrom5%to50%to95%atreceivedSPLsof140,160and180dBSPL,respectively.ThespecificaversionparametersusedinAIMareshowninTable5alongwiththeangulardegreeofaversion(‘turnaway’)forthedifferentlevels.
Table 5: Aversion Parameters
Received SPL (unweighted) Probability of Aversion Aversion Angle
140 dB 5% 20 away from source
150 dB 25% 30 away from source
160 dB 50% 40 away from source
170 dB 75% 50 away from source
180 dB 95% 60 away from source
Evaluation of Modeling Results
Eachsimulationproducedapproximately10GBofmodeloutputandwasanalyzedinatwo‐tierfashion.Thefirststepwasconductedononehourofmodeloutputatatime.Receivedlevelsduringtheturnsbetweensurveylegsweresettozero.ThenthehourlymaximumreceivedSPLandthetotalsoundintensity,cumulativeSEL(CSEL),foreach
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animatwascalculatedandstoredinasummaryfile.Thisreducedthenumberofobservationsfrom86,400to720rows.
Thesehourlymetricswerethenusedtocreatethemaximumunweightedreceivedsoundpressurelevel(MSPL)foreach24‐hrperiodofthe30‐daysurveydurationmodeledforeachanimat.Likewise,cumulativeSELmetricswerealsocalculatedforeach24‐hrperiodofthe30‐daysurveydurationmodeledforeachanimat.ThiscalculationincludedtheSELcorrection(added5dB)neededtoaccountforthethreeairgunarrayshotsthatoccurredduringeach30secondmodelstep.MeanMSPLandCSELvalueswerethencalculatedforeachanimat.Thesewerecomparedtothe160/180dBSPLcriteriafortraditionalLevelBandLevelAexposuresaswellastheSELcriteriaforTTSandPTSinSouthalletal.(2007),FinneranandJenkins(2012)andNOAA(2016).Southalletal.(2007)onlyproposedacriterionforPTS.ATTScriterionforM‐weightingwascreatedbysubtracting20dBfromthePTScriterion.TheSouthalletal.(2007)criteriawerealsousedfortheunweightedCSELmetrics,asnopreviouscriteriaexisted.Themeannumberofdailyexposuresthatexceededthosecriteria(i.e.,takes)resultedfromthisapproach.
Asstated,thisstudyisfocusedontheeffectsofsurveydesignandanimalbehaviorpatternsonexposureestimatesandnotassessingactualenvironmentalimpact.Thereforenocorrectionwasmadetoscalethemodeledanimaldensitiestolocalanimaldensities,asthiswouldonlyaddconfusionandanadditionalsourceofuncertainty.
Results
Source Characteristics
TheGundalfmodelwasusedtopredictthesourcelevelandspectrumoftheairgunarray.TheresultingsourcespectraareshowninFigure7.Bothspectraland1/3‐octavebandvaluesarepresented.Thesearethe‘unghosted’versionsofthespectrum,asthepropagationmodelexplicitlyconsiderstheeffectofsurfacereflection.
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Figure 7: Source spectra for the airgun array
Acoustic Sound Fields (TL Slices)
Theunweightedsoundfieldresultswereusedtoevaluatetheeffectofsourcemovementpattern(i.e.,2Dv.3D)aswellasanimatbehavior(aversionv.none,full4‐Dmovementv.surfaceanddivingonly).Thethreeweightingfunctions(M,TypeII,andNOAA)wereapplieddirectlytothesoundfieldsthemselves,andareillustratedbelowastotheirapplicationacrossthethreeanimalgroups(LF,MFandHF;Figures8,9,and10,respectively).
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Low‐Frequency Weighted Sound Fields
Figure 8: Airgun array sound field with four different low-frequency weighting functions applied.
Mid‐Frequency Weighted Sound Fields
Figure 9: Airgun array sound field with four different mid-frequency weighting functions applied.
