「インタラクション，98」平成10年3月

ACOUSTICINDEXING FOR SPOKEN DOCUMENT RETRIEVAL
Gαre妨J．ダ．Joneβ＊
DepartmentofComputerScience，UniversityofExeter，ExeterEX44PT，U．K．
Tel：＋441392264061Fhx：＋441392264067email：gareth4dc8．eX．aC．tik

ABSTRACT

uslngSPeeChrecognitiontechmique8．Unfortunatelyauto−

maticspeechrecognitionisnotcompletelyreliableamdall

Theretrievalofspokendocument＄preSentSneWprOblems
ininformationre七rievalandbrowslng．Thispaperreviews

recentexperimentalresearchintheautomatedretrievalofCu∬ent SPeeChrecognitionsystem＄havetechnicallimita−
tion＄．SDRresearchhasinvestiga七edvariou5apprOaChes

toindexingincl11dingthefollowlng：

SpOkendocumentsandou班nesanoperationalprototype WbrdSpotting：At〟Or4spotting（WS）systemuses
Which demons七rate＄that e鮎ctive vocabulary−，SPeikerL

anddomain−independentspokendocumentretrievalisnow
possible．

SpeeChrecognitionto atもempt toidenti柑occurTenCeS Of
Predefinedkeywordsinspokendocument＄［1】．Recognition
u凱ngthistechniqueisgenerallyquiterelial）1e，butsignif・

icantdrawbacksarethatthekeywordvocabularyistypi−

1．INTRODUCTION

Callylimitedtole＄SthenlOOword＄，andthatalldocuments
mustberecogni＄edagainifancwkeywordisadded．While

Large archive＄Ofdigital1y stored audio and video data
arebecomlnglnCreaLSinglycommon．Locatinginformation

WSmaybeusefulforclas＄i丘cationofdocument＄into丘ⅩCd

withinsuch訂Chive8POSeS neW prOblemsininfbrmation CategOries，itwi1lu＄uauynOtbee鮎ctiveinadhocretrieval
Whereuser8arefreetoformnewsearchrequests．
PhoneLattice Spotting：Anal七ernativeWStech−tionishowtoindexthecontentsofmultimediadoc11mentS．
Thedevelopmentofe侃cientteclmique＄fortheautomatedniqTleisphoneLa摘ce坤0情n9（PLS）【2】・lmPLS asub−
WOrdlatticeintheformofanaCyClic−graPhisconstruCted
retricvalofmultimediadocumentsisparticulaLrlyimpoト

retriev扇andbrowslng．Forexample，afundamentalqucs−

inthemain＄PeeChrecognitionpass．Whenasearchword

tantsincemanualbrowslngOfaudioandvideomaterialis

isenteredthesub−WOrdlatticeisscannedforsub−WOrdunit

ine瓜cientandverytimeconsumlng．

＄equenCeSCOrreSpOndingtothe＄earChword．PLSdoe＄nOt
havethevocabularyconstraintofstandardWS，butrecog−

The development of automated multimedia retrieval
SyStemSreqPre9theintegrationofvariousteclm0logiesin−nitionisgenerallyle8SaCC11rate．

Cludingmultimediahardwareand＄OftwBLre，informationre−
Large Vocabulary Recognition：Laryevoca♭tLLarytrievalandcontentindexing．ManySy＄temShavebeende−
recpgnitLon（LVR）attemptstocompletelytranSCribethe
Velopedforthecapture，prOCeSSlng釘1dreal−timeplayback
COnもentsofaspokendocument．Howeverde＄Pite recent
Ofmultimediadata．Thi＄paperCOnCentrateSOnadvance＄
rapidadvance＄inLVRteclm0logy，thesesystemsstillmake

andongolngreSearChinretrievalteclmologyof＄POkendoc−

ument8andoutlinesanOperationalprototypespokendoc−

mistakesandareunableちOreCOgnlSe WOrdsolltSide their
VOCabulary．Tlmsevenwithavocよbularyof60，000words
manyusefu1＄earChwords，Particularlypropernouns，Will
beoutsidethevocab山訂y．

