Upload File

convolution explained

7
Print article Published in SOS April 2005 : Close window There are three main sources of convolution impulse responses. The easiest thing to sample is a software plugin Convolution Processing with Impulse Responses How It Works Technique : Theory + Technical Although convolution is often associated with highend reverb processing, this technology makes many other new sounds available to you if you understand how it works. Martin Walker Convolution or 'sampling' reverbs are now extremely popular, and it's not hard to see why. They provide the sounds of real acoustic spaces that are far more realistic than most reverb effects (although these remain incredibly useful when you want more flexibility), and can also give your recordings the sound of being passed through an exotic mic, preamp, compressor, guitar amp, or indeed any other effect, both hardware and software. Each of these spaces or devices is encapsulated into what is called an 'impulse response' file that can be loaded into a compatible convolution playback device. Such devices range from freeware PC and Mac plugins to dedicated hardware such as Focusrite's Liquid Channel or Sony's DRE S777 reverb processor. As with most other technologies, many people will be content to use the IRs (impulse responses) bundled with their particular playback device, and to download other free ones from the Internet. (I provided a list of suitable sites for convolution reverb plugin owners in my recent roundup of PC Freeware in SOS July 2004). While capturing your own impulse responses to the standard of commercial libraries may be daunting, it's not particularly difficult to get respectable results with a little gear, and you don't have to restrict yourself to the usual halls, churches, and studios either. Effect specialists in the film, TV, and videogames fields are finding it extremely useful to capture IRs on location for use later on when placing overdubbed dialogue or effects into a real acoustic space. Moreover, not many people have cottoned on to the fact that you don't have to restrict yourself to IRs of existing spaces and gear — once you abandon realism and start convolving other audio files there's a bizarre new world of treatments out there for your audio tracks. Convolution Input Signals To capture the sound of a real space, plugin, or hardware processor, you need a suitable test signal. The most obvious approach is to play back a short impulse containing all frequencies, so that you can record the resulting response across the complete audio range — a single 0dBlevel pulse lasting a single sample could be used (and I've recommended this in the past for listening to the smoothness of reverb tails). If you don't want to cart loudspeakers about to generate this pulse in the space you want to capture, realworld alternatives include firing a starting pistol, popping a balloon, or in an emergency even clapping your hands — although judging by the results I've achieved, this latter option is of very limited use. However, there's a disadvantage in all these signals — their shortness results in a relatively poor signaltonoise ratio. In more practical terms, this means that the background noise in your IRs will be high. The best way round this limitation is to extend the test signal, which is why most serious experimenters use some sort of swept sine wave signal typically lasting twelve seconds or so. To capture particularly noisy environments such as those inside factories, on board ships/planes, and inside other vehicles as cleanly as possible, you can double this to 24 seconds, and of course swept tones are also the easiest way to capture the sound of software plugins, mic preamps, guitar amp/speaker combos, and so on. Some software convolution playback devices offer a function to convert the swepttone recordings you've captured into IRs. These include the Altiverb IR PreProcessor from Audio Ease, the latest version of Waves IR1, and the one that started it all on the PC some six years ago, Sonic Foundry's Acoustic Modeler (now Sony Media's Acoustic Mirror). Suitable test signals may be bundled with the software, or are available as downloadable files. In this article: Convolution Input Signals Lateral Thinking Convolution Engines Thirdparty IR Files Commercial IR Collections Convolution Software Reviews In SOS Pure Space IR Libraries Spectral Relativity IR Library Web Resources Kaleidoskopy IR Library Hints & Tips Impulse Power! Sound On Sound : Est. 1985

Upload: diseno-sonido

Post on 16-Sep-2015

249 views

Category:

Documents


0 download

Report

DESCRIPTION

Explicación del proceso de convolución para creación de efecto de reverberación

TRANSCRIPT

  • 8/6/2015 Convolution Processing with Impulse Responses

    http://www.soundonsound.com/sos/apr05/articles/impulse.htm?print=yes 1/7

    Printarticle

    PublishedinSOSApril2005:Closewindow

    Therearethreemainsourcesofconvolutionimpulseresponses.Theeasiestthingtosampleisasoftwareplugin

    ConvolutionProcessingwithImpulseResponsesHowItWorksTechnique:Theory+Technical

    Althoughconvolutionisoftenassociatedwithhighendreverbprocessing,thistechnologymakesmanyothernewsoundsavailabletoyouifyouunderstandhowitworks.

    MartinWalker

    Convolutionor'sampling'reverbsarenowextremelypopular,andit'snothardtoseewhy.Theyprovidethesoundsofrealacousticspacesthatarefarmorerealisticthanmostreverbeffects(althoughtheseremainincrediblyusefulwhenyouwantmoreflexibility),andcanalsogiveyourrecordingsthesoundofbeingpassedthroughanexoticmic,preamp,compressor,guitaramp,orindeedanyothereffect,bothhardwareandsoftware.Eachofthesespacesordevicesisencapsulatedintowhatiscalledan'impulseresponse'filethatcanbeloadedintoacompatibleconvolutionplaybackdevice.SuchdevicesrangefromfreewarePCandMacpluginstodedicatedhardwaresuchasFocusrite'sLiquidChannelorSony'sDRES777reverbprocessor.

