Transitions + Perception March 27, 2012

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…

!Xoo Oral and Nasal Vowels

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.

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.

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

Vowel Nasalization

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.

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.

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.

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 ( Hz) 4 cm 17.5 cm Anti-formant arises from a side tube of length  4cm AF1 = 2125 Hz

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

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

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

[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 ]

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

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

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

[j] vs. [i]

[w] vs. [u]

Vowel-Glide-Vowel [iji][uwu]

More Glides [wi:][ju:]

Transitions When stops are released, they go through a transition phase in between the stop and the vowel. From stop to vowel: 1.Stop closure 2.Release burst 3.(glide-like) transition 4.“steady-state” vowel Vowel-to-stop works the same way, in reverse, except: Release burst (if any) comes after the stop closure.

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

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?

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

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

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)

[hid] [hæd]

Formant Locus Whether in a front vowel or back vowel context... The formant transitions for alveolars tend to point to the same frequency value. (  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…

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:  Hz Backer (more velar) next to back vowels Locus is lower: < 1500 Hz F2 and F3 often come together in velar transitions “Velar Pinch”

The Velar Pinch [bag][bak]

“Velar” Co-articulations

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

Pattern Playback Picture

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

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 = Hz Source:

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

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

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.