Two Tube Vocal Tract Model

Computes the frequency response of a two-tube model excited at the glottis and terminated at lips.

In this MATLAB exercise the areas and lengths of a lossless, two-tube model of a human vocal tract are specified by the user, and the MATLAB exercise computes the transfer function of volume velocity from the glottis to the lips, where the reflection coefficient at the glottis is assumed to be r_G (in the range-1 ≤ r_G ≤1), and the reflection coefficient at the lips is assumed to be r_L, again in the range-1 ≤ r_L ≤1. Such a two-tube model is shown in Figure 2.1 of the User’s Guide (with tube lengths and areas of values l1 = 8 cm, A1 = 1 cm^2, l2 = 9 cm, A2 = 7 cm2), and the flow diagram of the composite system from the glottis to the lips is shown in Figure 2.2. This MATLAB exercise computes the transfer function of volume velocity from the glottis to the lips, plots the volume velocity transfer function (log magnitude spectrum), determines the locations of the formant frequencies (both center frequencies and bandwidths), whenever possible, and prints them to a designated ascii text file. The 2-tube model frequency spectrum is sampled and converted to a 2-tube model impulse response which is convolved with a periodic glottal train and played out so that the user can hear which vowel sound is produced using the two-tube model.