GettingStartedwithSmaart®v7:BasicSetupandMeasurementThisguideisanintroductiontothebasicmeasurementandoperationalconceptsembodiedinRationalAcoustics’Smaart®v7.Whileinnowayanexhaustivestudy,thisdocumentservesasastartingpointforuserstofamiliarizethemselveswiththefundamentalsofSmaart’ssingle‐anddual‐channelcapabilities,andprovideinstructionintheconfigurationandoperationofbasicmeasurementsetups.RegardlessofpastmeasurementexperiencewithpreviousversionsofSmaart,orotheranalysissystems,usersshouldtakethetimetofamiliarizethemselveswiththeprocessofConfiguringSmaartv7forMeasurementdetailedinthisdocument.Unlikepreviousversionswhichassumedasimpletwo‐channelI/O,Smaartv7caninterfacewithmultipleI/Odevicessimultaneously,eachwithmultipleinputandoutputchannels.Accordingly,Smaartv7makesnoassumptionsaboutauser’smeasurementrequirementsanduponfirstrun,beginsitsoperationun‐configured.Asinpreviousversionshowever,followinginitialsetup,Smaartretainsitsmeasurementconfigurationforsubsequentsessions.
Pleasenote:inthecaseofthefree/publicdemoversionofthesoftware,theSmaartmeasurementconfigurationisnotretainedfromsessiontosession,andmustbe
rebuiltforeachnewsession.Consideritpractice.Thisguideassumesareaderwithabasicunderstandingofprofessionalaudioequipmentandengineeringpractices.Itconcludeswithalistofrecommendedadditionalsourcesofinformationwhereuserscanfurthertheirunderstandingoftheseconcepts.
RationalAcousticsLLCisnotresponsiblefordamagetoyourequipmentresultingfromimproperuseofthisproduct.Besurethat
youunderstandandobserveproperinputandoutputlevels,impedancesandwiringconventionsofallsystemcomponentsbeforeattemptinganyofthemeasurementsdescribedinthisdocument.
©2009RationalAcousticsLLC.Allrightsreserved.
RationalAcousticsandSmaartareregisteredtrademarksofRationalAcousticsLLC.
TableofContents
GETTINGSTARTEDWITHSMAART®V7:BASICSETUPANDMEASUREMENT ................1
TableofContents .................................................................................................................................................... 2
GettingStarted:LoadingandLicensingtheSoftware ................................................................................ 3RecommendedComputerHardware ............................................................................................................................. 3RegisteringtheSoftware ..................................................................................................................................................... 3
FundamentalConcepts ......................................................................................................................................... 4Single‐Channelvs.Dual‐ChannelMeasurements...................................................................................................... 4TimeandFrequencyDomainAnalysis.......................................................................................................................... 5FFTs .............................................................................................................................................................................................. 6Smaartv7’sObject‐OrientedProgramArchitecture ............................................................................................... 7
ConfiguringSmaartv7forMeasurements ..................................................................................................... 7ConfiguringAudioI/ODevices ......................................................................................................................................... 8ConfiguringMeasurementGroups .................................................................................................................................. 9
TheSmaartv7GUI(GraphicalUserInterface) .......................................................................................... 11OperationModes...................................................................................................................................................................11GUIOverviews........................................................................................................................................................................11Navigation................................................................................................................................................................................13
SpectrumMeasurements .................................................................................................................................. 14SpectrumControls................................................................................................................................................................14RTA..............................................................................................................................................................................................15Spectrograph ..........................................................................................................................................................................15ApplicationExamples .........................................................................................................................................................16
TransferFunctionMeasurements ................................................................................................................. 19Magnitude ................................................................................................................................................................................19Phase ..........................................................................................................................................................................................20Coherence ................................................................................................................................................................................20TransferFunctionControls ..............................................................................................................................................21LiveIR ........................................................................................................................................................................................22DelayLocator/DelayTracking......................................................................................................................................22ApplicationExample:SettinganEqualizerforaLoudspeaker.........................................................................23
ImpulseResponseMeasurements ................................................................................................................. 25ImpulseResponseControls..............................................................................................................................................25Log/Lin/ETCViews .............................................................................................................................................................27FrequencyDomainView....................................................................................................................................................27IRModeSpectrograph ........................................................................................................................................................28
Appendices ............................................................................................................................................................ 28HotKeys....................................................................................................................................................................................29Self‐Help:WheretogoforAnswers..............................................................................................................................30RecommendedReading .....................................................................................................................................................30
GettingStarted:LoadingandLicensingtheSoftwareToinstallSmaartv7onacomputer,theuserrunstheWindowsinstaller(forWindowsOS’s)ordragsthesoftwareapplicationbundleintoyourapplicationsfolder(MacOS’s).
RecommendedComputerHardwareWhileSmaartv7willoperateonawiderangeofcomputerhardwareconfigurations,werecommendthefollowingminimumcomputerconfigurationfornewinstallations:
Windows®OperatingSystem:MicrosoftXP,VistaorWindows7(32&64‐bit)CPU:2GHzDual‐CoreIntelProcessororfaster(orcompatible)RAM:2GBorgreaterVideo:Graphicsprocessorwith128MdedicatedvideoRAM,minimum1024x600pixeldisplaySoundHardware:AudioHardwarewithOScompatibleASIO,Wav/WDMdrivers.
Macintosh
OperatingSystem:MacOSX10.5or10.6(LeopardandSnowLeopard)CPU:2GHzDual‐CoreIntelProcessororfaster(orcompatible)RAM:2GBorgreaterVideo:Graphicsprocessorwith128MdedicatedvideoRAM,minimum1024x600pixeldisplaySoundHardware:AudioHardwarewithOScompatibleCoreAudiodrivers.
