2. Vowels (yet again) February 25, 2010

3. Housekeeping Term project prospectuses? Today we’ll lay the groundwork for lab exercise #3. Due next Thursday. Wrap up Perturbation Theory And start in on the tube model of vowel production.

4. Adaptive Dispersion Theory Developed by Bjorn Lindblom and Johan Liljencrants (Swedish speakers) Adaptive Dispersion theory says: Vowels should be as acoustically distinct from each other as possible (This helps listeners identify them correctly) So…languages tend to maximize the distance between vowels in acoustic space Note: lack of ~ distinction in Canadian English.

5. Liljencrants + Lindblom (1972) Attempted to quantify “contrast” in the vowel space.  to emphasize the importance of perception in the formation of phonological structure. They start with an articulatory model of the limits of the vowel space: note: space is plotted in three formants… and in mels (auditory equivalent of frequency)

6. Liljencrants + Lindblom (1972) Quantification of contrast in the space: Given m pairs of n vowels, Where m = (n * (n-1)) / 2 And r i 2 = the Euclidean distance between the ith pair of vowels, in formant space. The perceptual goal of the system is: I.e., the more formant space between vowels, the easier they will be to distinguish from one another. Note: floating magnets analogy Also: crowded elevator analogy

7. An Auditory Interlude In the 1920s, psychophysicists noticed that: listeners can more accurately distinguish between pure tones of low frequency than between pure tones of high frequency. (there are interesting physiological reasons for this) To capture this fact, they developed the mel scale of frequency. A Mel = auditory analogue of Hertz (acoustic frequency) Twice the number of mels = twice as high of a perceived frequency.

8. Quiz Time Let’s try the Mel scale test! Match this tone: To the tone that is twice its frequency: Now try it for a higher frequency tone: Which tone is twice the frequency? Mels = 1127.01048 * ln (1 + F/700) where acoustic frequency (F) is expressed in Hertz.

9. The Mel Scale

10. Masking Another scale for measuring auditory frequency emerged in the 1960s. This scale was inspired from the phenomenon of auditory masking. One sound can “mask”, or obscure, the perception of another. Unmasked: Masked: Q: How narrow can we make the bandwidth of the noise, before the sinewave becomes perceptible? A: Masking bandwidth is narrower at lower frequencies.

11. Critical Bands Using this methodology, researchers eventually determined that there were 24 critical bands of hearing. The auditory system integrates all acoustic energy within each band.  Two tones within the same critical band of frequencies sound like one tone Ex: critical band #9 ranges from 920-1080 Hz  F1 and F2 for might merge together  The auditory system consists of 24 band-pass filters. Each critical band  0.9 mm on the basilar membrane. Each filter corresponds to one unit on the Bark scale.

12. Bark Table BandCenterBandwidthBandCenterBandwidth 15020-1001318501720-2000 2150100-2001421502000-2320 3250200-3001525002320-2700 4350300-4001629002700-3150 5450400-5101734003150-3700 6570510-6301840003700-4400 7700630-7701948004400-5300 8840770-9202058005300-6400 91000920-10802170006400-7700 1011701080-12702285007700-9500 1113701270-148023105009500-12000 1216001480-1720241350012000-15500

13. Bark Scale of Frequency The Bark scale converts acoustic frequencies into numbers for each critical band

14. Liljencrants & Lindblom (1972) In perceptually optimal systems… vowels tend to spread out around the edges of the available space. There is also a trend for more high vowel contrasts than are normally found in language.

15. Possible fixes: 1.A better quantification of contrast 2.Articulatory factors In particular: “ease of articulation”, or a principle of “least effort” 3. Syntagmatic aspects Conclusion: phonetics (and perception) are relevant to the study of language = it is not a strictly formal object.

