Title of the article

5.2.Acoustic analysis

In the current state of phonological research, embodied in e.g. laboratory phonology, much value is set on acoustic evidence for phonological analyses. Studies such as Sluijter (1995) and Sluijter and Van Heuven (1996) provide acoustic correlates for primary stress. In our study we are concerned with beat reduction and secondary stress shifts and we wonder whether or not the same acoustic correlates hold for secondary stress. Shattuck Hufnagel et al (1994) and Cooper and Eady (1986) do not find acoustic correlates of rhythmic stress at all. They claim that it is not entirely clear which acoustic correlates are appropriate to measure, since these correlates are dependent on the relative strength of the syllables of an utterance. The absolute values of a single syllable can hardly be compared without reference to their context and the intonation pattern of the complete phrase. Huss (1978) claims that some cases of perceived rhythmic stress shift may be perceptual rather than acoustic in nature. Grabe and Warren (1995) also suggest that stress shifts can only be perceived in rhythmic contexts. In isolation, the prominence patterns are unlikely to be judged reliably. In the remainder of this paper we try to find out if we can support one of these lines of reasoning. In other words, are we able to support our perceived rhythmic variability with a phonetic analysis? Therefore, we measured the duration, pitch, intensity, spectral balance and rhythmic timing of the relevant syllables as realized by subject P1.

Because Dutch is a quantity-sensitive language, the duration of the relevant syllable rhymes was considered. Onsets do not contribute to the weight of a syllable. In Figure 7, the duration analysis is shown for Type 2 data (left shifts). The four columns indicate, respectively, the duration of the rhyme of the first and second syllable in andante speech, and the duration of the first and second one in allegro speech. According to Sluijter (1995), duration is the main correlate of primary stress. As a starting point, we adopt her claim for our analysis of secondary stress. Our measurements would confirm our hypothesis and our auditive analysis, if the second column were higher than the first one and if the fourth column were lower than the third one. In that case, the subject would realize a word such as perfectionist as perfèctioníst in andante tempo and as pèrfectioníst in allegro tempo.

In the andante tempo, three out of six items show the dominant correspondence pattern and in the allegro tempo, four out of six items show the dominant markedness pattern. That is hardly a preference and it does not confirm our auditive analysis of the same data. Furthermore, if we consider the word pairs with different patterns, there is only one pair that has the ideal ratio: the patterns of amerikaan.





Figure 7. Duration (Left Shifts by Subject P1)
If duration does not enable us to confirm our auditive findings, maybe pitch is the main stress correlate for this speaker. However, pitch measurements reveal the same fuzzy result as the duration measurements. Again, only one pattern confirms the auditive analysis. This time it is not the item amerikaan, but the item perfectionist. Moreover, the differences in pitch in this item do not exceed the threshold of the 2.5%, which is the just noticeable difference for pitch. We also analyzed the mean intensity value of the relevant vowels without recognizable patterns between allegro and andante style. These results support the analyses of Sluijter (1995) and Sluijter and Van Heuven (1996), who also claim that the intensity parameter does not contribute much to the perception of stress.

Next, we considered the spectral balance. In order to rule out the influence of the other parameters, we monotonized the data for volume and pitch. Then we selected the relevant vowels and analyzed them as a cochleagram in PRAAT. The cochleagram simulates the way the tympanic membrane functions, in other words the way in which we perceive sounds. In Figure 8 we show two cochleagrams of the vowel [a] in the fourth syllable of, respectively, stúdietòelage 'study grant' (Type 1) in andante tempo and stúdietoelàge in allegro tempo. This item was taken from a pre-study. The allegro data show the expected increased perceived loudness in the higher frequencies, indicated by means of shades of gray; the darker gray the more perceived loudness.