umentretrieval（SDR）systerh．
2．IN甘ORMATION RETRIEVAI一

Subwofd（n−gram）Indexing：Avocabularyinde−

Informationretrieval（IR）teclmiquesareu＄edtosatisfyapendenttechniqueforspokendocumentindexingi＄tOuSe
user siriformationneedbyretrievlngdocument5fromun− n−gramSequenCeSOfsubwordunits【3］．Fbrretrievaln−

gramsareextractedh・OmthesearChword8enteredbythe
StruCturedconections．Inretrievaltheusertypicallyenter＄
userandmatchedagainstthosefoundinthedocuments．
asearChreque叫inresponse−othi8theIRsystemrettms

asetofpotentiallyrelevantdocuments七akenfromthecol−n−gramindexinglS particularly attractivefor genera．tive

1ection．DependingontheIR8yStemuSed，thesearchre−languagessuchasGerman where newcompound words，Whichwillbeoutsidethevocabul訂y OfanWRsystem，
q11eStmayeitherbeinnatural1anguageorusesomemore
formalBooleanstruCture．In声ddition，theretumeddocu− OCCl汀VeryCOmmOnly．

mentsmayoftenbeusefu11yranked，basedonamatching
SCOrebetweenthe甲Ieryandthedocument，Withthedoc−

umentsjudgedmostlikelytoberelevantatthetopofthe

4．EXPERIMENTAI−STUDIES

Anumberof＄tudieshaveinvestigatedspokendocunentre−

list．Fortextdocumentstheuser，sinformationneedis＄aレ
trieval．Thefir＄treBearCh11SedWSwithatopic−Classification

isfiedslmplybyreadingthereturneddoc11mentSl皿ntilthey techdqTle【1】．A＄yStemSimilartothishasrecentlybeen
findtheinformationtheyarelookingfor．

developedforJapane＄eneWSClassification［4］．TheRrst
projecttoproposetheuseofclassicalinformationretrieval

3．INDEXING SPOKEN DOCUMENTS

teclmiqpesinspokendocument

恥Ⅹtretrievalrepresentsthemost＄traightforwardIRenvi−

retrievalwas【3】，Where

Subwordindexingunits wereused toretrieve Swiss Geト
manneW＄＄tOries．Theu8eOfPLSindexingwa＄PrOpOSedronmentsincethecontent．softbedoc11mentSareaVailable
andinve＄tigatedin［2】．い／Rfor spokendocument re−foranalysis．ForSI）Rthe contentsmustfirstbeindexed

trievilisbeinginvestigatedintheInformediaproject［5］．

Acomparativestudyofautheseindexingtedmiquesha＄●Currently：Visiting Fe1low，R早SearCh and Developmcnt
Center，ToshibaCorporation，1KomukaiTo8hiba−Cho，Saiwai・ beencarriedoutwithintheVideoMailRetrievalprojectat
k叫Kaw鮎aki210，Japam
CambridgeUniversityandORL，Cambridge［6】，inwhich−125−Iparticipated．TheVMRprojectdemonstratedthate鮎c−tivespeaker−independentdomain−independentspokendoc−
umentretrievalispo＄8ible．0ureXperimentalresultsona＄mal1archiveof300voicemai1message＄ShowedSDRper−
formanceusingPLSorLVRofaround80％ofthatachieved
uslngmanualtextindexingofthemessages，andalsothat
COmbiningindexingteclmiquescanresultinimprovement
inretrievalperformancetoar0und90％ofthatfbrtext．
4．1．TRECSpokenDocumentRetrievalTr＆Ck

hterestinSDRhasincreasedgreatlyinrecentyearSand

in1997forthefirst七imeanSDRtrackwasincludedinthe
annualUSNISTTREC（TextREtrievdConftrence）［7］．

Althoughsti11acomparativelysmal1taskwithlessthan

Figure2：Videomai1retrievalGUI

2000documentsintheretrievalcollection，thi占repre8ented
thefir＄t time di鮎rent research6rs have had access to a

COmPOn SDRcollection．For each document the TREC
Organisersprovidedmanualtext transcription8and LVR
tranSCriptionsgeneratedbyIBM．WorkaspartoftheCity
Universitye鮎rt【8】，aPplyingtheIRtedhniquesusedinthe
VMRゝprojecttotheIBMtranSCription＄，Showedthatthe5e

