Properties of French Intonation at Fast Speech Rate

Effects of fast speech rate on French intonation in text reading are reported. Modifications at fast rate were found in both the shape of F0 curves and the prosodic organization of the text (phrasing and realization of underlying tones), with different patterns across speakers. The results suggest that F0 realization at fast rate is not a simple “speeding up” compared to normal rate but involves a prosodic reorganization. INTRODUCTION The realization of intonation patterns has been found to be influenced by several sources of variation, such as pitch range, sentence structure and length [5], or focus. However, very little is known about the effect of speech rate on intonation other than its effect on the number of intonational phrases [2, 8]. As far as we know, no systematic description has been done regarding the phonetic properties and phonological patterns of intonation when its physical domain of realization is shortened by an increase in rate. So far, the observation of the effects of speaking rate has mostly been restricted to the segmental domain. showing modifications in the temporal, spectral, and articulatory organization of speech. Articulatory data have shown that there are different strategies for overcoming alteration in articulation time; mainly, target undershoot with reduction of the magnitude of movements, and/or increase in stiffness for faster transitions between targets [6, 1]. If we assume that a tune is composed of a sequence of underlying tonal targets [7], we can use the same analysis techniques as used in studies of segmental articulation to observe the effect of fast rate on intonation. By examining F0 curves, we can test the hypothesis that there is a modification in the physical realization (F0 shape) of the underlying intonation structure as well as a reorganization of the prosodic structure. METHOD The text “La bise et le soleil" (“The wind and the sun", given in Table l) was read by one male and two female Parisian French speakers at self selected normal and fast rates, with three repetitions at each rate. The full text was analyzed for one of the female speakers (1F). For the two other speakers (2F, 3M) the comparison was limited to the first half of the text where most variation between fast and normal rate was found for Speaker 1F. Acoustic measurements were taken for each tonal pattem at the rising onset and falling offset (hereafter called F0 minima), and the peak (F0 maxima). Duration of accented syllables and intonational phrases were measured. Qualitative comparison of the prosodic structure is based on the model of French intonation developed in Jun & Fougeron [3] where the lowest tonally defined prosodic level is the Accentual Phrase (ILHLHI), and the highest prosodic level is the Intonational Phrase. RESULTS AND DISCUSSION A. Differences depending on the position in the text. The reduction of duration at fast rate for Subject IF was about 33% compared to her normal rate. While this reduction is constant for the whole text, the rate acceleration seems to have different effects on F0 depending on the position in the text. In the first part of the text (see Table 1), rate acceleration induced reductions in the shape of F0 curve, as well as some changes in the prosodic organization of the phrases. while in the second part of the text we observed only phrasing differences. _ In the first part (Fig. 1), F0 range IS reduced at fast rate (32%) with the highest F0 value being lowered and the base line (lowest F0 value) being stableICPhS 95 Stockholm In addition, the displacements between L and H targets are also reduced by significantly (p<.01) lowering the maxima (17%) more than the minima (9%). Despite this overall lowering of the peaks, the peaks at major prosodic boundaries (#3, 10, 12, 19 in Fig. 1), critical points of prosodic organization, are not reduced. Comparison of F0 movement velocity (displacement Hz/time) shows very little difference between the two rates. The movements are not stiffer at fast rate, with the reduction of displacement being proportional to the reduction of duration. In the second part of the text (Fig.2), rate acceleration induces a small reduction of F0 range (6%) but no change in displacement with small and equal degree of lowering of maxima (5.8%) and minima (5.5%). The velocity of F0 movements are not affected. Considering the prosodic organization of the text, we found there is a change in the realization of tonal patterns at fast rate: in an Accentual Phrase ILHLH/ [3], the initial underlying high tone (initial accent) is often not realized (63% and 73% for Ist and 2nd part). We also found fewer prosodic groups at fast rate. Intonational Phrase boundaries were reduced to lower level boundaries (50% and 42% for the first and second part), and some of the lowest boundaries (AP) were deleted (22% for both the first and second part). In sum. different strategies are adopted in the first and second parts of the text. When comparing the range of variation of F0 targets in the two parts. evidence is found for a saturation effect. In the first part. the F0 range is wide. which allows some variation in the displacement towards F0 targets without changing the prominence relations between successive targets. In the second part of the text, range of variation is reduced with a smaller F0 range (1241-12 compared to 213Hz in the first part). A second indication of saturation is found in the fact that the lowering of the maxima at fast rate is Proportional to their height at normal rate: as shown in Fig. 3, in both the first (Empty square) and the second (circle) Session 5 7.8 Vol. 3 Page 489 part of the text, the higher the peak is, the bigger the reduction is at fast rate (R2=0.28 at both positions).