PRACTICAL SPEECH USER INTERFACE DESIGN

Transcription

1 ; ; : : : : ; : ; PRACTICAL SPEECH USER INTERFACE DESIGN й fail James R. Lewis. CRC Press Taylor &. Francis Group Boca Raton London New York CRC Press is an imprint of the Taylor & Francis Group, an informa business

2 Contents Foreword Preface Acknowledgments The Author xi xiii xv xvii 1 Introduction 1 Foundations of Speech User Interface Design 1 A Focus on Research-Based Design Guidance 2 Organization of this Book 3 Summary 4 References 4 2 Speech Technologies 7 Speech Recognition 7 Finite State Grammars 8 VoiceXML 11 Statistical Language Models 14 Statistical Action Classification 14 Statistical Parsing 15 Dialog Management 16 Confidence and N-Best Lists 17 Detection of Emotion 17 Speech Production 18 Formant Text-to-Speech 18 Concatenative Text-to-Speech 19 Expressive Speech Production 19 The Components of Satisfaction with Speech Output 20 Recorded Speech Segments 20 Speech Biometrics 21 Summary 22 References 23 3 Key Concepts in Human Language and Communication 27 Implicit Linguistic Knowledge 27 Phonology 28 Coarticulation 29 Prosody 31 Conversational Discourse 32 Conversational Maxims 34 Grammaticality 36 v

3 vi Contents Discourse Markers 38 Timing and Turntaking 40 Social Considerations in Conversation 41 Summary 44 References 45 4 Self-Service Technologies 49 Service Science 49 Call Centers 51 Technology Acceptance and Readiness 53 Satisfaction with and Adoption of SSTs 57 Relationship of IVR to Other SSTs 60 Waiting for Service 62 Service Recovery 71 Consequences of Forced Use of SSTs 73 Summary 74 References 76 5 The Importance of Speech User Interface Design 81 User Acceptance of Speech IVR Applications 81 Market Research 81 Agent and Channel Costs 83 Scientific Research 84 Location on the "Hype Cycle" 85 The Disciplines of SUI Design and the SUI Design Team 87 The Consumers of SUI Design 88 Major SUI Objectives 89 The Components of SUI Usability 89 The Power of the SUI 90 Summary 90 References 91 6 Speech User Interface Development Methodology 93 Concept Phase 94 Requirements Phase 94 Analyzing Users 94 Analyzing User Tasks 99 Design Phase 102 Developing the Conceptual Design 103 Making High-Level Decisions 104 Making Low-Level Decisions 104 Defining the High-Level Call Flow 104 Creating the Detailed Dialog Specification 105 Prototyping 105 Development Phase 106

4 Contents vii Test Phase 107 System Verification and Customer Acceptance Tests 107 Grammar Testing 107 Dealing with Recognition Problems 112 Usability Testing 113 Automated SUI Usability Testing Methods 117 Deployment Phase 119 Tuning Phase 119 Surveys 120 Call Log Analysis 120 End-to-End Call Monitoring 122 Sample Design Documents 122 High-Level Call Flow 123 Detailed Dialog Specification (DDS) 124 Scenarios Derived from Detailed Dialog Specification 157 Recording Manifest 157 Availability of Sample Design Documents 158 Summary 159 References Getting Started: High-Level Design Decisions 169 Choosing the Barge-In Style 169 Lombard Speech and the "Stuttering Effect" 170 Comparing Barge-In Detection Methods 170 Selecting Recorded Prompts or Synthesized Speech 171 Creating Recorded Prompts 171 Using TTS Prompts 173 SUI Personality and Persona 177 Deciding Whether to Use Audio Formatting 180 Using Simple or Complex Speech Recognition 181 Evaluating the Need for Complex Speech Recognition 182 Flattening Menus 182 Flattening Forms 183 Adopting a Concise or Verbose Prompt Style 184 Allowing Only Speech Input or Speech plus Touchtone 185 Choosing a Set of Global Navigation Commands 186 Go Back 187 Exit 188 Using the Global Commands 189 Deciding Whether to Use Human Agents in the Deployed System Designing for In-Hours and After-Hours Operation 191 Managing Early Requests for and Transfers to an Agent 191 Choosing a Help Mode or Self-Revealing Contextual Help 193 Maximizing the Benefits of Self-Revealing Contextual Help 193

5 viii Contents Implementing Self-Revealing Contextual Help 193 Bailing Out 194 Summary 195 References Getting Specific: Low-Level Design Decisions 201 Creating Introductions 201 Welcome (Required) 202 Language Selection (Optional) 203 Purpose (Optional) 204 Short List of Global Commands (Optional) 204 Interrupt at Any Time (Optional) 204 Let's Get Started (Optional) 205 Initial Prompt (Required) 205 Putting It All Together 205 Avoiding Poor Practices in Introductions 206 Web Deflection Messages 206 Sales Pitches 207 Prompts for Touchtone versus Speech 208 Your Call Is Important to Us 208 Please Listen Carefully as Our Options Have Changed 208 This Call May Be Monitored or Recorded 209 Getting the Right Timing 209 Research on Turntaking Behaviors in Speech Recognition IVRs Setting the Noinput Timeout Value 211 Timing Pauses between Menu Items 212 Timing Pauses between Prompts and Prompt Extensions 215 Managing Processing Time 219 Designing Dialogs 221 Writing Directive Prompts 222 Making Nondirective Prompts Usable 223 Mixed-Mode Prompting 228 "Press or Say <X>" Prompting 230 Constructing Appropriate Menus and Prompts 231 Optimal Menu Length 232 Grouping Menu Items 240 Minimizing Error Declarations 240 Avoiding Touchtone-Style Prompts 241 Choosing a Complex Alternative 241 Crafting Effective Prompts 242 Managing Digressions 244 Stepping Stones and Safety Nets 246 Tips for Voice Spelling 247 Confirming User Input 251

6 Contents ix Implicit Confirmation 252 Explicit Confirmation 253 Immediate Explicit Confirmation: Separate Dialog Turns 254 Skip Lists 254 Delayed (Batch) Explicit Confirmation: Basic 254 Delayed (Batch) Explicit Confirmation: Improved 255 Comparison of Confirmation Strategies 257 Refining Confirmation and Error Correction with Confidence Levels and N-Best Lists 258 Summary 260 References From "Hello World" to "The Planets": Prototyping SUI Designs with VoiceXML 269 Sample 1: Hello World! 270 Some VoiceXML Concepts 270 Sample 2: Hello Worlds 271 Sample 3. Adding More Complex Features to Hello Worlds 274 Playing an Introduction Once 274 Defining Always-Active Commands with Links 278 Using Grammar Tags to Classify Responses 279 Setting Variables to Document-Level Scope 280 Directing the Call Flow with If Statements in the Filled Section Using the Document-Level Variables and Unconditional Return to the Main Menu 281 Exiting without Confirmation 282 Sample 4. Even More Features 283 Creating Self-Revealing Help 283 Defining an Unconditional Go Back 284 Defining a Conditional Go Back 286 Exiting with Confirmation 286 Integrating Audio Tones 289 Simulating Data Acquisition from a Backend Server 289 Playing the Data 290 Using Breaks to Fine-Tune Timing 292 Using Recorded Speech 310 Replacing TTS with Recorded Speech 310 Editing Recorded Audio Segments 310 Dynamic Selection of Audio Segments 310 Using an Application Root Document 312 Summary 312 References 313

7 X Contents 10 Final Words 315 I Appreciate Your Patience 315 Please Hold for the Next Available Research 315 Thanks for Reading, Goodbye! 317 Index 319