Djambarrpuyŋu is spoken by approximately 4,000 people in northeast Arnhem Land (Australian Bureau of Statistics, 2021a). It is a member of the Yolŋu subgroup of the Pama-Nyungan language family (Bowern, 2023), and is one of a small number of Australian Indigenous languages that are used in day-to-day life and learned by children at home (see Koch & Nordlinger, 2014 for discussion). Today, speakers live in a number of communities including Galiwin’ku, Gapuwiyak, Milingimbi, and Ramingining (Wilkinson, 2012; Yunupingu, 1996). Djambarrpuyŋu is now a main community language of these communities, which are not all traditional Djambarrpuyŋu clan and language affiliation areas. Speakers are often multilingual and multidialectal with knowledge of related varieties, other Australian languages, Australian English, and Kriol.

The vowel system proposed by Wilkinson (2012) in her grammatical analysis of Djambarrpuyŋu is symmetrical, consisting of six vowels distinguished by height, backness, and—in the first (stressed) syllable of the word—length. To reflect the tendency for vowels in Australian Indigenous languages to have less extreme cardinal-like articulation and more variation within each quality category, the following symbols are used here: /ɪ, ɪː, ɐ, ɐː, ʊ, ʊː/ (Busby, 1980; Fletcher & Butcher, 2014). The length contrast is exemplified in the following near minimal pairs: weṯi /wɪːʈːɪ/ “wallaby,” wiṯitj /wɪʈːɪc/ “olive python”; gorrum /kʊːrʊm/ “to be high,” gurrum’ /kʊrʊmʔ/ “soft”; and gäna /kɐːnɐ/ “alone,” gana’ /kɐnɐʔ/ “enough” (Wilkinson, 2012). The restriction of contrastive vowel length to the initial syllable (i.e., the stressed syllable) is commonly reported for Pama-Nyungan languages that have a length contrast (Baker, 2014; Dixon, 2002; Fletcher & Butcher, 2014).

A preliminary acoustic study of Djambarrpuyŋu vowel duration from words in isolation confirmed that duration significantly differed between phonemically short and long vowels in the first syllable of CV.CV words with short vowels having a mean duration of 126 ms and long vowels a duration of 211 ms (Jepson & Stoakes, 2015). Wilkinson (2012) notes, however, that the phonetic contrast can be lost in fast connected speech, which results in the collapsing of minimal pairs. She additionally noted that in reduplicated forms, reduplicants do not retain the long vowel, for example, yolŋu’-yulŋu /jʊːlŋʊʔjʊlŋʊ/ “people” (Wilkinson, 2012; see also Heath, 1980 on Ritharrŋu).2

There are 25 consonants in Djambarrpuyŋu: Six places of articulation for stops, for which there are fortis and lenis series (with the former represented by length in the following), /pː, p, t̪ː, t̪, tː, t, ʈː, ʈ, cː, c, kː, k/, and nasals /m, n̪, n, ɳ, ɲ, ŋ/, as well as one trill /r/, three central approximants /w, ɹ, j/, two lateral approximants /l, ɭ/ and glottal stop /ʔ/. The fortis/lenis contrast is yet to be acoustically analysed. Note that the transcription convention adopted here of using the length diacritic for fortis stops does not imply ambisyllabic association, rather it is used to capture that these stops are hypothesised to differ primarily in closure duration, rather than voicing (Butcher, 2004; Round, 2023). Round summarises that languages of Arnhem Land (including Yolŋu languages) with two series of stops usually make the distinction by closure duration, in contrast to languages of Cape York, which primarily use voicing. Further, this convention was adopted in previous phonetic research on the language (e.g., Jepson et al., 2021). Phonologically, stops are limited in where they are considered contrastive in Djambarrpuyŋu—only in morpheme internal intercontinuant position. The contrast between the fortis and lenis stop series has a very low functional load, though near minimal pairs do exist (Wilkinson, 2012). For example: bäba /pɐːpɐ/ “gall,” bäpa /pɐːpːɐ/ “father”; gadharra /kɐt̪ɐrɐ/ “coral,” watharr /wɐt̪ːɐr/ “white”; and räga /ɹɐːkɐ/ “white berry bush,” räkay /ɹɐːkːɐj/ “Eleocharis dulcis.” These specific minimal pairs were not a focus of data collection and the differences between the fortis and lenis stop series are not investigated acoustically in the current paper.