RegisteringtheSoftwareFollowinginitialinstallation,onfirstrunofthesoftware,theuserispresentedwithanactivationscreencontainingthatcomputer’s10‐digit“MachineID”andisaskedforan“ActivationCode”toauthorizethisinstallation.ThisMachineIDisauniquecodeforthatidentifiesthatcomputer.Likewise,theActivationCodeisauniquecodethatwillonlyworkforthecomputerwiththatMachineID(muchthesameasSmaartLivev5’sPIC).Iftheinstallationisonacomputerthatisconnectedtotheinternet,theusercanchoosethe“ActivateOnlineNow”optiontoacquirethenecessarycodeandactivatetheinstallation.Otherwise,theusershouldmakenoteoftheMachineIDandaccessSmaart’slicensingsystemathttp://my.RationalAcoustics.comviaanothercomputertoacquirethenecessarycodetoactivatethisinstallation.Ineithercase,theusermustentertheirSmaartv7licensenumber(20alpha‐numericcharacters:XXXXX‐XXXXX‐XXXXX‐XXXXX),andthepasswordfortheuseraccounttowhichthelicenseisregistered.IftheSmaartv7Licensehasnotyetbeenregisteredtoauseraccount,theusermustfirsteithercreateanewaccountandpassword,orchooseanexistingaccounttoregisteritto(i.e.yourSmaart6licenseaccount.)EachlicenseofSmaartv7allowsfortwoinstallationsofthesoftware.UsersmaypurchaseadditionalinstallationsforanylicensebycontactingRationalAcousticsorauthorizedrepresentative.
Note:Smaartsoftwareislicensedtoasingle“user”–definedaseitherasinglepersonorcompany.Allsoftwareinstallationsforagivenlicensemustbeperformeduponcomputersownedbythatuser.
FundamentalConceptsDependingupontheapplication,operatingSmaarteffectivelyrequiresaworkingunderstandingofwiderangeofsystemmeasurementconceptsandprofessionalaudioengineeringpractices.Whileitisoutsidethescopeofthisdocumenttocoverthemall,thissectionhighlightsafewcriticalconceptsthatwillsignificantlyassistinunderstandingSmaartv7’soperationanditsapplication.Thisdocumentincludesanappendiceswhichhasalistofrecommendedadditionalsourcesofinformationwhereuserscanfurthertheirunderstandingoftheseconcepts.
Single‐Channelvs.Dual‐ChannelMeasurementsInitsessence,Smaartperformstwodistincttypesofmeasurement:single‐channel(signalanalysis)anddual‐channel(responseanalysis).Singlechannelmeasurementsexamineasignalatsinglepointinasystem,andcouldbestbedescribedassignalanalysismeasurements.Theseoperationsquantifyaspectslikesignallevelandfrequencycontent,andappearinSmaartasSpectrum(RTAandSpectrograph)andSPLmeasurements.Withsingle‐channel,theuseracquiresasignalviaanelectricalprobe(signalsplit)oranacousticalprobe(microphone),andexaminesthecontentofthatsignaldirectly.Single‐channelmethodsprovideanabsolutemeasurement,andhelptoansweranengineer’squestionslike“howmuch1kHzenergyisinthatsignal?”“whatisthatfrequency?”or“whatistheSPLatthisplaceinthevenue?”.Dual‐channelmeasurementscomparetwosignalsinordertoexaminetherelationshipbetweenthem.InSmaart’simplementations,wecomparetheinputsignalofasystem(reference)toitscorrespondingoutputsignal(measurement)toexaminewhatthesystemisdoingtothesignalsthatpassthroughit.Thesecouldbestbedescribedassystemresponsemeasurements,andinSmaart,werelyondual‐channelmethodstomeasurebothasystem’sfrequencyresponse(transferfunction)andimpulseresponse.Dual‐channelmethodsprovidearelativemeasurement(inputvs.output),andhelptoanswerquestionslike“whatisthecrossoverfrequencyinoursystem”“howmuchboost/cut?”or“whenistheenergyfrommymainspeakerarrivingatthemic?”Bothtypesofmeasurement,single‐anddual‐channel,areextremelypowerfultoolsfortheaudioengineerwhounderstandstheirindividualstrengthsandweaknesses–whounderstandwhattheyaremeasuring,andjustasimportantly,whattheyare
not.Fartoooften,baddecisionswhenusingananalyzeraretheresultofengineersconfusing/conflatingthesemeasurementtypes.InSmaartv7,themeasurementprocessbeginswiththe“group”configurationprocesswherewedictatewhatsingle‐channel(Spectrum)anddual‐channel(Response)measurementswewishtouse.
TimeandFrequencyDomainAnalysisAbasicunderstandingoftherelativestrengthsanddifferencesbetweenTimeandFrequencyDomainanalysisiscriticaltoleveragingthemeasurementpowerpresentedinSmaart.Asproblemsolvingengineers,theabilitytoexamineameasurementfrommultipleperspectives(domains)isextremelyusefulintheprocessofanalyzingasignalorsystemresponse.EachofSmaartv7’sprimarymodesofoperation(Real‐TimeandImpulseAnalysis)includebothTimeandFrequencyDomainmeasurementviews.TimeDomainanalysisrefersexaminingoursignalsandsystemresponseovertime.Atimedomainplot(amplitudevs.time)ofasignalprovidesaviewofthewaveform–acriticalviewforsoundeditors.Atimedomainviewofasystemresponse(impulseresponse)showsthesignaldelaythroughthesystem,andwhetheranylatearrivingmultiplesofthesignal(reflections/reverberence)arepresent. FrequencyDomainanalysisreferstoexamingoursignalsandsystemresponsesoverfrequency.Afrequencydomainplot(amplitudevsfrequency)ofasignalprovidesaviewofitsspectrum–anextremelyhelpfulviewwhenidentifyingtonalcontentorlookingforfeedback.Afrequencydomainviewofsystemresponse(transferfunctionorfrequencyresponse)providesanexcellentlookatthetonalresponseofasystemaswellasitstime/phaseresponsebyfrequency.Inthefigurebelow,anexcellentexampleofthepowerofutilizingbothtimeandfrequencydomainviewsforexaminingsystemresponseisclearlydisplayed.TheFrequencyResponsemeasurementdepictsaresponsewithaseriesoflinearlyspaceddipsandpeaksinitsmagnitudetrace(lowertrace).Howeverthatrippleisthesymptom‐thecauseofthisripplecanbeclearlyseenintheTimeDomainviewofthesystemresponse–anobvioussecondarrivalintheimpulseresponseisthesourceofthecombfilterrippleseeninfrequencydomain.
