Which vowels are affected by syllable stress

Almost all syllables in English contain a vowel sound; therefore, we usually say that syllables are stressed or unstressed. Every multi-syllable English word contains at least one stressed syllable.

For example:. Listeners depend on stress as a cue to recognize words. I NI tiate. E LA borate. SMAR ter. Ful FILL. Cre ATE. MA nager. Com PU ter. Ad MIRE. We find several differences of note between the pronunciation of vowels from non-initial syllables in the two different stress patterns. This might raise the concern that, despite discarding the data from speakers who seemed to place secondary stress on the final syllable in the antepenultimate-stress words, there was some degree of secondary stress on word-final vowels in these words.

In both duration and vowel quality, we see a significant difference between word-final unstressed vowels coming from words with antepenultimate versus penultimate primary stress.

Further, we again see a difference in both duration and vowel quality between vowels from non-edge unstressed syllables based on the stress pattern. The two unstressed vowels from penultimate-stress words are closer in quality as well as in duration than the unstressed vowels from non-edge and word-final syllables from antepenultimate-stress words are.

Thus, the difference between a non-final unstressed vowel and a word-final unstressed vowel is accentuated in the antepenultimate-stress words the red circle and square in Figure 3 ; that is, the vowel of the final syllable is much less reduced while the vowel of the non-edge unstressed syllable is more centralized, compared with word-final and non-final unstressed vowels from penultimate-stress words the blue oval and rectangle in Figure 3.

The hypothesis put forward here, that a phonetic rhythm continues through the two unstressed syllables in the antepenultimate-primary-stress pattern, explains the differences between the sets of vowels from words with antepenultimate and those with penultimate primary stress. Under both stress patterns, non-final unstressed vowels are naturally reduced and word-final unstressed vowels are naturally longer and less reduced. We see here that an unstressed vowel in a penult, coming after antepenultimate stress, is further reduced, and an unstressed vowel in a following word-final syllable is even longer and even less reduced than would otherwise be found in word-final position.

Both the enhanced phonetic weakness of the penult and the enhanced phonetic strength of the final vowel contribute to the rhythm of the word, while actually occurring in a stress lapse.

As noted by a reviewer of this paper, this brings the phonetics of the final vowel very close to something like phonological stress. The fact that word-final syllables are found to have phonetic strength under both stress conditions shows that at least the lower level of word-final augmentation exists outside of the metrical system. The difference in duration and vowel quality between word-final vowels under antepenultimate stress and those under penultimate stress is less than is found between initial-syllable vowels that are unstressed and those that bear secondary stress.

It is therefore more plausible to take the phonetic strength of word-final vowels under antepenultimate stress as a variation of the phonetic effect of final lengthening found in all final syllables.

The findings of the differences among non-final vowels and among word-final vowels leads to the question of whether one or both of these differences is perceptually consequential. The production experiment described in Section 2 found four levels of duration and vowel reduction in unstressed non-initial syllables. The vowels that occurred as part of a stress lapse showed a greater difference in duration and F1, F2 than vowels from the equivalent but non-adjacent unstressed syllables that were part of an alternating stress pattern.

The hypothesis is the phonetic duration and less reduced vowel quality due to final lengthening can contribute to the perception of continued alternation in the case of final stress lapse, while not interrupting the rhythm when there is no final stress lapse.

The production experiment found that the presence or absence of a final stress lapse correlates both with different average durations of vowels in word-final syllables, and also with different average durations of the word-internal unstressed vowel. While the vowel of a final syllable was longer under stress lapse, the vowel of the penultimate syllable was shorter under stress lapse compared to an unstressed vowel in antepenultimate position in a word without final stress lapse.

These same relative differences were found to extend to the degree of centralization of the vowels of non-edge unstressed syllables as well. While the production study results support the hypothesis that final lapse still shows a phonetic-level alternation, we need a perception study to investigate whether this alternation is perceptible and, if so, to what degree the various factors contribute.

Following Lunden to appear , a stressed and an unstressed syllable were copied into five-syllable strings in either an alternating pattern or a non-alternating one with stress lapse two adjacent unstressed syllables or stress clash two adjacent stressed syllables either initially or finally.

