Objetivos específicos

In this section we will inspect the influence of some aspects of context on various parameters in the production of the preposition of. This includes the influence of the type (vowel or consonant) of neighbouring segments, and the influence of phonetic voicing in the neighbouring segments on relevant measures in the realisations of the preposition of. With regard to the previous research (cf. Section 1.2.1.1) it seemed relevant to inspect the influence of context type on measures relating to temporal organisation. In addition, we observed the context type influence on the first formant measure (Bark distance F1 - F0) indicating the degree of openness of the vowel. As for the influence of phonetic voicing, we inspected the temporal measures, and the measure of friction intensity in the fricative.

The normalised durations seemed to differ somewhat depending on the type of segment both preceding and following the preposition of. The mean normalised durations were 107 ms for words preceded by consonants and 117 ms for items preceded by vowels. The mean normalised word duration values for items depending on the immediately following segment type were 105 ms and 116 ms, for words followed by consonants and vowels, respectively. Figure 3.22 displays the means of normalised durations in the word of followed by different segment types (consonant or vowel) for different speaker groups and speaking styles.

We can observe that apart from the group of spontaneous items produced by the Czech speakers, the normalised durations are longer in items followed by vowels. Since Levene’s test indicated unequal variances with high significance (p< 0.001) we performed the statistical tests using non-parametric tests inspecting the effect of left and right context type. Kruskal-Wallis tests showed that while there was no significant effect of the preceding segment type (χ2 (1)= 2.16; p= 0.141), the following segment type affects the normalised durations significantly (χ2 (1)= 4.91; p= 0.027).

Figure 3.22: Normalised duration means (in ms) in the word of followed by different segment types (consonant or vowel), for speaker groups with different L1 backgrounds (CZ=Czech, EN=English, NO=Norwegian) and different speaking styles (R=read, S=spontaneous).

The vowel proportion within the word duration seemed to be influenced by the right segment type as well, the mean vowel proportions being 50% for items followed by consonants and 43% for items followed by vowels. On the contrary, the preceding segment type had almost no effect (means being 49% vs. 51% for items preceded by consonants and vowels, respectively). An analysis of variance with the factors L1 background, speaking style, left segment type and right segment type, however, showed neither a significant effect of L1 background and speaking style, nor a significant effect of the preceding or following segment type on this variable.

The proportion of phonetically voiced fricative part within the duration of fricative also proved to be slightly influenced by both the preceding and following segment types. The mean fricative voicing proportions were 74% for items preceded by consonants and 69% for items preceded by vowels. The means for items depending on the type of following segment were 72% (for items followed by consonants) and 79% (for items followed by vowels). Here, too, Levene’s test indicated unequal variances with high significance (p< 0.001). Therefore, we performed the statistical tests using non-

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CZ-R CZ-S EN-R EN-S NO-R NO-S

ms consonant

parametric tests inspecting the effect of left and right context type. Kruskal-Wallis tests showed that neither the preceding segment type (χ2 _{(1)< 1) nor the following segment}

type (χ2 _{(1)= 2.44; p= 0.118) had a significant effect on the proportion of voicing in}

fricatives.

As for the measures of vowel quality, we found that the mean F1 - F0 Bark distance, corresponding to vowel openness, varied consistently depending on the type of preceding segment. The values were lower when the preposition of followed consonants (2.9 Bark) than when it followed vowels (3.4 Bark). This finding is not surprising, considering the expected positions of the articulators for the basic classes of speech sounds, specifically the presumably more open vocal tract for the articulation of vowels. The F1 - F0 values for items followed by segments of different types did not differ at all (3.0 Bark for items followed by both types of speech sounds). The mean F1 - F0 values for the three speaker groups and different speaking styles, depending on the type of preceding segment are presented in Figure 3.23.

Figure 3.23: Mean F1 - F0 distances (in Bark) in the vowel of the word of preceded by different segment types (consonant or vowel), for speaker groups with different L1 backgrounds (CZ=Czech, EN=English, NO=Norwegian) and different speaking styles (R=read, S=spontaneous).

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CZ-R CZ-S EN-R EN-S NO-R NO-S

Bark consonant

It can be observed that the effect of the preceding segment type is consistent for all speaker groups with different L1 backgrounds and both speaking styles. An analysis of variance with the factors L1 background, speaking style, left segment type and right segment type, however, showed only a significant effect of speaking style (F(1, 248)= 4.77; p= 0.030) but surprisingly no significant effect of preceding segment type (F(1, 248)= 3.29; p= 0.071). Since previous analyses have shown that the F1 - F0 Bark distance values in our data differ between speakers of different genders, we also carried out an analysis of variance with gender as a factor, apart from the previously mentioned factors. The results of this analysis confirmed a significant effect of preceding segment type (F(1, 231)= 3.99; p= 0.047) and an effect of speaker gender (F(1, 231)= 5.72; p= 0.018) on the F1 - F0 Bark distance measure.

