Effect of formant transition rate variation on the differentiation of synthesized child and adult /w/ and /r/ sounds

Although a primary acoustic property differentiating /w/ and /r/ is the onset frequency of the second formant transition (F2) relative to the onset of the third formant transition (F 3), it has been hypothesized that the rate of change of F2 may provide additional cues to this glide distinction. In order to investigate this supposition, transition rate of F2 was systematically varied while holding F2 onsets constant for stimuli modeled after child and adult vocal tracts. Eight subjects each participated in the child and adult conditions. The results showed that rate significantly affected the perception of /r/ and /w/ for only the adult condition. However, the results were generally opposite hypothetical predictions. That is, as transition rate increased, /w/ identification significantly decreased. These findings a re interpreted as supporting the perceptual salience of a slow transition rate for /w/, which is important in the glide-stop contrast in adult speech. Moreover, the results support the conclusion, that transition rate is not an important property in the differentiation of /r/ and /w/ relative to hypothetical predictions.