16. H & H Theory In later work, Lindblom recognized the need to temper the needs of the listener with speaker-based articulatory constraints. “Unconstrained, a motor system tends to default to a low- cost form of behavior.” = Speakers tend to be lazy (or efficient), for biological reasons. For similar biological reasons, speech is adaptive. = responds to changing conditions and listener needs. “If the speech system operates so as to minimize 'articulatory effort', we should expect it to undershoot phonetic targets quite often, but not necessarily in every single instance. The key point is: Speakers have a choice.”

17. H & H Theory The articulatory result: speech can vary between hypo- and hyper-articulation. Hypoarticulation: speakers undershoot phonetic targets Energy is conserved  speakers are happy Speech quality is reduced  listeners job is tougher Hyperarticulation: speakers exert greater effort to reach phonetic targets Sounds are more distinct  listeners’ job is easier More energy is consumed  speakers are less happy "Clear speech is not merely normal speech produced louder. It also involves reorganization of articulatory gestures and acoustic patterns."

18. The Upshot “…our story conforms with accounts of speech production that view it as a continual tug-of-war between demands on the output on the one hand and system-based constraints on the other…” Lindblom’s approach is a novel way of dealing with the problem of invariance. “there is simply no way to define a phonetic category in purely acoustic terms.” --Liberman and Mattingly In H&H Theory, variance is a natural extension of the adaptive demands of the speech communication task. (i.e., it’s not really a problem) “…adaptive behavior is the reason for the alleged lack of invariance in the speech signal.”

19. Cost/Benefit In the production of vowels, a lip rounding gesture always comes at an articulatory cost. (it’s an extra gesture) H & H Theory predicts: Vowels will only be rounded if rounding improves the vowel’s contrastiveness. “Bang for your buck” Let’s check out some numbers…

20. Raw Numbers Number of languages with the following unrounded vowels (out of 316, from the UPSID database): i: 271 : 46 : 4 : 54 e: 83 : 4 (e: 113) : 77( : 6) : 116 : 6 : 4 æ: 38 a: 14(a: 274) : 22

21. Raw Numbers Number of languages with the following rounded vowels (out of 316, from the UPSID database): y: 21 : 6u: 254 : 3 : 48 ø: 15o: 88 : 5(o : 133) œ: 7 : 100 : 0 : 5

22. Rounded/Unrounded Ratio of number of languages with rounded vowels divided by number of languages with unrounded vowels, for particular parts of the vowel space:.077.13063.5.056.07722.0.065(22.2).060 25.0.000.227

23. The Good, the Bad and the… High, front region of the vowel space: Unrounded vowels are preferred (good) (271) Rounded vowels are dispreferred (bad) (21) High, back region: Unrounded vowels are bad (4) Rounded vowels are good (254) Low, back region: Unrounded vowels are better (22) Rounded vowels are worse (5) Low, front region: Rounded vowels are really bad. (0)

24. Bad Vowel #1: [y] [y] has both labial and palatal constrictions Why is this bad?

25. Bad Vowel #2: [ ] [ ] has only a velar constriction Why is this bad?

26. Bad Vowel #3: [ ] [ ] has a pharyngeal and a labial constriction Why is this bad?

27. Really Bad Vowel #4: [ ] [ ] has both laryngeal and labial constrictions Why is this bad?

28. Advanced Tongue Root Some languages have an added articulatory feature for vowels, called advanced tongue root found in a lot of West African languages What are the acoustic consequences of advancing the tongue root?

29. Ultrasound This is a speaker of Kinande. Kinande is spoken in Congo. (from Gick, 2002)

30. Ultrasound: +ATR vs. -ATR advanced (+ATR)retracted (-ATR)

31. ATR vowels in Akan Akan is spoken in Ghana

32. +ATR vs. -ATR

33. ATR Vowel Spaces DhoLuo is spoken in Kenya and Tanzania

34. F3 and, revisited English has pharyngeal, palatal and labial constrictions These constrictions conspire to drastically lower F3

35. F3 and [y] [y] has both labial and palatal constrictions What effect would these constrictions have on F3?

36. [i] vs. [y] [li][ly]

37. Lab Exercise! Let’s walk through it…