Differential Thresholds of Perception of Sound Duration in Different Phonetic Contexts

The paper presents the results of the study which was aimed at obtaining the values of differential thresholds for Russian stressed vowels. Two types of psychoacoustic experiments were conducted. The experimental material was formed taking into account the segmental and prosodic context. The segmental context of the vowel stimuli was relatively similar while prosodic context varied. Each vowel was presented in several word types which involved one-syllable words and three-syllable words with different stress patterns. Each word was embedded into an affirmative utterance (initial/medial/final position), an interrogative utterance (final position), and an utterance with a contrastive stress on the word. The subject listened to a sample word containing a target vowel and its modifications with increased or decreased vowel duration. The gradual increment or decrement was 1 F0 period or 10 ms on average. The task was to click the modification when the duration difference was perceived. Then the differential thresholds are calculated by means of statistical analysis. The average differential threshold was found to be 2-4 F0 periods which is approximately about 20-40 ms. The threshold value does not seem to be influenced by word duration (in syllables) or stress pattern.