This dissertation investigates how native speakers of Northern Sixian (NS) Hakka produce the six lexical tones in isolation, in tonal coarticulation, and in tone sandhi, motivated by the disagreement in the descriptions of the tone system of NS Hakka among previous studies due to differences in research approaches adopted or procedures for processing acoustic data, and to the sparsity in studies of interaction between adjacent tones and the nature of tone sandhi in NS Hakka.
To achieve our research goal, methodologically, tones on mono-syllabic and disyllabic words produced by 6 male and 6 female middle-aged native speakers were collected for acoustic and statistical analysis. For the speech corpus, we addressed the issue of efficacy of F0 normalization strategies for speaker variability. The study found a log z-score normalization method optimal in reducing F0 variation across speakers from the raw data, and this normalization strategy was applied to converting all the raw F0 data for acoustic and statistical analysis into log z-score values so as to attain an accurate understanding of the acoustics of tones in NS Hakka. Meanwhile, we also proposed a mixed method of polynomial and statistical modeling, which affords acoustic indices for the mean F0, linear slope, and curvature of tonal contours, and estimate differences in these aspects between tones.
Regarding the issue of tonal representations for the tone system of NS Hakka, our data on the T-value normalized (Shi, 1990) F0 values for the isolated tones showed that the tone values calculated in this study for the six individual tones are highly consistent with those suggested by Chang (1995) to the exception of the checked Yang Ru tone. The study clarified the confusing tonal contrast between Yin Ru and Yang Ru found in Chang (1995), who annotated the contrast as [52] vs. [53], by proposing the contrast as [52] vs [55], a contrast of more differential distinctiveness.
With respect to the issues associated with tonal coarticulation, the study found that: (1) both carryover and anticipatory tonal coarticulation were attested for NS Hakka with the former predominantly assimilatory and the latter dissimilatory, as reported in most previous studies for other tone languages; (2) however, unique to NS Hakka, word-final falling tones, such as T2 [51], T4 [52], T5 [31], were susceptible to assimilatory carryover effects primarily triggered by a word-initial rising T1, whereas the word-final rising T1[35] was prone to dissimilatory carryover effects induced by the two high level T3 [55] and T6 [55] in the word-initial position; based on (2) therefore, (3) a Contour/Level asymmetry was suggested regarding better effect undergors for carryover coarticulation, a pattern different from the High/Low asymmetry reported in previous studies on tonal coarticulation for other tone languages; (4) in terms of anticipatory coarticulation, patterns were quite consistent with findings from the past studies for other tone languages in that a High/Low asymmetry was found with respect to the better effect triggers, i.e. the low onset of a word-final mid-falling T5 [31] triggering a pitch raising effect on the word-initial tones, and with respect to better effect undergoers, i.e. the high pitch target of a word-initial tone that was particularly raised due to the dissimilatory anticipatory effects from the word-final T5 [31]; (5) the effect size associated with different coarticulation directions depended on the specific tones. Carryover effect size was not necessarily bigger than the anticipatory effect size; and finally (6) to make accurate interpretation of tonal coarticulation, not only phonetic groundings but also phonological motivations should be taken into account..
Finally, the acoustic study on tone sandhi in NS Hakka addressed the phonetic motivation underlying the pattern of the Yin Pin T1 sandhi in NS Hakka, and the completeness of tonal neutralization of the sandhi T1 [31] with the lexical T5 [31], to which T1 is alleged to turn in the sandhi contexts. We proposed that the synchronic phonological tone sandhi pattern in NS Hakka was a phonologized result of phonetic interactions between the word-initial Tone 1 [35] and the following sandhi context tones. First, a reduced rising form of the word-initial T1 was induced due to a high offset loss when the high offset raised the pitch level of the following sandhi context tones, and in the meantime, it was absorbed or realized in the following sandhi context tones. Second, in the T1T1 sequence, a contour dissimilatory effect was on the word-initial T1 in a reduced form by the following T1, whereby an already-reduced rising T1 in the word-initial position gradually turned a mild mid-falling tonal contour. Third, when T1 preceded the two high level T3 [55] and T6 [55], a pitch level dissimilation occurred on the realization of T1 in reduced form by the two following high level tones; in other words, a dissimilatory effect maximally lowered the pitch of the word-initial T1 to the lowest pitch range. Finally, the word-initial position, where tone sandhi occurs, is “prosodically weak,” implying that tones in this position tend to be affected by the word-final tones, and also leaving less time to fully realize the high offset target of the word-initial T1. Regarding the issue of completeness in neutralization, the study found the nature of tone sandhi in NS Hakka was gradient instead of categorical given the statistically significant differences in the realizations of tonal F0 contours and velocity contours between the sandhi T1 [31] and the lexical T5 in the same sandhi contexts.
Key words: Northern Sixian Hakka, tonal representations, isolated tones, tonal
coarticulation, tone sandhi, tonal neutralization, and polynomial modeling