«Year: 2016 On the origin of post-aspirated stops: production and perception of /s/ + voiceless stop sequences in Andalusian Spanish Ruch, Hanna; ...»
The total duration of the voiceless interval in hC-sequences will be quantified by summarizing voice termination time, duration of the oral stop closure, and voice onset time.
This procedure is based on the idea that one underlying glottal gesture is present for each aspirated /s/ + stop sequence. Although no physiological data for Andalusian Spanish is so far available, the idea of a single glottal opening gesture is supported by acoustic data provided by Torreira (2012), who found a consistent co-variation between the sum of pre-aspiration and closure duration and VOT, as well as by Parrell (2012), where preaspiration duration co-varied with post-aspiration duration.
Figure 5 displays the total duration of the voiceless interval in hC- and C-sequences.
The values appear to be very stable not only across variety and age group, but also across place of articulation. It is further apparent that the total duration of the voiceless interval is greater in hC-sequences than in C-sequences in all four speaker groups and among all three places of articulation. A mixed model with the total duration of the voiceless Ruch and Peters: On the Origin of Post-Aspirated Stops Art. 2, page 17 of 36 interval as the dependent variable, with Age, Variety, and Sequence as fixed factors, and with Word and Speaker as random factors showed a significant three-way interaction (χ2 = 4.0, p 0.05). The interaction might have come about because of younger WAS speakers displaying a slightly shorter total duration for the intervocalic stop /t/, while the other three speaker groups showed slightly longer total durations in this context.
Post-hoc Tukey tests confirmed what is evident from Figure 5 that C- and hC-sequences clearly differed in all four speaker groups (p 0.001), and that there was no influence of Age or Variety on this measure. These results show that speakers of Eastern and Western Andalusian Spanish distinguish C- from hC-sequences in production, the latter being produced with a very long voiceless interval (mean = 155.8 ms) which is almost twice as long as in intervocalic stops (mean = 82.4 ms).
The next step is to analyze the duration of the preceding vowel in hC-sequences. If the gradual shift from pre- to post-aspiration came about because of a rightwards shift of the glottal opening, i.e., because the glottal opening takes place later in time, we would expect younger speakers to produce a longer preceding vowel than older speakers. Indeed, some studies (Carlson, 2012; Figueroa, 2000; Resnick & Hammond, 1975) suggest that lengthening of the preceding vowel compensates for /s/-weakening (in their case, /s/deletion) in some varieties of Spanish. The question in the present study is if the fading of Figure 5: Total duration of the voiceless interval in intervocalic stops (yellow) and in hC-sequences (green) according to place of articulation, variety, and age group.
Art. 2, page 18 of 36 Ruch and Peters: On the Origin of Post-Aspirated Stops pre-aspiration (not the debuccalisation of /s/) is compensated for by vowel lengthening.
The preceding vowel duration will be quantified by measuring the interval between the onset of the preceding vowel (V1.Onset) and the offset of voicing (V1.Offset). C-sequences are taken into account by way of comparison.
In 120 hC-tokens (9.6%) and in 189 C-tokens (24.6%), VTT was negative, meaning that voicing extended into the oral closure. In these cases, the interval between V1.Onset and Cl.Onset was used instead to assess vowel duration. The duration of the preceding vowel is shown in Figure 6. Vowels preceding C-sequences are slightly longer than those preceding hC-sequences. This difference is, however, not very consistent: vowel duration preceding hC-sequences appears to be longer in Eastern than in Western Andalusian Spanish, and in Western Andalusian Spanish slightly longer for older than for younger speakers. Taken together, vowels preceding C- or hC-sequences seem to be shorter when produced by young WAS speakers than when produced by older WAS speakers, which may be attributed to the observed differences in speech rate (see Figure 4).
In a first step the influence of phonological sequence (hC vs. C), age, and variety on vowel duration was tested using a mixed model in which Speaker and Word were included as random factors. This model showed a significant effect of Sequence (χ2 = 27.0, p 0.001) and Age (χ2 = 22.1, p 0.001) on Vowel Duration. Since there was a two-way interaction between Age and Sequence (χ2 = 19.6, p 0.001), post-hoc Tukey tests were conducted and indicated that Vowel Duration preceding /C/ and /sC/ differed only in older (p 0.001), but not in younger speakers. There was no significant difference in Vowel Duration between older and younger speakers in any of the phonological sequences.