    Aswithmostothertechnologies,manypeoplewillbecontenttousetheIRs(impulseresponses)bundledwiththeirparticularplaybackdevice,andtodownloadotherfreeonesfromtheInternet.(IprovidedalistofsuitablesitesforconvolutionreverbpluginownersinmyrecentroundupofPCFreewareinSOSJuly2004).Whilecapturingyourownimpulseresponsestothestandardofcommerciallibrariesmaybedaunting,it'snotparticularlydifficulttogetrespectableresultswithalittlegear,andyoudon'thavetorestrictyourselftotheusualhalls,churches,andstudioseither.

    Effectspecialistsinthefilm,TV,andvideogamesfieldsarefindingitextremelyusefultocaptureIRsonlocationforuselateronwhenplacingoverdubbeddialogueoreffectsintoarealacousticspace.Moreover,notmanypeoplehavecottonedontothefactthatyoudon'thavetorestrictyourselftoIRsofexistingspacesandgearonceyouabandonrealismandstartconvolvingotheraudiofilesthere'sabizarrenewworldoftreatmentsoutthereforyouraudiotracks.

    ConvolutionInputSignals

    Tocapturethesoundofarealspace,plugin,orhardwareprocessor,youneedasuitabletestsignal.Themostobviousapproachistoplaybackashortimpulsecontainingallfrequencies,sothatyoucanrecordtheresultingresponseacrossthecompleteaudiorangeasingle0dBlevelpulselastingasinglesamplecouldbeused(andI'verecommendedthisinthepastforlisteningtothesmoothnessofreverbtails).Ifyoudon'twanttocartloudspeakersabouttogeneratethispulseinthespaceyouwanttocapture,realworldalternativesincludefiringastartingpistol,poppingaballoon,orinanemergencyevenclappingyourhandsalthoughjudgingbytheresultsI'veachieved,thislatteroptionisofverylimiteduse.

    However,there'sadisadvantageinallthesesignalstheirshortnessresultsinarelativelypoorsignaltonoiseratio.Inmorepracticalterms,thismeansthatthebackgroundnoiseinyourIRswillbehigh.Thebestwayroundthislimitationistoextendthetestsignal,whichiswhymostseriousexperimentersusesomesortofsweptsinewavesignaltypicallylastingtwelvesecondsorso.Tocaptureparticularlynoisyenvironmentssuchasthoseinsidefactories,onboardships/planes,andinsideothervehiclesascleanlyaspossible,youcandoublethisto24seconds,andofcourseswepttonesarealsotheeasiestwaytocapturethesoundofsoftwareplugins,micpreamps,guitaramp/speakercombos,andsoon.

    Somesoftwareconvolutionplaybackdevicesofferafunctiontoconverttheswepttonerecordingsyou'vecapturedintoIRs.TheseincludetheAltiverbIRPreProcessorfromAudioEase,thelatestversionofWavesIR1,andtheonethatstarteditallonthePCsomesixyearsago,SonicFoundry'sAcousticModeler(nowSonyMedia'sAcousticMirror).Suitabletestsignalsmaybebundledwiththesoftware,orareavailableasdownloadablefiles.

    Inthisarticle:ConvolutionInputSignalsLateralThinkingConvolutionEnginesThirdpartyIRFilesCommercialIRCollectionsConvolutionSoftwareReviews

    InSOSPureSpaceIRLibrariesSpectralRelativityIRLibraryWebResourcesKaleidoskopyIRLibraryHints&TipsImpulsePower!

    SoundOnSound:Est.1985

  • 8/6/2015 Convolution Processing with Impulse Responses

    http://www.soundonsound.com/sos/apr05/articles/impulse.htm?print=yes 2/7

    chain,sincethiscanbecapturedentirelywithinasinglesoftwareapplication,asshowninthetopdiagramusingWavelabasanexample.Capturingthesoundofahardwaredeviceisonlyslightlymoredifficult,requiringasoundcardsendreturnlooptobesetup,whilecapturingthesoundofarealacousticspacegenerallyrequiresaloudspeakerandmicrophonecombination,althoughsomeacousticnoisescanalsobeusedinplaceoftheloudspeaker.

    Formorerealisticsampledinstrumentlibraries,Tascam'sGigastudio3usesitsGigapulseconvolutionenginetoprovidePedalUpandDownresonancesforitslatestGigapianoIIlibrary.Youcanalsousethesameconvolutiontechnologytomodeldifferentmicresponses,asshownhere.

    Theycanevenbegeneratedbysomeutilities.Forinstance,forPCusersthere'sVoxengo'sDeconvolver(reviewedinSOSOctober2004),whichisageneric$23utilitywhichcangenerateswepttonetestsignalsthatyoucantransfertoanyaudioplaybackdeviceforuseinthefield.YoucanthenuseanyDATorotheraudiorecordertocapturesuitableresponserecordings,andDeconvolvercanconverttheserecordingsbackintoimpulseresponses.Sincemostpeoplewillendupwithloadsoftestrecordings,therearebatchprocessingoptionsinthesoftwaretoconvertthemallinonehit.