Djambarrpuyŋu allows for syllables that are maximally CV(C)(C)(ʔ); all syllables (and words) are consonant initial with the exception of a very small number of words, predominantly in the “baby talk” register (Wilkinson, 2012, p. 45), for example, anyany /ɐɲɐɲ/ “cute.”

Cross-linguistically, contrastive vowel length is most commonly reported with two levels of contrast; generally, “long” vowels are distinguished from “short” (Odden, 2011). A pattern of three levels is rare (Remijsen, 2014 on Dinka). Phonetically, long and short categories are correlated with larger or smaller duration values respectively, with the exact values for each category being language specific (Odden, 2011, p. 465). The raw duration values can vary considerably. For example, in Thai utterance-medial words, short vowels are, on average, 160 ms, and long vowels are 320 ms (Roengpitya, 2001, p. 30), while in Hungarian accented utterance-medial words, short vowels are 54 ms and long vowels are 94 ms (White & Mády, 2008). The ratio or proportional difference between vowel length categories can also show substantial variation. For example, in Marshallese the ratio is approximately 1:2.8 (Choi, 1992, p. 64), but in Czech, the ratio is 1:1.63, averaged across five vowel pairs (Podlipský et al., 2009, p. 134).

Vowel duration is well known to also be conditioned by several other factors, such as metrical strength, accentuation, voicing and manner of the following consonant, vowel quality, syllable structure, number of syllables in the target word, whether uttered in isolation or in an utterance, and the vowel’s position within the target word (e.g., Lehiste, 1970; Port & Dalby, 1982; Turk, 2012). These factors can affect the duration of long and short vowels differently, and consequently, the proportional differences between the categories may also change (e.g., de Jong & Zawaydeh, 2002, p. 62, their Figure 1, on Ammani-Jordanian Arabic and effects of stress; White & Mády, 2008 on Hungarian and syllables per word). Of particular interest here is syllable structure; position within the utterance is also considered.

Cross-linguistically, vowels in closed syllables are found to be phonetically shorter than in open syllables (Maddieson, 1985). This effect has been observed in languages that have contrastive vowel length such as Dutch (Jongman, 1998; Rietveld & Frauenfelder, 1987), Arabic (Broselow et al., 1997; de Jong & Zawaydeh, 1999; Khattab, 2007), and Malayalam (Broselow et al., 1997), as well as those which do not such as Italian (Farnetani & Kori, 1986; Hajek et al., 2007). The position of the word within the utterance is also found to have an effect on segment duration, with vowels in words uttered in utterance-final position having longer duration than comparable vowels in words in other positions (White & Mády, 2008 on Hungarian). For Hungarian, final-lengthening interacts with vowel length category such that final long vowels show a greater effect of position than short vowels, being lengthened approximately 40 ms, while short vowels only lengthened an estimated 21 ms (White & Mády, 2008). See also Paschen et al. (2022) for a discussion of the interaction between vowel length and finality.

Beyond duration, contrastive vowel length is also correlated with spectral differences for monophthongs. Typically, membership in the long category corresponds to being more peripheral in the vowel space, whereas being short corresponds to a more centralised acoustic realisation. This is based on a more general assumption that longer duration of a vowel corresponds with more extreme articulation because articulators are able to move to more peripheral positions, while in shorter periods of time the movement that is possible is restricted (Cho, 2004; Lehiste, 1970, p. 31; Lindblom, 1963, p. 1780). However, vowel length is not always found to affect formant structure (cf. Behne et al., 1996, on Norwegian). And, the prediction does not hold for short versus long vowels in some Australian languages (Fletcher & Butcher, 2014). Of relevance here, however, is Graetzer’s (2012) analysis of vowels in Gupapuyŋu, a Yolŋu variety closely related to Djambarrpuyŋu, in which she found that long vowel centroids tended to be more peripheral in the vowel space in at least one dimension: the pair /ʊ/ and /ʊː/ differed in F2, while the pairs /ɪ/ and /ɪː/ and /ɐ/ and /ɐː/differed in F1 (Graetzer, 2012, pp. 187–188). It is possible that there are also minimal vowel formant differences in Djambarrpuyŋu due to articulatory mechanisms that result in differences which are not sufficient to posit vowels of different qualities.

