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Linguistics 580 Phonetics Vowel Articulation
Goals (1) to develop some familiarity with the relationship between articulatory parameters relevant to the production of vowels and their acoustic consequences. (2) to learn how to distinguish particular vowels in terms of articulatory parameters.
Model We will use a model of the vocal tract called CASY (Configurable Articulatory Synthesis) to adjust the positions of vocal tract articulators. From those positions, a 3D vocal tract shape is calculated (2D midsagittal version is plotted), the resonances of that tube are calculated (from the physics), a filter function is calculated and is used to filter a glottal-like buzz. The resulting sound can be played.
The articulators that can be moved are shown by little '+' markers on the Vocal Tract Display. They are labelled the figure below. 2
The articulators can be moved by positioning the mouse pointer over one of these markers, then holding down the button and dragging it to a new position. As you are dragging, the articulator will move and the vocal tract shape will be updated appropriately. A new filter function and formants will also be displayed, and a new sound can be played.
The articulator positions are defined relative to one another in a dependence hierarchy. The lower lip, tongue body, and tongue tip are dependent on the position of the jaw, so when the jaw moves, these articulators more along with it. The tongue tip is dependent on the position of the tongue body. The upper lip is dependent on the position of the lower lip. For this exercise with vowels, you should be able to produce decent approximations to English vowels by manipulating only the jaw, tongue body, and lips.
Procedure
(a) Downloaded the CASY folder here. (b) Launch the application MATLAB. (c) Set Matlab's current directory to the CASY folder by dragging the icon for the folder onto the command line. (e) Type casy at the Matlab prompt. Three windows will appear: Vocal Tract, Spectrum (Transfer Function), and Area Function. The spectrum window shows the filter function associated with the vocal tract shape shown, and the frequencies of the formants are listed. You will not need the Area Function window. (f) To hear the sound that the vocal tract generates, type p
Attempt to generate the palatal vowels as suggested by the tense-lax theory discussed in class. • "heed" and "hid" should have the same jaw height but different tongue body displacements from the jaw. You can achieve this by making a good "heed" and saving it to disk (see below), then seeing if you can make a good "hid" by manipulating only the tongue body. • "heed" and "hayed" should have the same tongue displacements, but different jaw heights. You can do this by re-loading your saved "heed" (see below on how to load), and seeing if you can make a plausible "hayed" by manipulating only the jaw. • "hid" and "head" should differ only in jaw height... OK. You get the idea of how to do that... 3
(h) When you have a good approximation to a given vowel, type >>saveKey(‘name’); where ‘name’ is, e.g., ‘heed’, ‘hid’, etc. You need to actually put single quotes around the name. For example: >>saveKey(‘heed’) This will save the articulator positions in a file called