Influence of context on the realisations of the word to

As in Section 3.3.3.3, this section will examine the influence of neighbouring segment type and voicing on selected parameters of the realisation of the function word to. We considered it relevant to inspect the influence of segment type on measures relating to temporal organisation and on the first formant measure indicating the degree of openness of the vowel. As for the influence of phonetic voicing in the neighbouring segment, we inspected the normalised duration measure, vowel proportions, and the measure of friction intensity in the plosive release.

The item durations varied considerably depending on the type of following segment, the mean normalised durations being 130 ms for items followed by consonants and 157 ms for items followed by vowels. Figure 3.29 displays the normalised duration means in the word to for speaker groups with different L1 backgrounds and different speaking styles, depending on the type of following segment. It can be seen that the items followed by

vowels have consistently longer normalised durations than items followed by consonants. The type of preceding segment, on the other hand, did not have a very noticeable effect (mean values being 131 ms vs. 136 ms 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 showed, as expected, only a significant effect of right segment type (F(2, 263)= 6.66; p= 0.010). No other effect or interaction reached significance.

Figure 3.29: Normalised duration means (in ms) in the word to 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 proportions also varied depending on the type of following segment (mean vowel proportions being 26% vs. 30% for items followed by consonants and vowels, respectively). An analysis of variance with the factors L1 background, speaking style, and left and right segment type showed only a marginally significant effect of right segment type (F(1, 262)= 3.80; p= 0.052), while no other effect or interaction reached significance. The proportion of plosive release, on the other hand, seemed to be influenced by the preceding segment type. The mean release proportions were higher for words preceded by consonants (55%) than for words preceded by vowels (49%). It

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

ms consonant

is important to realise that the release proportion is a percentual complement to closure proportion, and the higher values of release proportion thus indicate a shortened closure phase. Surprisingly, an analysis of variance with the factors L1 background, speaking style, and left and right segment type showed only a significant effect of speaking style (F(1, 262)= 6.27; p= 0.013) but no significant effect of left segment type (F(1, 262)= 1.44; p= 0.232), nor any other effects or interactions.

As for the influence of neighbouring segment type on vowel openness, the values of the F1 - F0 Bark distance varied depending on the type of following segment. Mean F1 - F0 Bark distances depending on the following segment type for speaker groups with different L1 backgrounds in the two speaking styles, are shown in Figure 3.30.

Figure 3.30: Mean F1 - F0 distances (in Bark) in the vowel of the word to 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 Bark distance values were lower when the preposition to was followed by consonants (2.0 Bark) than when it was followed by vowels (2.4 Bark). Similar to the effect of left segment type on the first formant measure in the word of, this difference is likely to be a consequence of the degree of opening of the articulators in the speech

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

Bark consonant

sound directly adjacent to the observed vowel. An analysis of variance with the factors L1 background, speaking style, and left and right segment type showed only a significant effect of right segment type (F(1, 210)= 6.40; p= 0.012). Since previous analyses have shown that the F1 - F0 Bark distance differs depending on speakers’ gender, we also carried out an analysis of variance with gender as a factor, apart from the previously mentioned factors. The results confirmed a significant effect of following segment type (F(1, 193)= 6.70; p= 0.010) as well as an effect of L1 background (F(2, 193)= 6.02; p= 0.003) and speaker’s gender (F(1, 193)= 13.3; p< 0.001).

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 to. The normalised word durations seemed to vary depending on the voicing of the following segment (115 ms vs. 138 ms in items with following voiceless vs. voiced segment). Figure 3.31 displays the normalised duration means for items followed by voiceless and voiced segments for the three speaker groups with different L1 backgrounds in the two speaking styles. An analysis of variance with the factors L1 background, speaking style and presence of phonetic voicing in the preceding and following segment confirmed a significant effect of following segment voicing on normalised duration (F(1, 262)= 14.5; p< 0.001). No other significant effects or interactions were found.

Furthermore, we inspected the effect of phonetic voicing in the neighbouring segments on segment proportions in the realisations of the word to. We found higher vowel proportions in items followed by voiced segments (23% vs. 28%, for items with voiceless vs. voiced right context). An analysis of variance with L1 background, speaking style and presence of phonetic voicing in the preceding and following segment as factors confirmed, apart from a significant effect of L1 background, the effect of following segment voicing (F(1, 261)= 4.30; p= 0.039). No other effects or interactions reached significance. As for the effect of phonetic voicing in the neighbouring segments on friction intensity in the plosive release phase, an analysis of variance with the factors L1 background, speaking style and presence of phonetic voicing in the preceding and

following segment showed no significant effects or interactions apart from the effect of L1 background.

Figure 3.31: Normalised duration means (in ms) in the word to followed by voiceless/voiced segment, for speaker groups with different L1 backgrounds (CZ=Czech, EN=English, NO=Norwegian) and different speaking styles (R=read, S=spontaneous).

As in the previous sections, here we will also describe 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)= 10.6; p= 0.06 and χ}2_{(5)= 10.2; p= 0.071, for left and right segment type}

distributions, respectively). Also the distribution of voiced/voiceless segments preceding the word to was not found to differ significantly for the groups based on the speakers’ L1 background and speaking style (χ2(5)= 3.02; p= 0.697). The distributions of phonetically voiced/voiceless segments following the tokens of the function word to, however, differed significantly between the groups (χ2_{(5)= 20.2; p= 0.001). The}

distributions of phonetically voiced/voiceless segments following the word to for

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ms voiceless

groups of items based on the speakers’ L1 background and speaking style are shown in Figure 3.32. As in the following segment voicing distributions for the word of, the number of tokens with voiceless following segments is higher among the English items compared to items produced by non-natives. This difference is very noticeable, especially in spontaneous speech. Due to that, we have to consider the possibility of confounding the effects of the L1 background and speaking style with the effects of unevenly distributed voicing in right segment (see Section 3.4 below).

Figure 3.32: Distributions of phonetically voiced/voiceless segments following the word to (numbers of tokens), for speaker groups with different L1 backgrounds (CZ=Czech, EN=English, NO=Norwegian) and different speaking styles (R=read, S=spontaneous).