Our voice is generated from vocal fold (cord) vibration in the larynx, see the left frame of Fig. 2.1 for its anatomy and position in the head and neck region. The vocal folds form a pair of soft walls that move into (closing) and away (opening) from each other under the pressure of air flow from the lung to the lips, see the right frame of Fig. 2.1 for a top view of an open vocal fold. The vertical cross section of the larynx is shown in Fig. 2.2. A full cycle of vocal fold motion from opening (abduction) to closing (adduction) and back to opening is in Fig. 2.3. We shall begin with mechanical models of vocal fold motion, then similar models of vocal tract. The combined action of the two serves as a source and filter for voiced sound production. Mathematical abstraction and extension for unvoiced consonants will come next.