Acoustics and perception of velar softening for unaspirated stops

This paper provides articulatory, acoustic and perceptual data in support of the hypothesis that the velar softening process through which /k/ becomes /tʃ/ is based on articulation rather than on acoustic equivalence if operating on unaspirated stops. Production data for unaspirated /k/ are analyzed for five speakers of Majorcan Catalan, where the velar stop phoneme exhibits (alveolo)palatal or velar allophones depending on vowel context and position. Data on several parameters, i.e., contact anteriority and dorsopalatal contact degree, burst spectral peak frequency, energy and duration, and F2 and F3 vowel transition endpoints and ranges, suggest that /tʃ/ may have originated from (alveolo)palatal stop realizations not only before front vocalic segments but also before low and central vowels and word finally. Perception results are consistent with the production data in indicating that the most significant /tʃ/ perception cues are burst energy before /a, u/ and burst duration word/utterance finally. They also suggest that velar softening for unaspirated /k/ before front vocalic segments is triggered by an increase in burst frication energy and duration resulting from the narrowing of an (alveolo)palatal central channel occurring at stop closure release. These findings are in agreement with the existence of contextual and positional (alveolo)palatal stop allophones of /k/, and with evidence from sound change, in the Romance languages.