    LateralThinking

    Apartfromtheobviousacousticspaces,youcanalreadyfindquiteafewimpulseresponsescapturedfrommicpreamps,guitaramps,loudspeakers,speakersimulators,tapemachines,andsoon.Thesecanbeagreatwaytoaddsonicinteresttoanotherwiseblandelectronicsound,andtheirtypicallyshortIRsoftenactlikecomplexEQswithresponsesfarmorecomplexthanmostresonatorplugins.

    However,alittlelateralthinkingrevealsthatthereareplentyofothersoundsthatcanbepressedintoservicetoprovideverymusicalresults.Youcouldforinstancecapturetheuniquecollectionofresonancesbelongingtothebodyofanacousticguitarorviolin,orthesympatheticresonancesofapianosoundboard,andapplythemtootherinstrumentsorsounds.Sincetheseresonances'ring'slightlylongerthantheoriginalsound,thiswillalsoimpartsome'timesmearing'towhateveryou'retreating,likeaveryshortreverb.Whilethiswon'tconvertanelectricguitar/pianosoundintoanacousticone,theresultwillcertainlyhavesomeoftheacousticinstrument'scharacteristics,aswellasaddingextralifeandinterest.

    OtherpossiblesourcesforIRsamplingincludetelephonesandhumanspeechingeneral,soyoucangiveonesoundsomeofthecharacteristicsofanotherthiscanbeaveryfruitfulareaforanyoneworkingonfilmorgamesoundtracks,orindeedmusiciansinsearchofnewandexcitingsounds.

    However,youdon'thavetohaveanendresultinmind,andsomeofthemostinterestingresultscanbeachievedifyoucompletelythrowcautiontothewindandloadanyWAVfileintoaconvolutionplugintoactasanIR.Ofcoursetheresultswillbeunpredictable,butforthesonicexperimenterthisisallpartoftheexcitementdrumloopsandsyntharpeggioscanbeturnedintounusualechounitspadsoundsresultindrones,ambientwashes,andbackgroundtexturesandshortfilesprovideexoticcombfiltering.

    Conversely,youcanalsotryloadingimpulseresponsesintovariousotherpluginstoproduceyetmoreoutlandishresults.Candidatesincludevocodersthatcanloadaudiofilesforuseascarrierwaves(suchastheoneinPropellerheadReason,ProsoniqOrangeVocoder,ortheWavesMorphoder),additivesoftwaresynthslikeCamelAudioCameleon5000andWhiteNoiseAdditive,orother'morphing'pluginssuchastheProsoniqMorphVSTplugin.Alloftheseusethecharacteristicsofonesoundasthebasisfortreatinganotherit'snotconvolution,butit'stheresultsthatcount.

    ConvolutionEnginesTherearenowquiteafewconvolutionpluginssupportingdifferentformatsandplatforms,andtherearealsoconvolutionfunctionsbuiltintovariousstandaloneapplicationslikeAdobeAudition,BiasPeak,SteinbergNuendo,andMagixSamplitude.ThereseemstobeafarwiderrangeavailableforPCsthanforMacs,andsomeofthebestareonlyavailableononeformatortheother.Forinstance,AudioEase'AltiverbandAppleSpaceDesignerareonlyavailabletoMacusers,whilethehighlyregardedVoxengoPristineSpaceandTascamGigapulse(andofcoursethefreewareSIR)arePConly.DigidesignProToolsuserswillnodoubtbeinterestedinlookingatTrilliumLabsTLSpace(whichisavailableforbothMacandPC),whileWavesIR1alsocoversbothMacandPC,includingRTASandMASoptions.ProsoniqRayverbisalsocrossplatform,butasmentionedinthemaintestisratherdifferentfromaconvolutionreverb.There'sevenaconvolutionengineavailableforLinuxandUnix(BruteFIR),andafewinnovativeplugins,suchasDelayDots'SpectrumworxandSpectralMorpher,offerconvolutionalongsideotherfrequencydomaineffects.Itseemsthatalmosteverymonthanewconvolutionpluginofsomedescriptionisreleased,aswellasnewupdatesforsomeoftheexistingones.AnuptodatelistthatI'vefoundusefulcanbeseenatSpiritCanyonAudio'swebsite,whichdescribesallthelatestcontendersandwhatplatformstheyeachsupport.Youcanreaditatwww.spiritcanyonaudio.com/convolvers.php.

    ThirdpartyIRFiles

    AlthoughthemoreexpensiveIRhostslikeWaveIR1arebundledwithworldclasslibrariesofreverbresponses,others(likeVoxengo'sPristineSpaceandthefreewarePCutilitySIR,forinstance)comewithnone,tokeepbothcostsanddownloadtimesdown.However,mostusersareinterestedinaddingtotheirIRcollection,andtherearenowquiteafewwebsitesofferingfreelydownloadableIRfilescreatedbyusersmanyofthecommercialconvolutionplugindevelopershostuploadsofferedbytheirusers,andtherearealsositeslikeNoisevaultmaintainedbyenthusiasticusers.

    Sincecapturingtheessenceofrealspacesisquiteanarttodotoahighstandard,themajorityofsuchfilestendtobecapturesofhardwaredevicessuchasreverbsandamplifiers,andtherearesomegemstobefoundifyou'vegotafastmodemandplentyoftime.However,freeIRstendtobeofwildlyvaryingquality,sothereareafewthingstolistenoutforwhenauditioningthemifyouwanttopickoutandusethebest.