In addition to analysing the effects of the type of neighbouring segments (consonant or vowel), we examined the influence of phonetic voicing in the neighbouring segments on the realisation of the function word of. The normalised durations were considerably shorter in items preceded by a voiceless segment (101 ms) as compared to items preceded by a voiced segment (113 ms). The following segment voicing, on the other hand, did not seem to have an effect on the normalised duration of items (108 vs. 107 ms, for items followed by voiceless or voiced segment, respectively). Since Levene’s test indicated unequal variances with high significance (p< 0.001) we performed the statistical tests using non-parametric tests inspecting the effect of phonetic voicing in preceding and following segments. Kruskal-Wallis tests showed that there was a significant effect of preceding segment voicing (χ2 (1)= 8.85; p= 0.003), but as could be expected, the effect of phonetic voicing in the following segment did not reach significance (χ2 _{(1)< 1).}

The proportion of vowel within the word duration also seemed to be influenced by voicing in the neighbouring segments. The mean vowel proportions were 46% when preceded by a voiceless segment, and 51% when preceded by a voiced segment. The proportion also varied depending on the phonetic voicing in the segment following the preposition, amounting to 46% vs. 50% for items followed by a voiceless and voiced

segment, respectively. An analysis of variance with L1 background, speaking style and presence of phonetic voicing in the preceding and following segment as factors, showed, apart from significant effects of the speakers’ L1 background and speaking style, and an interaction between these two factors, a significant effect of phonetic voicing in the following segment as well (F(1, 270)= 4.71; p= 0.031). The effect of phonetic voicing in the preceding segment, however, did not reach significance.

When we consider the phonetic voicing in neighbouring segments, an especially large effect could be expected on the proportion of voicing within the fricative. While voicing in the preceding segment did not have a large influence on the voicing proportion (72% vs. 76% for items preceded by voiceless and voiced segments, respectively), the voicing proportion difference due to voicing in the following segment was considerable (52% vs. 85% for items followed by voiceless and voiced segments, respectively). Figure 3.24 shows the influence of following segment voicing on the proportion of fricative voicing for speaker groups with different L1 backgrounds and different speaking styles.

Figure 3.24: Proportions of voicing in the fricative (in %) in the word of followed by a voiceless/voiced segment, for speaker groups with different L1 backgrounds (CZ=Czech, EN=English, NO=Norwegian) and different speaking styles (R=read, S=spontaneous).

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% Voiceless

Here Levene’s test also indicated unequal variances with high significance (p< 0.001). Therefore, we performed the statistical tests using non-parametric tests inspecting the effect of voicing in the preceding and following segment. Kruskal-Wallis tests showed that while there was no significant effect of preceding segment voicing (χ2 (1)< 1), the voicing in the following segment had a highly significant effect on the proportion of voicing within the fricative (χ2 _{(1)= 62.6; p< 0.001). Moreover, we can observe larger}

differences between items with voiceless and voiced context in spontaneous speaking style (52% vs. 95%) than in read speech (52% vs. 74%), as can be observed in Figure 3.24. The Kruskal-Wallis tests carried out separately for read and spontaneous items showed that the right context voicing effect was highly significant both in read (χ2 (1)= 11.5; p< 0.001) and spontaneous speech (χ2 _{(1)= 70.3; p< 0.001).}

Lastly, we inspected the influence of context voicing on friction intensity, an acoustic variable closely related to the proportion of voicing in the fricative. As was expected, we found a large difference in the mean values due to voicing in the following segment (-15 dB vs. – 31 dB for items with voiceless vs. voiced right context). As with the previous measure of fricative voicing proportion, here, too, Levene’s test indicated unequal variances with high significance (p< 0.001). Therefore, we performed the statistical tests using non-parametric tests inspecting the effect of phonetic voicing in the preceding and following segment. Kruskal-Wallis tests showed that while there was no significant effect of preceding segment voicing (χ2 _{(1)< 1), the voicing in the}

following segment had a highly significant effect on the friction intensity in the fricative (χ2 (1)= 58.3; p< 0.001).

Apart from describing how context factors may influence the realisations of the preposition of, we were also interested in the distribution of the various aspects of context in the present dataset. First we inspected the distributions of segment types of the immediately neighbouring left and right context, comparing the groups of items based on the speakers’ L1 background and speaking style (see Tables 3.4 and 3.5 on page 98). Pearsons’ Chi-squared tests showed that neither the left segment type distributions nor the right segment type distributions varied significantly between the

groups (χ2(5)= 8.43; p= 0.134 and χ2(5)= 7.42; p= 0.191, for left and right segment type distributions, respectively). In a similar way, we inspected the distributions of voiced/voiceless segments preceding and following the word of, for the subgroups based on the speakers’ L1 background and speaking style. Pearsons’ Chi-squared tests showed that while the distributions of phonetically voiced/voiceless preceding segments did not vary significantly between the groups (χ2_{(5)= 4.75; p= 0.447), the distributions}

of phonetically voiced/voiceless segments following the tokens of the function word of differed significantly between the groups (χ2(5)= 26.5; p< 0.001). The distributions of phonetically voiced/voiceless segments following the word of for groups of items based on the speakers’ L1 background and speaking style are displayed in Figure 3.25. We can observe that the number of tokens with a voiceless following segment is noticeably higher among the English items in both speaking styles. The possibility of confounding the effects of L1 background and speaking style with the effects of unevenly distributed voiced/voiceless following segments has to be taken into consideration when interpreting the results.

Figure 3.25: Distributions of phonetically voiced/voiceless segments following the word of (numbers of tokens), for speaker groups with different L1 backgrounds (CZ=Czech, EN=English, NO=Norwegian) and different speaking styles (R=read, S=spontaneous).

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voiceless voiced