3.1 Posterior articulations: Velars and uvulars

The acoustic distinctions between uvular and velar consonants are rarely addressed in the literature, although it is acknowledged that this contrast is particularly interesting since it might be hard to perceive (Shosted Reference Shosted and Heriberto2011). Across languages, uvular and pharyngeal consonants are often associated with vowel lowering and backing (Bessell Reference Bessell1998, Wilson Reference Wilson2007, Shosted Reference Shosted and Heriberto2011, Denzer-King Reference Denzer-King2013, Sylak-Glassman Reference Sylak-Glassman2014).^{Footnote 1}

Shosted (Reference Shosted and Heriberto2011) compared the effects of velars and uvulars on a preceding vowel in the Mayan language Q’anjob’al, observing that uvulars tend to lower F2 and raise F1. Denzer-King (Reference Denzer-King2013) finds that uvulars lower the F2 of the following /a/ in Tlingit (Na-Dene), compared to velars. The lowering and retraction effects of uvulars are also found for Nuu-chah-nulth (Wakashan) by Wilson (Reference Wilson2007) and for Interior Salish languages by Bessell (Reference Bessell1998), although these two studies compare uvulars and pharyngeals to both velars and coronals. Sylak-Glassman (Reference Sylak-Glassman2014: 69) – in a large typological sample – finds that vowel backing is much more common next to uvular consonants than next to pharyngeals. His sample also shows that backing is mostly non-neutralizing, i.e. allophonic, and that lowering is common for most post-velar consonants.

The velar–uvular distinction often manifests itself differently for preceding vs. following vowels, and for different vowel qualities. In Q’anjob’al, the F2 effects of uvulars are more pronounced for front vowels [i e] (Shosted Reference Shosted and Heriberto2011). Similarly, the results in Alwan (Reference Alwan1986) suggest that in Arabic the uvular consonants lower F2 of a following front vowel /iː/ much more drastically than for /aː uː/ (see especially pp. 70–77 and Figure 3.10). Wilson (Reference Wilson2007) reports varying degrees of lowering and backing for different vowels in Nuu-chah-nulth.

Based on these findings, we expect that Mee allophone [ɢ^ʁ] may have a backing and/or lowering effect on the preceding vowels. We also anticipate that these effects may be realized differently for different preceding vowel qualities.

3.2 Lateral acoustics

In this section, we review the existing literature on the acoustics of velar laterals, and laterals in general, in order to infer possible hypotheses about the acoustics of the velar lateral in Mee. We expect only one of the relevant allophones in Mee to have a lateral release, and therefore it is important to also summarize the acoustic characteristics of laterals that set them aside of fricatives.

One such characteristic is periodicity. As Maddieson (Reference Maddieson1984) uncovers in his typological study, lateral consonants tend to be sonorants in the languages of the world. This also means that they are part of the class of sounds exhibiting spontaneous voicing (Rice & Avery Reference Rice, Peter, Carole and Jean-François1991, among others).^{Footnote 2} Similarly, Maddieson & Emmorey (Reference Maddieson and Karen1984) report that even voiceless lateral approximants tend to anticipate the voicing of the following vowels more than the corresponding fricatives. Therefore we expect that lateral release in Mee velars will exhibit periodicity, and it will be less likely to undergo devoicing than [ɢ^ʁ], even in contexts where obstruents may be fully or partially devoiced. On the other hand, the fricated release of [ɢ^ʁ] may be more susceptible to devoicing than [ɡᶫ].

Laterals are also characterized by the presence of formant structure, and since in their articulation the passage of air has a side branch, the acoustic models of laterals include an anti-formant (Fant Reference Fant1970, Bladon Reference Bladon, Harry and Patricia1979, Stevens Reference Stevens1998, Johnson Reference Johnson2012). However, laterals exhibit a high degree of variability in their acoustics (Stevens Reference Stevens1998, Proctor Reference Proctor2009, Tabain et al. Reference Tabain, Butcher, Breen and Beare2016), and Ladefoged (Reference Ladefoged2003: 148) notes that the place of articulation of lateral consonants is not easily inferred from the acoustic signal. The existing classical acoustic models of coronal laterals are also different in a number of respects. As we will see, these models are underdeveloped for velar laterals, primarily due to lack of articulatory data. Stevens (Reference Stevens1998: 543–554) estimates the first three resonances for English onset (i.e. light) /l/ at 360 Hz, 1100 Hz and 2800 Hz with a clustering of at least three additional formants in the region between 3500 Hz and 4500 Hz. However, according to Stevens, the F4 at 3500 Hz is effectively canceled by the anti-resonance which is estimated at around 3400 Hz. Fant (Reference Fant1970: 162–168) presents an acoustic model of the Russian non-palatalized /l/ which also predicts a separation of F2 and higher resonances. However, Fant estimates the anti-formant for Russian /l/ at about 2 KHz, much lower than the estimate for English by Stevens. Fant also estimates a clustering of several resonating frequencies in the higher-frequency region above 2250 Hz.

