Abstract
We have been investigating the effect of speech rate alteration on Japanese speech intelligibility, especially the differences caused by phonetic feature. We evaluated this difference in intelligibility using the Japanese Diagnostic Rhyme Test (DRT) on artificially speed-altered speech, such as time-expanded speech (1.6 times the original length, or 60% time expansion) and time-contracted speech (0.6 times the original length). Artificial speaking rate alteration was shown to have some effect or degradation on the Japanese speech intelligibility depending on the phonetic feature, initial consonant feature, and succeeding vowel context. Nasal and voiced affricates were relatively unaffected by speed alteration. Syllables with vowel context /i/ showed 10% higher intelligibility when time-expanded. Furthermore, we showed that the intelligibility was affected by only the time length of the initial consonant by comparing the evaluation results of simple expansion/contraction and phonetic expansion/contraction. These results suggest guidelines for feature-dependent intelligible speed alteration methods.