SCaledupsuccessfu11y andp寧rformedwdlincomparison
withre＄ultsobtainedbyother・teamSuSlngeithertheIBM
transcriptionsortheirown＄PeeChrecognitionoutput．
5．THE VIDEO MAIL RETRIEVAI．SYSTEM

VMR U●●rlnt●け■亡●Figure3：Thevideomailbrowser

6．REFERENCES【1】R．C．Rose．釣c加i9ue∫か旬わrm8如n月efr血dJ如m郎0加n〟…叩eβLincohLaboratoryJoumd，4（1），pp45−60，1991【2】D．A．Jame＄．乃eAppLicationqfCta8SicaLIhfbrmation
月efri即8JTbc加ねue∫わ郎0た印加cumenねPbDtbか＄is，CambridgeUmiver8ity，1995

P】U．GlaYit8ChandP．Schjhble．ASy8temhrRetrievin9

Figurel‥Blockdiagramofvideomai1retrievalsystem郎0たen加cu爪印ねProcee血ng80ftbe15tbACMSト
GIRConLbrence，Pp168−176，Copenhagen，1992【4］Y．ArikiandM．SaktJraiCLas8勘atioTtqfNews郎eech
A′rがcJeβ ♭y∬eyword郎○丑山g Proceedimgs ofもbeAcousticalSocictyofJapanand AeousticalSociety
OfAmericaThirdJointMeeting，pPlO15−1020，1996

IntheVMRprojectwedevelopedane鮎ctiveproto− 【5］A．G．Hauptmann

and M．J．Witbrock Ih−

typeSDRapp追cation，describedindetai1in［9］．Figqrel

わrmedねJ〃紺…恥加mqnd〟u損medね坤rm8如nShowsablockdiagramoftheVMRsystem．Theprototype

AcqtJis摘onandRetriet，aL，inlmteuigentMultimedia
InformationRetrieval（ed・M・T．Maybufy），pp215−240，

Sy＄temuSeSOnlyPLSindexing．Whennewme＄SageSarrive
SPeeChrecognitionl＄Performedtogenerateaphonelattice．

Atretrievaltimewhenauserentersaqperythela．tticei8

TheAAAIPress／TheMITPress，1997
P］G．ユ．F．Jones，，．T．Fbote，K．SpartkJones and＄CannedforoccurrenCeSOfeachqueryword．AfterPLSis

COmpleteaquery−me8SagematChingscoreiscomputedfor
eachmessage，andarankedlist ofmessageさisgeneraもed

S・J・YounglRetrievin9郎ohenDoctJment3byCombirl−
ing肌叫〆e血de∬β川「轡Procee血g80fthe19tb
ACMSIGIRConference，PP30−38，Z血ch，1996【7］D・K・HarmanandE・M・Voo血ees（editor＄）JneS血thanddisplayedtotheu5erintheinterfaceshowninFigtlre

飛∬亡月βfrie川JCo一重renc8「mβαりGaither砧wg，

2．

Sincebrowslngbylistening to complete＄pOkenmes−

SageSfromthebeginnmg18Verytimeconsum）ngWede−

MD，NIST，1998［8］S．Walker，S．E．Robertson，M．Bo11ghanem，G．J．F．

Velopedagraphicalbrowserapplication，ShowninFigure
3．A me88agei8repreSentedas horizontaltimeline，andrecognised＄earChternsaredisplayedgraphicallyalongit．

Jonesand KISparckJones．Okapiat TREC−6：atL−ねmd如dd九叫yエC，rOU如仇β鮎ri叩αndQβか月in【7】【9］M．GBrown，J．T．Foote，G．J．F．Jone8，K．SparckJones

Theu＄erCanStart meSSagePlaybackatanytlmesimply

by・Clickingatthedesiredpointinthetimebar；thi8lets

andS．J．Ybung QpeTl・V♭cobtLtary郎eech九de3in9for

theu＄erSelectivelyplayreg）OnSOfintere＄t，raもherthanthe
entiremessage・

Multimedia，PP307−316，Boston，1996

ー126−

VbLcemdⅥdeoMaiLRetriet］aLProceeding＄OfACM