Figure1:TheFourierTransformmovingsignalsbetweenthetimeandfrequencydomains.Upper
exampleshowstheconversionbetweenatimesignal(voicesample)anditsspectrum;lowerexampleistheconversionbetweenanimpulseresponseandafrequencyresponse(transferFunction).
FFTsSmaartusesFastFourierTransforms(FFTs)andInverseFourierTransforms(IFTs)totranslatedatabetweenTimedomainandFrequencydomainviews.Ineffect,anFFTtakesasectionofaTimedomainwaveformandprovidesthefrequencycontentofthatselectedpieceofsignal.WhilearigorousunderstandingofthismathematicalprocessesisnotrequiredtooperateSmaart,itisusefultoappreciatetheinverselyproportionalrelationshipbetweendatainthetwodomains,whereFrequencyResolution=1/TimeConstant(FR=1/TC).Inotherwords,toincreasetheresolutionofspectrumdata,onemustuselargertimeslicesoftheinputsignal.OfparticularnotehereisSmaartv7’sdefaultFFTsettingforTransferFunctionmeasurements,MTW(Multi‐TimeWindow.)InsteadofusingoneFFTofasinglefixedlength,MTWusesmultipleFFTsofdecreasinglengthwithincreasingfrequency.Thisefficientprocessprovidestransferfunctiondatawithaconsistentresolutionofgreaterthan48thoctaveabove60Hzwithacoherencefunctionthatisincreasinglysensitivetolatereflectivedatainthehigherfrequencies.ThefigurebelowshowsacomparisonofthesametransferfunctionmeasurementmadewithMTWvs.asingle16kFFTsettings.NoticethatMTWFFThasbetterresolutionintheLFwhilethe16ktracehasexcessresolutionintheHF.
Figure2:TransferFunctionsMTWvs.Single16kFFT
Formoreinformationonthissubject,anin‐depthtreatmentofFFTscanbefoundintheSmaartLive®TechNote“FFTFundamentals.”
Smaartv7’sObject‐OrientedProgramArchitectureOneofthemostpowerfulaspectsofthenewSmaartv7platformisitsobject‐orientedprogramarchitecture.Effectively,theprogramisbuiltofmanyindividualcodemodulesthatarerunasindependent,inter‐relatedprograms(objects).Dataacquisitionishandledbytheinputmodule(s),single‐channelanddual‐channelmeasurementsarehandledbyindividualspectrumandresponseobjects,andthegraphingandGUI(graphicuserinterface)aretheirownseparateobjectsaswell.Thisarchitecturecreatesameasurementenvironmentthateasilyscalabletoauser’sindividualrequirements.Ineffect,youcanrunasmanysimultaneoussingle‐channel(spectrum)anddual‐channel(response)measurementsasyourPCandaudioI/O(Input/Output)hardwarewillallow.ThisalsomeansthatSmaart’smeasurementplotsareseparateobjectsfromthedatatheygraph.Theimmediatebenefitofthisrelationshipistheuser’sabilitytochangedisplayparameters(smoothing,banding,spectrographrange,coherenceblanking,tracecolor)ontheflywithouthavingtorecalculate/re‐measurethedataforthenewdisplayparameters.
ConfiguringSmaartv7forMeasurementsThemeasurementprocesswithSmaartv7beginswiththeconfigurationofsingle‐channel(spectrum)anddual‐channel(response)measurements.Thissectiondetailstheprocessandfunctionsinvolvedinconfiguringthesoftwareformeasurement.Unlikepreviousversionsofthesoftwarewhichassumedasimpletwo‐channelI/O,Smaartv7caninterfacewithmultipleI/Odevices,eachwithmultipleinputand
outputchannels.Accordingly,Smaartv7makesnoassumptionsaboutauser’sI/Ocapabilitiesandmeasurementrequirements,andsouponfirstrun,beginsitsinitialoperationun‐configured.Asinpreviousversionshowever,followinginitialsetup,Smaartretainsitsmeasurementconfigurationforsubsequentsessions.
Note:inthecaseofthefree/publicdemoversionofthesoftware,Smaart’smeasurementconfigurationisnotretainedfromsessiontosession,andmustberebuiltforeachnewsession.
Smaartv7isabletoacquireinputsignalsfromanydeviceswith.wav,CoreAudio,orASIOdriversthatarerecognizablebythecomputer’sOperatingSystem(OS).Infact,itcangrabmultiplesignalsfrommultiplesourcessimultaneously.(Note:onlyoneASIOsourcecanbeaccessedatatime)
WhenSmaartv7starts,theuserispresentedwiththissplashscreen.Whilethisisdisplayed,SmaartcheckstoseewhatI/OdevicesareavailabletoyourOS.ItisherethatSmaartbuildsitslistofinputdevices,andonceadevicehasbeendiscovered,itwillcontinuetoshowupforconfigurationinsubsequentruns–evenifitisnotconnectedatlaterstartups.
Note:WhileanI/OdevicemayshowupinSmaart’slistofconfigurabledevices,itmustbeconnectedtoyourcomputeratthetimeofstartuptobeaccessibleduringprogramruntime.