  • 8/6/2015 Convolution Processing with Impulse Responses

    http://www.soundonsound.com/sos/apr05/articles/impulse.htm?print=yes 3/7

    Youdon'thavetolimityourselftoreverbwhenusingconvolutionplugins.Anyaudiofilescanbeloadedinasanimpulseresponse,providingavastrangeofcomplexeffects.Hereyoucanseesomeofthe863effectsoftheSpectralRelativitylibrary(reviewedinthisarticle)loadedintothefreewareSIRplugin.

    First,thevastmajorityoffilestendtobe16bit,andallofthesecompromisethedynamicrangeof24bitsignalsbeingtreated.Second,andrathermoreobviousinmanycases,I'venoticedmanysignsofpoorsetup,withhighlevelsofbackgroundnoise,missingreverbtailends,orstillvaguelyaudibletesttonewhines(againmostobviousneartheend).

    CommercialIRCollections

    Althoughtheytookalongtimetoappear,therearenowalsosomeexcellentcommercialthirdpartyIRlibraries,andI'llbelookingatafewofthesefortheremainderofthisarticle.However,beforeyouthinkofinvestinginanyoftheseyoushouldbeawareofvariouspotentialrestrictionstotheiruseifyouwanttoavoidfrustration.

    Forexample,whilethemajorityofuswouldideallylikeauniversalaudiofileformattobeusedforIRs,it'snotsurprisingthatcommercialdeveloperswhobundlehugeIRlibrarieswiththeirconvolutionproductstendtouseavarietyofproprietaryformatsforthemafterall,suchlibrariesareahugeinvestmentoftime,expertise,andmoney,anddevelopersdon'twantthempassedaroundtheglobeforallandsundrytousewithotherproducts.

    Fortunately,mostconvolutionpluginsthatusetheirownIRfileformatcanalsoacceptmorestandardones,whichmakesitfairlyeasytousethemwithcommerciallibraries.ThetwomostwidelyadoptedIRimportformatsareWAVfilesforPCandAIFFfilesforMac.SincemanyMac/PCaudioapplicationsacceptbothofthesefiletypesit'sgenerallyfairlyeasytoconvertlibrariesfromonetotheotherifnecessary,toloadthemintoaparticularconvolutionplugin.AudioEaseAltiverbisslightlymoretricky,sinceitonlyacceptsaleftrightpairofSDII(SoundDesignerIIformat)files,althoughonceagainMacDAWsoftwaresuchasBiasPeak,MOTUDigitalPerformer,andAppleLogicshouldbeabletoperformtheconversionforyou.

    However,afewconvolutionpluginsmightyetgiveunexpectedresultswithcommerciallibraries.Forinstance,whileWaves'IR1hasanexcellentreputationforitsaudioqualityandworldclasslibrary,itcurrentlyrestrictsitsIRstoamaximumofsixsecondsinlength,andsimplytruncatesanylongerresponsesatthispoint.Wavestoldmethiswasbecausemanyhostsdon'tallowreallocationofmemorylateron,soIR1grabssixsecond'sworthwhenit'sinitiallyloadedwhen96kHzstereoIRsaresupported,aswellasmultipleinstancesoftheIR1plugin,thiswaschosenasareasonablecompromise.

    Unfortunately,thisrestrictionwillpreventyoufromusingmanyoftheexcellentresponsesfromthecommercialIRlibrariesreviewedhere,exceptthoseinthedeliberatelyshortercollectionprovidedbyKaleidoskopy.Nuendo'sAcousticStampconvolutionenginesimilarlyhasanarbitrary12secondlimit,althoughthishasfarfewerlibraryimplications.AnotherthingtolookoutforisthattheReversefunctionofTrilliumLane'sTLSpacetruncatesanyIRlongerthanfiveseconds.

    Prosoniq'sRayverbisslightlyunusualinnotbeingastandardconvolutionplayer.Instead,ituses'inverseraytracing'tomodelrealacousticspaces,andprovidescomprehensivecontroloveritsroommodel.Thismakesitextremelyversatileforreverbpurposes,andyoucanstillimportandanalysethirdpartylibraryfiles(althoughbothMacandPCversionsonlyacceptAIFFfiles),buttheywillbeinterpretedbyRayverb'salgorithms,andwillprobablysoundcompletelydifferentfromwhattheirdevelopersoriginallyintended.

