Measuring and Modeling Speech Production Figure 3: The source-filter model for selected vowels. Three different vocal tract shapes are shown corresponding, from top to bottom, to the vowels "ah" (/a/), "ee" (/i/), and "oo" (/u/). In this example, we have used schematized vocal tract shapes from the Haskins Laboratories articulatory synthesizer. Plotted in the same graph for each tract shape is the smoothed transfer function that is computationally derived by the synthesizer, and the hypothetical energy spectrum that would result from using these functions to filter a glottal source spectrum with a fundamental frequency of 100 Hz. Note that although all three vowels have the same fundamental frequency, their spectra differ according to the filter characteristics of the different vocal tract shapes.   Introduction | Acoustic Theory | Measuring Production Tract Model | Gestural Modeling | State of the Art