Five-syllable strings were chosen because this is the minimum number needed to set up a true rhythm i. Test strings were made by putting syllables originally produced as unstressed word-initially or word-finally in a position to potentially work as part of the rhythmic pattern perceptually cause stress lapse or to interrupt the rhythmic pattern cause the perception of stress clash.

We want to test the effect of word-final syllables not only under stress lapse, where they might contribute to the rhythm, but also in strings with a penultimate stressed syllable, where the potential for these word-final syllables for interrupting rhythmic stress can also be assessed. While the focus is the effect of the syllables originally produced in word-final position, test syllables from initial position were also used in order to demonstrate that any initial strengthening effects e.

Having syllable strings with initial stress lapse, stress clash, and initial test syllables also forces subjects not to become hyper-focused on only the ending of the syllable strings. None had been subjects in the production study. Average vowel quality depending on Word-Stress and Position for selected subject circled compared with averages of all other subjects. The selected subject female, age 21 shows somewhat more difference between the vowels from unstressed non-edge syllables and between the word-final vowels than the average, but neither difference was the most extreme among the production study subjects.

The acoustic characteristics of each of the selected syllables are given in Figure 5 , 4 which is organized so as to clearly show from which stress pattern and position each was taken. Word-edge syllables are underlined, and, in the case of final syllables, subscripted for how many syllables away from the primary stress they are. Each syllable is given a letter identifier just below it which will be referenced when discussing results. Both are identified as b , and will be represented without color coding in the stimuli strings.

When word-initial syllables are used in the stimuli, that syllable is always taken from a word pronounced with antepenultimate stress, and therefore it does not bear any secondary stress. Concatenated strings of five syllables were created. The control stimuli are visually represented in Figure 6. Control strings either have i alternating stressed and unstressed syllables, ii two like syllables at the beginning, or iii two like syllables at the end.

The lapse set was based around alternating strings with a stressed antepenult e. The clash set was based around alternating strings with a stressed penult e. As can also be seen in Figure 6 , all six of these types were made with each type of unstressed syllable: Those that were originally pronounced as unstressed antepenultimate syllables— e in Figure 5 —and those that were originally produced as unstressed penultimate syllables c.

All stimuli were made with both unstressed syllables as the production study found a significant difference between both the duration and the F1, F2 of such syllables, and it was noted that the relative weakness of the unstressed penultimate c contributed to the rhythmic difference between the final two unstressed syllables in a word with antepenultimate stress.

Alternating control strings and initial test strings were each included twice, which, in the case of the former, resulted in a balanced number of alternating and non-alternating control strings, and, in the case of the latter, a balanced number of initial and final test strings. Given these doublings, there were also a balanced number of control strings and test strings. Each of the four sets i. This resulted in 64 stimuli, which were repeated twice in a multiple forced choice experiment administered through Praat.

Because sample strings played to subjects to explain the task had to include one or the other unstressed syllables—i. All subjects received all versions of the stimuli in the experiment itself.

The model was run with Subject as a blocking factor. The perception study was set up to establish whether the phonetic differences between vowels from word-internal unstressed syllables— c vs. The comparison between final test strings can most clearly be shown through a ranking with respect to the percentage identified as alternating estimated means.

We find the opposite progression between the final-lapse-type strings and the final-clash-type strings, as shown in Figure 8. In the bottom row we find that strings with unstressed penultimate syllables c and word-final syllables that were originally non-adjacent to the main stress syllable d had the reverse effect.

As previously established, word-final syllables produced directly after the main stress f were significantly shorter see Section 2. Likewise, the source of the unstressed syllables in the strings also has an effect, which goes in the expected direction. Vowels from unstressed antepenultimate syllables e were found to be the stronger of the two types of vowels from non-edge unstressed syllables, in the sense of having a longer duration and a significantly higher F1 than a vowel from a non-edge syllable pronounced under stress lapse c.