    ConvolutionSoftwareReviewsInSOSAudioEaseAltiverb:May2002.

    www.soundonsound.com/sos/may02/articles/altiverb.asp

    DelayDotsSpectrumWorx:August2004.

    www.soundonsound.com/sos/aug04/articles/delaydotsspectworx.htm

    DelayDotsSpektralBundle:PluginFolderJune2002.

    www.soundonsound.com/sos/jun02/articles/plugin0602.asp

    EmagicSpaceDesigner:December2003.

    www.soundonsound.com/sos/dec03/articles/spacedesigner.htm

    ProsoniqRayverb:October2004.

    www.soundonsound.com/sos/Oct04/articles/prosoniqrayverb.htm

    SIR(SuperImpulseResponse):PCMusicianJune2004.

    www.soundonsound.com/sos/jul04/articles/pcmusician.htm

    SonyMediaSoftwareAcousticMirror:January1998.

    www.soundonsound.com/sos/jan98/articles/acoustic.htm

    TascamGigapulse:inTascamGigastudio3reviewJanuary2005.

    www.soundonsound.com/sos/jan05/articles/gigastudio3.htm

    VoxengoPristineSpace:September2004.

    www.soundonsound.com/sos/sep04/articles/voxengo.htm

    WavesIR1:May2004.

    www.soundonsound.com/sos/may04/articles/wavesir1.htm

    PureSpaceIRLibraries

  • 8/6/2015 Convolution Processing with Impulse Responses

    http://www.soundonsound.com/sos/apr05/articles/impulse.htm?print=yes 4/7

    Ifyou'reconsideringbuyingIRlibraries,notallconvolutionplaybackpluginsmaybetotallysuitable.WavesIR1forinstanceonlysupportsresponsesuptosixsecondsinlength,andanylibraryresponselongerthanthiswillbetruncatedasshown.

    ThefirstofthethirdpartyIRlibrariesI'mgoingtolookatcomesfromErnestCholakis,whowillalreadybewellknowntomanymusiciansforhiscreationoftheDNAGrooveTemplates.Hehasbeenexploringreverberationimpulseresponsesforthelasttenyears,andhasalreadyreleasedsampleCD'susingthisextensiveknowledge,includingtheacclaimedDroneArcheology(reviewedinSOSDecember2000).

    EachPureSpaceseriesCDROMcontainsasetofimpulseresponsefilesavailablein16bitat44.1kHzor48kHzsamplerates,orin24bitat44.1,48,88.2,96,176.4,and192kHzforprofessionalsthisimmediatelyplacesthepotentialaudioqualityaboveandbeyondthatofmostotherofferingsfromthirdpartdevelopers.AvailablefileformatsareWAVforthePCandSDIIfortheMAC.

    Usinghisownextensiverecordingsofspacessuchasconcerthalls,cathedrals,monasteries,andeventheambienceinsidetheGreatPyramidKufuatGiza,ErnesthasresynthesisedtheimpulseresponsesinthePureSpacelibraries,whichmeansthattheresultssufferfromnoneofthelimitationsofrealworldrecordingsforinstance,becauseofthewayErnestgenerateshisresponses,the24bitversionsofferadynamicrangeofmorethan140dB,whiletheirfrequencyresponsesarevirtuallyflat,soyoucanEQyoursourcestotastebeforeconvolvingthem.

    TherearecurrentlytwolibrariesavailableClassical&MysticalandFilm&Sacredandeachcontains55impulseresponsescleverlyorganisedinorderofacoustic'size'.Eachresponsehasthreefurthernumbersassociatedwithit,thatcompareitslow,mid,andhighfrequencydecaytimestotheaverageforthatset.Whenyou'relookingforasuitablereverberationimpulseforarecording,thisapproachcanmakealotmoresensethanwadingthroughnameslikeLargeHallorStLuke'sChurchRow42.

    Afterallthiscarefulpreparation,theIRsthemselvescertainlydon'tdisappoint,anddon'trunawaywiththeimpressionthatsincetheyareresynthesisedtheymightsoundunnaturalorlackcharacter.TheseareamongthecleanestandmostsilkysmoothreverbsI'veeverheard,withnoneofthegrittiness,lumpiness,ormetallicovertonesthatcharacterisemanysynthesisedreverbs.Therearesomegorgeoustailsintherewithoodlesofcharacter,andtheyencompassahugerangeofdecay'timbres'.

    Itriedouttheselibrarieswithclosemikedsoloinstruments,vocals,andevenanechoicallyrecordedorchestralsnippets,andwithoutexceptiontheysoundedverynaturalindeed.Therearenosmallrooms(thesmallestspaceintheClassicalserieshasatwosecondtail)buttherearechambers,halls,churches,cathedrals,andmagicalspacesgalore.

    Theseareextremelyprofessionallibrariescontainingworkcreatedovertenyears,andwithpricetagstomatch,rangingfrom$299(16bit),to$399(forthemostpopular24bitversions),to$599forthe24bit/192kHzversion.Thisisstillfarcheaperthanbuyingadecenthardwarereverb(thatstillprobablywon'tsoundasgood),butifyouwanttobuyjustoneofthetwolibrariesIwouldpersonallyoptforthemoreversatileClassical&Mystical,sincethiscontainstheshortestandlongestreverbs(plusloadsinbetween),rangingfromtwoto10seconds,andeachonesoundsquitedifferent.

    SinceErnestsellshisCDsdirectlytotheenduserwww.numericalsound.com,hecangivethemanindividualregistrationnumberand'installerlockcode',whichpreventsthecasualcopierfromunpackingandinstallingthefiles.EachfileontheCDalsoemployshisuniqueSonicTracedigitalwatermarkprotectionsystem,whichencryptstheuser'snameintoeachandeveryreverbimpulse,soitcanbetracedtotheoriginalownerevenwhenusedinmultitrackaudiorecordings.Finally,there'salsoan11pointlicenseagreementtosignbeforeuse,whosetermsmaydismayafewpotentialusers,socheckitoutbeforebuying.Otherthanthat,thePureSpacelibrariesaresuperbresourcesforprofessionals,andwon'tdisappoint.