In contrast, Johnson (Reference Johnson2012) models the English lateral with a schwa-like tube with a side track and predicts 531 Hz, 1594 Hz and 2656 Hz resonances for a uniform tube. Johnson notes that F1 is likely to be lowered by the fact that the cavity in front of the constriction is smaller in diameter than the cavity behind it. F2 is possibly also lowered for velarized (i.e. dark) /l/, which in English occurs syllable-finally. The small pocket of air trapped on top of the tongue just behind the alveolar constriction is expected to yield an anti-formant at around 2125 Hz, although Johnson’s acoustic data from Thai suggest a higher frequency for the anti-formant.

Acoustic studies of laterals also uncover a lot of cross-linguistic variation, even in supposedly similar sounds. In a cross-linguistic study on laterals by Bladon (Reference Bladon, Harry and Patricia1979), F1 is found to be uniformly low (200–500 Hz), and F2 varies considerably depending on the language surveyed. Additionally, Bladon suggests two anti-formants at 1 KHz and 2 KHz–3 KHz for most lateral consonants. He also reports some variation for F3 based on place of articulation and thus finds that a low F1 and the two anti-formants identify laterals as a class.

Comparing laterals in three different Australian languages at different places of articulation (alveolar, dental, retroflex and palatal), Tabain et al. (Reference Tabain, Butcher, Breen and Beare2016) find that for the F2 and F3 of alveolar laterals the estimates by Johnson (Reference Johnson2012) are more or less accurate (1620 Hz and 2840 Hz, respectively), whereas F1 (370 Hz) is closer to Fant’s (Reference Fant1970) and Stevens’ (Reference Stevens1998) suggestions. Based on their acoustic measurements, Tabain et al. (Reference Tabain, Butcher, Breen and Beare2016) also suggest that the largest gap in lateral resonances is between F1 and F2 rather than between F2 and F3, as suggested by Fant (Reference Fant1970) and Stevens (Reference Stevens1998). This is interpreted as potential evidence of an anti-formant with much lower frequency than previously estimated.

Out of the laterals investigated by Tabain et al. (Reference Tabain, Butcher, Breen and Beare2016), the palatal lateral is closest to the type of articulation observed in the release of the Mee velar lateral, since its place of articulation is closest to the velum. Tabain et al. (Reference Tabain, Butcher, Breen and Beare2016) find that the palatal lateral has a significantly higher F2 and a slightly lower F1 than the alveolar lateral. They conclude that Centre of Gravity (CoG) is enough to distinguish places of articulation in lateral consonants.^{Footnote 3} The palatal lateral has a higher CoG (around 2800 Hz) than the alveolar and retroflex places of articulation.^{Footnote 4} The CoG is considered to be more robust in distinguishing places of articulation in laterals, since the individual formants show a greater inter-speaker variation. Similarly, Bladon’s (Reference Bladon, Harry and Patricia1979) study on laterals in several European languages yields the highest F2 for palatal laterals, compared to other coronal laterals. Recently, both Wong (Reference Wong2017) and Charles & Lulich (Reference Charles and Lulich2018, Reference Charles and Lulich2019) found that the palatal lateral in Brazilian Portuguese can be distinguished from the alveolar lateral by a considerably higher F2 and a slightly lower F1.

In contrast to palatal laterals, velarized alveolar laterals are reported to have a lower F2 than their non-velarized counterparts, and hence a smaller gap between F2 and F1, see Sproat & Fujimura (1993), among others, on English ‘dark l’, and Ladefoged & Maddieson (Reference Ladefoged and Ian1996: 196) for a survey of existing results on Russian, Bulgarian and Albanian. As we shall see, these comparatively low F2 values make the velarized alveolar laterals rather distinct from velar laterals acoustically. For this reason, we do not include velarized laterals in our summary in Table 3.