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High‐Frequency Weighed Sound Fields
Figure 10: Airgun array sound field with four different high-frequency weighting functions applied
Exposure Results
Foreachanimat,30dailyvaluesofunweightedMSPLandCSELforeachsimulationscenariowasexaminedandanalyzedonsequential24hrperiods,aswellascontinuousmeasurementsovertheentire30‐dayduration.Figure11displaysthe30‐daytrackofaselectedDeep‐divingMFcetaceanwithanoverlayofthe2Dsurveygrid.Figure12providestherecordedexposurehistory(hourlyMSPL)forthissameanimaloverthe30‐dayperiod.Inthisexample,itcanbeinferredthatduringthemiddleofthe30‐dayperiodthesourcetracksandanimaltrackdidnotsignificantlyoverlapsincetheanimalhadnoMSPLgreaterthan160dB.
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Figure 11: Illustration of 2-D Survey Grid and a single animat track.
Figure 12: Exposure History of the animat in the previous figure. Received Sound Pressure
Levels are shown as blue circles. The alternating vertical gray and white bars indicate successive days
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Comparison of 2D v. 3D Acoustic Exposures
SeparatehistogramswerecalculatedofthenumberofanimalsexposedatunweightedMSPLsandCSELsovertheentire30‐dayperiodforeachanimaltype.Thesefigurescomparetheunweightedexposurelevelsbetweena2‐Danda3‐Dsourcepatternforthefourdifferentanimaltype(Figures13‐16).
Therearenomeaningfuldifferencesamongtheanimaltypesintheshapesofthesedistributions.However,thenumbersofexposures,bothMSPLandCSEL,aregreaterforthe2Dsurvey,asthesurveycoveredasignificantlylargerarea(greaterpotentialformoreanimalstobeexposed)thanthe3Dsurvey.ThenumbersofexposuresarealsohigherfortheShallow‐divingMFcetaceansastheyareprincipallyintheupperwatercolumnwheretheexposurelevelsaremoreconsistentlyhigherwithrangethanatdepth.
Figure 13: Distribution of MSPL and CSEL values for LF cetaceans with full 4-D movement with
no aversion behavior
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Figure 14: Distribution of MSPL and CSEL values for shallow MF cetaceans with full 4-D
movement with no aversion behavior
Figure 15: Distribution of MSPL and CSEL values for deep diving MF cetaceans with full 4-D
movement with no aversion behavior
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Figure 16: Distribution of MSPL and CSEL values for HF cetaceans with full 4-D movement with
no aversion behavior.
Comparison of 2D v. 3D Acoustic Exposures vs. Animat Movement Behavior
Figure17presentsthenumberofmeandailyMSPLexposures>160dBforallanimaltypesforbothsurveytypesandallthreemovementmodalities(fullmovementwithandwithoutaversion,anddivingonly).TheoverallresultsareconsistentwiththedistributionsshowninFigures13‐16,withthe2Dsurveyhavingmoreexposures>160dBthanthe3Dsurvey,aspreviouslydiscussed.
Theexplanationfortheapparentlylargernumberofexposuresforfullmovementanimatsoverdivingonlyanimatswouldappeartobebecausethedivingonlyanimatswillonlybeexposedathigherlevelsatthemomentthesurveyvesselpassescloseby,whereasthemovinganimals(withoutaversion)mayintheirgeneralcircuitousmeanderingscrossoverthesourcepathmorethanonce.Themoststrikingresultisthenumberofexposuresofanimalsallowedtoavert,whichresultsinthelowestexposurecountofallscenarios.
Figures18through25displaythenumberofanimalsexposedatunweightedMSPLsandCSELsovertheentire30‐dayperiodforeachanimaltypeforbothsurveytypeswithaversionandwithoutaversion.Theresultsshowthepowerfuleffectofaversiononexposurehistories.
23
Figure 17: The distributions of daily 160 dB exposures for all animal types are shown for the
different source movement patterns (2-D, 3-D) and animat behavior (No Aversion, Surface and Dive only, and With Aversion).
