The method of studying speech perception by means of a formant synthesizer has been facilitated by the use of a small digital computer to control the synthesizer, record the listeners' responses, and analyze the results. This method has been applied to the perception of the semivowels /w, r, l, y/ in isolated CV syllables. It has been found that the frequency of the locus of the first formant greatly affects the quality of the perceived sounds, and that the shape of the first‐formant transition is rather critical in the case of /l/ before open‐front vowels.