    SpectralRelativityIRLibrary

    Describedas'exoticambientimpulsesforelectronicmusicians',SpectralRelativityisavast635MBcollectionofover80016bit/44.1kHzfiles.Theyaredeliberatelynotintendedtoproviderealisticreverbs,andalthoughsomecanprovidestrangeandoftenetherealreverbtreatmentswhenusedasimpulseresponses,mostcreatesometimesbizarreandsometimesverybeautifultonalcolours,drones,andambientwashes.

    ThefirstfoldercontainsColors88extremelyshortfilesrangingfromninesamplesto64mS.Theseinvolvepreciouslittletimesmearing,insteadofferingahugerangeofEQs,butwithfarmoreexoticresponsesthansimplecombfilters.Likemostoftheotherimpulsesinthiscollectiontheyarebestused100percentwetformaximumeffect,althoughtherearenorules.

    ThenextfolderisnamedCosmic,andhereweenteraweirdandwonderfulworldofimpulsesthatlastanywhereupto16seconds.Some,likethedeepanddoomladenBlackSun,theplummetingmetallicdronesofSpiralDescent,andhaunting

  • 8/6/2015 Convolution Processing with Impulse Responses

    http://www.soundonsound.com/sos/apr05/articles/impulse.htm?print=yes 5/7

    echoesofNearMiss,couldbedescribedasweirdscifireverbs,whilewithsomeofthelongeronesthetimesmearingbecomessogreatthattheoutputsignalsbecomebarelyrecognisable.

    Theresultsareperfectforambientwashesandbackgroundtextures,andIfoundvocalrecordingstobeparticularlyeffectivesources,asyoucangeneratehauntinghumanlikedrones.Forinstance,HeliopauseandLunarMonolithprovideinspiring2001styleangelicchoirsfromalmostanysourcesignal,whilePlanetaryNebulacreatespitchedmetallicdrones.

    TheFantasy&Fictionfolderevokesimagesfromliteratureandthemedia,withplentyofscifiandfantasyfilmsandbooksmakinganappearance.IparticularlyenjoyedtheshortmetallicsmearsofGomJabbar,themultiplegatedrepeatsofPickledPeppers,andthereverseflangeddronesofSkynet.Horror&Paranormalgivesus,amongmanyothers,thewhisperingAngels&Demons,theeeriehollownessofBurningMan,thelongmoaningofHeartOfDarkness,andthemenacingHidingInTheAttic.

    ThecontentsoftheImpressionsfolderaredesignedtoevokeanimageinthelistener'smind.IfoundthefallingpitchesofBombsAwayquitehauntingwhentreatingcompletesongs,asweretheevenweirderCetaceanMatingCallandthehighpassanimationsofDustInTheGroove.ThosewithdarkerleaningsshouldlovetheIndustrialfolder,includingthepulsingmetallicArmorPlate,thegatednoiseofCrackedPiston,andthepowerofFeelItThroughTheFloor.Isimplyhaven'tgotenoughspacetocovertheremainingMiscellaneousfolders,the102weirdobjectsinthePeriodicTablecollection,the83hightechwashesandfiltersoftheScience&Technologysection,andthe167combinedinhabitantsofWeirdandWeirderStill.

    Iabsolutelylovedthiscollection,andit'sobviouslybeenareallabourofloveforitscreatorDarrenBurgan,evendowntothefilenames.ThedescriptionsofeachtreatmentinthePDFmanualareabsolutelyinvaluableinguidingyoutosuitablecandidates,althoughyou'llneverknowexactlyhowtheysoundwithaparticularsourcesignaluntilyoutryit.It'sgreatifyou'renotfeelingparticularlyinspiredIfounditalmostimpossiblenottobecomecatapultedintocreativitywithinafewminuteseverytimeIusedthislibrary.It'salsoincrediblevalueformoneyatjust$24.99,andanyonewhoownsacompatibleconvolutionreverbpluginshouldmakeittheirdutytobuyitimmediately!

    WebResourcesAcoustics.netisthenewandofficialsourceofIRsfortheWavesIR1range,withlotsofinfoabouthowWaves

    captureandcreatetheirownlibraries,plentyofIR1impulsestodownload,plusauserforum.

    www.acoustics.net

    AudioEaseprovideasimilarresourceforAltiverbusers.

    www.audioease.com

    EchoChamberisaGermansitewithfreeIRdownloads.

    www.memi.com/echochamber/responses

    NoisevaultisthebiggestfreewareIRdownloadsource.Italsohasarticlesoncreatingyourown,andveryhelpfulforums

    http://noisevault.com

    CKSDEhasbothcommerciallibrariesandfreedownloads.

    www.cksde.com

    PureSpaceambientimpulses.

    www.numericalsound.com/purespac.html

    SpiritCanyonAudio'swebsiteishometotheIRlibrariesreviewedinthisfeature,plusarangeoffascinatingfreeReaktorv4ensemblesusedtoprovidesomeoftheirtextures.