ConfiguringAudioI/ODevicesWhilethisconfigurationisnotrequiredtousedevicesincreatingandperformingmeasurements,I/Odevice(s)canbe“configured”bytheuserintheI/OOptionsdialog.Thisconfigurationcomprisesadjustingthedevice’ssamplerate,bitdepth,andassigningthedeviceanditschannels“friendlynames”‐namesthathelpusersidentifysignalsanddevicesastheyconfiguretheirindividualmeasurements.The“AudioI/O”OptionsDialogueisaccessedviathe“OptionsMenu”orbyusingthehotkeycommand[Opt+A](“HotKeys”areSmaart’sbuilt‐in,keyboard‐basedcommands). Figure3:OptionsMenu
Options:AudioI/Odialog
• Userselectsdevicefromthedrop‐downlist(populatedatstart‐up).
• Usercanassign“friendlynames”tothe
deviceandindividualchannels.
Note:Remembertopress[enter]aftertypingfriendlynames,ortheywillnotberetained.
ConfiguringMeasurementGroupsToperformmeasurementswithSmaartv7,ausermustconstructtheirmeasurementconfiguration.Remember,insteadofafixedmeasurementtopology,Smaartv7’sobject‐orientedarchitectureallowsausertoconfigureasmanysingle‐channel(Spectrum)anddual‐channel(Response)measurementobjectsastheywishfromtheAudioI/Ochannelsavailable.Moreover,thesemeasurementscanberuneitherindividuallyorsimultaneously,dependingupontheuser’srequirements.Inordertostructureandmanageourconfiguration,weorganizeourmeasurementsintoSpectrumandResponse“Groups.”Thisisaccomplishedinthe“GroupManager”OptionsDialogwhichisaccessedeithervia“OptionsMenu”,byusingthehotkeycommand[Opt+G],orbyclickingontheGroupManagerbuttonlocatedinthemeasurementcontrolsareaoftheuserinterface.FromtheGroupManagerDialog,auserdefinestheirmeasurementobjectsandorganizesthemintogroups.Theleftsideofthisdialogisdedicatedtoa“treeview”ofthemeasurementconfiguration.Hereoneviews/creates/copies/deletesSpectrumandResponsegroupsandviewsthe
Figure6:TheGroupManagerDialogapowerfulinterfaceforconfiguring,controllingandadaptingourmeasurementsystem.
Figure5:GroupManagerButton
Figure4:OptionsAudioI/O
individualmeasurementsassignedtoeach.Thistreealsoactsasthenavigation/selectorforthe“GroupTabView”ontheleftsideofthisscreen.Onceagrouphasbeencreated,ausercanselectitfromthetreeandaddameasurementtothegroupbyclickingonthe“NewInput”(Spectrum)or“NewPair”(Response)button.
Whenconfiguringanewsingle‐channelmeasurementwithinaSpectrumgroup,theuserselectsthedesiredI/Odeviceandinputchannel.Whenconfiguringanewdual‐channelmeasurementwithinaResponsegroup,theuserselectsthedesiredI/Odeviceanda“measurement”anda“reference”channelforthatobject.Inbothcases,thedrop‐downmenuswillshow“friendlynames”forthedeviceandinputchannelsthatwereconfiguredforthatdevice.
Note:Meas.AndRefchannelsforaResponsemeasurementmustbeselectedfromthesameI/Odevice.
Fromthe“TabView”sectionoftheGroupManagerdialog,ausercanorganizeeachmeasurementgroup;adjusttheorderthateachappearsinonthemainUI,changetheselectedinputsignals,set/changethenameandcolorforeachtrace,andconfigurelive“Average”measurements(usingthe“NewAverage”button.)LiveAveragesaremeasurementswhicharecalculatedfromaveragesofotheractivemeasurementsinthatgroup.EachmeasurementobjectconfiguredintheGroupManagerDialogisbasicallyacompleteSmaartmeasurementengineinitself‐eachwithitsowndefinablesetof
Figure7:InputButtoncreatesanewsinglechannelmeasurement. Figure8:NewPaircreatesanewdual
channelmeasurementobject.
Figure9:GroupTabViewsectionoftheGroupManagerdialogshowingliveaveragesetup
measurementparameters.Consequently,eachobjectinthegrouphasitsown“Tab”inthisviewwhereuserscanaddressthoseindividualmeasurementparametersifrequired.TheglobalandindividualcontrolofmeasurementparametersfromwithintheGroupManagershallbecoveredinmoredetailforeachtypeofmeasurementlaterinthisdocument.
Note:Whileitisrelativelyeasytoconfigureandsimultaneouslyrunmultipleresponsemeasurements,itisHIGHLYrecommendedthatnew(andevenexperienced)usersstartwithsimpleconfigurationsandbuildupslowlyastheygetusedtomanagingmultiplesimultaneousmeasurements.
TheSmaartv7GUI(GraphicalUserInterface)ThissectionprovidesabasictouroftheSmaartv7userinterfaceandreviewsitsprimarynavigationaltoolsandconcepts.Asthefeaturesetandfunctionalityofv7expands,thiswillalwaysbeanareaofcontinualenhancement,however,thestandardlayouts,navigationtoolsandparadigmsdetailedherewillstillpersist.
OperationModesSmaartoperatesintwodistinctmeasurementmodes:Real‐TimeandImpulseResponse.Whilebothmodeshavetheabilitytoactivelymeasureanddisplayfrequencydomainandtimedomaindata,thefundamentaldistinctionbetweenthesemodesistheiroperationalfocus.Real‐Timemodeisdesignedasanenvironmentforefficientlymeasuringandcapturingspectrumandresponsemeasurements–ofteninmultiples–specificallyoptimizedforin‐situsystemalignmentandmixengineeringwork.ImpulseResponsemodeisdesignedtoprovidearobustandintuitivesetoftoolsformeasuringandexaminingtheacousticalresponseofsystemsandenvironments.Smaartv7’sImpulseResponsemodehasbeensignificantlyexpandedfrompastversions(andwillcontinuetoexpand)toincludemuchofthefunctionalityfromtheSmaartAcousticToolssoftwarepackage.