Table 3 Summary of model predictions and acoustic findings in existing literature. Antiformants abbreviated as ‘AF’.

To summarize, the existing studies of coronal, including palatal, laterals seem to converge on relatively low F1 values. Multiple studies report comparatively high F2 for palatal laterals. The values of anti-formants are to some extent debated, and even the resonating frequencies are often variable within a particular language. There are at least three different acoustic models of laterals, and at present it seems premature to claim that one of these models matches the data better.

The available data on velar lateral acoustics is much more scarce than for coronals. Steed & Hardie (Reference Steed, Peter and Catherine2004) propose a preliminary model for velar laterals that is similar to the one proposed by Johnson (Reference Johnson2012) except the constriction is further back and the side branch of the tube is shorter. No estimates of the actual length of the tube or of the side cavity can be made since articulatory measurements of velar laterals (such as x-ray or ultrasound) are not available. Ladefoged & Maddieson (Reference Ladefoged and Ian1996) found that velar laterals in Melpa and Mid-Wahgi have a higher F1 than laterals at other places of articulation in these languages. On the other hand, F2 of the velar laterals is expected to be higher than that of alveolars since it is expected to be inversely related to the volume of oral-pharyngeal cavity behind the constriction (Bladon Reference Bladon, Harry and Patricia1979, Ladefoged & Maddieson Reference Ladefoged and Ian1996, Steed & Hardie Reference Steed, Peter and Catherine2004). Indeed, this relatively high F2 is reported by Ladefoged et al. (Reference Ladefoged, Cochran and Disner1977) and Ladefoged & Maddieson (Reference Ladefoged and Ian1996) for Mid-Wahgi, although F2 is lower in this latter language for the velar laterals than it is for the laminal dental lateral.

Based on the existing descriptions of laterals, we expect that the two /ɡᶫ/ allophones will have different release spectra, although we also anticipate that this prediction is hard to test in practice since [ɡᶫ] and [ɢ^ʁ] occur in front of different vowels. If the closure and parts of the release undergo partial devoicing, we would expect that [ɢ^ʁ] is more likely to be aperiodic than [ɡᶫ]. The existing data on formant values of velar laterals, and the acoustic models (which mostly pertain to coronal laterals) unfortunately do not yield enough consistent predictions for us to formulate an informed hypothesis about the formant values in the release of the [ɡᶫ] allophone.

3.3 Summary

Our study addresses several specific hypotheses about the realization of the Mee velar lateral. First, we hypothesize that the velar lateral has two allophones realized as [ɡᶫ] vs. [ɢ^ʁ] and distributed complementarily, according to the following vowel quality. These distributional facts will be tested in our elicitation study (Section 4) which attempted to elicit a representative sample of Mee words with a dorsal.

Second, we expect that the two allophones of the velar lateral will have a different effect on the preceding vowel: the uvular allophone is expected to exhibit comparatively more lowering and backing, and this can be addressed by measuring the preceding vowel’s formant values. Finally, we expect that the two allophones will also differ in the acoustics of their release. The release of [ɢ^ʁ] may be more likely to exhibit aperiodicity than that of [ɡᶫ]. The exact formant values of lateral release are hard to extrapolate from the existing literature, most of which deals with coronal laterals. We may also expect the CoG of [ɡᶫ] to be higher compared to [ɢ^ʁ], based on the measurements for the similar palatal laterals by Tabain et al. (Reference Tabain, Butcher, Breen and Beare2016). The predicted acoustic differences will be assessed in a more detailed acoustic study described in Section 5.

4.1 Method

The main goal of our elicitation study was to address our initial intuition about the positional allophony of the Mee velar lateral. An additional goal is to confirm that the allophony pattern is robust across speakers and across items. These goals predetermined many aspects of the methods we used.

