Stop-vowel syllables were synthesized by use of both the cascaded resonant circuit (POVO) and the dynamical vocal tract analog (DAVO). Variation of formant positions or of articulatory configurations, intensity envelope, and inflection of fundamental frequency were controlled. A noise source was used as excitation for unvoiced stop consonants. Unvoiced stops generated by DAVO are much superior to those generated by POVO when a noise source is inserted at the constriction point of the vocal tract. In comparing utterances produced by POVO with those produced by DAVO some interesting differences have been found. These will be discussed and an explanation will be offered. Methods involving both absolute judgments and paired comparisons have been used. [This work was supported in part by the U. S. Army (Signal Corps), the U. S. Air Force (Office of Scientific Research, Air Research and Development Command), and the U. S. Navy (Office of Naval Research); in part by Air Force Cambridge Research Center Contract AF 19(604)-2061; and in part by the National Science Foundation.]