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Figure 18: Shallow MF cetacean, 2-D survey, with and without aversion
Figure 19: Shallow MF cetacean, 3-D survey, with and without aversion
25
Figure 20: LF cetacean, 2-D survey, with and without aversion
Figure 21: LF cetacean, 3-D survey, with and without aversion
26
Figure 22: HF cetacean, 2-D Survey, with and without aversion
Figure 23: HF cetacean, 3-D survey, with and without aversion
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Figure 24: Deep-diving MF cetacean, 2-D survey, with and without aversion
Figure 25: Deep-diving MF cetacean, 3-D survey, with and without aversion
InAppendixIwesummarizeeachoftheexposureassessmentmetricsbeginning
withasummaryforeachanimaltypeusingthehistoricbehaviorthresholdSPL>160dBre1Pa,andthehistoricinjurythreshold>180dBre1Pa.ThetablestabulatingPTSexposureclearlyshowthedramaticeffectofaversion,asdoFigures18‐25,butalsothevaryingeffectsofthethreeauditoryweightingfunctions.
Consideration of Combination of Auditory Weighting Function and Criteria
Theauditoryweighting/criteriaassessmentsaremorecomplexinexplanationduetosubtleeffectsoftheweightingfunctionshapesforM,TypeIIandNOAA(2016)inrelationtothechangesinPTScriteriathatareassociatedwitheachfunction.Theresultof
28
changingbothweightingfunctionandcriteriaseeminglyprovidewhatappearstobeconflictingresultsfortheHFanimalsinparticularastabulatedinTable5ofAppendixI,copiedbelowforeaseofreferral.
Appendix I - Table 5
Species – PTS (values shown in dB re 1�Pa2-sec)
2-D Pattern
Weighting Functions and Associated Criteria
Stationary Source, Diving
Animals
Moving Source, Diving
Animals
Moving Source, Moving Animals
Moving Source,
Moving and AVERTING
animals
Unweighted – 198 dB 9 0 0 0
M-weighted – 198 dB 0 0 0 0
Type II – 172 dB 22 2 3 3
Draft NOAA – 155 dB 0 0 0 0
3-D Pattern
Weighting Functions and Associated Criteria
Stationary Source, Diving
Animals
Moving Source, Diving
Animals
Moving Source, Moving Animals
Moving Source,
Moving and AVERTING
animals
Unweighted – 198 dB 9 10 0 0
M-weighted – 198 dB 0 0 0 0
Type II – 172 dB 22 14 3 1
Draft NOAA – 155 dB 0 0 0 0
Inthistable,theTypeIIfunctionresultsinhigherexposureestimatesinthefinal
assessmentthanthemuchsteeperNOAA2016function.Therationalecomesfromacombinationoftwofactors.First,thesoundsourceenergyisconcentratedinthespectrumbelow1kHz,andthelow‐frequency“bulge”oftheTypeIIweightingfunctionallowsasignificantamountofthatenergytobeappliedtothebroadbandreceivedleveloftheHFanimal.ThedifferenceinLFenergybetweentheTypeIIandtheNOAAfunctionsisontheorderof30dB(theTypeIIfunctionis30dBgreaterthantheNOAAfunctionatLF).Secondly,theTypeIIHFcriterion(172dB)is17dBgreaterthantheNOAAHFcriterion(155dB),butthis17dBdifferenceinthecriteriaislessthanthe30dBdifferenceinthefunctions.TheresultishigherexposuresundertheTypeIIweightingfunction/criteriacombination.
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Comparison of Long‐term Modeling with Current 24 hour‐reset based regulatory
framework
NOAA’sacousticguidance(NOAA,2016)incorporatestheconceptof“24‐hourreset”inanimalexposureestimates.The“24‐hrreset”meansthattheintegrationtimeforCSELandtheevaluationperiodforbehavioral(maximumSPL)metricsaresetto24hours.Thesemodeloutputvaluesarethencomparedwithregulatorythresholdsandthenumberof‘takes’isdeterminedfora24‐hourperiod.Typically,thesedailynumbersaresimplymultipliedbythenumberofdaysoverwhichtheactivityisanticipatedtooccurtoproducetotaltakeestimates.Thisrequirementhasmeaningfulpracticalimplicationsonmodelingconductedtopredicttheimpactofahumanactivity.
