Chapter 1 Introduction 1.1 Research background 1.2 Purpose of the study 1.3 Significance of the study 1.4 Research questions and hypotheses Chapter 2 Literature review 2.1 Articulation and acoustics of obstruents 2.1.1 Articulation of obstruents 2.1.2 Acoustics of obstruents 2.2 Theoretical frameworks 2.2.1 Theories on the phonological acquisition order 2.2.2 Theories on discontinuity and continuity 2.3 Previous studies 2.3.1 Studies related to the phonological acquisition order 2.3.2 Studies related to continuity and discontinuity of speech development 2.4 Summary Chapter 3 Experiment one��Stops 3.1 Methodology 3.1.1 Participants 3.1.2 Materials 3.1.3 Procedures 3.1.4 Transcription analysis 3.1.5 Acoustic analysis 3.1.6 Statistical analysis 3.2 Results 3.2.1 Acoustic properties of stops 3.2.2 Acquisition order suggested by transcription analysis 3.2.3 Acquisition order and issue of continuity suggested by acoustic analysis 3.3 Discussion 3.3.1 Acoustic properties of stops 3.3.2 Acquisition order of stops 3.3.3 Issue of continuity 3.4 Summary Chapter 4 Experiment two��Fricatives 4.1 Methodology 4.1.1 Participants 4.1.2 Materials 4.1.3 Procedures 4.1.4 Transcription analysis 4.1.5 Acoustic analysis 4.1.6 Statistical analysis 4.2 Results 4.2.1 Acoustic properties of fricatives 4.2.2 Acquisition order suggested by transcription analysis 4.2.3 Acquisition order and issue of continuity suggested by acoustic analysis 4.3 Discussion 4.3.1 Acoustic properties of fricatives