4.2 Elicitation results

The recordings from our elicitations are compatible with the categorical velar lateral allophony pattern.^{Footnote 5} The velar lateral is realized phonetically with dorsal closure and lateral release, transcribed [ɡᶫ], before front vowels and corresponding diphthongs /ei eu/, see (1a). Before back vowels /a o u/ and corresponding diphthongs /ai au ou/, it is realized with uvular closure and fricative release, transcribed [ɢ^ʁ], as in (1b). We will tentatively write the corresponding Mee phoneme, i.e. the mental unit comprising both allophones as /ɡᶫ/ – this is discussed further in Section 4.3

1. (1) Examples of Mee posterior lateral

   

Short /i e/ are reduced and highly lateralized after [ɡᶫ], transcribed with a breve sign in (1c) and in what follows. The reduction process is more pronounced in connected speech and in non-initial syllables. The contrast between /ɡᶫi/ and /ɡᶫe/ in non-initial syllables, as in the last two words in (1c) appears to present a perceptual challenge to us, as non-native listeners. Our consultants do distinguish such words. Moreover, short word-final /i/ vs. /e/ serve as distinct subject agreement markers in some tenses, including after /ɡᶫ/, where /-i/ corresponds to ‘masculine 3sg’, and /-e/ to ‘1pl’ and ‘2sg’ (Doble Reference Doble1987). The cues for differentiating [ɡᶫĭ] vs. [ɡᶫĕ] sequences in Mee remain to be further investigated.

We illustrate the variation in Mee velar lateral realization with some representative spectrograms (Figures 2–5). As mentioned in Section 4.1.2, our elicitation sessions were not conducted in an attenuated booth, and show some level of background noise. In an attempt to present the clearest possible illustrations, we present the spectrograms from S01 obtained from later booth recordings (see Section 5.1.1). Therefore, the level of noise in spectrograms from speaker S01 is lower than that for S02. The speech rate also differed for our two speakers. The vowel–consonant boundaries are presented only as rough pointers.

Figure 2 Spectrograms and waveforms: [aɡᶫe] ‘floor/ground’.

Figure 3 Spectrograms and waveforms: [boɢ^ʁomai] ‘to collapse’.

Figure 4 Spectrograms and waveforms: [emiɡᶫeuwi] ‘go and throw it in!’

Figure 5 Spectrograms and waveforms: [aɢ^ʁapi] ‘midday, noon’.

As can be seen in these Figures, the Mee velar lateral is characterized by the presence of a clearly identifiable closure or constriction phase. Even when the constriction was apparently not complete, i.e. in cases of lenition, the constriction phase is distinct from surrounding vowels and from the release. The constriction is also relatively long, similar in duration to that of stops.

The variability in closure and release duration observed in the figures is probably accounted for by the speech rate differences across different speakers and elicitation sessions. Our elicitations did not suggest a difference in closure or release duration for the two allophones.

Finally, the spectral properties of the release reveal several typical /ɡᶫ/ realizations. Before front vowels, the [ɡᶫ] allophone has a lateral release. One common realization of this release involves formant continuity with the following vowel (V2), as can be observed in Figure 2 (especially left panel). V2 sounds lateralized to us in these cases.

The release of the allophone [ɢ^ʁ] is often, but not always, characterized by diffuse high-frequency noise (over 4 KHz), as apparent in Speaker S01’s pronunciation in Figure 3 (left panel). This noise may coincide in time with the formant transitions from the following vowel (see Figure 3). This high-frequency noise is characteristic of fricatives, and the release is heard as fricated.

Figures 4 and 5 illustrate the realization of velar lateral release that does not have as much temporal overlap with the following vowel. For the allophone [ɡᶫ], the release in these cases shows formant discontinuity relative to the following vowel, and the release often starts with a transient. This realization of [ɡᶫ] is shown in Figure 4.

Before back vowels, the allophone [ɢ^ʁ] is often realized with a fricated release occurring before the onset of formant structure for V2 (see Figure 5). Unlike for [ɡᶫ], both release and closure were often at least partially devoiced in these cases.

To summarize, both allophones show considerable variability in the temporal overlap between the release and the following vowel. The release of the uvular allophone [ɢ^ʁ] is often associated with high-frequency frication noise and with partial devoicing.

4.3 Discussion of elicitation results

Overall, our elicitations confirmed that for both speakers the velar lateral has two allophones which are distributed according to the backness of the following vowel. This allophony pattern has not been previously reported either for Mee or for velar laterals in other languages. The obligatory closure in Mee velar lateral is unlike the optional closure in Mid-Wahgi (Ladefoged et al. Reference Ladefoged, Cochran and Disner1977, Ladefoged & Maddieson Reference Ladefoged and Ian1996) or the optional and possibly incomplete or very short closure in Kuman (Steed & Hardie Reference Steed, Peter and Catherine2004). In Hiw, the velar lateral is obligatorily pre-stopped (François Reference François2010), but the closure duration is short, judging from the spectrograms presented by François. On the other hand, the closure of the Mee velar lateral is usually relatively long in our elicitation data – an impression to be verified in our controlled acoustic study in Section 5.

