To find out whether people indeed prefer triplet patterns in allegro speech, we ran a pilot experiment in which we tried to elicit fast speech. Six subjects participated in a multiple-choice quiz in which they competed each other in answering twenty simple questions as quickly as possible. In this way, we expected them to speak fast without concentrating too much on their own speech. In Table 3 one of the quiz items is depicted.
Table 3. Quiz item
Q4 President Bush is een typische ‘President Bush is a typical ’
A1 intellectueel ‘intellectual’
A2 amerikaan ‘American’
A3 taalkundige ‘linguist’
We categorized the obtained data as allegro speech. As a second task the subjects were asked to read out the answers at a normal speaking rate embedded in the sentence ik spreek nu het woord … uit 'now I pronounce the word … '. This normal speaking rate generally means that the subjects will produce the words at a rate of approximately 180 words per minute, which we categorize as andante speech. All data were recorded on minidisk in a soundproof studio and normalized in CoolEdit in order to improve the signal-noise (S/N) ratio. Normalizing to 100% yields an S/N ratio approaching 0 dB.
Six trained listeners judged the data auditively and indicated where they perceived secondary stress. After this auditive analysis the data were phonetically analyzed in PRAAT (Boersma and Weenink, 1992). We compared the andante and allegro data by measuring duration, pitch, intensity, spectral balance and rhythmic timing (Sluijter, 1995; Couper-Kuhlen, 1993; Cummins & Port, 1998; Quené & Port, 2002; a.o.). Sluijter claims that, respectively, duration and spectral balance are the main correlates of primary stress. In our experiment, we are concerned with secondary stress.
For the duration measurements, the rhymes of the relevant syllables were observed. For example, in the allegro style answer A2 amerikaan in Table 3, we measured the first two rhymes and compared the values in Msec. with the values for the same rhymes at the andante rate. In order to make this comparison valid, we equalized the total durations of both realizations by multiplying the duration of the allegro with a so-called 'acceleration factor', i.e. the duration of the andante version divided by the duration of the allegro version. According to Eefting and Rietveld (1989) and Rietveld and Van Heuven (1997), the just noticeable difference for duration is 4,5%. If the difference in duration between the andante and the allegro realization did not exceed this threshold, we considered the realizations as examples of the same speech rate and neglected them for further analysis.
For the pitch measurements, we took the value in Hz in the middle of the vowel. The just noticeable difference for pitch is 2,5% ('t Hart et al, 1990). For the intensity measurements, we registered the mean value in dB of the whole syllable.
The next parameter we considered concerns spectral balance. Sluijter (1995) claims that the spectral balance of the vowel of a stressed syllable is characterized by more perceived loudness in the higher frequency region, because of the changes in the source spectrum due to a more pulse-like shape of the glottal waveform. The vocal effort, which is used for stress, generates a strongly asymmetrical glottal pulse. As a result of the shortened closing phase, there is an increase of intensity around the four formants in the frequency region above 500 Hz. Following Sluijter (1995) we compared the differences in intensity of the higher and lower frequencies of the relevant syllables in both tempos.
Finally, we considered rhythmic timing. The idea is that the beats in speech are separated from each other at an approximately equal distance independent of the speech rate. In other words, a speaker more or less follows an imaginary metronome. If he/she speaks faster, more melodic content will be placed between beats, which results in a shift of secondary stress. This hypothesis will be confirmed if the distance between the stressed syllables in the andante realization of an item, e.g. stu and toe in studietoelage, approximates the distance between the stressed syllables in the allegro realization of the same item, e.g. stu and la. If the quotient of the andante beat interval duration divided by the allegro beat interval duration approximates 1, we expect perceived restructuring.
Before we can present an auditive analysis of the data, we have to find out whether or not the quiz design was successful. The results show that the quiz indeed triggers faster speech by all subjects. Figure 2 shows their acceleration factors. Subjects 1, 2 and 4 turned out to be the best accelerating speakers, whereas subjects 3, 5 and 6 showed less difference in duration between andante and allegro realizations. The mean acceleration factor for the three fast speakers is 1.31, whereas the mean acceleration factor for the three slow speakers is 1.13.
igure 2. Acceleration factors of all subjects
Figure 3 shows the mean durations of the items at both speech rates. It shows that the best accelerating speakers are also the fastest speakers. We expect to find more restructured patterns for these speakers, mainly subjects 1 and 4, in comparison to the slower speakers, such as subjects 3 and 6.
igure 3. Mean word durations
Figure 4 shows that most subjects prefer patterns in which from a phonological point of view markedness constraints dominate the correspondence constraints at both rates for right and left shift data, but not for beat reduction data. There are slightly more restructured patterns in allegro tempo, although the differences are quite small.
Figure 4. All subjects: Number of restructured items per type
When we take the results of two fast subjects apart, subjects 1 and 4, we observe a stronger preference for restructuring in allegro speech and no restructuring in andante speech, as shown in Figure 5. In other words, the fast subjects display both a greater difference in word durations in andante and allegro speech, and more variability in their speech patterns due to tempo than the slow subjects do.
igure 5. Fast subjects: Number of restructured items per type
bviously, the preference for restructuring the rhythmic pattern in allegro speech is not an absolute preference. Sometimes restructuring does not take place in allegro speech, but on the other hand restructured patterns also show up in andante speech.46 Some items were realized with the same rhythmic pattern irrespective of the tempo. Therefore, we also looked at the word pairs with a different rhythmic pattern in both tempos for each subject. We observe that the relatively fast speakers p1, p2 and p4, show the expected pattern according to our hypothesis, which means that they show a restructured pattern in allegro tempo, as shown in Figure 6 for the right shifts.
Figure 6. Right Shifts: Expected combinations
Two of the relatively slow speakers, p3 and p6, show one counterexample each, where the subject prefers the restructured patterns in andante tempo. The other slow speaker, P5, displays no different patterns in andante and allegro at all. Clearly, we have two different groups of speakers and this observation strengthens our claim that restructuring relates to speech rate.
Some items, such as hobbywerkruimte (Type 1) 'hobby room', never show a stress shift and other items, such as viriliteit (Type 2) ‘virility’, prefer the shifted pattern in both tempos for all subjects. Possibly, the syllable structure plays an important role; open syllables seem to lose stress more easily than closed ones.