Determining the temporal interval of segments with the help of F0 contours

The temporal interval of a segment such as a vowel or a consonant, which is essential for understanding coarticulation, is conventionally, though largely implicitly, defined as the time period during which the most characteristic acoustic patterns of the segment are to be found. We report here evidence for a need to reconsider this kind of definition. In two experiments, we compared the relative timing of approximants and nasals by using F-o turning points as time reference, taking advantage of the recent findings of consistent F-o-segment alignment in various languages. We obtained from Mandarin and English tone- and focus-related F-o alignments in syllables with initial [j], [w] and [(sic)], and compared them with F-o alignments in syllables with initial [n] and [m]. The results indicate that (A) the onsets of formant movements toward consonant places of articulation are temporally equivalent in initial approximants and initial nasals, and (B) the offsets of formant movements toward the approximant place of articulation are later than the nasal murmur onset but earlier than the nasal murmur offset. In light of the Target Approximation model (TA) originally developed for tone and intonation [Xu & Wang. (2001). Pitch targets and their realization: Evidence from Mandarin Chinese. Speech Communication, 33, 319-337], we interpreted the findings as evidence in support of redefining the temporal interval of a segment as the time period during which the target of the segment is being approached, where the target is the optimal form of the segment in terms of articulatory state and/or acoustic correlates. This new definition may have implications for our understanding of many issues in speech, including, in particular, coarticulation and temporal coordination in speech motor control. (c) 2006 Elsevier Ltd. All rights reserved.