    www.spiritcanyonaudio.com

    FokkevanSaane'ssitehaslotsofIRsofeverydayobjectssuchastelephones,buckets,factories,domesticenvironments,andmusichardware.

    www.xs4all.nl/~fokkie/IR.htm

    KaleidoskopyIRLibrary

    ThissecondIRLibraryfromSpiritCanyonAudioisaslightlymoresubtlecollectionthanSpectralRelativity,intendedtobeusefulinawiderrangeofmusicalstyles.Itmanagesthisbyrestrictingitsfilelengthssothattheendresultsaren'tso'smearedout',whichmeansthatpercussivesourceslikedrumsandmostloopsdon'tlosetheirsenseoftiming.Thistimeallthefilesare24bit,whichwillpleaseaudiopuristswhowanttomaintainthemaximumdynamicrangeintheirmusic,andthereare2025ofthemtotalling684MB.

    Ahugeselectionoffilesarespecificallyintendedforuseatcertaintempos,providingexoticbeatsync'edeffects.TheIRsaregroupedintofoldersaccordingtotempo,covering80150bpm,eachfoldercontainingaround90IRs.Toprovidethemaximumrhythmiccompatibility,there'ssomeoverlapbetweenthefoldercontents,withquiteafeweffectsprovidedinmultipleversionstosyncwithmultipletempos.Ifyouwantanevenclosermatchforaspecifictempo,youcanimporttheclosestversionintoyourfavouriteaudioeditorandtimestretchittofitexactly.

    OfthishugesectionofthelibraryIparticularlylikedthefeedbackclusterechoesofLargePrintEdition,thetinklingchimeslinesofBinkertell,andtheguitarhistrionicsofHeavyOnTheHarmonics.Thebeautyofallthese

  • 8/6/2015 Convolution Processing with Impulse Responses

    http://www.soundonsound.com/sos/apr05/articles/impulse.htm?print=yes 6/7

    WeacceptthefollowingpaymentmethodsinourwebShop:

    AllcontentscopyrightSOSPublicationsGroupand/oritslicensors,19852015.Allrightsreserved.

    Thecontentsofthisarticlearesubjecttoworldwidecopyrightprotectionandreproductioninwholeorpart,whethermechanicalorelectronic,isexpresslyforbiddenwithoutthepriorwrittenconsentofthePublishers.GreatcarehasbeentakentoensureaccuracyinthepreparationofthisarticlebutneitherSoundOnSoundLimitednorthepublisherscanbeheldresponsibleforitscontents.

    Theviewsexpressedarethoseofthecontributorsandnotnecessarilythoseofthepublishers.

    Alwaysbearinmindthatwhenusingconvolutionplugins,theirCPUoverheadisdirectlyrelatedtothelengthoftheimpulseresponsehereyoucanseeVoxengo'sPristineSpacetakingjusttwopercentofmyPentiumIV2.8GHzprocessorwitha100mSimpulse,butninepercentwhenrunninga10secondone.

    PublishedinSOSApril2005

    treatmentsisthatwhileyoucanusethem100percentwetforunbelievabletransformations,addingalittleprocessingunderablanddrumloop,forexample,canturnitintosomethingreallyunique.

    Therearefivefoldersdevotedtosingleshoteffects,andineachonethecontentshavebeensubdividedintoshort,medium,andlongIRs,indicatingtheamountoftimesmearing.TheModulatorsaretheshortest,andIparticularlylikedthemachinegunburstof60HzMassage,theswellingchordaldronesofBadYearBlimp,thecartooncoughanddrillingofDon'tLookNow,thebouncingjuddersofLogisticalLogic,thetelephonicechoesofFondlingTheLeadedCrystal,andtheshimmeringmetallicovertonesofTungstenGlow.

    ThemediumandlongReverbfolderscontainsuchgemsastherisingmetallicpitchesofI'mHuntingWabbit,thedistantringingtonesofStainlessSteelBalls,andthepianoclustersofAluminiumDiminished.TheRoomscontainveryshorttailsandevensomevaguelynormalreverbtreatmentssuchasthechimedecaysofMessagesInTheGroundLoopHum,thedistantslapbackofHubcapWallpaper,andthetwintonesofTwelveStoryAtrium.

    ThetimesmearingoftheWeirdfoldersisstillgenerallylessthanonesecond,butthetreatmentsaremoreextreme,withmorepitchshiftingandpanningeffects.IparticularlylikedthetimepiecechimingofAtTheToneItWillBeTwoO'Clock,thehauntingechoesofBrainStemDysfunction,andthedistantcavernsofFloatingCity.

    Overall,whileSpectralRelativityexcelsincreatinglongerdronesandtreatmentsthatareoftenaspringboardforcreativity,Kaleidoskopyseemstoworkbetteratjumpstartingexistingsongsthatneedrejuvenating,sinceyoucangenerallystillrecognisetheoriginalmaterialbeneath,underitsnewsuitofclothes.Kaleidoskopyisjust$34.99,oryoucanbuyitasabundlewithSpectralRelativityforjust$49.99.Togethertheyareatourdeforceofinventivebeautyandweirdness,andshouldbeownedbyanyonewhowantstoexplorenewsonicterritory.