Firstly,thisapproachdoesnotdifferentiatebetweenthenumberof“acousticexposures”andthenumberof“exposedindividuals”.An“acousticexposure”isdefinedhereaswhenanindividualanimalisexposedtoasoundlevelthatexceedsaregulatorythreshold(e.g.,160dBrmsforairguns).An“exposedindividual”isananimalthatexperiencesoneormoreacousticexposuresduringthedurationofanactivity.Givenanimalandsourcemovement,individualanimalscouldexperiencemultipleacousticexposureswithinone24‐hrperiodorovermanydaysofanactivity.
Thisissueiscompoundedwhenanestimateoftheactivity’simpactonapopulationiscomputed.Anactivity’spredictedtakenumbersareoftencomparedtopopulationsizeestimates.Withasufficientlylongactivity,therecanbemore‘24hour’takesthanthereareindividualsinthepopulation.
Apotentialsolutiontothisquandaryisillustratedthroughlong‐termanimatmodeling.Bymodelingtheentiredurationofanactivity,thenumberofexposuresthateachindividualexperiences,aswellasthenumberofexposedanimalsandthetraditionalmetricofthetotalnumberofexposurescanbecalculated.Thusinthisapproach,thenumberofexposedanimalscannotexceedthenumberofanimalsinthepopulation,andthepotentialimpactonindividualanimalsiselucidatedthroughdirectmodelingresults.
Inthiscasestudy,the30‐daymodelingresultswereevaluatedusinganincreasing‘window’ofpotentialexposuretime.TakewasdefinedasthenumberofindividualanimalsthatreceivedamaximumRLexceedingtheregulatorythreshold,whichwasdeterminedforanincreasingperiodoftimefromonedaytothefull30daysduration.ThesolidlinesinFigures26and27showthenumberofexposedindividualsovertheentiredurationoftheactivity.Thismeasureoftakewascomparedagainstthetraditionalmethod,wherethenumberoftakesovera24hourperiodismultipliedbythenumberofdaysoftheactivity,whichisshownwiththestraightdashedlinesinFigure26andFigure27.Inallcases,thenumberofindividualsexposedatmaximumRLasdeterminedwiththe24‐hrresettimewasgreaterthantheactualnumberofindividualsexposedatmaximumRLoverthedurationoftheactivity.
30
Figure 26: 2-D Source. The solid lines show the increase in the number of exposed individuals at maximum RL based on direct measurement of long-term model output. The dashed lines show the number of exposed individuals at maximum RL using the “24-hour reset” method.
Figure 27: 3-D Source. The same presentation is repeated for a 3D source.
31
Anotherwaytoconsiderthiseffectisahypotheticalpopulationof100individualsforwhich10individualsexperiencemaximumRLsthatexceedtheregulatorythresholdovera24‐hrperiod(i.e.,the‘24hour’takepredictionis10).Overa30‐dayactivity,thetotalpredictedtakewouldbe300(30daysx10animals/day),or3xthepopulationsize.Onecouldassumethattheanimalsinthispopulationhadextremelyhighresidencyorsitefidelity.Insuchacase,itcouldbethatfor30days,thesame10animalsareexposedrepeatedly.Thusthenumberofexposedanimalswasactuallyonly10,while300exposureswerepredicted.
Toexaminetheeffectthatresidencymighthaveonexposureestimates,wealsocalculatedthenumberofdaysthateachindividualwasexposedtoanunweightedsoundlevelof160dBrms.Thepercentageofindividualsexposedonmultipledayswasdeterminedandcomparedwithmovementparameters.Thiswasdoneforeachanimatspeciesandsourcemovementpattern(Table6).Thepercentagesofmultipleexposureswereplottedagainstthelinearityindexforeachspeciessurveytype(Figure28).
Table 6: Percentage of Individuals exposed more than once.
These results are for normal four-dimensional movement with no aversion using
unweighted sound levels.