Since we could record only two speakers, both living outside of their native community at the time of recording, it remains to be seen how robustly these results would generalize to a broader community of native speakers. Although practical circumstances prevented us from undertaking a full fieldwork trip to the native Mee communities, our preliminary travel allowed for some observations of Mee speech in Nabire, in Dogiyai, and in Enarotali (Indonesia). Based on these observations, velar lateral allophony was also present in these Mee-speaking communities. Another indirect indication that the patterns found with our speakers are representative of a broader community comes from the speakers’ dialects. Based on familiarity with different parts of the Mee lexicon, and on background information from our two speakers, it was clear that they speak slightly different dialects of Mee (see Section 4.1.1). However, our results in Section 4.2 show that the patterns of velar lateral allophony appear to be very similar for the two speakers. Thus although our findings may be further refined by future data from native Mee communities, we do not anticipate that new data would be completely incompatible with what we find here.

In line with Reference DobleDoble (Reference Doble1987), our elicitations revealed that the Mee velar lateral has an obligatory closure or constriction phrase, and that both /k/ and /ɡᶫ/ may undergo some lenition between vowels. Thus the velar stop /k/ is often lenited to [x/χ] inter-vocalically, and occasionally lenition also applies to /ɡᶫ/, thus yielding a variant closer to [ɣᶫ]. In our impression, lenition is less pronounced for the voiced sound.

Some other phonetic details noted by Reference DobleDoble (Reference Doble1987) do not match our elicitation results. We attribute these differences (all noted below) to a possible dialectal difference in the studied speakers. Doble (Reference Doble1987: 58) reports that /k, ɡᶫ/ undergo labialization following back vowels, but we did not observe labialization in our data (it is possible that a more controlled acoustic analysis would reveal some labialization). The reduction of short /i e/ after [ɡᶫ] is also not mentioned by Doble (Reference Doble1962, Reference Doble1987), yet it is prominent in the speech of our consultants.

Although our elicitations are mainly phonetic, our results have implications for the phonological status and underlying representation of the Mee velar lateral. Our results are consistent with the existing phonological descriptions which interpret /ɡᶫ/ as a laterally released stop (Doble Reference Doble1962, Reference Doble1987; Hyman Reference Hyman2008; François Reference François2010; Hyman & Kobepa Reference Hyman and Niko2013). Our data do not allow us to distinguish between laterally released stops and affricates with a lateral release, and our transcription should be interpreted as indeterminate between the two interpretations. The Mee sound patterns with other non-continuants in several respects. First, it is consistently realized phonetically with a closure phase. Second, both /k/ and /ɡᶫ/ undergo lenition between vowels to some extent. Third, the Mee velar lateral also derives historically from a stop. Evidence for this comes from Moni, where the corresponding sound is described as a stop [kʰ/g] in most contexts (Larson & Larson Reference Larson and Larson1958). See Larson & Larson (Reference Larson and Larson1972) on the relation between Mee, Wodani and Moni, and Tebay (Reference Tebay2018b) for a list of cognate words. Fourth, our consultants seem to associate [ɡᶫ~ɢ^ʁ] with other stops, as evidenced by their orthographic intuitions. While the consultants were not aware of a standardized orthography for Mee, they agreed that the velar lateral sound should be written with the <g> symbol, rather than <l> or <r>. Finally, Mee /ɡᶫ/ occupies the place of /ɡ/ in the consonant inventory.

At the same time, it would be hard to derive the Mee velar from an underlying plain stop for the simple reason that /ɡᶫ/ is never realized as a stop proper. Our consultants are aware of the special release properties of /ɡᶫ/ and the phonetic salience of the release manifests itself in loanword adaptations such as [tekoɢ^ʁa] ‘school’ from Indonesian sekolah [səkolah]. Based on all this evidence, we will analyze the Mee velar lateral as an underlying laterally released stop/affricate, transcribed /ɡᶫ/. We hasten to add that our data are mostly phonetic, and a more thorough investigation of Mee phonology may uncover additional synchronic phonological evidence for this interpretation.

