Other context effects

Table 3.10 presents an overview of the results of the statistical analyses relating to the effects of the preceding segments’ identity as nasal (for the word in) and the neighbouring segments’ phonetic voicing (for the words of and to), on the relevant temporal and spectral measures. Apart from the context influences on normalised durations and vowel proportions, we inspected the effect of the preceding segments’ identity as nasal on the degree of nasalisation of the vowel in the word in, and on the

degree of nasalisation of the segment immediately following the preposition in. Further, we inspected the effects of the neighbouring segments’ phonetic voicing on fricative voicing proportion and friction intensity in the fricative (in the word of), and on the friction intensity in the plosive release (in the word to). The cells corresponding to measures that were not observed for a given function word are crossed out, while the cells where the statistical tests did not find any significant effects on the observed measure are marked with “Ø”. In the following paragraphs, all the statistically significant results will be discussed.

Table 3.10: Overview of results of statistical analyses relating to the effects of neighbouring segments’ identity as nasal (for the word in) and neighbouring segments’ phonetic voicing (for the words of and to) on relevant measures of the realisation of the function words.

IN OF TO

Normalised duration L1:left nasal * Left voicing ** Right voicing ***

Vowel proportion Left nasal ** Right voicing * Right voicing *

Fricative voicing

proportion Right voicing ***

Vowel nasalisation

degree Left nasal ***

Following segment's

nasalisation degree Ø

Friction intensity in

fricative Right voicing ***

Friction intensity in

The first column in Table 3.10 lists the effects of the preceding segments’ identity as nasal on the relevant variables observed in the realisations of the preposition in: normalised duration, vowel proportion, vowel nasalisation degree and the degree of nasalisation in the segment following the preposition. As for the normalised word duration, we observed a significant interaction of the context and the speakers’ L1 background. There was a strong tendency for longer word durations following a nasal in items produced by native English speakers, and still considerably longer durations after a nasal in items produced by Norwegian speakers. Czech speakers, however, showed a weak opposite tendency. Further, vowel proportion was found to be affected by the preceding segment’s identity as nasal. The items following a nasal had higher vowel proportions than words following a non-nasal segment. This was mainly due to the increased duration of vowels, while the duration of nasal was only slightly shorter in the words following a nasal. In addition, a large effect of the preceding segment’s identity as nasal was found on the auditorily determined degree of vowel nasalisation. The fact that vowels preceded by nasals (in fact surrounded by nasals, since all observed vowels were also followed by nasals in the word in) were produced with a significantly higher degree of coarticulatory nasalisation is not surprising. Perhaps more interestingly, there was no interaction with the L1 background. This indicates a comparable amount of nasal coarticulation for the three speaker groups. The data therefore support the assumption that since the L1 of all involved speaker groups has no phonological distinction of nasality in vowels, the coarticulatory nasalisation of vowels takes place to a similar degree in all speaker groups. In contrast to the large effect of the preceding segment’s phonological identity as nasal on the vowel in the preposition in, we did not find any effect of this factor on the degree of nasalisation of the segment following the word in.

As to the effects of phonetic voicing in the neighbouring segments that we observed in the function words of and to, the normalised durations varied considerably depending on the phonetic voicing of the neighbouring segments. For the word of, it was the preceding segment’s voicing, while the word to was influenced by the phonetic voicing in the following segment. In both words, the normalised durations were shorter in the

neighbourhood of a voiceless segment. Vowel proportion in the function words also seemed to be influenced by the presence of phonetic voicing in neighbouring segments. In both of and to, the vowel proportion was higher in words followed by voiced segments. In the word to, we could observe that vowel durations are considerably longer when followed by a phonetically voiced segment. The duration of plosives in such cases was also longer, although this was less noticeable. In the preposition of, we could observe slightly longer fricative durations before a voiceless following segment, while the vowel durations were shorter in these contexts. The pattern found in the function word to is consistent with a well-known effect of voicing in the following consonant on vowel duration (e.g. House and Fairbanks, 1953; House, 1961; Kluender et al., 1988; van Santen, 1992) although it should be noted that our material is not controlled for stress, utterance position and other factors that were found to interact with this effect. The pattern found in the word of seems rather complex and less clear to interpret. In addition to the previously discussed temporal measures, we expected a large influence of neighbouring segments’ phonetic voicing on the two measures related to voicing (fortis/lenis character) of the fricative in the preposition of: the fricative voicing proportion and the friction intensity in the fricative. As expected, the analyses revealed a large influence of the phonetic voicing in the segment immediately following the fricative on both measures. The voicing proportion was greater and the friction intensity lower in fricatives followed by voiced segments, consistently in the three speaker groups with different L1 backgrounds. Moreover, this effect appeared to be stronger in spontaneous than in read speech. It can be speculated that this consistent effect of the following segment voicing is due to similar regressive voicing assimilation processes existing in the three languages (cf. Section 1.3.3). As opposed to the effects of neighbouring segments’ phonetic voicing on the observed measures related to voicing in the word of, the measure of friction intensity in the release portion of the plosive in the word to was not found to be affected by the presence of phonetic voicing in either the preceding or following segment.

Apart from describing the effects of some of the context properties, we also inspected the distributions of context with regard to the segments’ identity as nasal (for the word

in) and the neighbouring segments’ phonetic voicing (for the words of and to), in the groups of items based on the speakers’ L1 background and speaking style. The distribution of nasals preceding the preposition in was found not to differ between the groups. Similarly, the distribution of the voiced and voiceless preceding segment did not vary significantly between the groups based on the speakers’ L1 background and speaking style in either of or to. In contrast to that, the distributions of phonetic voicing in the following segment in both the function words of and to differed significantly. In both function words, we found that native English speakers had significantly larger proportions of voiceless following contexts. In the word to, the difference between speaker groups was more noticeable in spontaneous speech, where both non-native groups had extremely low proportions of voiceless following contexts. These findings are very important to keep in mind when interpreting the results of measures that were shown to be strongly affected by the following segment voicing. Based on the previous analyses, this would include the normalised durations in the word to, the vowel proportions in both of and to, and especially the voicing proportion and friction intensity in the preposition of, which will be discussed in the next sections.