The percentages in Figure 8 are shown separated into the ba -strings and the ga -strings in Figure 9. We see notably consistent results through both sets of syllables, and so will return to discussing the combined results. The pairwise comparisons between the strings most identified as alternating from each set and the other final test strings in the same set are shown in Figure Among the lapse set we see that while the string most identified as alternating contains the weaker word-internal unstressed syllable—an unstressed penult; c —and the stronger word-final syllable—under antepenultimate stress; d , it differs significantly only from strings in which both syllable types have been changed, to the stronger word-internal unstressed syllable—an unstressed antepenult; e —and the weaker word-final—under penultimate stress; f.

Changing only one of these two does not result in the string being significantly less likely to be identified as alternating. The differences between both the unstressed word-internal syllable types and the word-final syllable types have an important effect when combined, since strings with the combined effect of stronger word-internal unstressed syllables e and weaker word-final syllables f are much less likely to be identified as alternating.

The comparison in the fourth line in Figure 10 shows a significant difference between strings with unstressed antepenultimate syllables e that differ only in the source of the final syllable— d vs. Among the clash set, we do not see the same pattern in reverse; rather, the source of the word-internal unstressed syllable does not have an effect, while the source of the final syllable does. Strings with a stronger final syllable—under antepenultimate stress; d —make an alternating string significantly less likely to be identified as alternating.

The perception study tested the degree to which vowels from words with different stress patterns final stress lapse, no stress lapse influenced the perception of an alternating rhythm. Vowels originally produced in word-final syllables under stress lapse d were significantly more likely to upset the perception of alternating rhythm when occurring after a stressed penult than vowels originally produced in word-final syllables that followed a stressed penult f.

This finding is consistent with the longer duration and less reduced vowel quality that was found for word-final vowels that are part of a stress lapse d. Thus, the relative strength of the stress-lapse word-final vowels d and the relative weakness of the stress-lapse non-final vowels c found in the production study have been shown to have perceptual consequences.

The fact that there are four levels of non-initial unstressed vowels— c versus e ; d versus f , however, offers an explanation for how a word-final syllable can be perceived as contributing to the rhythm of a word under final stress lapse but does not create the perception of clash when following a stressed penult. Marry gives some support for a more general durational difference between word-final rhymes under and not under stress lapse.

Her production study used English words paired for final rhymes where one member of the pair has penultimate stress and the other has final stress e. The experiments presented here are an in-depth investigation into whether syllables under word-final stress lapse in English can nevertheless be heard to have something of an alternating rhythm.

Support for this hypothesis was found both in the differences in duration and in F1, F2 for vowels involved in a final stress lapse and in the differences these syllables made to the perception of alternating rhythm. The present studies offer a resolution to this paradox through the finding that the degree of final lengthening and vowel reduction varies as a consequence of the stress pattern of the word.

Word-final vowels in a syllable following a stressed penult were found to show less final lengthening and greater reduction than those that occurred as part of a stress lapse, meaning they were significantly less likely to be perceived as interrupting the rhythm of the word.

The fact that duration and vowel quality were found to differ in syllables that were part of a word-final stress lapse supports the hypothesis that binary stress languages that tolerate final stress lapse nevertheless have a phonetic-level alternation over the final two syllables. It is an open question how the phonetic differences, in particular the relatively strong difference in degrees of final lengthening and vowel quality of word-final syllables, interact with the phonological stress system.

While the proposal that there is a phonetic-level alternation which carries the rhythm through the end of the word is meant to broadly account for the typological fact that final lapse is not uncommon in binary-stress languages, it is unknown at this point whether other languages also show the phonetic differences between final vowels that have been found in the current English study.

It may be that the standard level of final lengthening is enough to perceptually continue the rhythm in some languages, and that we do not generally find additional phonetic augmentations. If this is the case, it may be that English has non-crucially enhanced the phonetic difference. If, on the other hand, further investigation finds this phonetic augmentation is consistently part of the phonetic realization of final lapse, then the question of how it comes about is particularly important because the augmentation would appear to be crucial to the tolerance of final lapse.

Further work will hopefully give insight into the domain of the phonetic differences found here. Production study linear models of z-duration, z-F1, and z-F2. Production study results of word-final and secondary stressed vowels by subject.

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