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Transitions + Perception

Transitions + Perception. April 1, 2014. Palatography Preparations!. We will do the palatography demo on Tuesday of next week. We’ve already gotten a volunteer for a speaker! We also need someone to volunteer for: Photography Transcription I’ll bring the goodies!

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Transitions + Perception

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  1. Transitions + Perception April 1, 2014

  2. Palatography Preparations! • We will do the palatography demo on Tuesday of next week. • We’ve already gotten a volunteer for a speaker! • We also need someone to volunteer for: • Photography • Transcription • I’ll bring the goodies! • Now: let’s do a perception experiment!

  3. 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.

  4. Lateral Palatography

  5. 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.

  6. 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

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

  8. 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

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

  10. [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 ]

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

  12. 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.

  13. 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

  14. [j] vs. [i]

  15. [w] vs. [u]

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

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

  18. 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.

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

  20. 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?

  21. 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

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

  23. 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 downwards. • 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)

  24. [hid] [hæd]

  25. 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…

  26. 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”

  27. The Velar Pinch [bag] [bak]

  28. “Velar” Co-articulations

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

  30. Pattern Playback Picture

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

  32. Categorical Perception • Categorical perception = • continuous physical distinctions are perceived in discrete categories. • In the in-class experiment: • 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

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

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

  35. 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.

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