    Hints&Tips

    ThemostimportantgeneralpieceofadviceIcangiveyouaboutusingIRpluginsandtheirlibrariesisthattheCPUoverheadisnearlyalwaysdirectlyrelatedtothelengthoftheresponsebeingused.Thismakessense,sinceeachsampleofincomingaudiomustbeprocessedforthefulllengthoftheconvolution'tail'thelongerthisis,themorecalculationsarebeingcarriedoutatanypointintime.Soifyoudon'twanttorunoutofprocessingpowerinyoursongs,trytokeepyourreverbdecaytimeswithinreason.

    Ifyoufancyhavingagoatcapturingyourownimpulses,eachdeveloperthatoffersasuitableconvolutiontestsignalwillalsogenerallyprovidestepbystepinstructionsonhowbesttouseit,andtherearealsoothermoregeneralguidesontheInternet.Itshouldgowithoutsayingthattocaptureanacousticspaceaccuratelyyouneedtousehighqualitymics,preamps,amplifiers,andspeakerswithaflatfrequencyresponse.Omnidirectionalorcardioidmicresponsesgivethebestresults,althoughanypolarresponseshouldworkreasonablywell.

    Ingeneral,thespeakerthatplaysyoursweepsignal(orthestartingpistol,orballoon,orwhatever)shouldbeplacedwheretheperformerwouldbe,whilethemiccapturingtheacousticresponseshouldbepositionedintheaudience,althoughobviouslytheyareyourimpulseresponsessoyoucanpointthingswhereyoulikewithinreason!Ifyou'vegotamultitrackrecorderandplentyofmicsyoucaneventrycapturingIRsurroundreverbbysimultaneouslyrecordingthesweeptoneatvariousdifferentpositions,andimportingthemintosuitablesurroundconvolutionpluginslikeWavesIR360,VoxengoPristineSpace,orTascamGigapulse.

    ImpulsePower!

    Finally,ifyou'researchingforexotictransformations,don'tforgetthat,justlikeanyotherplugin,youcanchainthosewithconvolutionfunctions.Asingleconvolutionplugincanprovideresultsthatareeitherextremelyrealisticortotallybizarre,soimaginewhattwoorthreeofthemcansoundlikeinseries!

  • 8/6/2015 Convolution Processing with Impulse Responses

    http://www.soundonsound.com/sos/apr05/articles/impulse.htm?print=yes 7/7

    Websitedesigned&maintainedbyPBAssociates|SOS|RelativeMedia


The Convolution Operationsrihari/CSE676/9.1 ConvOperation.pdf · 4.Discrete convolution viewed as matrix multiplication 3. Deep Learning Srihari What is convolution? •Convolution

NonLinear Convolution

Exercices corrigés CONVOLUTION

Convolution Ds248

Convolution ppt

circular shift and convolution [وضع التوافق]site.iugaza.edu.ps/.../2010/02/circular_shift_and_convolution_.pdf · The circular convolution is very similar to normal convolution

SPECTRAL APPROXIMATION OF CONVOLUTION OPERATORS ANDstaff.ustc.edu.cn/~kuanxu/pubs/18conv.pdf · based convolution matrices that approximate Volterra convolution operators de ned by

Introducing Convolution

Convolution 2

Chapter08 Convolution

Convolution Decode

DT Convolution (1A) - Wikimedia · 19.12.2013  · DT Convolution 13 (1A) Convolution Sums in FIR Systems Computing Convolution Sums of an FIR Flip and Slide Form LTI Form Convolution

03 Convolution

Active Convolution, Deformable Convolution ―形状・スケールを学習可能なConvolution―

Convolution theorem

Convolution and Filtering Raed S. Rasheed 2012. Convolution and Filtering – Convolution is the fundamental neighborhood operations of image processing

Convolution Coding

Argaw; Convolution

22.058 - lecture 4, Convolution and Fourier Convolution Convolution Fourier Convolution Outline Review linear imaging model Instrument response function

Convolution Neural Network Computer visionnlp.jbnu.ac.kr/AIJBNU2020/slides/aijbnu2020_cnn.pdf · 2020. 10. 28. · Why Convolution neural network? Input size 224x224 Convolution layer

Convolution Reverb Requirements Document - Weeblyusfconvolutionreverb.weebly.com/uploads/2/4/9/7/24978057/... · Convolution Reverb Requirements ... Project V-IR-Bull’s Convolution

Convolution final slides

4. DSP Theory III - LSV - Universität des Saarlandes Convolution in DFT DFT • In DFT convolution property holds, but in cyclic convolution sense. Q. How to get Linear convolution

Convolution Properties

Mit Convolution

Convolution Fourier Convolution - MIT OpenCourseWare · Convolution Fourier Convolution Outline • Review linear imaging model • Instrument response function vs Point spread function

Convolution - NCKU

Convolution Integral

Convolution Separable

Convolution Soup:

Convolution Graphical

Invariants to convolution

convolution codes

documentneed.comdocumentneed.com/.../2017/02/LP-Signals-and-Systems.docx · Web viewImpulse response representation and properties, Convolution, convolution sum and convolution integral

Introduction to Convolution