In a second step the influence of age and variety on vowel duration was tested for hC-tokens with a positive VTT only. A mixed model with Vowel Duration as the dependent variable, Age and Variety as fixed factors, and Word and Speaker as random factors revealed no significant effects. This suggests that younger and WAS speakers Figure 6: Duration of the vowel preceding singleton stops (yellow) and hC-sequences (green).
Each boxplot contains one mean value per speaker.
Ruch and Peters: On the Origin of Post-Aspirated Stops Art. 2, page 19 of 36 do not realize the glottal abduction (devoicing gesture) later in time than older and EAS speakers; in other words, there is no rightwards shift of the devoicing gesture in apparent-time.
As a last step, closure duration in C- and hC-words will be looked at. Figure 7 suggests that closure duration is longer in hC- than in C-sequences, a tendency that seems to be more marked in EAS than in WAS. A mixed model with Closure Duration as the dependent variable, Age, Variety, and Sequence (hC- vs. C-words) as fixed factors, and Speaker and Word as random factors confirmed that Closure Duration was significantly longer in hC-sequences than in singleton stops (χ2 = 55.5, p 0.001) in both varieties.
Furthermore, there was a significant interaction between Sequence and Age (χ2 = 7.7, p 0.01) as well as between Sequence and Variety (χ2 = 30.5, p 0.001). The results of post-hoc Tukey tests displayed highly significant differences between C- and hCsequences for all four speaker groups (p 0.001), and a significant difference in Closure Duration of hC-sequences between young WAS speakers and the two EAS speaker groups (p 0.05). This means that younger WAS speakers produced shorter closure durations.
There was no significant effect of Age or Variety on the closure duration in C-words.
The results for closure duration have to be interpreted with caution because of the slightly faster speech rate of young WAS speakers (see Section 2.2.1). It might be the case that the reduction processes due to a faster speech rate affect the long closure duration in hC-sequences to a greater extent than in singleton stops. If this is the case, then the Figure 7: Duration of the oral closure in intervocalic stops (yellow) and hC-sequences (green).
Each boxplot contains one mean value per speaker.
Art. 2, page 20 of 36 Ruch and Peters: On the Origin of Post-Aspirated Stops smaller difference between C- and hC-sequences in young WAS speakers cannot be traced back to the sound change, but to speech reduction processes that affect long segments to a greater degree than short segments.
2.3 Discussion In this section further durational parameters have been analyzed that might be related to the change from pre- to post-aspiration in Andalusian Spanish: the total duration of the voiceless interval in (h)C-sequences, the duration of the preceding vowel, and the duration of the stop closure. The aim of these analyses was to shed light on the stability and variation of these durational parameters, and to investigate whether the sound change is associated with a change in one of these parameters.
The total duration of the voiceless interval was significantly longer in hC-sequences than in intervocalic stops for both varieties and age groups. The analysis further demonstrated that the total duration of hC-sequences—as inferred from the total duration of the voiceless interval—is very stable across varieties, place of articulation, and age groups, and is not affected by the sound change.
There was no effect of age or variety on the duration of the preceding vowel, suggesting on the one hand that, relative to the onset of the preceding vowel, the glottal opening gesture does not take place later in time in younger than in older speakers. At the same time, this finding does not support compensatory vowel lengthening that has been suggested as taking place in Eastern Andalusian (Carlson, 2012), in Cuban (Resnick & Hammond, 1975), and in Puerto Rican Spanish (Figueroa, 2000). By contrast, vowels were slightly shorter when followed by a phonological /s/ + voiceless stop than when preceding intervocalic stops. This finding, again, does not support the assumption of vowel lengthening as a compensation for /s/-lenition. An inter-dialectal comparison at this point, however, is difficult because of the different methods used to measure pre-aspiration and vowel duration. In an auditory or manual segmentation procedure, for instance, the breathy part of the vowel (voiced aspiration) can be treated either as part of the vowel or as pre-aspiration (see Gerfen, 2002, for a discussion of this issue).