While the elicitation study confirmed that the Mee velar lateral has two allophones, our results were imperfect in a number of ways. First, the recordings were made in a quiet room with portable recording equipment which necessarily also captured some environment noise – this is apparent in spectrograms from Speaker S02 in Figures 2–5. The elicitation data are thus not sufficient to perform detailed acoustic analysis. The speech rate, context and aspects of the recording situation are also not controlled for in this study, and therefore our judgment of the difference between [ɡᶫ] and [ɢ^ʁ] allophones remains impressionistic and preliminary at this point.

In order to study the difference between velar lateral allophones in more detail, we conducted a controlled acoustic study where all relevant words were recorded in the same context. The recordings for the acoustic study were made in a sound-attenuated booth, thus reducing the levels of background noise captured. The acoustic study is described in what follows.

5.1 Acoustic study: Method

5.1.2 Acoustic study: Materials

Stimuli for the acoustic study consisted of words with /ɡᶫ/ in a diverse set of vocalic contexts. Our words were minimally disyllabic, and were not controlled for tone, syllable structure or morphological complexity – controlling these factors appeared impractical given the lack of tonal annotation and the overall relatively small size of our main dictionary source (Steltenpool Reference Steltenpool1969). Three tokens were later excluded from acoustic measurements since extraneous noise was present or the realization of /ɡᶫ/ was clearly deviant (see Section 5.1.3). The stimuli words and fillers used in the acoustic study are listed in Appendix A.

Our final token set contained about the same number of /ɡᶫ/ before front vowels (158 tokens of 52 words) and /ɡᶫ/ before back vowels (154 tokens of 45 words). In designing the word sets we attempted to include at least three distinct words with /ɡᶫ/ in each V_V context. From now on, we will refer to the vowel preceding the velar lateral as V1 and to the vowel following it as V2. In principle, all vocalic contexts were recorded, except V1 was never a diphthong – this facilitated later formant transition analysis.

In some of the vocalic environments we could not identify enough words that would be familiar to our consultant. This problem was particularly pronounced for /u/, which is the least frequent vowel of Mee. To balance our stimulus set, we included more repetitions of the available words in those cases. Table 4 presents the number of distinct words (types) with /ɡᶫ/ in each environment in our stimuli set. Table 5 presents the number of individual tokens/repetitions.

Table 4 Stimuli words by environment. V1 and V2 stand for vowels before and after /ɡᶫ/.

Table 5 Stimuli tokens by environment. V1 and V2 stand for vowels before and after /ɡᶫ/.

In the /i_u/ environment, only a few words could be found in the dictionary (Steltenpool Reference Steltenpool1969), and none of these words were familiar to our consultant. For all other environments, we recorded at least nine tokens in each case. The total number of target tokens we analyzed was 312.

The 312 stimuli tokens were randomly interspersed with 300 filler tokens. Our fillers were 100 disyllabic or longer frequent Mee words identified in our elicitations. Each filler word was repeated three times to yield 300 tokens. As with the target words, some of our fillers were morphologically complex. None of the fillers contained the phoneme /ɡᶫ/. All items were recorded in a carrier phrase given in (2).^{Footnote 6}

1. (2)

   

5.2 Results

Mean duration of the closure interval in our dataset was found to be 34.2 ms (s.d. 17 ms), and closure duration did not present a substantial difference between [ɡᶫ] and [ɢ^ʁ] allophones: mean 33.4 ms (s.d. 16.4 ms) for [ɡᶫ] vs. mean 35 ms (s.d. 17.6 ms) for [ɢ^ʁ].

5.2.2 V1 formants and transitions

For the vowel preceding /ɡᶫ/ (V1), formants were measured at thirty time points from the beginning until the end of the vowel interval. Vowel formant measurements were not normalized since they all come from one speaker. To assess the variability of formant trajectories, each formant track was then modeled with SSANOVA with /ɡᶫ/ allophone place (velar vs. uvular) and interval number (1:30) as main effects.

Figure 6 shows formant trajectories as estimated by the model with Bayesian 95% confidence intervals. For comparison, a graph of raw formant means is presented in Appendix B. In Figure 6, the most relevant part of each curve is the stretch roughly from the midpoint until the end. Since the left context of each vowel is not controlled in our dataset, formant values closer to the vowel beginning are expected to show relatively high variability.

