Perturbation Theory, part 2 November 4, 2014 Before I forget Course project report #3 is due! I have...
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Transcript of Perturbation Theory, part 2 November 4, 2014 Before I forget Course project report #3 is due! I have...
Before I forget• Course project report #3 is due!
• I have course project report #4 guidelines to hand out.
• I’m still working on the grading of the Korean stops lab exercise.
• Let’s check out the mystery spectrogram!
SummaryMale Formant Averages
200
300
400
500
600
700
800
900
1000
10001500200025003000
F2
F1
palatal
glottal
labial
pharyngeal
A Note About F3• What about F3 distinctions?
• They’re unusual.
• For acoustic reasons:
• Intensity of voicing harmonics drops off at the higher end of the frequency scale
• (spectral tilt)
• And also auditory reasons:
• Sensitivity to frequency distinctions drops off in the higher frequency regions
• Note: F2 and F3 often merge for [i]
Decreasing F3
• If we wanted to decrease F3...
• Where we would make constrictions?
• Constrict at:
lips
“velum”
pharynx
English • English is distinctive because it has a very low F3.
• It has labial, post-alveolar (retroflex), and pharyngeal constrictions.
Synergy• The labial, retroflex and pharyngeal constrictions all work together to lower F3.
• Similarly, both labial and velar constrictions lower F1 and F2 in high, back (round) vowels
• Synergy
• Interestingly, labial-velar vowels are far more common in the languages of the world than either:
• labial vowels
• velar vowels
Life’s Persistent Questions• Let’s step back and review what our standing wave patterns look like in an open tube…
• And where they come from, exactly.
Back to Perturbation Theory• Basic idea #1: vocal tract resonances (formants) are the result of standing waves in the vocal tract
• These standing waves have areas where velocity alternates between high and low (anti-nodes), and areas where velocity does not change (nodes)
Perturbation Principles• Basic Idea #2: constriction at a velocity anti-node decreases a resonant frequency
anti-node
anti-node
Perturbation Principles• Basic Idea #3: constriction at a velocity node increases a resonant frequency
node
node
Labial
• Constrictions in the labial region are at anti-nodes for both F1 and F2.
• Labial constrictions decrease both F1 and F2
Labial
• Constrictions in the palatal region are at an F2 node and near an F1 anti-node
• F1 decreases; F2 increases
Palatal
Labial
• Constrictions in the velar region are at an F2 anti-node and near an F1 anti-node
• F1 decreases; F2 decreases
PalatalVelar
Labial
• Constrictions in the pharyngeal region are at an F2 anti-node and near an F1 node
• F1 increases; F2 decreases
PalatalVelarPharynx
Labial
• Constrictions in the laryngeal region are at an F2 node and an F1 node
• F1 increases; F2 increases
PalatalVelarPharynxLarynx
Different Sources• For a particular articulatory configuration, the vocal tract will resonate at a certain set of frequencies…
• no matter what the sound source is.
• Let’s check out what Peter Frampton can do with a talk box…
• and the “Sonovox”
• Now let’s see what happens when we change our sound source to a duck call…
Duck Call Vowels
http://www.exploratorium.edu/exhibits/vocal_vowels/vocal_vowels.html
duck call is placed here
• Now let’s filter the duck call with differently shaped plastic tubes….
• Care to make any predictions?
Philosophical Fragments• Consider the Cardinal Vowels, again.
• An age-old question:
• Why are the high, back vowels rounded…
• And everything else unrounded?
• Rounding back vowels takes advantage of an acoustic synergy…
• which lowers both F1 and F2.
• But is there anything wrong with rounding the other vowels?
Five Vowel Spaces• Many languages have only three or five vowels, separated evenly in the vowel space in a triangle
• Here’s a popular vowel space option:
i u
e o
a
A “Bad” Vowel Space• Five vowels in a vowel system are rarely, if ever, distributed thusly:
[i]
[e]
[æ]
• Why?
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.
Unrounded Vowel Stats• 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
Rounded Vowel Stats• Number of languages with the following rounded vowels (out of 316, from the UPSID database):
y: 21 : 6 u: 254
: 3 : 48
ø: 15 o: 88
: 5 (o : 133)
œ: 7 : 100
: 0 : 5
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 .130 63.5
.056
.077 22.0
.065 (22.2)
.060 25.0
.000 .227
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)