Species Survey Type
Linearity Index
Dive Depth (m)
Percentage of Individuals Exposed more than once
Shallow MF Cetacean 2D 0.83 72 29.39%
HF Cetacean 2D 0.94 600 34.21%
Deep MF Cetacean 2D 0.68 800 49.36%
LF Cetaceans 2D 0.54 51 43.51%
Shallow MF Cetacean 3D 0.83 72 33.50%
HF Cetacean. 3D 0.94 600 37.29%
Deep MF Cetacean 3D 0.68 800 55.84%
LF Cetacean 3D 0.54 51 54.69%
32
Figure 28: The percentage of indivdiuals exposed more than once is shown as a function of the
linearity index of each animat. Multiple exposures increase with decreased linearity. The 3D survey produced higher ‘takes’ than the 2D survey.
Figure28showsastrongrelationshipbetweenthelinearityofananimat’smovementandhowoftenanindividualwas‘taken’onmultipledays.Consideringthepercentageofanimalsexposedmorethanonce,a50%valuewouldindicatethat,onaverage,eachanimatwasexposedtwice.Generally,asthelinearityoftheanimat’scoursedecreases,theamountoftimespentinthesameareaincreases.Likewisethepercentageofmultipleexposuresincreases.
Amoredetailedanalysisexaminedtheeffectofsurveytype,linearityindexandmeananimaldivingdepthonthepercentageofmultipleexposures.AnANOVAmodelwasstatisticallysignificant(F(3,4)=41.3,p=0.0018).Themodelfoundthatthe3Dsurveytype,whichconcentratesairgunactivitywithinasmallarea,hadasignificantlylargerpercentageofmultipleexposurescomparedtothe2Dsurvey,whichoperatesoveralargerarea.Lowerlinearityindexvaluescontributedtoasignificantlylargerpercentageofmultipleexposuresthanhigherlinearityindexvalues.Also,deeperdivinganimalswerefoundtohavesignificantlymoremultipleexposuresthantheshallowerdivers.
Thissensitivitystudyshowsthatmodelingthefulldurationofanactivityresultsinabetterunderstandingofthenumberofindividualsexposedandthenumberofexposures
33
perindividual.Thesearekeyparametersfordeterminingpotentialimpacts,particularlyforprotectedspecies.Thereforebothmetricscouldbeevaluatedandsuchanapproachwouldprovideinsightintotraditionalpredictionsoftakenumberslargerthanpopulationsizes.
Thevalidityofthelong‐durationmodelingresultsarestronglyinfluencedbytheaccuracyofthebehavioralparametersusedtocreatethesimulations.Reliabledataontheresidencypatternsanddivingbehaviorsofspeciesandpopulationsbeingmodelediscriticaltovalidmodeloutputs.
Considering the effect of group size on number of predicted exposures
Thebasicmodelingapproachconsistsofcreatingan‘overpopulated’simulation,wherethemodeldensityistypicallymuchgreaterthanthatofthereal‐worldsituationandeachanimatrepresentsanindividualanimal.Oncethesimulationhasbeenrun,theoutputsareexaminedtodeterminethenumberofexposuresthatexceedregulatorythresholds.Whenanimatsareconsideredasindividuals,thescalingrelationshipisquitesimple,asexpressedinthefollowingequation.
∗
Typically,thenumberofmodeledexposuresisapointestimatebasedonthemodelingresults.However,anestimateofuncertaintyintheexposureestimatescanbecalculatedusingresampling,inwhichcasethemodeledexposuresvaluecouldbeameanofresampledestimateswithanassociatedmeasureofvariation(e.g.,S.D.orC.V.).
Tomovethemodelingscenariotowardsamorerealisticreflectionofanimaldistribution,however,itisimportanttoconsiderthatmostanimalsnaturallyoccuringroupsofvariablesize.Themeanvalueofanexposureestimatewillnotchangebecausethedensityofanimalgroupsistheindividualanimaldensityvalue(animals/area)dividedbythemeangroupsize.Thefactorthatwillchangeisthemeasureofvariationaroundthatmean,whichreflectsthevariabilityinthedistributionofgroupsizeinwildpopulations.