Figure 6 Smoothing Spline ANOVA model curves for F1, F2 and F3 of the vowel before /ɡᶫ/. Lines show model estimates with Bayesian 95% confidence intervals. Vowels before [ɡᶫ] shown as solid lines in coral, vowels before [ɢ^ʁ] shown as dashed lines in teal.

Most vowels preceding a uvular [ɢ^ʁ] show a clear lowering of F2 towards the endpoint, and lowering usually becomes more pronounced towards the vowel offset. An exception to this pattern is seen for [o], where no clear difference in F2 can be observed. The F2 of [u] seems to pattern in the same general direction but also seems more variable than the formants for other vowels. The formants of [u] may be hard to track automatically since F1 is close to F2, leading to more mistracking. Interestingly, the F1 tracks do not seem to show a robust difference in velar vs. uvular context. Thus Figure 6 shows no obvious lowering effect before [ɢ^ʁ].

The effects of velar lateral allophones on the preceding vowel are expected to be observed most robustly towards the end of the vowel. The transitional formant values for each vowel, taken at 90% duration, are plotted in Figure 7. Note that our stimuli set limits the set of V1 qualities to simple vowels – hence diphthongs do not appear.

Figure 7 Formant transitions from the preceding vowel into [ɡᶫ] (dotted line) and [ɢ^ʁ] (solid line), taken at 90% of the vowel interval.

As seen in Figure 7, at the 90% time point all vowels with the exception of /o/ show a clear separation between the formant transitions into [ɡᶫ] and the formant transitions into [ɢ^ʁ]. This distinction is based primarily on F2 rather than F1, consistent with the trend already observed in Figure 6.

We analyzed F2 transitions into /ɡᶫ/ at 90% of V1 duration with a linear mixed effects regression model taking V1 quality and consonant place (velar vs. uvular) as fixed effects and including item and repetition number as random effects (see Table 6). The model compared each vowel to the V1 vowel /a/ and the velar place to the uvular. Vowels before [ɢ^ʁ] were found to have a significantly lower F2, consistent with backing. An expected significant effect of V1 quality was also found for all vowels.

Table 6 Linear mixed effects model results for the second formant of the vowel before /ɡᶫ/, taken at 90% of the vowel duration.

The difference in F2 values is particularly pronounced for /e/, as witnessed by a significant interaction between V1 being /e/ and consonant place. On the other hand, as observed above, the effect of /ɡᶫ/ allophones on V1 F2 transitions is particularly small for the vowel /o/ – the interaction between V1 being /o/ and consonant place was marginal. These interactions are also seen in Figure 7, where the F2 values for /e/ are very clearly distinct between the two contexts while the F2 values for /o/ are hardly separable.

Based on Figures 6–7, /ɡᶫ/ allophony does not seem to have a consistent effect on the first formant of the preceding vowel. F1 transitions into /ɡᶫ/ at 90% of V1 duration were analyzed with a linear regression model similar to the model for F2 transitions. The model showed an expected significant effect of V1 quality, but the effect of consonant place was not significant (see Table 7). Thus we do not find numeric evidence of vowel lowering before [ɢ^ʁ].

Table 7 Linear mixed effects model results for the first formant of the vowel before /ɡᶫ/, taken at 90% of the vowel duration.

5.3 Discussion of acoustic study results

Our results on closure duration confirm that the Mee velar lateral has a relatively long closure or constriction phase. In this way it contrasts with velar laterals in other languages such as Mid-Wahgi (Ladefoged et al. Reference Ladefoged, Cochran and Disner1977, Ladefoged & Maddieson Reference Ladefoged and Ian1996), Kuman (Steed & Hardie Reference Steed, Peter and Catherine2004), and Hiw (François Reference François2010), discussed in Section 4.3.

Our acoustic results also align with our main hypothesis that Mee /ɡᶫ/ is realized as a velar [ɡᶫ] before front vowels but uvular [ɢ^ʁ] before back vowels. We find a distinction in release periodicity: on average [ɡᶫ] release was more periodic than for [ɢ^ʁ]. This is consistent with the release target being a fricative rather than a sonorant for [ɢ^ʁ] and with a higher likelihood of partial devoicing for [ɢ^ʁ] release. The release for [ɡᶫ] was also found to have a higher CoG than that of [ɢ^ʁ], consistent with the high CoG for palatal laterals in Tabain et al. (Reference Tabain, Butcher, Breen and Beare2016).