GUIOverviewsThegenerallayoutoftheGUIforReal‐TimeandImpulseResponsemodes:
Figure10:TheSmaartv7InterfaceRealTimeMode
Figure11:TheSmaartv7UserInterfaceImpulseAnalysisMode
Eachmodecontainsa“ControlStrip”ontherightsideoftheinterface,andtheReal‐TimemodeincludesaDataStorageareaonitsleftside.Themajorityofeachmode’sGUIhoweverisdedicatedtotheplotarea.Theuppermostportionofthissectionisdevotedtoacursorreadoutthatdisplaysthecoordinatesofthemousecursorin
amplitude,frequencyortimeunits,dependingonthecharttype,whenthemousecursorispositionedoveranyofthemaindataplots.
NavigationTherearethreebasicelementsinnavigating,controllingandconfiguringSmaartv7:GUIviamousecontrols,menus/optiondialogs,andhotkeys.Inmostcases,therearemultiplewaysofcontrollingthesamefunction–thisisparticularlyimportantforusecaseswhereonemethodispreferableoveranother(e.g.auseroperatingonatabletcomputerwherekeyboardcontrolarenotconvenient.)Acomplete,currentlistingofthehotkeyfunctionsisalwaysavailableinthesoftware’shelpfiles.Thatsaid,Smaartv7’sGUIisbuiltformouse‐basedcontrolasitsprimaryinteractionmode–eitherthroughbuttonsanddatafieldsinthecontrolstripanddataareas,orthrough“clickanddrag”controlsinthedataplotareas.Manyofthevariouscontrolsforeachmodewillbecoveredinthespecificsectionsofthisdocumentthatdealwiththespecificmeasurementtypes.Herehowever,wewillcoverthecontrolsthatdealspecificallywithmeasurementandmodeselection,andviewcontrol.MeasurementSelection:Inthedatawindowsforbothmodes,theusercanselectthemeasurement/plottypethatisdisplayedineachwindowbyselectingadrop‐downmenufromtheplottypelabelintheupperleftcorneroftheplot.WindowLayoutSelection:Layoutselectorbuttonsinthecontrolstripsetthenumberofdatawindows(1or2)andinthecaseofTransferFunctiondisplays,toggledisplayoftheoptionalliveimpulseresponse(LiveIR)display.Whenoperatingwithasplitdisplay,oneofthetwomainchartsisconsideredtheactive,orselectedchart.Thecolorofthemarginssurroundingtheplotindicateswhichofthetwoiscurrentlyselected.
Note:TheControlStripandDataStorageareasintheRealTimeModealwayscorrespondwiththeactivedatawindowmeasurementtype.
DirectlyabovetheWindowLayoutbuttonsintheReal‐TimeModearetwobuttonsthatrecallstandard,pre‐setmeasurementviews.The“Spectrum”buttondisplaysasingleplotwindowwith“RTA”asthechosendatatype.The“Transfer”buttonsswitchestoatwo‐windowdisplaywithPhasedisplayedintheupperwindowandMagnitudeinthelower.
Figure12:PlotTypeSelectionforRealTimeModeDataWindows
Figure13:WindowLayoutButtonsforRealTimeMode
Figure14:PreSetViews
ModeSelection:UserscantogglebetweenmeasurementmodesusingeithertheModebuttonsinthecontrolstrip,viathe“Mode”menu,orbyusingthe[I]and[R]hotkeys.Zooming:Userscanzoominanyofthedatawindowsbyusinga“rubberband”zoombyeitherholding[command]+(leftbutton)clickinganddragging,or(rightbutton)clickinganddraggingazoomareaontheplot.Hotkeysarealsoavailableforzoomcommands.
Note:ClickingontheX(horizontal)orY(vertical)axisofanydataplotwillresetitszoomrangestodefault.
SpectrumMeasurementsSmaart’ssingle‐channelSpectrummeasurementsallowausertoexaminethespectralcontentofaudiosignalsthroughouttheirsystem.Thesemeasurementsareextremelyusefulinmanyapplications,includingthelocationoffeedbackfrequenciesinsoundreinforcement,noiseandsoundexposuremeasurements,cinemasystemoptimization,aswellasgeneralsignalmonitoringtasks.DatafromSmaart’sSpectrummeasurementsareviewableasastandardRTA(RealTimeAnalyzer)plots,orgraphedovertimeinathree‐dimensional(levelvs.frequencyvs.time)Spectrographplot.
SpectrumControlsOnceconfigured,individualSpectrummeasurementsappearaselementsintheSpectrumcontrolstrip.Here,theusercanchoosewhichmeasurementstoactivelyrun ,monitortheinputlevelofthesignal,andshow/hidethetrace.GlobalSpectrumSettings:Bydefault,allSpectrumobjectsusethesameglobal,user‐configurablemeasurementanddisplayparameters(FFT,Averaging,WeightingandScale).TheglobalScaleandAveragingsettingscanbeadjusteddirectlyfromtheSpectrum
Figure15:SpectrumControlStrip
ControlStrip,whileallglobalsettingscanbeaddressedintheGroupManagerdialog.Moreover,AveragingandWeightingcansetseparatelyforeachmeasurement(ifdesired)intheindividualmeasurement’stabintheGroupManagercontrols.
RTAThereal‐timeanalyzer,orRTA,isafamiliartooltoaudioprofessionals.Byadjustingthescaleandaveraging,auserisablerefinetheirmeasurement’sresolutionandresponsivenesstofitthetaskathand.