Themoststraightforwardapproachtoincorporatinggroupsizeintotheeffectsanalysisistousearesamplingprocedure.Inthisstudy,asetofdistributionsofgroupsizeswascreatedbasedonobservedgroupsizeestimates(Maze‐FoleyandMullin,2006),asshowninTable7.Groupsizeminimumandmaximumvalueswerecreatedforeachspeciesusingalognormalfunction,roundedtointegersandtruncatedtothelargestreportedgroupsize.
Bothindividualsandgroupshaveacommonsourceofvariabilityinhowmanyanimatsinaselectedsamplewillhaveareceivedlevelthatexceedsaregulatorythreshold.GroupSizeintroducesanadditionalsourceofvariation(i.e.,thenumberofanimalsrepresentedbyasingleanimat)notfoundintheindividualanalysis.Therefore,withtwosourcesofvariation,theaprioiriexpectationisthatthevariancearoundthegroup‐basedmeanestimateshouldbegreaterthanthatforindividuals.
34
Table 7: Group Size Data for Gulf of Mexico
Animat Type Mean
Group Size SE Min Max N
LF Cetacean 2.0 0.33 1 5 14
Deep MF Cetacean 2.6 0.16 1 11 164
HF Cetacean 2.0 0.12 1 8 133
Shallow MF Cetacean 20.6 2.49 1 220 151
Theresamplingprocedureselected100samplesfromtheacousticexposuredata
andthegroupsizedistribution.Thenumberofsamplesthatexceededaregulatorythreshold(e.g.,160dBRMS)alongwiththeircorrespondinggroupsizewasdetermined.Thesumofthegroupsizesampleswasreturnedasthenumberofindividualsexposedtothatthresholdlevel.Thisprocesswasrepeated10,000timestoproducearesampleddistributionofthenumberofexposedindividuals.Themeanandstandarddeviationoftheseresampleddistributionswerecalculated.Thustheresamplingapproachprovidesanadditionalmethodtoestimatingconfidencelimitsaroundtheexposureestimate.
Theresamplingprocedurewasconductedforthe2‐Dand3‐Dsurveygeometrieswithfullymoving(non‐averting)animats.Theprocedurewasrepeatedforanimatsconsideredasindividualsaswellasgroups.TheresultsarepresentedinFigure29andFigure30.Thecentraldotforeachspeciesrepresentsthemeanofthedistributionandtheerrorbarsare+/‐onestandarddeviation.Thebluelinesrepresentresamplingdistributionsbasedonindividuals(groupsize=1)andtheredlinesrepresentdistributionsbasedonactualgroupsizesfoundintheGulfofMexico.
35
Figure 29: Resampling Results for 2D-Survey showing modeled 160 dB exposures.
Figure 30: Resampling Results for the 3-D Survey showing modeled 160 dB exposures. There
is no meaningful difference in the mean exposure estimates. However, the variation around these estimates are greater when group sizes are considered.
Asexpected,incorporatinggroupsizehadnomeaningfuleffectonthemeanestimateofthenumberofexposures.Forexample,shallow‐divingMFcetaceansinthe3‐Dsurveyscenariohadapointestimateof829LevelBexposures.Theresampledvaluesusinganimatsasindividualwas826.5,andconsideringanimatsasgroupsreturnedameanof849.6.
36
Inallcasesthestandarddeviationsweregreaterwhenanimatswereconsideredasgroupsratherthanindividuals.Furthermore,thesizeofthestandarddeviationincreasedasafunctionofgroupsize.Thusitcanbeconcludedthatincorporatinggroupsizeestimatedatawill(realistically)increasetheuncertaintyaroundthemeannumberofpredictedexposureswithoutmeaningfullychangingitsvalue.