The results on release CoG, and possibly even on Harmonics-to-Noise ratio, should be interpreted with caution since these measures could be affected by V2, which is different after each allophone. For example, measured CoG could be influenced by the highest-amplitude resonant of the following vowel – in the relevant frequency range (0.5–7KHz) this would be F2. The front vowels after [ɡᶫ] will have a higher F2 than the back vowels after [ɢ^ʁ], and this could be contributing to the CoG difference we found, which is in the same direction.

The acoustic cues to the release quality likely reside not only in the release interval, but also in the quality of the following vowel. We found that the lateral release of [ɡᶫ] is very highly variable in its formant structure. This variability probably stems from several factors: the inherent variability in lateral formants and their relative weakness (Stevens Reference Stevens1998, Steed & Hardie Reference Steed, Peter and Catherine2004, Proctor Reference Proctor2009, Tabain et al. Reference Tabain, Butcher, Breen and Beare2016), as well as the variation in temporal overlap between the release and the following vowel (see Figures 2–5). A detailed investigation of the Mee velar lateral release would thus compare the vowels after /ɡᶫ/ to vowels in other contexts. Our materials do not allow for such a controlled comparison, but this is a likely future direction.

Our analysis of V1 formants and transitions into /ɡᶫ/ revealed that the uvular allophone had a backing effect on the preceding vowel, as evidenced by lower F2 values before [ɢ^ʁ]. The relative timing of F2 lowering may be slightly different for different vowels, but overall lowering occurs towards the end of the vowel, and it usually starts after the vowel’s temporal midpoint (Figure 6). This is consistent with F2 lowering being a local coarticulation effect and with a difference in constriction location for [ɡᶫ] vs. [ɢ^ʁ] consonant closure. Our results also match the reports of vowel retraction next to uvulars in other languages (Bessell Reference Bessell1998, Wilson Reference Wilson2007, Shosted Reference Shosted and Heriberto2011, Sylak-Glassman Reference Sylak-Glassman2014). A typological survey by Sylak-Glassman (Reference Sylak-Glassman2014) found that vowel backing occurs particularly commonly next to uvulars, out of all post-velar consonants. In Mee, the difference in F2 effects between [ɢ^ʁ] and [ɡᶫ] appears to be the most pronounced for /i e a/, and the least pronounced for /o/. Interestingly, Shosted (Reference Shosted and Heriberto2011: Figure IV–4) also finds that /i e a/ are the most distinct in his study of velar vs. uvular distinction in Q’anjob’al.

We did not find a significant lowering effect on the vowel before [ɢ^ʁ], or at least uvular [ɢ^ʁ] showed no more lowering than velar [ɡᶫ]. A number of existing studies of vowels next to uvulars show either just lowering or just backing for some vowels or for some contexts (Alwan Reference Alwan1986, Wilson Reference Wilson2007, Sylak-Glassman Reference Sylak-Glassman2014). It is interesting to observe that in Mee vowel backness is affected by uvulars more robustly than vowel height. This finding contributes to our understanding of how uvulars and velars are distinguished perceptually across languages.

Coarticulation between the vowels before and after /ɡᶫ/ likely also contributes to the F2 effects we observed. However, the salient difference in release quality between the two allophones also suggests that V–V coarticulation cannot be the whole story: the quality of the intervening consonant is also affected by coarticulation. In other words, although none of our acoustic measurements pertain to the closure interval itself, together the differences in release and V1 formant transitions suggest that the constriction location for the closure is likely also distinct.

A reviewer asks if glottalization could have affected our acoustic results or boundary annotation. Our elicitation study did not yield any auditory impressions of high glottalization word-medially. The only context where we did observe some glottalization was phrase-initial, and indeed initial glottalization is common across languages (see e.g. Garellek Reference Garellek2013). For /ɡᶫ/-initial words, glottalization usually did not appear to extend over an interval longer than the consonant closure. The presence of glottalization did not obscure the boundaries of the closure interval. Although it is possible that glottalization would affect our measurements of /ɡᶫ/ release periodicity (measured as HNR) in phrase-initial context, this factor would apply to both velar lateral allophones about equally since we recorded a roughly equal number of tokens of initial [ɡᶫ] (24 tokens) and [ɢ^ʁ] (27 tokens; see Table 5). For that reason glottalization would not explain the difference in release periodicity between the allophones that we found.