perturbation theory, part 2
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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.TRANSCRIPT
Perturbation Theory, part 2
March 20, 2014 Lifes Persistent Questions
Lets 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 Palatal Labial Constrictions in the palatal region
are at an F2 node and near an F1 anti-node F1 decreases; F2
increases Velar Palatal Labial Constrictions in the velar region
are at an F2 anti-node and near an F1 anti-node F1 decreases; F2
decreases Pharynx Velar Palatal Labial Constrictions in the
pharyngeal region are at an F2 anti-node and near an F1 node F1
increases; F2 decreases Larynx Pharynx Velar Palatal Labial
Constrictions in the laryngeal region are at an F2 node and an F1
node F1 increases; F2 increases 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. Lets
check out what Peter Frampton can do with a talk box and the
Sonovox Now lets see what happens when we change our sound source
to a duck call Duck Call Vowels Now lets filter the duck call with
differently shaped plastic tubes. Care to make any predictions?
duck call is placed here Another View [i] Duck Call
Spectrograms
[i] Duck Call Spectra [i] How About These? duck call is placed on
this side [i] vs. [e] [i][e] [u] vs. [o] [u][o] 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
Heres a popular vowel space option: iu eo a Five-Vowel Spaces
Gujarati Vowel Space A Bad Vowel Space Five vowels in a vowel
system are rarely, if ever, distributed thusly: [i] [e] [] 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) Solanguages tend to maximize the
distance between vowels in acoustic space Note: lack of
~distinction in Canadian English. Swedish Unrounded Vowel Stats
Number of languages with the following unrounded vowels (out of
316, from the UPSID database): i: : : 4 : 54 e: : 4 (e: 113): 77( :
6) : : : 4 : 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: : 6u: 254 : : 48 : o: 88 : 5(o : 133) : : 100 :
: 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: .056 .065(22.2) 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) Bad Vowel #1: [y] [y] has both labial and palatal
constrictions
Why is this bad? Bad Vowel #2: [ ] [] has only a velar constriction
Why is this bad? Bad Vowel #3: [ ] [ ] has a pharyngeal and a
labial constriction
Why is this bad? Really Bad Vowel #4: [] [ ] has both laryngeal and
labial constrictions Why is this bad? 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?
Ultrasound This is a speaker of Kinande. Kinande is spoken in
Congo.
(from Gick, 2002) Ultrasound: +ATR vs. -ATR
advanced (+ATR)retracted (-ATR) ATR vowels in Akan Akan is spoken
in Ghana +ATR vs. -ATR ATR Vowel Spaces DhoLuo is spoken in Kenya
and Tanzania F3 and, revisited English has pharyngeal, palatal and
labial constrictions These constrictions conspire to drastically
lower F3 F3 and, revisited Retroflex Vowels Retroflexion is a
feature which may be superimposed on other vowel articulations.
Retroflexion is contrastive in vowels in Badaga, a language spoken
in southern India. Retroflex Vowel Spectrograms
[be] F3 and [y] [y] has both labial and palatal constrictions
What effect would these constrictions have on F3? [i] vs. [y]
[li][ly] Overrounded Vowels Note: there is typically more rounding
on [u] than [o] and on [o] than all the way down the line... It is
possible to have [u]-like rounding on lower vowels over-rounding in
Assamese Assamese is spoken in Bangladesh. Overrounded Vowel
Spectrograms Overrounded Vowel Spectrograms