Relative Contributions of Spectral and Temporal Cues to Korean Phoneme Recognition

This study was aimed to evaluate the relative contributions of spectral and temporal information to Korean phoneme recognition and to compare them with those to English phoneme recognition. Eleven normal-hearing Korean-speaking listeners participated in the study. Korean phonemes, including 18 consonants in a /Ca/ format and 17 vowels in a /hVd/ format, were processed through a noise vocoder. The spectral information was controlled by varying the number of channels (1, 2, 3, 4, 6, 8, 12, and 16) whereas the temporal information was controlled by varying the lowpass cutoff frequency of the envelope extractor (1 to 512 Hz in octave steps). A total of 80 vocoder conditions (8 numbers of channels × 10 lowpass cutoff frequencies) were presented to listeners for phoneme recognition. While vowel recognition depended on the spectral cues predominantly, a tradeoff between the spectral and temporal information was evident for consonant recognition. The overall consonant recognition was dramatically lower than that of English consonant recognition under similar vocoder conditions. The complexity of the Korean consonant repertoire, the three-way distinction of stops in particular, hinders recognition of vocoder-processed phonemes.