Considering the Effect of Movement of Sources and Animals
Someofthesimulationsincludedstationarysources(SS)and/ormarinemammalanimatsthatcouldsurfaceanddiveonly(SD)butnotmovehorizontally.Thenumberofindividualsexposedoverthe30‐dayperiodto160dBwasexaminedasafunctionofspeciesaswellassourceandreceiverbehavior.TheresultsareshowninFigure31.Thefirsttwosetsofcolumnsrepresenttheresultswith2Dand3Dsurveys,respectively,withnormalanimatbehaviorandnoaversionresponse(NoAv).Asreportedpreviously,the2Dsurveyshaveahighernumberofexposuresperspeciesthandothe3Dsurveys.Thenexttwosetsofbarsrepresent2Dand3Dsurveys,respectively,withanimatsthatsurfaceanddiveonly(SD).Thereductioninthenumberofexposuresisclear.Again,thehighernumberofexposuresunderthe2Dcasereflectsthelargerareacoveredbythesurveyvessel.Finally,thelowestnumbersofbehavioralexposuresareseenwithastationarysourceandanimatsthatcannotmovehorizontally.
Figure 31: Comparison of Level B exposures between moving and stationary sources and
receivers
37
Figure 32: Comparison of TTS exposures between moving and stationary sources and
receivers.
WhentheSELmetricsareconsideredforTTS(Figure32)andPTS(Figure33)thepatternchangessomewhat.InFigure32therelativeincreaseinHFcetaceanvaluescomparedtotheotherspeciesisduetothelowTTSthresholdforhigh‐frequencyhearinganimals.Overall,thefirstthreesetsofbarslargelyshowthesamepatternastheLevelBexposureresults.Howeverthe3DandstationarysourceswithsurfacinganddivingonlyanimatshaverelativelyelevatedvaluescomparedtotheLevelBexposures.Againthisisduetothelimitedscopeofsourcemovementandtheinabilityofreceiveranimatstomoveaway.ThiseffectisclearlyvisibleinthePTSresults(Figure33).TherearebarelyanymodeledPTSexposuresintherealisticscenarios.However,inthe3Dandstationarysourcescenarios,withreceiveranimatsthatcannotmoveaway,thenumberofPTSexposuresismuchgreaterthanelsewhere.Thisistheclearresultofanimatsthatremaininpositionwithasourcethatmoveslittleornotatall,andtheanimatscontinuetoaccrueacousticenergy,leadingtotheseartificiallyhighPTSexposurenumbers.
39
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Appendix I: Numbers of Animals exposed to Sound Levels exceeding
criteria thresholds
Notethatthenumericalexposureandtakevaluesresultingfromthissensitivity
studywerebasedonamodeldensityof0.01animatspersquarekilometerforeachanimaltype,anddonotrepresentactualanimalexposures.Furthermore,theLFcetaceantypewasdistributedthroughouttheGulfofMexicoforcomparisonpurposesonly;thisdistributiondoesnotrepresentknownLFcetaceandistributionsintheregion.
Table I-1
160 dB
2-D Pattern
Animal Type
Stationary Source, Diving
Animals
Moving Source, Diving
Animals
Moving Source, Moving Animals
Moving Source, Moving
and AVERTING
animals Shallow-diving MF
cetacean 5 319 1073 206
LF Cetacean 4 334 632 175
HF Cetacean 5 308 857 237 Deep-diving MF
cetacean 2 301 537 219
3-D Pattern
Stationary Source, Diving
Animals
Moving Source, Diving
Animals
Moving Source, Moving Animals
Moving Source, Moving
and AVERTING
animals Shallow-diving MF
cetacean 5 20 786 28
LF Cetacean 4 17 425 9
HF Cetacean 5 10 564 11 Deep-diving MF
cetacean 2 12 234 7
42
Table I-2
180 dB
2-D Pattern
Animal Type
Stationary Source, Diving
Animals
Moving Source, Diving
