Spherical Microphone Array Processing for Acoustic Parameter Estimation and Signal Enhancement

177 Pages·2013·16.84 MB·English

by  D. P. Jarrett

Spherical Microphone Array Processing
for Acoustic Parameter Estimation
and Signal Enhancement
by
Daniel P. Jarrett
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Copyright declaration
ThecopyrightofthisthesisrestswiththeauthorandismadeavailableunderaCreative
CommonsAttributionNon-CommercialNoDerivatives licence. Researchersarefreeto
copy,distributeortransmitthethesisontheconditionthattheyattributeit,thattheydo
notuseitforcommercialpurposesandthattheydonotalter,transformorbuilduponit.
Foranyreuseorredistribution,researchersmustmakecleartoothersthelicenceterms
ofthiswork.

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Statement of originality
Ideclarethatthisthesisandtheresearchtowhichitrefersaretheproductofmyown
workundertheguidanceandsupervisionofDrEmanuëlA.P.Habetsandmythesis
supervisorDrPatrickA.Naylor. Anyideasorquotationsfromtheworkofothers,
publishedorotherwise,arefullyacknowledgedinaccordancewithstandardreferencing
practice. Thematerialofthisthesishasnotbeenacceptedforanydegree,andhasnot
beenconcurrentlysubmittedfortheawardofanyotherdegree.

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Abstract
Inmanydistantspeechacquisitionscenarios,suchashands-freetelephonyorteleconfer-
encing,thedesiredspeechsignaliscorruptedbynoiseandreverberation. Thisdegrades
boththespeechqualityandintelligibility,makingcommunicationdifficultorevenim-
possible. Speechenhancementtechniquesseektomitigatetheseeffectsandextractthe
desiredspeechsignal.
Thisobjectiveiscommonlyachievedthroughtheuseofmicrophonearrays,which
takeadvantageofthespatialpropertiesofthesoundfieldinordertoreducenoiseand
reverberation. Sphericalmicrophonearrays,wherethemicrophonesarearrangedina
sphericalconfiguration,usuallymountedonarigidbaffle,areabletoanalyzethesound
fieldinthreedimensions;thecapturedsoundfieldcanthenbeefficientlydescribedin
thesphericalharmonicdomain(SHD).
Inthisthesis,anumberofnovelsphericalarrayprocessingalgorithmsareproposed,
basedintheSHD.Inordertocomprehensivelyevaluatethesealgorithmsunderavariety
of conditions, a method is developed for simulating the acoustic impulse responses
betweenasoundsourceandmicrophonespositionedonarigidsphericalarrayplaced
inareverberantenvironment.
Theperformanceofspeechenhancementalgorithmscanoftenbeimprovedbytaking
advantageofadditionalaprioriinformation,obtainedbyestimatingvariousacoustic
parameters. Methodsforestimatingtwosuchparameters,thedirectionofarrival(DOA)
ofasource(staticormoving)andthesignal-to-diffuseenergyratio,areintroduced.
8 Abstract
Finally,thesignalsreceivedbyamicrophonearraycanbefilteredandsummedby
abeamformer. Atradeoffbeamformerisproposed,whichachievesabalancebetween
speechdistortionandnoisereduction. Thebeamformerweightsdependonthenoise
statistics,whichcannotbedirectlyobservedandmustbeestimated. Anestimationalgo-
rithmisdevelopedforthispurpose,exploitingtheDOAestimatespreviouslyobtained
todifferentiatebetweendesiredandinterferingcoherentsources.
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Acknowledgements
Firstandforemost,Iwouldliketothankmysupervisor,PatrickNaylor,forencour-
agingmetoundertakethisPhD.Inaddition,Iamthankfulforhissupport,guidance
andoptimismthroughoutmytimeasaPhDstudent. Iwouldalsoliketoexpressmy
appreciationtoEmanuëlHabetsforhissupervision,adviceandrelentlessattentionto
detail,aswellashiswillingnesstogivehistimesogenerously. DuringmyPhDIspent
fourmonthsatInternationalAudioLaboratoriesErlangen,andIamgratefultoEmanuël
forthisopportunity. IthankmyfriendsandcollaboratorsMarkThomasandNikolay
Gaubitchfortheirhelpwithmyresearch.
Inaddition,IwouldliketothankmyfriendsandcolleaguesintheCommunications
&SignalProcessing group,including Felicia,James,Jason,Marco,SiraandZiggy,
andmyfriendsoutsidetheoffice,inparticularBenoît,Letizia,Lise,Marine,Nicolas,
Pietro, Quentin and Sophie, for making my time as a PhD student more fun and
keepingmyspiritshigh. Iwouldliketooffermyspecialthankstomyparentsandsister
forenduringthisprocesswithme,andfortheirloveandmoralsupport.
Finally, I would like to acknowledge the financial support of the Engineering and
PhysicalSciencesResearchCouncil(EPSRC)intheformofaDoctoralTrainingGrant.
DanielJarrett