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An important point…

An important point…

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An important point…

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  1. An important point… • When discussing source-filter theory, the sound source was the glottal spectrum • When discussing stops (and fricatives and affricates), we introduce a new sound source, noise produced within the oral cavity • However, source-filter theory still holds even though the sound source is different…the vocal tract still filters the sound source, whether it is the complex periodic signal from vocal fold vibration, or a transient aperiodic signal produced during a stop release

  2. Unit 4The Articulatory System II • The Diphthongs • The Glides • The Liquids • The Stops • The Fricatives • The Affricates • The Nasals

  3. Fricatives • Place • Labiodental /f/ /v/ • Interdental // // • Alveolar /s/ /z/ • Palatal // // • Glottal /h/ • Voicing • Voiced /v/ // /z/ // • Voiceless /f/ // /s/ // /h/

  4. Fricatives • Manner of production • severe vocal tract constriction • Air pressure behind constriction builds up • Air flow through the constricted path is very high • At a critical point, the airflow becomes turbulent • Turbulent flow is heard as noise – frication

  5. Fricatives • Aerodynamics • Airflow for vowels is laminar – molecules are moving along in an orderly fashion (like the flow of water in a river or cars on the freeway) • Airflow for fricatives is turbulent – molecules are moving is a disorderly way – (like the eddies of water when a large rock impedes the river’s flow)

  6. Fricatives • The physics of turbulence • For a given constriction/obstruction, there is a critical flow velocity above which turbulence occurs -Reynolds number

  7. Fricatives Equation for turbulence Re= V*h/ • Re: Reynolds number • V: flow velocity • : kinematic coefficient of viscosity (.15 cm/sec for air) • h: characteristic dimension (size of constriction) • Critical Re for speech ~1800

  8. Fricatives • In theory, the spectral characteristics of “white” noise, which has all frequencies in equal amplitude • sound source characteristics should be the same regardless of place of articulation

  9. Fricative source spectrum Amplitude Frequency

  10. Fricatives • Question… • How do we distinguish different fricatives if the sound source is the same?

  11. Fricatives • Answer… • The transfer function of the vocal tract will shape the otherwise flat spectrum

  12. Fricative: Vocal tract features

  13. Fricative: Vocal tract features • Vocal tract has • a back cavity (behind the constriction) • a front cavity (in front of the constriction) • Front cavity plays a more important role in shaping the fricative spectrum • Longer the front cavity the lower the resonant frequencies

  14. Fricatives: • Labiodental/interdental • very short front cavities = very high resonant frequencies • Practically, there is little effect on shaping the noise energy • Low energy diffuse spectrum

  15. Labiodental /f/

  16. Fricatives: • Alveolar • front cavity length ~ 2.5 cm • F1=34000/4*2.5 = 3400 Hz • Intense energy at/above 3400 Hz

  17. Alveolar /s/

  18. Fricatives: • Palatal • front cavity length longer than for /s/ • Intense energy around 2000 Hz • Lip rounding increases front cavity length and helps to reduce the frequency of the prominent energy

  19. Palatal //

  20. // vs. /s/ /s/ //

  21. Fricatives: • Glottal • Spectrum shaped by whole vocal tract • Low energy diffuse noise with apparent vowel-like formant values

  22. Glottal /h/

  23. Voiced/voiceless distinction • Voiced fricative have two simultaneous sound sources • Glottal sound source (voicing) • Frication (noise) • Both sound sources are shaped by the vocal tract shape • Voiced fricatives will have low frequency energy in the spectrograph (voice bar)

  24. /z/ /s/

  25. /z/ /s/

  26. /s/ /z/ // // - The stridents • These fricatives have much greater energy when compared to others • Teeth serve as an obstacle to the airflow, which increases the turbulence and amplitude of the noise energy

  27. Transitions • Formant transitions also play a role in fricative identity • More prominent cue for “weak” fricatives such as /f/ and // since energy for these is typically low and diffuse

  28. Unit 4The Articulatory System II • The Diphthongs • The Glides • The Liquids • The Stops • The Fricatives • The Affricates • The Nasals

  29. Affricates • Place: • palatal (/t/, /d/) • Voicing: • Voiceless (/t/) • Voiced (/d/)

  30. Affricates • Manner of production • Features of both stop and fricative • Vocal tract occlusion • Release from occlusion into a severe constriction • Spectral features of // • “Rise-time” of burst differs for stop and affricates

  31. Affricate Silent gap frication /t/

  32. Rise-time: stops vs. affricates /t/ /t/

  33. Nasal • Place • Bilabial /m/ • Alveolar /n/ • Velar // • Manner of production • Velopharyngeal port is open • Oral cavity is closed • Sound source: glottal spectrum

  34. Nasals • Distinct vocal tract configuration Nasal cavity (open) Oral cavity (closed) Pharyngeal cavity

  35. Nasal • Acoustically, nasals are characterized by • Antiformants • Nasal formant

  36. Nasal • Closed oral cavity produces antiformants in the transfer function • Antiformants are regions where energy is damped • Location of antiformants is related to place of articulation • As place of articulation moves back, the frequency of the anti-formant increases

  37. Nasals • /m/:antiformants 750-1200 Hz • /n/: antiformants 1450-2200 Hz • //: antiformants > 3000 Hz

  38. Nasals • Nasal formant • Strong low frequency band 250-500 Hz • Most prominent acoustic feature of nasals

  39. Nasals • Have formant transitions similar to oral stops Initial position • Bilabial-rising F1 and F2 • Alveolar-rising F1 and dropping F2 • Velar-F2 and F3 “C” shaped

  40. Nasals bilabial alveolar velar

  41. XI. THE NASALS A. Define an antiformant and how their values change with place of articulation. B. Draw the vocal tract configuration for a nasal. C. What is a nasal formant?

  42. Outline: Articulation I. THE VOCAL TRACT II. SOURCE FILTER THEORY OF SPEECH PRODUCTION III. CAPTURING SPEECH DYNAMICS IV. THE VOWELS V. THE DIPHTHONGS VI. THE GLIDES VII. THE LIQUIDS VIII. THE STOPS IX. THE FRICATIVES X. THE AFFRICATES XI. THE NASALS XII. PUTTING IT ALL TOGETHER: STUDYING CONNECTED SPEECH PROCESSES

  43. Name those acoustic events!

  44. XII. PUTTING IT ALL TOGETHER: STUDYING CONNECTED SPEECH PROCESSES A.Identify how coarticulatory processes may be revealed in speech-related signals. B. Distinguish between the phonetic properties of speech and suprasegmental features of speech. C.Identify and describe suprasegmental properties of speech. D.Identify some key “problems” features that speech production theories must address. E. Describe how speech disorders may be revealed in articulatory processes.

  45. What is coarticulation?

  46. What is coarticulation? • “An event in speech production in which adjustments of the speech production system are made simultaneously for two or more speech sounds” (Kent)

  47. What is coarticulation? • In other words, the features of speech elements will vary depending upon the context in which they are produced

  48. Terms used that refer to this general concept • Coarticulation • Coproduction • Contextual variation

  49. Kinds of coarticulation • A speech event can be influenced by a previous event OR • A speech event can be influenced by an upcoming event

  50. Coarticulation • Anticipatory (right-to-left) coarticulation • A segment’s features are influenced by upcoming segment S1 S2