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Figure 8. Cochleagrams of [] in studietoelage
The right cochleagram (stressed [a]) in Figure 8 shows increased perceived loudness in the regions of approximately 5 to 22 Bark in the allegro version of [a] in comparison with the left cochleagram (unstressed [a]). This confirms the results of the study of primary stress in Sluijter (1995). If we convert this perceptive, almost logarithmic, Bark scale into its linear counterpart, the Hertz scale, this area correlates with the frequency region of 3 to 10 kHz.

In order to measure perceived secondary stress, we will measure the relative loudness in the different frequency regions in Phon._⁴⁷ According to Sluijter (1995) stressed vowels have increased loudness above 500 Hz compared to the same vowel in an unstressed position. This can be shown if we take a point in time from both cochleagrams in Figure 8 in which the F1 reaches its highest value (following Sluijter, 1995). In Figure 9 the values in Phon are depicted for these points and plotted against the Bark values in 25 steps.

F
igure 9. Loudness in Phon
The white line in Figure 9 indicates the pattern of the allegro stressed [a] in studietoelage and the black line indicates the pattern of the andante unstressed [a]. We see increased loudness in the region of 13 to 21 Bark, which correlates with the most sensitive region of our ear. The mean Phon value in Figure 9 between 5 and 21 Bark is 43.6 Phon for the andante unstressed [a] and 47.4 Phon for the allegro stressed [a]; a mean difference of 3.8 Phon.

Now, let us see whether or not we can find similar results for our subject P1. Figure 10 shows that the spectral balance confirms the leftward stress shift we perceived in the allegro realization of amerikaan. The first syllable vowel in allegro tempo is characterized by more loudness in the higher frequency regions than its andante counterpart. In the second syllable vowel it is just the other way around.

Figure 10. Spectral balance comparison of the first two vowels of amerikaan
Unfortunately, not all spectral balance data confirm our auditive analysis. For example, we claimed that the pitch analysis of the stress shift in perfectionist did confirm our auditive analysis. Therefore, we expected more loudness in the allegro realization of the first vowel and less loudness in the allegro realization of the second vowel, but it appeared that there is relatively more loudness in the andante realization of per. This result contradicts our auditive and our pitch analysis.

We have to conclude that the different phonetic analyses contradict each other. Sometimes the perceived stress shift is characterized by a longer duration of the stressed syllable; sometimes a relatively higher pitch characterizes it. The results of our spectral balance analysis show that the differences in loudness pattern with differences in duration. In our perceived stress shift in allegro perfectionist, pitch turned out to be the decisive correlate, whereas duration and spectral balance measurements indicated no shift at all. On the other hand, the perceived shift in allegro amerikaan was confirmed by the duration and spectral balance analyses together, whereas pitch measurements indicated the opposite pattern. For most perceived stress shifts, however, the acoustic correlates did not give any clue.

Finally, we will consider whether the perception of restructuring depends on rhythmic timing. Just as in music, speech can be divided into a melodic string and a rhythmic string as partly independent entities. With respect to speech, the melodic string seems to be more flexible than the rhythmic one. Imagine that the rhythm constitutes a kind of metronome pulse to which the melodic content has to be aligned. The listener expects prominent syllables to occur with beats. This behavior is formulated as the Equal Spacing Constraint: prominent vowel onsets are attracted to periodically spaced temporal locations (Couper-Kuhlen, 1993; Cummins & Port, 1998; Quené & Port, 2002; a.o.). Dependent on speech rate the number of intervening syllables between beats may differ. Suppose the beat interval is constant at 300 msec., there will be more linguistic material in between in allegro speech, e.g. the two syllables die and toe in stúdietoelàge, than in andante speech, e.g. only one syllable die in stúdietòelage.

If indeed the perception of secondary stress shifts depends on rhythmic timing, i.e. the beat interval between prominent syllables in andante and allegro speech is approximately equal, than we expect that the duration quotient of the interval between, for example, stu and toe in the andante realization of studietoelage and stu and la in the allegro realization approximates 1.

In our pre-study, the interval between the vowel onsets of the first and third syllable in studietoelage (andante) is 0.358 sec, whereas the interval between the first and the fourth syllable in the allegro realization of the same word is 0.328 sec. This means that the duration quotient is 1.091, which indeed approximates 1. In other words, this example supports the idea of the Equal Spacing Constraint.

Does the same result hold for our present data? We measured the beat intervals between all possible stress placement sites for all six subjects. Figure 11 depicts the duration quotients for subject 1. Figure 12 shows the beat intervals of the same data. It depicts as well the duration interval between the first and the third, as the first and fourth syllable for both speech rates. We expect restructuring for those data in which the line of the first to third syllable interval (andante (black line)) coincides with the line of the first to fourth syllable interval (allegro (white line)).

Figure 11. Quotient beat intervals of Subject P1





Figure 12. Beat intervals of Subject P1
The Figures 11 and 12 indicate that the relevant beat intervals of the items 1, 4 and 7, studietoelage 'study grant', kamervoorzitter 'chairman of the House of Parliament' and winkelopheffing 'closing down of a shop', respectively, coincide. In other words, we expect to hear restructuring in exactly these three items.

Unfortunately, our auditive analysis indicates only attested combinations of restructuring in items 2 and 6: wegwerpaansteker 'disposable lighter' and gemeente-inschrijving 'municipal registration', respectively. Obviously, rhythmic timing is not the decisive characteristic of perceived restructuring in allegro speech either.