Closure duration appeared to be an important parameter for distinguishing C- and hCsequences in production, displaying significantly longer durations in hC- than C-sequences in all four speaker groups. This effect, however, appeared to be less marked in younger Western Andalusian speakers, who also pronounced the longest post-aspiration (see Section 2.2.1). The long stop closures that were found not only for younger, but also for older speakers in both varieties suggest that long stop closures did not arise to compensate for the shortening of pre-aspiration, but might have arisen previous to the sound change to compensate for /s/-weakening (see Gerfen, 2002; Ruch & Harrington, 2014).
Taken together, the results of the closure duration, the duration of the voiceless interval, and the previous vowel suggest that the shortening of pre-aspiration came about because the oral closure is formed earlier in time, while the timing of the glottal abduction relative to the preceding vowel remains relatively constant across age, variety, and place of articulation.
3 Perception In order to test whether the sound change from pre-aspiration to post-aspiration also affects perception, a forced-choice perception experiment was conducted. A VOT-continuum was synthesized between the minimal pair pasta [ˈpatha] – pata [ˈpata], with pata having a short VOT (15 ms) and pasta having a long VOT (55 ms). If post-aspiration is used as a cue to /st/, then listeners of Andalusian Spanish are expected to distinguish the stimuli Ruch and Peters: On the Origin of Post-Aspirated Stops Art. 2, page 21 of 36 of the VOT-continuum in a categorical manner. If the sound change also affects perception and if there is a relationship between the production and perception of post-aspiration, then younger and Western Andalusian listeners should be more sensitive to VOT as a cue for /st/ than older and Eastern Andalusian listeners. That is, younger and WAS listeners are expected to need a shorter VOT to perceive pasta, and they should differentiate more consistently between the two words (i.e., show a more categorical perception).
3.1 Method As a baseline for the VOT-continuum, the utterances Digo pasta ‘I say paste’ [ˈdiɣo ˈpatha] and Digo pata ‘I say paw’ [ˈdiɣo ˈpata], produced by a 31-year-old female speaker from Seville, were used. The VOT in the originally produced tokens was 55 ms for [ˈpatha], and 13 ms for [ˈpata]. Measures of the preceding and the following vowel V1 and V2 and the oral closure are summarized in Table 3. The pasta-continuum was generated by shortening the long VOT of pasta (55 ms) in eight equal steps (5 ms each) to 15 ms using the Akustyk plugin in Praat (Boersma & Weenink, 2011). Therefore, all nine stimuli of the pasta-continuum showed exactly the same acoustic properties except for VOT. The patacontinuum was generated by replacing the short original VOT of pata (13 ms) by the long VOT of pasta (55 ms). The long VOT was then shortened using the same procedure as in the pasta-continuum, generating 9 stimuli that differed only in VOT. The reason for doing so was that pata and pasta differ not only in VOT, but also in other acoustic parameters such as the duration of stop closure and the duration of the preceding vowel (see Table 3).
If listeners use closure duration as a cue to the minimal pair pata-pasta, then they might answer pasta to all stimuli within the continuum. In the original pasta token, the C:V1relationship turned out to be greater than in pata. These differences will be taken into account in the analysis and the discussion of the results. The 18 stimuli of the two continua were multiplied, resulting in 9 (steps) × 2 (continua) × 10 (repetitions) = 180 stimuli, and embedded in a randomized order in an online perception experiment using Percy (Draxler, 2011).
Listeners were told that they would hear an Andalusian woman saying the word “pata” or “pasta”. They were asked to judge for each stimulus if they heard pata or pasta and mark the corresponding box with the orthographic form on the computer screen. They could listen once to every example, and there were no training tokens. All listeners used Beyerdynamic DT-770 Pro Studio headphones and ran the experiment in a quiet room.
The whole experiment took between 10 and 30 minutes.
Seventy-nine listeners participated in the perception experiment. Because of technical problems, 5 subjects judged fewer than 170 out of 180 stimuli, so we removed their data. The remaining 74 subjects completed between 94 and 100% of the experiment (9 or 10 repetitions of each stimulus). As in the production study, there were an approximately equal number of subjects from Seville (39; 14 women and 25 men) and Granada