Figure17:SpectrumRTAScaleandAveragingAdjust
SpectrographWhiletheRTAhashistoricallybeen,byfar,themostcommonlyusedviewofaSpectrumforprofessionalaudioengineers,anotherwayofdisplayingthisdataisextremelyilluminatingandhasbeencommonlyappliedforyearsinthefieldsofvoicerecognition,vibrationanalysisandunderwateracoustics(onsubmarines).Smaart’sSpectrographdisplay(orSpectrogram,asitismoregenerallyknown)isaplotofasignal’sspectrumovertime.ThishybriddisplaygraphsacontinuousseriesofSpectrummeasurementswithfrequencyononeaxis,timeonanother,andlevelindicatedbythetracecolor.InSmaart,thisgraphisfundamentallygovernedbysettingthethresholdlevelatwhichdatabeginstoappearonthegraph.Whenafrequencybandinthespectrumisoverthelowerthreshold,itshowsupontheplot,startingwithadarkbluecoloratlowerlevels,andtransitioningthroughgreen,
Figure16:GlobalSpectrumSettingsfromGroupManager
yellow,orangeandredwithhigherlevel–eventuallyshowingupaswhiteifthelevelreachesorexceedstheupperthreshold.Thekeytocreatingausefulspectrographisinsettingthedynamicrangeforthedisplay–insettingthethresholdsforshowing/hidingthespectraldata.Settherangetoowideandthedisplaylosesdefinition,andimportantfeaturesmaygetlost.Setittoonarroworthelowerthresholdtoohighanddatamightgetmissedaltogether.OneofthepowerfulnewfeaturesinSmaartv7istheThresholdAdjustmentHandlesthatareavailableontheleftaxisofRTAandSpectrographplots.Withthesecontrols,ausercanadjustspectrographthresholdsdynamically–withouthavingtoreacquirethedata.Moreover,Smaartv7’sspectrographretainsahistoryofthelast“x”slices(spectrummeasurements),andausercanscrollthedisplaybackthrougholderdatainthehistoryifithaspassedoffofthedisplay.Ausercanaccessandadjustthesizeofthishistoryfile,aswellasthedisplaywidthforeachslice,intheSpectrumOptionsdialog.
Note:Smaartonlygraphsdatafromthe“active”spectrummeasurement–evenifmultiplesinglechannelmeasurementsarerunningsimultaneously.
ApplicationExamplesWhatfollowsaretwoexamplesofspectrummeasurementsusedincommon,“realworld”applications.ThefirstusesbothRTAandSpectrographforexaminingfrequencycontent–specifically,inidentifyingfeedbackfrequencies.Thesecondusesthespectrographtoexamineinteractionpatterns(combfiltering)thatarecausedbydirectsoundinteractingreflectionswithnearboundaries.FeedbackIdentification:
Figure18:SpectrographThresholds
Figure19:SpectrographSettingsinSpectrumOptions
Inthisexample,avocalmicrophoneisroutedthroughasimplesoundsystem.ForourSpectrummeasurementweacquiretheoutputsignalofthemixingconsole.Thevocalmicgainisraiseduntilwegetfeedback.
Thefeedbacktonecanbeidentifiedasaverticalbarat1.24kHzintheRTAdisplay.However,becausethereisalsoothersignalgoingthroughthesystematthesametimeasthefeedback,itiseasiertodistinguishtheverticallineoftheconstantfeedbacktoneintheSpectrographplot.
Figure21:FeedbackDisplayedinRTAandSpectrographPlots
Figure20:SystemConfigurationforMonitoringFeedback
ExaminingInteractionPatternswithSpectrograph:ThefollowingisasimpletechniquethatusestheSpectrographforexaminingcoverageandinteractionpatternsinloudspeakersystems.Simplyput,theuser
excitesthesystemwithpinknoise–whichshouldproducearelativelyconstantlevel/coloratallfrequenciesonaspectrographplot–andthenmovesthemeasurementmicthroughthelisteningenvironment.Levelvariationsfrominteractions,liketheaudiblecombfilteringcausedbyreflections,canbeseenasinteractionpatternsonthespectrographplotofthemicsignal.Adjustingthedynamicrangehelpstobetterhighlighttheinteractionpatterns.
Figure23:SystemConfigurationforInteractionStudy
Figure22:CombFilterInteractionPatternsViewedintheSpectrographPlot
TransferFunctionMeasurementsTransferFunctionisadual‐channelmeasurementthatdeterminesasystem’sfrequencyresponsebycomparingitsinputsignal(reference)toitsoutputsignal(measurement).Thismeasurementshowsthedifferencebetweenthosetwosignalsinbothmagnitudeandphaseandrepresentstheprocessingbehaviorofthesystemasafunctionoffrequency.
Smaart’sTransferFunctionmeasurementallowsausertoexaminethefrequencyresponseofvariouscomponentsoftheirsoundsystem,bothelectrical(EQ’s,mixers,processors)andelectro‐acoustical(loudspeakers,theirenvironmentandtheirdriveelectronics).Thesemeasurementsareextremelyusefulinmanyapplications,includingloudspeakerdesign,equipmentevaluation,equalizationandsystemoptimization.DatafromSmaart’sTransferFunctionmeasurementsareviewableasfourseparatetraces,onthreeseparateplots/windows:magnituderesponseandcoherence(samewindow),phase,andliveIR(timedomainplot).
Note:AstoredTransferFunctionmeasurementcomprisestheMagnitude,PhaseandCoherencetraces–LiveIRisnotcaptured.
MagnitudeTheMagnitudewindowshowsboththeMagnitudeportionofthetransferfunction(frequencyresponse),andtheCoherencetrace(seebelow).Inthemagnitudeplot,gainandlossshowupasdeviationfromthecenter0dB
line.
Theusercanclickanddragamagnitudetraceupanddowntomoveitverticallyontheplot.
PhaseThePhaseplotdisplaysthePhaseportionoftheTransferFunctionmeasurement.Thisplotshowsthedifference(indegrees)betweenthereferenceandmeasurementsignals,andprovidesanindicationofoverallrelativetimingbyfrequency,phaseshiftduetofilteringandsystempolarity.Thephaseplotis“circular”through360o–thetopoftheplot(180o)isthesameplaceasthebottomoftheplot(‐180o).Thephasetracebelowshowsacontinuoustracethatleavesthebottomoftheplotandcontinuesonfromthetop.
Theusercanclickanddragaphasetraceverticallytochangethepositionofthe0opoint.Regardlessofthepositionof0o,thephasetracealwaysdisplaysarangeof360oinitsstandard,“wrapped”displayformat.
