Transitions + Perception

1. Transitions + Perception March 27, 2012

2. Tidbits • First: Guidelines for the final project report • So far, I have two people who want to present their projects to the class • Last time, we went over the acoustics of nasals • Today we’ll get into the acoustics of liquids, glides and transitions. • + some perception • I’ll pass out the last homework of the semester for you on Thursday. • Due: Tuesday, April 10th • Oh yeah: something about the singer’s formant…

3. !Xoo Oral and Nasal Vowels

4. Nasal Vowel Acoustics • The smearing of vowel formants can obscure F1 (vowel height) differences • high vowels sound low • low vowels sound high • Note: American South “pen” vs. “pin” • French: [le] vs. • [lo] vs.

5. Measuring Nasality • One method of measuring oral and nasal airflow simultaneously involves using an airflow mask. • The mask contains pressure transducers in separate nasal and oral chambers.

6. Airflow Samples • The airflow mask spits out readings of the amount of air flowing out of the nose and the mouth at the same time. • nasal vowels: concomitant airflow through both mouth and nose • nasal stops: airflow only through nose

7. Vowel Nasalization

8. http://www.kayelemetrics.com/Product%20Info/6400/6400.htm Nasometer • A tool which has been developed for studying the nasalization of vowels (and other segments) is the Nasometer. • The Nasometer uses two microphones to measure airflow through both the mouth and nose at the same time.

9. Laterals • Laterals are produced by constricting the sides of the tongue towards the center of the mouth. • Air may pass through the mouth on either both sides of the tongue… • or on just one side of the tongue.

10. Lateral Acoustics • The central constriction traps the flow of air in a “side branch” of the vocal tract. • This side branch makes the acoustics of laterals similar to the acoustics of nasals. • In particular: acoustic energy trapped in the side branch sets up “anti-formants” • Also: some damping • …but not as much as in nasals.

11. 17.5 cm 4 cm • Primary resonances of lateral approximants are the same as those of for vocal tract length of 17.5 cm • 500 Hz, 1500 Hz, 2500 Hz... • However, F1 is consistently low (300 - 400 Hz) • Anti-formant arises from a side tube of length  4cm • AF1 = 2125 Hz

12. Laterals in Reality • Check out the Mid-Waghi and Zulu laterals in Praat Mid-Waghi: [alala]

13. Velarization of [l] • [l] often has low F2 in English because it is velarized • = produced with the back of the tongue raised • = “dark” [l] • symbolized • Perturbation Theory flashback: • There is an anti-node for F2 in the velar region • constrictions there lower F2

14. Dark vs. Clear /l/ • /l/ often has low F2 in English because it is velarized. [alala]

15. [l] vs. [n] • Laterals are usually more intense than nasals • less volume, less surface area = less damping •  break between vowels and laterals is less clear [ ] [ n ]

16. [l] vs. • [l] and are primarily distinguished by F3 • much lower in • Also: [l] usually has lower F2 in English [ ] [ ]

17. Glides • Glides are vowel-like sonorants which are produced… • with slightly more constriction than a vowel at the same place of articulation. • Each glide corresponds to a different high vowel. • Vowel Glide Place • [i] [j] palatal (front, unrounded) • [u] [w] labio-velar (back, rounded) • [y] labial-palatal (front, rounded) velar (back, unrounded) • Each glide’s acoustics will be similar to those of the vowel they correspond to.

18. Glide Acoustics • Glides look like high vowels, but… • are shorter than vowels • They also tend to lack “steady states” • and exhibit rapid transitions into (or from) vowels • hence: “glides” • Also: lower in intensity • especially in the higher formants

19. [j] vs. [i]

20. [w] vs. [u]

21. Vowel-Glide-Vowel [iji] [uwu]

22. More Glides [wi:] [ju:]

23. Transitions • When stops are released, they go through a transition phase in between the stop and the vowel. • From stop to vowel: • Stop closure • Release burst • (glide-like) transition • “steady-state” vowel • Vowel-to-stop works the same way, in reverse, except: • Release burst (if any) comes after the stop closure.

24. Stop Components vowel closure voicing formant transitions stop release burst • From Armenian: [bag] another closure

25. Confusions • When the spectrogram was first invented… • phoneticians figured out quite quickly how to identify vowels from their spectral characteristics… • but they had a much harder time learning how to identify stops by their place of articulation. • Eventually they realized: • the formant transitions between vowels and stops provided a reliable cue to place of articulation. • Why?

26. Formant Transitions • A: the resonant frequencies of the vocal tract change as stop gestures enter or exit the closure phase. • Simplest case: formant frequencies usually decrease near bilabial stops

27. Stops vs. Glides “baby” • Note: formant transitions are more rapid for stops than they are for glides. “wave”

28. Formant Transitions: alveolars • For other places of articulation, the formant transition that appears is more complex. • From front vowels into alveolars, F2 tends to slope downward. • From back vowels into alveolars, F2 tends to slope upwards. • In Perturbation Theory terms: • alveolars constrict somewhat closer to an F2 node (the palate) than to an F2 anti-node (the lips)

29. [hid] [hæd]

31. Formant Locus • Whether in a front vowel or back vowel context... • The formant transitions for alveolars tend to point to the same frequency value. ( 1650-1700 Hz) • This (apparent) frequency value is known as the locus of the formant transition. • In the ‘50s, researchers theorized: • the locus frequency can be used by listeners to reliably identify place of articulation. • However, velars posed a problem…

32. Velar Transitions • Velar formant transitions do not always have a reliable locus frequency for F2. • Velars exhibit a lot of coarticulation with neighboring vowels. • Fronter (more palatal) next to front vowels • Locus is high: 1950-2000 Hz • Backer (more velar) next to back vowels • Locus is lower: < 1500 Hz • F2 and F3 often come together in velar transitions • “Velar Pinch”

33. The Velar Pinch [bag] [bak]

34. “Velar” Co-articulations

36. Testing the Theory • The earliest experiments on place perception were conducted in the 1950s, using a speech synthesizer known as the pattern playback.

37. Pattern Playback Picture

38. Haskins Formant Transitions • Testing the perception of two-formant stimuli, with varying F2 transitions, led to a phenomenon known as categorical perception.

39. Categorical Perception • Categorical perception = • continuous physical distinctions are perceived in discrete categories. • In the in-class experiment from last time: • There were 11 different syllable stimuli • They only differed in the locus of their F2 transition • F2 Locus range = 726 - 2217 Hz • Source: http://www.ling.gu.se/~anders/KatPer/Applet/index.eng.html

40. Stimulus #1 Stimulus #6 Stimulus #11 Example stimuli from the in-class experiment.

41. Identification • In Categorical Perception: • All stimuli within a category boundary should be labeled the same.

42. Discrimination • Original task: ABX discrimination • Stimuli across category boundaries should be 100% discriminable. • Stimuli within category boundaries should not be discriminable at all. In practice, categorical perception means: the discrimination function can be determined from the identification function.