Animals
Moving Source, Moving Animals
Moving Source, Moving
and AVERTING
animals Shallow-diving MF
cetacean 0 25 26 0
LF Cetacean 0 26 23 1
HF Cetacean 0 41 52 17 Deep-diving MF
cetacean 0 25 43 15
3-D Pattern
Stationary Source, Diving
Animals
Moving Source, Diving
Animals
Moving Source, Moving Animals
Moving Source, Moving
and AVERTING
animals Shallow-diving MF
cetacean 0 13 17 0
LF Cetacean 0 7 23 0
HF Cetacean 0 9 26 1 Deep-diving MF
cetacean 0 8 26 0
43
Table I-3
Shallow-diving MF cetacean – PTS (values shown in dB re 1Pa2-sec)
2-D Pattern
Weighting Functions and Associated
Criteria
Stationary Source, Diving
Animals
Moving Source, Diving
Animals
Moving Source, Moving Animals
Moving Source, Moving
and AVERTING
animals
Unweighted- 198 dB 5 0 0 0
M-weighted – 198 dB 1 0 0 0
Type II - 198 dB 0 0 0 0
Draft NOAA – 185 dB 0 0 0 0
3-D Pattern
Weighting Functions and Associated
Criteria
Stationary Source, Diving
Animals
Moving Source, Diving
Animals
Moving Source, Moving Animals
Moving Source, Moving
and AVERTING
animals
Unweighted - 198 dB 5 11 1 0
M-weighted – 198 dB 1 0 0 0
Type II – 198 dB 0 0 0 0
Draft NOAA – 185 dB 0 0 0 0
44
Table I-4
LF Cetacean – PTS (values shown in dB re 1Pa2-sec)
2-D Pattern
Weighting Functions and Associated
Criteria
Stationary Source, Diving
Animals
Moving Source, Diving
Animals
Moving Source, Moving Animals
Moving Source, Moving
and AVERTING
animals
Unweighted – 198 dB 7 1 1 0
M-weighted – 198 dB 7 1 1 0
Type II - 198 dB 3 0 0 0
Draft NOAA – 183 dB 33 33 22 1
3-D Pattern
Weighting Functions and Associated
Criteria
Stationary Source, Diving
Animals
Moving Source, Diving
Animals
Moving Source, Moving Animals
Moving Source, Moving
and AVERTING
animals
Unweighted – 198 dB 7 9 1 0
M-weighted – 198 dB 7 9 1 0
Type II – 198 dB 3 0 0 0
Draft NOAA – 183 dB 33 23 25 0
45
Table I-5
HF Cetacean Species – PTS (values shown in dB re 1Pa2-sec)
2-D Pattern
Weighting Functions and Associated
Criteria
Stationary Source, Diving
Animals
Moving Source, Diving
Animals
Moving Source, Moving Animals
Moving Source, Moving
and AVERTING
animals
Unweighted – 198 dB 9 0 0 0
M-weighted – 198 dB 0 0 0 0
Type II – 172 dB 22 2 3 3
Draft NOAA – 155 dB 0 0 0 0
3-D Pattern
Weighting Functions and Associated
Criteria
Stationary Source, Diving
Animals
Moving Source, Diving
Animals
Moving Source, Moving Animals
Moving Source, Moving
and AVERTING
animals
Unweighted – 198 dB 9 10 0 0
M-weighted – 198 dB 0 0 0 0
Type II – 172 dB 22 14 3 1
Draft NOAA – 155 dB 0 0 0 0
46
Table I-6
Deep-diving MF cetacean – PTS (values shown in dB re 1Pa2-sec)
2-D Pattern
Weighting Functions and Associated
Criteria
Stationary Source, Diving
Animals
Moving Source, Diving
Animals
Moving Source, Moving Animals
Moving Source, Moving
and AVERTING
animals
Unweighted – 198 dB 3 0 0 0
M-weighted – 198 dB 0 0 0 0
Type II – 198 dB 0 0 0 0
Draft NOAA - 185 dB 0 0 0 0
3-D Pattern
Weighting Functions and Associated
Criteria
Stationary Source, Diving
Animals
Moving Source, Diving
Animals
Moving Source, Moving Animals
Moving Source, Moving
and AVERTING
animals
Unweighted – 198 dB 3 9 1 0
M-weighted – 198 dB 0 0 0 0
Type II – 198 dB 0 0 0 0
Draft NOAA – 185 dB 0 0 0 0