CoherenceTheCoherencetracedisplaysthestabilityoftheTransferFunctiondataoverthegivenseriesofmeasurements/averages,andisexpressedasapercentagefrom0(badcoh.–inconsistentdata)to100%(highlyconsistentdata.)IftheTransferFunction’saveragerissetto“instantaneous”,Coherenceisnotcalculated.
TheCoherencetraceisplottedusingtheupper½oftheMagnitudewindow.Therearethreegeneralcausesofreducedcoherence.First,aproblemwiththemeasurementsystem–mostcommonly,nothavingthemeasurementdelaysetproperly(seebelow).Second,environmentalnoisecausingmeasurementcontamination–lossofsignal‐to‐noise.Andthird,excessreverberance/dropofDirect‐to‐Reverbratiointhemeasurementsystem.Onanongoingbasis,theCoherencetraceprovidesanexcellentindicationofsystemintelligibility,andisagoodsourceoffeedbackonsystem/measurementquality.
SmaartutilizesablankingfunctionthatwillhideTransferFunctiondatafromtheplotatfrequencieswhereCoherenceisbelowasetblankingthreshold.TheusercansetthisinTransferFunctionoptions,orusetheadjustmenthandleonthemagnitudeplot(nexttothecoherencescaleintheupperright).
TransferFunctionControlsLikeSpectrum,allTransferfunctionmeasurementsbydefaultusethesame“GlobalTFSettings”forFFT,Averaging,Smoothing,etc,‐unlesstheyaresettoignorethosesettingsinthemeasurement’sindividualtabintheGroupManager.
Averaging:Averagingameasurementstabilizesthemeasurementandhelpsrejectuncorrelatednoise.TheSmaartv7usesastandardFIFO(FirstIn,FirstOut)forthelowerlevelsofaveraging(2,4,8,16)andthenswitchestoaccumulatorsabovethat(1sec,2sec,etc).TheseaccumulatorsprovidesignificantimprovementsinstabilityoverpastlargerFIFO’sandarepreferredforacousticmeasurements.Smoothing
Smaartv7includesnew“FractionalOctave”smoothingalgorithmsforreducingtherippleinTFtracesandaidinginviewingthegeneraltrendsofthedatacurves.
LiveIRTheTransferFunctioncanbeviewedasa“LiveIR”.ThisdisplayshowstheImpulseResponseinalinearscale,timedomainviewwiththeTFmeasurementdelaytimelocatedatthecenterofthescreen.LiveIRsettingscanbeadjustedintheTransferFunctionOptionsdialog.
DelayLocator/DelayTrackingTransferFunctioniscalculatedbycomparingthesignaloninputtoasystemtoit’scorrespondingoutputsignal.Mosttimes,thereissomedelaythroughthesystem,oftentheresultoflatencyintheprocessing,signaldelayandacousticpropagationtime.Eachtransferfunctionobjecthasameasurementdelaythatcanbeusedtodelaytheinput/referencesignaltoitsoutput/measurementsignal.Accordingly,Smaarthasabuilt‐in“DelayLocator”functionthatperformsanimpulseresponsemeasurement,and
returnsthetimeassociatedwiththetallestpeak–normallythedelaytimeassociatedwiththearrivalofthedirectsound.Foreachmeasurementobject,thisfunctioncanbecalledwiththe“Find”buttoninitsindividualmeasurementcontrol.Alternatively,theusercanchoosetohaveanindividualmeasurementobjectcontinuouslytrackthemeasurementdelay(usingthesamebasicfunctionasLiveIR)bypressingthe“Track”buttonorindicatorlightlocatedinthemeasurement’sindividualcontrol.
Note:The“Track“functiondoesconsumesomeprocessorresources,soifyourmeasurementdelayisnotchanging(themicorspeakerisnotactivelymoving,)itisprobablybesttoturntrackoffoncethemeasurementdelayhasbeenacquired.
ApplicationExample:SettinganEqualizerforaLoudspeakerInthisexample,anengineermeasurestheTransferFunctionofaloudspeaker,andthenadjustsanequalizerto“flatten”itsoverallresponse.Here,theuserhasamulti‐channelI/O,someasurementsoftheEqualizer(MixOutcomparedtoEQOut)andcompleteloudspeakersystem(MixOutcomparedtoMicrophone)canbeperformedsimultaneously.Thisexamplecouldalsobeaccomplishedperformingthosemeasurementsindividually/sequentially.Thisexampleusesthefollowinghardwareconfiguration.
Thisconfigurationproducesthefollowinginitialmeasurements.
Nextwecapturetheloudspeakerresponsetrace,adjusttheEQandviewtheresultsintheactive“MicOne”measurementofthetotalsystem.NotethattheEQmeasurementhasbeensettographinverted,sowecanlaytheEQdirectlyoverthestoredresponsetrace.Thishelpswithrefiningfilterwidthandfrequency.
ImpulseResponseMeasurementsImpulseResponsemodeisdesignedtoprovidearobustandintuitivesetoftoolsformeasuringandexaminingtheacousticalresponseofsystemsandenvironments.Smaartv7’sImpulseResponsemodehasbeensignificantlyexpandedfrompastversions(andwillcontinuetoexpand)toincludemuchofthefunctionalityfromtheSmaartAcousticToolssoftwarepackage.Inthismode,wecanalsoanalyzepreviousIRmeasurements(orothertime‐domaininformation)thathavebeenstoredinstandard.wavor.aiff(MAC)audiofileformat
ImpulseResponseControlsInIRMode,ausercanperformanImpulseResponsemeasurementbychoosinganyResponseMeasurementtheycurrentlyhaveconfigured,settingthemeasurementparameters(primarilyFFTsize/TC),acquiringsignalsandpressingstart.Alternatively,theusercanchoosetoloadastoredfileviathe“File”menu.Oncetheuserhascapturedorloadedanimpulseresponsemeasurement,theycanusetheviewingtoolsbelowtoanalyzeit.AtthetopoftheIRmodeGUIisawindowdisplayingtheentireimpulseresponseinlinearview.This“Nav”windowisusedforselectingthetimedomainzoomforthelowerdatawindows.AsinReal‐Timemode,rightClickanddragtochooseyourzoomwindow,andclickonthedataaxistoclearthezoom.
