Table Of ContentSPRINGER BRIEFS IN ELECTRICAL AND
COMPUTER ENGINEERING SPEECH TECHNOLOGY
K. Sreenivasa Rao
N. P. Narendra
Source Modeling
Techniques for Quality
Enhancement in
Statistical Parametric
Speech Synthesis
123
SpringerBriefs in Speech Technology
Studies in Speech Signal Processing, Natural Language
Understanding, and Machine Learning
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K. Sreenivasa Rao • N. P. Narendra
Source Modeling Techniques
for Quality Enhancement
in Statistical Parametric
Speech Synthesis
123
K.SreenivasaRao N.P.Narendra
DepartmentofComputerScienceand AaltoUniversity
Engineering Espoo,Finland
IndianInstituteofTechnologyKharagpur
Kharagpur,WestBengal,India
ISSN2191-737X ISSN2191-7388 (electronic)
SpringerBriefsinSpeechTechnology
ISBN978-3-030-02758-2 ISBN978-3-030-02759-9 (eBook)
https://doi.org/10.1007/978-3-030-02759-9
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Preface
Speechisthemostnaturalwayforhumanstocommunicatewitheachother.Synthe-
sis of artificial human speech provides efficient human-computer communication.
Nowadays, the speech synthesis systems are widely used in various applications
such as screen readers for visually challenged people, speech interface for mobile
devices,navigation,andpersonalguidancegadgets.Ashumansareverysensitivein
perceiving even the slightest distortions in the speech signal, speech synthesizers
with suboptimal quality make them unfit for usage in commercial applications.
The main goal of this book is to improve the quality of statistical parametric
speech synthesis (SPSS) by efficiently modeling the source or excitation signal.
The excitation signal used in synthesis should preserve all natural variations so
that the synthesized speech is close to natural quality. The work presented in this
bookconfinesitsscopetothe(1)accurateestimationofpitch(F )and(2)precise
0
modeling of excitation signal. For modeling the excitation signal, both parametric
andhybridapproachesareexplored.Inthiswork,creakyvoicehasbeensynthesized
atappropriateplacesbyproposingappropriatemethodsandmodels.
Thecontentsofthebookareusefulforbothresearchersandsystemdevelopers.
For researchers, the book will be useful for knowing the current state-of-the-
art excitation source models for SPSS and further refining the source models
to incorporate the realistic semantics present in the text. For system developers,
the book will be useful to integrate the sophisticated excitation source models
mentioned in the book to the latest models of mobile/smart phones. The book has
beenorganizedasfollows:
• Chapter 1 introduces the topic of text-to-speech synthesis. Different speech
synthesisapproachesarebrieflydiscussed.
• Chapter2providesareviewofthestate-of-the-artmethodsforF0estimationand
parametricandhybridsourcemodelingapproaches.
• Chapter3discussesthedesignofavoicingdetectionandF estimationmethod
0
by adaptively choosing appropriate window size for zero-frequency filtering
method.
• Chapter4presentstwoparametricsourcemodelingmethods.
v
vi Preface
• Chapter 5 describes two proposed hybrid methods of modeling the excitation
signal.
• Chapter 6 deals with the generation of creaky voice by addressing two main
issues, namely, automatic detection of creaky voice and source modeling of
creakyvoice.
• Chapter7summarizesthecontributionsofthebookalongwithsomeimportant
conclusions. Directions toward the scope for possible future work are also
discussed.
WewouldespeciallyliketothankallprofessorsoftheDepartmentofComputer
Science and Engineering, IIT Kharagpur, for their consistent support during the
course of editing and organization of the book. Special thanks to our colleagues
at Indian Institute of Technology, Kharagpur, India, for their cooperation to carry
outthework.Wearegratefultoourparentsandfamilymembersfortheirconstant
supportandencouragement.Finally,wethankallourfriendsandwell-wishers.
