The duration aspect of tones Jiahong Yuan University of Pennsylvania Tone is realized on and synchronized with its tone-bearing unit. On the one hand, the duration of the tone-bearing unit is affected by many contextual factors such as speaking rate and intonation. On the other hand, tone as an articulatory event has an intrinsic duration. For example, it takes longer time to realize a rising tone than a falling one over the same pitch range, because the maximum speed of pitch change is slower for pitch rises (Ohala and Ewan 1973). The question then is, how do the two aspects interact, is one more basic than the other? The answer is not easy to find. For example, it is observed that long vowels and sonorant rimes are more likely to carry contour tones (Gordon, 2001). The phonological accounts for the distribution of contour tones have made different assumptions (explicitly or implicitly) about which is more basic in determining the duration of a tone, the tone itself or its tone-bearing unit: A contour tone occupies two moras or tonal positions (Duanmu 1994, Akinlabi and Liberman 2001). ⇒ Tone-bearing units are more basic. When a contour tone is associated with a short tone-bearing unit, the rankings of the faithfulness constraints on tone and duration determine whether contour flattening or rime lengthening will occur (Zhang 2000). ⇒ Neither tone nor its tone-bearing unit plays a deterministic role, the two interact with each other in a Optimality-Theoretic grammar. The durational properties of contour tones are better explained in terms of the interplay of articulatory and perceptual effects in tone realization (Yu 2010). ⇒ Tones are more basic. I will present several tone duration patterns in Mandarin Chinese, which shed light on the question. 1. Tone2 is longer than Tone4 There are four lexical tones in Mandarin Chinese, referred to as Tone1, Tone2, Tone3 and Tone4. The F0 contours of the tones in isolation are high level, rising, low dipping (or just low) and falling respectively. It is repeatedly observed that Tone2 is longer than Tone4. This is consistent with that pitch rises take longer time than pitch falls. But on the other hand, Tone2 has a smaller pitch range than Tone4. Therefore, the underlying rising and falling targets might not be adequate to explain the duration difference between the two tones (Phonetic evidence in support of unitary contours in Chinese tonal representation can be found in Xu 1999). By examining the F0 trajectories of the rising and falling tones when they are focused, we can see that Tone2 has a lengthened L and a raised
H whereas Tone4 has only a raised H but not a lengthened L. This suggests that the underlying representation of Tone2 is L*+R and that of Tone4 is H*+F. The duration difference between Tone2 and Tone4 thus results from two combined effects: low tones are longer than high tones, and rising tones are longer than falling tones.
Figure 1. The beginning Tone2 is focused (dark circles) vs. unfocused (open circles)
Figure 2. The beginning Tone4 is focused (dark circles) vs. unfocused (open circles).
2. The effect of speaking rate on the duration of sentence final Tone2 and Tone4. Thirty speakers of Mandarin Chinese read a list of sentences, which are minimal pairs of statements and questions, in slow, normal, and fast speaking rates. The effect of speaking rate on the duration of sentence final Tone2 and Tone4 in statements is shown in Figure 3. We can see that speaking rate has similar effects on Tone2 and Tone4, and also that the duration difference between Tone2 and Tone4 is consistent across all speaking rates. This result suggests that the effects of speaking rate and tonal targets on the duration of tone are orthogonal.
Figure 3. The effect of speaking rate on the duration of sentence final Tone2 and Tone4.
3. The effect of intonation on the duration of sentence final Tone2 and Tone4. The effect of intonation on the duration of sentence final Tone2 and Tone4 is shown in Figure 4. We can see that the final Tone4 is longer in question intonation than in
statement intonation whereas the final Tone2 has similar duration in the two intonation types, and the pattern is the same across all speaking rates. First, this result confirms that the speaking rate effect is orthogonal to the effect of tonal targets on the duration of tone. Secondly, question intonation has different effects on the duration of final Tone2 and Tone4. Yuan (2004) proposed that a mechanism of question intonation in Mandarin Chinese is to change the slope of contour tones, i.e., to flatten the final falling tone and to steepen the final rising tone. The change of tonal targets is, however, blind to its consequence to the duration of tone.
Figure 4. The effect of intonation on the duration of sentence final Tone2 and Tone4.
In summary, the study suggests that tonal targets and tone-bearing units have orthogonal effects on tonal duration. The effect of tonal targets on its duration is not controlled, it is blind to the output duration. To investigate the duration aspect of tones may inform a full understanding of the underlying representation of tone. References: Akinlabi, A. and Liberman, M. (2001). “Tonal Complexes and Tonal Alignment,” NELS 31. Duanmu, S. (1994). “Against contour tone units,” Linguistic Inquiry, 25, 555-608. Gordon, M. (2001). “A typology of contour tone restriction,” Studies in Language, 25, 405-444. Ohala, J. J., and Ewan, W. G. (1973). “Speed of pitch change,” J. Acoust. Soc. Am., 53, 345. Xu, Y. (1999). “Effects of tone and focus on the formation and alignment of F0 contours,” Journal of Phonetics 27: 55-105. Yu, A. (2010). “Tonal effects on perceived vowel duration,” Laboratory Phonology 10. Yuan, J. (2004). Intonation in Mandarin Chinese: Acoustics, Perception, and Computational Modeling, PhD dissertation, Cornell University. Zhang, J. (2000). A Formal Optimality-Theoretic Model for Tone-Duration Interaction, PhD dissertation, UCLA.
