Tonal Representations and Coarticulation in Ta-pu Hakka

This present study aims (1) to investigate the correlation of phonological representations and phonetic realizations of Ta-pu Hakka tones, and (2) to explore the tonal coarticulation in different kinds of contexts.
There are two major Hakka sub-dialects spoken in Taiwan, the Hai-lu and the Suu-hsien systems. Another sub-dialect, Ta-pu Hakka, is spoken mainly in some townships in central Taiwan by about 60,000 people. Different sub-dialects of Hakka have their own tonal systems that have been described in detail in previous literature. However, most of the tonal representations used in the literature with regard to tones were based on auditive perception and phonological description. As a result, those phonological tonal representations were more impressionistic.
This study first investigated the correlation between phonological representations and phonetic realizations of the Ta-pu Hakka tones by taking acoustic and statistical approaches. Six informants, including three males and three females, were recruited in this study. Two sets of inventories were adopted as the test stimuli: the first was a set of monosyllabic words, and the other was a set of disyllabic words. The monosyllabic words were used to verify the citation tones, while the disyllabic words were used to verify the sandhi tones. Meanwhile, the tonal representations in different prosodic positions, i.e., in word-initial (WI) and in word-final (WF) positions were also investigated.
The second research question in this study was to explore tonal coarticulation in disyllabic words in Ta-pu Hakka. Tonal coarticulation refers to tonal variations in consecutive speech, which has been a great concern to many phoneticians (Xu, 1994, 1997, 1999, 2001, 2004; Gandour et al., 1994 & 1999; Peng, 1997; Shen, 1990 & 1992). In this study, we investigated tonal variations in different prosodic positions, tonal contexts, and in a context with different neighboring tones. Target Approximation model (Chen & Xu, 2006; Xu, 1997, 1999, 2004; Xu & Wang, 2001) was used to help explain the tonal variations found in this language.
To answer the above two research questions, we measured the average pitch height (F0) of the beginning point (BP), the ending point (EP), the maximum pitch (F0_Peak), the minimum pitch (F0_valley), and the average pitch of the syllable (Mean_F0). Besides, we also calculated the mean slope and the mean duration of the whole syllable. For Yang-Ping tone, the F0 valley alignment was calculated. As for falling tones and checked tones, the F0 peak alignment was calculated instead.
In investigating tonal representations, we adopted Fon and Chiang’s (1999) postulated formulae and Shi’s (1990) logarithmic function. In the first section with regard to verifying the tonal representations in Ta-pu Hakka, the revised T-scales (5-scaled tonal system) of the seven citation tones were suggested as follows: Yin-Ping as [33], Yang-Ping as [313], Shang as [31], Chü as [53], Yin-Ju as [3], Yang-Ju as [4], and Supra-Yin-Ping as [34], based on the data from monosyllabic words.
As for the tones in disyllabic words, the T-scales showed great incongruence between the results obtained via the two calculation methods. The results suggested that tonal representations in disyllabic words should not be considered as the norms of tonal representations. As for the three sandhi tones (ST), we found that the revised T-scales via Shi’s function were more appropriate to show their phonetic realizations. The three sandhi tones were suggested as ST-Yin-Ping as [324], ST-Yang-Ping as [323], and ST-Chü as [44], respectively. However, the revised T-scales in fact represented the phonetic realizations of the sandhi tones under the influence of tonal coarticulation, so we would still adopt the original T-scales, ST-Yin-Ping as [35], ST-Yang-Ping as [33], and ST-Chü as [55], when sandhi tones were involved in investigating tonal coarticulation effect.
The phonetic realizations of tones in Ta-pu Hakka showed that the seven citation tones included one level tone, two falling tones, two checked tones, one rising tone, and one concave tone. The tones in this language could be paired off, one belonged to the lower register, whereas the other belonged to the higher register. Note that the T-scales of the two checked tones were very close to each other. The statistical results of comparing means of the measured parameters in the two checked tones indicated that not only the pitch height but also the falling slope served as the criterion of distinguishing one from the other, within which the lower checked tone, Yin-Ju [3], had a steeper falling F0 slope.
As for tonal coarticulation, we explored the tonal variations from different aspects. First we investigated the tonal variations of tones according to their position in disyllabic words, namely in WI and WF positions. Afterward, Xu’s (1994) classification of different tonal combinations into a compatible or a conflicting context was examined and modified based on the tonal combinations in Ta-pu Hakka. We proposed a third type of tonal context, which was termed as a contour compatible context, referring to a context where a rising tone followed by a falling tone, or a falling tone followed by a rising tone. Then the influence of adjacent tones on their preceding or following tone was compared and discussed.
The results of tonal coarticulation in Ta-pu Hakka were summarized as follows. First, in regard with the position effect, final-lengthening was found in all the non-falling tones and the Yang-Ju [4]. However, the duration of Yin-Ju [3] and Shang [31] was longer in WI rather than in WF. Furthermore, the mean F0 slope of these two tones was steeper in WF position, indicating an abrupt fall at the end of the utterance. As for Supra-Yin-Ping [34], however, the mean slope was steeper when it was in SI than in SF. The most interesting finding was that the F0 valley alignment of Yang-Ping [313] was closer to the onset in WI, and it became closer to the middle of a syllable when in WF.
With regard to the tonal variations in a compatible or conflicting context, we found that Shang [31] showed a steeper slope in a contour compatible context than in a conflicting context. The result also suggested that a contour compatible context was very similar to a compatible context. As for Supra-Yin-Ping [34], the slope was even steeper in a contour compatible context than in a compatible context.
As for the results of the influence of adjacent tones on each other, carryover assimilation effect was found in Yin-Ping [33], Yang-Ping [313], Supra-Yin-Ping [34], Chü [53] and Yang-Ju [4]. Anticipatory assimilation was found in Shang [31], Chü [53] and Yin-Ju [3]. For Yang-Ju [4], anticipatory effect was also found, but the influence of its following tones on its tonal variations showed both assimilation and dissimilation effect. Furthermore, we also found a positive correlation between the offset F0 in syllable 1 (WI) and the onset F0 in syllable 2 (WF).
Furthermore, the tonal variations found in Ta-pu Hakka could be explored via Xu’s Target Approximation model. Both anticipatory assimilation and carryover assimilation phenomena supported Xu’s claim that “when two pitch targets occur next to each other, if the offset of the first one is different from the onset of the second one, the second one will appear as if it has been assimilated or partially assimilated to the second” (Xu and Wang 2001, p. 329). As for the anticipatory dissimilation, the effect could be found in Yin-Ping sandhi rule ([33] turning [35]) and Yang-Ping sandhi rule ([313] turning [33]). On the other hand, the anticipatory assimilation could also be seen in Chü sandhi rule ([53] turning [43]).
We stipulate that tone sandhi rules are in fact the historical products of tonal coarticulation, and the phonological aspect of tone sandhi rules is either to show greater contrast between adjacent tones or to ease the effort of articulation.
To sum up, both the phonetic realizations of tonal representations and tonal coarticulation effect in Ta-pu Hakka aim to show either harmony or contrast. The phonetic realizations of tonal representations and coarticulation in this language also help group all the tones into different natural classes: such as non-falling vs. falling, and non-checked vs. checked.