In a production study, Bulgarian, English and German verses with regular poetic metrical metres of different types and elicited prose utterances with varied accentual patterns are produced in textual and iterative (dada) form and measured at syllable level according to the pairwise variability index (PVI) principle. Systematic differences in PVI values show that the measure is sensitive to metrical differences. But variations for utterances with the same metrical structure and comparable measures for accentually different utterances show the measure to be insensitive to the temporal distribution of accents. A perceptual experiment with Bulgarian, English and German subjects confirms the hypothesis that the perceived strength of rhythmicity in a line of verse is determined not only by its temporal structure, but also by other acoustic properties, most clearly by F₀ change within the metrical foot.

Quasi-spontaneous dialogues from six languages which, according to recent discussion of rhythmic types, belong to three rhythmic groups ± Russian and Bulgarian as`stress-timed', Italian and Greek as`syllable-timed' and Polish and Czech as an intermediate`mixed' type ± were examined for the following segmental reduction phenomena: reduction of consonant clusters, weakening of consonant articulation, residual properties from elided consonants in the original context segments, phonetic schwa-isation and syllable elision. The hypothesis tested was that there are comparable reduction phenomena in all languages since all languages allow for variation in the time and effort invested in any given part of an utterance as a means to support the relative weight of elements within the information structure. This hypothesis was borne out in principle, though there were a small number of exceptions across the six languages to the occurrence of reduction types examined.

Contextual predictability variation affects phonological and phonetic structure. Reduction and expansion of acoustic-phonetic features is also characteristic of prosodic variability. In this study, we assess the impact of surprisal and prosodic structure on phonetic encoding, both independently of each other and in interaction. We model segmental duration, vowel space size and spectral characteristics of vowels and consonants as a function of surprisal as well as of syllable prominence, phrase boundary, and speech rate. Correlates of phonetic encoding density are extracted from a subset of the BonnTempo corpus for six languages: American English, Czech, Finnish, French, German, and Polish. Surprisal is estimated from segmental n-gram language models trained on large text corpora. Our findings are generally compatible with a weak version of Aylett and Turk's Smooth Signal Redundancy hypothesis, suggesting that prosodic structure mediates between the requirements of efficient communication and the speech signal. However, this mediation is not perfect, as we found evidence for additional, direct effects of changes in surprisal on the phonetic structure of utterances. These effects appear to be stable across different speech rates.

We investigated the influence of prosodic structure and information density on vowel space size. Vowels were measured in five languages from the BonnTempo corpus, French, German, Finnish, Czech, and Polish, each with three female and three male speakers. Speakers read the text at normal, slow, and fast speech rate. The Euclidean distance between vowel space midpoint and formant values for each speaker was used as a measure for vowel distinctiveness. The prosodic model consisted of prominence and boundary. Information density was calculated for each language using the surprisal of the biphone Xn|Xn−1. On average, there is a positive relationship between vowel space expansion and information density. Detailed analysis revealed that this relationship did not hold for Finnish, and was only weak for Polish. When vowel distinctiveness was modeled as a function of prosodic factors and information density in linear mixed effects models (LMM), only prosodic factors were significant in explaining the variance in vowel space expansion. All prosodic factors, except word boundary, showed significant positive results in LMM. Vowels were more distinct in stressed syllables, before a prosodic boundary and at normal and slow speech rate compared to fast speech.