Note:Whenmeasuringanimpulseresponse,itisveryimportantthatyouhaveastrongreferencesignal(givethemeasurementagood“view”ofthesignalyouarelookingfor),andmakesureyourTCissettoatleastfivetimes(5x)thelengthofthetotalsystemresponse(includingreverberantdecay)youaremeasuring.
Log/Lin/ETCViews
FrequencyDomainView
IRModeSpectrograph
Appendices
HotKeysMeasurement Controls
[O] Selected Measurement On/Off
[Cmd/Ctrl] + [O] All On (run all live measurements of selected type)
[Cmd/Ctrl] + [Alt] +[O] All Off (stop all llive measurements of selected type)
[V] Reseed Averages
Delay Controls
[D] Track Delay (toggles Delay Tracking for selected Transfer Function measurement)
[Cmd/Ctrl] +[D] All Track (turn on Delay Tracking for all active Transfer Function measurements)
[L] Find Delay (for selected Transfer Function measurement)
[Cmd/Ctrl] + [L] Find All Delays (find delays for all active Transfer Function measurements)
[,<] Increment Delay (for selected Transfer Function measurement)
[.>] Decrement Delay (for selected Transfer Function measurement)
Data Storage and File Operations
[Space] Capture Trace (captures the front trace on the selected graph into the selected storage slot)
[Cmd/Ctrl] + [F] Capture and File Trace (creates a permanent file on disk while capturing)
[Cmd/Ctrl] +[S] Save to File (.wav or .srf/trf depending on the operating mode)
[Del] Clear Selected Storage Slot
Display Controls
[I] IR Analysis Mode
[R] Real-Time Mode
[S] Spectrum
[T] Transfer Function
[Cmd/Ctrl] + [I] Live IR (Show/Hide)
[Y] Clear Y Offset (Selected)
[Cmd/Ctrl] + [Y] Clear Y Offset (All)
[Z] Cycle Z Order (Forward)
[Shift] + [Z] Cycle Z Order (Back)
[+] Zoom In Y
[–] Zoom Out Y
[Cmd/Ctrl] +[+] Zoom In X/Y
[Cmd/Ctrl] +[–] Zoom Out X/Y
[Cmd/Ctrl] + [Alt] +[+] Zoom In X
[Cmd/Ctrl] + [Alt] +[–] Zoom Out X
[Up Arrow] Scroll Up*
[Down Arrow] Scroll Down*
[Left Arrow] Pan Left
[Right Arrow] Pan Right *Or roll "roll" the (wrapped) Phase display. [Cmd/Ctrl] means press the [Ctrl] key on a Windows computer or the [Cmd] key (sometimes called the Apple Key or "flower" key) on a Macintosh computer. The Alt key on a Windows system maps to the Option key on
Self‐Help:WheretogoforAnswersUltimately,theuser,asengineerandoperator,isresponsibleforansweringtheirownspecificapplicationquestions.Inordertoassistinthisprocess,RationalAcousticssuggeststhefollowingsources:
1. UsetheHELPFILESinthesoftware–alotofveryhelpfulinformationaboutSmaart’sfunctionsandfeaturesisthere,anditisfullysearchable.
2. TheSmaartuserforumsatRationalAcoustics.com3. SmaartTrainingsessions4. PreviouslypublishedSmaartandSmaartLiveManualsandTechnical
Notes–thesecanbefoundontheRationalAcousticswebsiteat:http://www.rationalacoustics.com/pages/New_Documentarium
5. The“RecommendedReading”sourcescitedinthelastsectionofthisdocument.
6. OrevencontactRationalAcousticsdirectlyviaemail(preferred)orphone.
TrainingsessioninformationandcontactinformationforRationalAcousticsandauthorizedrepresentativescanbefoundathttp://rationalacoustics.com.
RecommendedReadingD.Davis,C.Davis:SoundSystemEngineering,2ndedition.Carmel,IN:SAMS.1994.M. Mehta, J. Johnson, C. Rocafort: Architectural Acoustics: Principles and Design.
UpperSaddleRiver,NJ:PrenticeHall.1999.AmericanNational Standard: Specification for Sound LevelMeters, ANSI S1.4‐1983.
NewYork,NY:AcousticalSocietyofAmerica.1983.R. Cabot, B. Hofer, R. Metzler: Standard Handbook of Video and Television
Engineering: Chapter 13.3: “Nonlinear Audio Distortion”, 4th edition.McGraw‐HillProfessional.2003.
OSHA Standard: Occupational Noise Exposure, OSHA 1910.95. Washington, DC:
OccupationalSafety&HealthAdministration.1996.
Criteria foraRecommendedStandardOccupationalNoiseExposure,RevisedCriteria1996,DHHS(NIOSH)PublicationNo.96.Atlanta,GA:NationalInstituteforOccupationalSafety&Health.1996.
MotionPictures BChain Electroacoustic Response Dubbing Theaters, Review
RoomsandIndoorTheaters,SMPTE202M‐1998.WhitePlains,NY:SocietyofMotionPictureandTelevisionEngineers.1998.
If you have an interest in furthering your knowledge of the engineering concepts behindFFT‐basedmeasurement,youmayfindthefollowingtextsuseful:
A.Oppenheim,A.Willsky,S.Nawab:SignalsandSystems,2ndedition.UpperSaddleRiver,NJ:PrenticeHallInc.1997.
A.Oppenheim,R.Schafer,J.Buck:DiscreteTimeSignalProcessing,2ndedition.Upper
SaddleRiver,NJ:PrenticeHallInc.1999.
Recommended