Kharagpur,India K.SreenivasaRao
Espoo,Finland N.P.Narendra
Contents
1 Introduction .................................................................. 1
1.1 Introduction ............................................................. 1
1.2 SpeechSynthesisMethods ............................................. 2
1.2.1 FormantSynthesis.............................................. 2
1.2.2 ArticulatorySynthesis.......................................... 3
1.2.3 ConcatenativeSynthesis........................................ 3
1.2.4 StatisticalParametricSpeechSynthesis ....................... 4
1.2.5 HybridSynthesisMethods ..................................... 5
1.3 ObjectivesandScopeoftheWork ..................................... 5
1.4 ContributionsoftheBook.............................................. 6
1.4.1 RobustVoicingDetectionandF EstimationMethod........ 6
0
1.4.2 ParametricApproachofModelingtheExcitationSignal..... 7
1.4.3 HybridApproachofModelingtheExcitationSignal......... 7
1.4.4 GenerationofCreakyVoice.................................... 7
1.5 OrganizationoftheBook............................................... 8
References..................................................................... 9
2 BackgroundandLiteratureReview ....................................... 11
2.1 HMM-BasedSpeechSynthesis......................................... 11
2.1.1 HiddenMarkovModel ......................................... 12
2.1.2 SystemOverview............................................... 14
2.1.3 DurationModeling.............................................. 15
2.1.4 DecisionTree-BasedContextClustering...................... 15
2.1.5 Synthesis ........................................................ 16
2.2 VoicingDetectionandF Estimation:AReview...................... 16
0
2.3 SourceModelingApproaches:AReview.............................. 19
2.4 GenerationofCreakyVoice:AReview................................ 22
2.5 Summary ................................................................ 24
References..................................................................... 25
vii
viii Contents
3 RobustVoicingDetectionandF EstimationMethod................... 29
0
3.1 F ModelingandGenerationinHTS .................................. 29
0
3.2 ProposedMethodforVoicingDetectionandF Estimation.......... 30
0
3.2.1 Zero-FrequencyFilteringMethodforDetectingthe
InstantsofSignificantExcitation .............................. 31
3.2.2 VoicingDetection............................................... 32
3.2.3 InfluenceofWindowSizeontheStrengthofExcitation ..... 34
3.2.4 F Estimation................................................... 38
0
3.2.5 PerformanceEvaluation........................................ 40
3.3 ImplementationoftheProposedVoicingDetectionandF
0
ExtractioninHTSFramework ......................................... 43
3.4 Evaluation ............................................................... 45
3.4.1 EvaluationofVoicingDetection............................... 46
3.4.2 SubjectiveEvaluation........................................... 48
3.5 Summary ................................................................ 50
References..................................................................... 51
4 ParametricApproachofModelingtheSourceSignal ................... 53
4.1 Parametric Source Modeling Method Based on Principal
ComponentAnalysis.................................................... 53
4.1.1 GenerationofPitch-SynchronousResidualFrames........... 53
4.1.2 ParameterizationofResidualFrameUsingPCA.............. 55
4.1.3 SpeechSynthesisUsingtheProposedPCA-Based
ParametricSourceModel....................................... 57
4.1.4 Evaluation....................................................... 58
4.2 Parametric Source Modeling Method Based on the
DeterministicandNoiseComponentsofResidualFrames ........... 60
4.2.1 AnalysisofCharacteristicsofResidualFrames............... 60
4.2.2 OverviewofProposedParametricSourceModel............. 62
4.2.3 ParameterizationofDeterministicComponent................ 63
4.2.4 ParameterizationofNoiseComponent ........................ 64
4.2.5 SpeechSynthesisUsingtheProposedDeterministic
andNoiseComponent-BasedParametricSourceModel ..... 66
4.2.6 Evaluation....................................................... 67
4.3 Summary ................................................................ 71
References..................................................................... 73
5 HybridApproachofModelingtheSourceSignal........................ 75
5.1 OptimalResidualFrame-BasedHybridSourceModelingMethod... 75
5.1.1 ComputationofOptimalResidualFrameforaPhone........ 75
5.1.2 ClusteringtheOptimalResidualFrames ...................... 77
5.1.3 Speech Synthesis Using the Proposed Optimal
ResidualFrame-BasedHybridSourceModel................. 78
5.1.4 Evaluation....................................................... 80
Contents ix
5.2 Time-DomainDeterministicPlusNoiseModel-BasedHybrid
SourceModel............................................................ 82
5.2.1 DecompositionofDeterministicandNoiseComponents..... 88
5.2.2 ClusteringtheDeterministicComponents..................... 88
5.2.3 StoringNaturalInstanceofNoiseSignalAlongwith
theDeterministicComponent.................................. 89
5.2.4 ParameterizingtheNoiseComponents........................ 90
5.2.5 SpeechSynthesisUsingtheProposedTime-Domain
DeterministicPlusNoiseModel-BasedHybridSource
Model............................................................ 91
5.2.6 Evaluation....................................................... 93
5.2.7 Discussion....................................................... 100
5.3 Summary ................................................................ 102
References..................................................................... 103
6 GenerationofCreakyVoice................................................. 105
6.1 HMM-BasedSpeechSynthesisSystemforGeneratingModal
andCreakyVoices ...................................................... 105
6.2 AutomaticDetectionofCreakyVoice ................................. 107
6.2.1 AnalysisofEpochParameters ................................. 108
6.2.2 ComputationofVarianceofEpochParameters ............... 110
6.2.3 ClassificationUsingVarianceofEpochParameters .......... 111
6.2.4 PerformanceEvaluation........................................ 111
6.3 HybridSourceModelforGeneratingCreakyExcitation ............. 115
6.3.1 GenerationofCreakyResidualFrames........................ 117
6.3.2 DeterministicPlusNoiseDecompositionforEvery
PhoneticClass .................................................. 118
6.3.3 SynthesisofCreakyVoiceUsingProposedHybrid
SourceModel ................................................... 119
6.3.4 Evaluation....................................................... 120
6.3.5 Discussion....................................................... 122
6.4 Summary ................................................................ 123
References..................................................................... 123
7 SummaryandConclusions ................................................. 125
7.1 SummaryoftheBook................................................... 125
7.2 ContributionsoftheBook.............................................. 127
7.3 DirectionsforFutureWork............................................. 128
References..................................................................... 128
Index............................................................................... 131
