Corpus annotation and analysis using Praat

1. Corpus annotation and analysis using Praat Marc Brunelle University of Ottawa marc.brunelle@uottawa.ca Trường Đại Học Khoa Học Xã Hội và Nhân Văn, TP. Hồ Chí Minh, June 22th, 2013

2. Outline • Summary of spectrogram reading, with an emphasis on consonants • Summary of basic Praat functions • Corpus annotation in Praat • Automatic analysis of prosody in Praat

3. Spectrogram reading

4. Vowels

5. Vowels • Formants tell us about the shape of vocal tract during vowel production • Size of back cavity • Size of front cavity • The first three formants are usually enough to determine the quality of a vowel

6. First Formant (F1) • F1 correlates with vowel height • Low vowel = High F1 • Male = 750 Hz, Female = 850 Hz • High vowel = Low F1 • Male = 250 Hz, Female = 300 Hz • This is a pretty robust correlation

7. Second Formant (F2) • Second formant correlates with vowel frontness/backness • Low F2 = Back vowel • Male = 850 Hz, Female = 900 Hz • High F2 = Front vowel • Male = 2300 Hz, Female = 2800 Hz • However: • Lip rounding affects F2 • Vowel height has some effect on F2 as well

8. F1 and F2 i e ɛ ɨ ə a u o ɔ

9. Third Formant (F3) • F3 is typically higher for front vowels, but doesn’t vary much between central and back vowels • However, this is far from being systematic

10. Diphthongs • Some vowels are composed of a steady state and a glide • VN real diphthongs ia, ua, ưa • Sometimes, there is no or very little steady state, just gliding • Let’s look at VN diphthongs in Praat

11. Semi-vowels (glide) • On a spectrogram, semi-vowels look like vowels • They do not have a stable state, they just glide • The difference between vowels and semi-vowels is phonological, not phonetic • VN false diphthongs ai, ay, ao, au, iêu, oeo. (q)uơi…

12. Consonants in Praat

13. Stops

14. Closures and releases • Closure: Silence • Release: Burst • Zero VOT: no lag between release and vowel • Praat: look at your own bursts • Double burst in velars

15. Voice • On a wide-band spectrogram, voiced stops are identified by: • their voice bar (negative VOT) • their vertical striations

16. Aspiration • Noise between the release and the vowel • Positive VOT

17. Closure and aspiration in Vietnamese

18. Places of articulation • No way of identifying the place of articulation from the closure • The cues are: • In the vowel transitions • In the aspiration (if any) • Release

19. Transitions • Locus • Apparent point of origin of the formants • Velars have two loci • F3 transitions are less important, but not negligible

20. Textbook example of transitions • Note the velar pinch

21. Real example of transitions

22. Importance of transitions • Same transitions in oral and nasal stops • The place of articulation of a stops (oral or nasal) can be retrieved from its transitions only

23. Aspiration • Frequency of noise is a good cue for place of articulation (not much use in VN) • Front cavity determines the frequency of noise • Front stops: high noise frequency • Backs stops: low noise frequency • No high-energy frequency range for labials because of the absence of a front cavity

24. Release • Velar stops often have a double burst • Typically, Vietnamese coda stops are not released, so only useful for onsets

25. Fricatives

26. Places of articulation 2500 Hz 4000 Hz

27. Noise frequency • Front fricatives have higher frequencies than back fricatives • Short front cavity: Low frequency • Long front cavity: High frequency • However, labio-dentals and interdentals have no front cavity, so no clear peak

28. Voiced fricatives

29. Transitions • Fricative-Vowel transitions exist, but • Weaker than stop-vowel transitions • Mostly seen on F2 • Locus is the peak noise frequency of the fricative

30. Transitions in voiceless fricatives

31. Northern VN fricatives f v s z x ɣ

32. Affricates • Stop closure + fricative • No real burst • Not always

33. Sonorants

34. Nasals • Nasal stops • Closure in the mouth • Airflow through the nasal cavity

35. Nasal formants • The nasal cavity is like an unconstricted tube • Nasal formants are roughly the same for all places of articulation (they depend on the length and shape of the nasal cavity) • 250-500 Hz • 1750-2250 Hz • 2750-3250 Hz

36. Anti-formants • As the oral cavity is closed, some waves are absorbed. This is anti-resonance. • Anti-resonance (or anti-formants) depends in theory on the oral articulation • In practice, it is almost impossible to determine the place of articulation based on anti-formants • Overall, anti-formants reduce the amplitude of nasal formants

37. Nasal-Vowel transitions • Loci are the same as for oral stops • Same place of closure • Same effect on speech signal once the nasal cavity is closed • Transitions can be difficult to see in nasalized vowels, because they have both oral and nasal formants

38. VN nasals on spectrograms

39. Approximants • Approximants have formants • However, • These formants are more changing than vowel formants • The intensity of these formants is an important cue

40. Formants of English approximants

41. Liquids • Formant structures similar to vowels • 500 Hz, 1,500 Hz, 2,500 Hz • Anti-formant • Because of the tongue closure, there is an anti-resonance around 2000 Hz

42. Southern VN approximants lu ru

43. Trills and taps • Usually, one can see interruptions in the spectrogram because trill vibration and taps correspond to brief closures

44. Pitch (and tone)

45. Pitch • Pitch corresponds to vocal fold vibrations • Thus, anyvoicedsoundcan have a pitch • In Vietnamese, tones tend to berealized on the entirerhyme • However, consonants have an allophoniceffect on pitch, and thus on tones

46. Vietnamese tones

47. Corpus annotation

48. A Cham example • Story NVT • Designed to test the effects of intonation in Cham • Several tiers • See textgrid

49. Segmentation • Segment the Sun and Wind story (recorded by James Kirby) in small teams • In IPA (Lenz) • phoneme by phoneme • Files • 01a (3 sec) – together? • 01b (4 sec) • 01c (9 sec) • 01d (11 sec) • 01e (5 sec) • 01f (6 sec)

50. Glosses and translation • Normal practice • Native script (quốc ngữ) • Word for word glosses under the transcription • Full translation, sentence by sentence