Prebens phonetics assignment: Real-time F1-F2 plotter
Rather than following the given assignment, I have tried to make a real-time F1-F2 plotter. It didn't come out as expected, but incidentally it illustrates some of the difficulties and inconcistencies in using the first and second formants as a way of capturing aspects of speech production/perception.
The program records from a microphone and at a regular interval calculates f1 and f2 values, and plots them as a small dot on a graph. (figure 1-3) Although there is a striking resembelance between my vowel production (fig.2) and the traditional way of illustrating the placement of vowels in a vowel triangle (fig.1), the scaling of the triangle is done to fit the data, and not the other way around.
There is an individual vowel-space coordinate system that is different between speakers. Using my coordinate system on two other persons vowel production illustrates this, as can be seen in figure 3 and 4.
I started on a procedure of scaling every persons vowel space by mapping it onto the cardinal vowels I, A, and O and using affine transformation techniques used in 3D graphics to automatically scale and move the space. The project is not finished yet, but time is running out....
Perhaps I will find it useful, and finish it later as a part of my PhD project.
Standard vowel triangle
figure 1. standard vowel triangle
Prebens vowels
figure 2. Prebens vowels
Annas vowels
figure 3. Annas vowels
Gunillas vowels
figure 4. Gunillas vowels
The program was built in Tcl/Tk and uses the 'snack' package developed at CTT for the sound processing.