Lab assignment 3 on "Calculating the length of the vocal tract"

Ling 600.01 Phonetic Theory

We will do this lab in the second class meeting of Week 4. So prepare the first part of your report for that day. The final report on this lab should be submitted as an appendix to the field project report on your language consultant's vowel space.

Practice producing something like a schwa vowel -- i.e., a vowel with as neutral a vocal tract as possible -- with modal voice at a comfortable pitch level that you can sustain for two to three seconds. We will use a recording of this production to try to calculate the "resting" length of your vocal tract, so it needs to be as close to a uniform tube as you can make it. If you succeed in making a perfectly "neutral" vowel, what should the relationship be among the first three formants?

Now think of an articulatory maneuver that should change the effective length of the resonating cavity from its length in this "neutral" vowel. This could be a maneuver that shortens the vocal tract or one that lengthens it. Practice producing the "changed length" sound in the same way that you did the "neutral" vowel. If your maneuver is successful, what effect should it have on the formant pattern relative to the pattern that you predicted for the perfectly neutral vowel?

When you feel comfortable with your productions, record yourself producing the two sound types. Try to maintain each of the postures for at least two seconds.

Also, demonstrate the schwa sound for your language consultant and ask him or her to produce it for you to record. Bring a digitized recording of the three productions to class or have it available for downloading in class.

Now try to get a rough estimate of your vocal tract length, by doing the following (or by asking a friend or your language consultant to do it for you). Take a carpenter's square or a large stiff sheet of paper such as a square of cardboard, and hold it by the side of your head so that one side is parallel with the middle of your neck and the other side is parallel with the lateral your side teeth meet when you close your mouth, as in the following schematic drawing of aligning a carpenter's square against the side of Peter Ladefoged's vocal tract.


Photo from Peter Ladefoged (2001). A course in phonetics, 4th edition. Harcourt College Publishers.

Make a mark on the vertical edge at the position of your larynx. (This is your "Adam's apple" if you're an Adam.) Make another mark on the horizontal edge of the cardboard at the anterior position of your lips. Then measure the lengths of the two edges between these marks and the corner of the box that is between this crossing point and the bottom end of the vertical chopstick and the length between this crossing point and the front end of the horizontal one. Add up these two lengths to get a very rough estimate of your vocal tract size. Make the analogous measurements to get a rough estimate of your consultant's vocal tract size, too. Are these sizes comparable? If not, which one of you has the longer vocal tract? What effect should this have on the relationship between your schwa and the consultant's schwa?

Your list of materials should include a summary of the measured lengths of the two vocal tracts and a statement of the gesture that you made to change the vocal tract length.