Not infrequently, a complementary duration relationship between a vowel and the following consonant is described, most often when the vowel is stressed. The duration relationship is inverse, with consonant duration being longer when the vowel is shorter, and shorter when the vowel is longer. This is reported to occur in, for example, Arabic (Khattab, 2007), the Shetland dialect of English (Sundkvist & Gao, 2015; van Leyden, 2004), German dialects (Kleber, 2020), Italian dialects (Baroni & Vanelli, 2000), Norwegian (Behne et al., 1996), Swedish dialects (Elert, 1965; Schaeffler, 2005), Thai (Abramson, 1960), Washo (Yu, 2008), and Guienagati and Ozolotepec Zapotec (Benn, 2021; Leander, 2008). There are a range of phonological, phonetic, and prosodic motivations associated with this type of durational relationship; sometimes the pattern is attributed to the vowel, sometimes to the consonant, and sometimes to another syllable weight or duration requirement.

For Washo, “[p]ost-tonic consonant gemination after short stressed vowels may be viewed as a compensatory response to the monomoraicity of short vowels” (Yu, 2008, p. 517). This interpretation of preserving moraic weight is discussed within phonological theory (Gordon, 2016; Hayes, 1989) and is observed in some Australian languages (Baker, 2014; see also Harvey & Borowsky, 1999 on Warray). For Ngalakgan, an Australian language of the Gunwinyguan family, Baker (2008, pp. 75–82) describes a bimoraic minimum for monosyllabic words which can be achieved through a closed syllable containing a short vowel, or the phonetic lengthening of vowels if the syllable is open. In the moraic theory view of compensatory lengthening, the lengthening of a vowel conditioned by the loss of a coda consonant would not occur if the language’s codas are non-moraic for other purposes, such as stress assignment or minimal word requirements (Gordon, 2016, p. 160). Most Australian languages are described to be weight insensitive regarding stress assignment (Baker, 2014; Fletcher & Butcher, 2014; Jepson & Ennever, 2023), irrespective of whether consonants are moraic or not. There is a preference for minimally bimoraic monosyllabic words in Djambarrpuyŋu, despite a small number of exceptions (discussed in Section 2.3). The possibility of a phonetic bimoraic minimum requirement for stressed syllables is discussed in sections 4.3 and 6.

For the Shetland dialect of English, van Leyden (2004) found that consonants were lengthened in a compensatory manner with the shortening of vowel duration. It was reported that a 100 ms shortening in vowel duration was reflected by a 49 ms lengthening of the following consonant. Van Leyden (2004, p. 39) concluded that, while there is an inverse relationship between vowel and consonant duration in the Shetland dialect, it is strongest for some sets of words considered to constitute pairs, particularly local dialect words.

In Thai (Abramson, 1960; Abramson & Ren, 1990), semivowels and nasals in syllables containing short vowels have longer duration than those in syllables containing long vowels, but again, durational differences are not as great as they are for vowels and do not fully compensate for the difference in duration between long and short vowels: /n/ in /sǐn/ was 150 ms while the /n/ in /sǐːn/ was 110 ms long (Abramson, 1960, p. 132), whereas short and long vowels were on average 85 ms and 165 ms, respectively (Abramson & Ren, 1990). In languages with geminate consonants, such as Makasar for example, singleton /n/ is found to be 100 ms while geminate /n/ is 205 ms on average (Tabain & Jukes, 2016); that is, it is on par with durational differences observed for contrastive vowel length.

When longer vowels are only observed with shorter consonants and shorter vowels with longer consonants, difficulty can arise in determining whether the vowel or the consonant has contrastive length. In Thai and the Shetland dialect of English there is a smaller difference in duration between consonants, leading to vowel length being analysed as the primary determiner of vowel duration and, consequently, determining the duration of the following consonant. However, this is not always so clear cut (e.g., in Swedish Schaeffler, 2005). Central Bavarian presents an interesting case showing the difficulty of determining the motives for varying duration or neighbouring segments (Kleber, 2020). In Central Bavarian, tense (long) vowels occur before lenis stops, and lax (short) vowels occur before fortis stops. Prior to Kleber (2020), there were two proposed phonological solutions to this: Firstly, that the fortis/lenis contrast is phonological while vowel duration is predictable; secondly, that there is a contrast between the complementary length of VC sequences and that prosodic quantity specifies either the vowel or stop to be long, and the other is then predictably short. Kleber concluded that, because lengthening was observed for sonorants (which do not otherwise have a length contrast) and not exclusively for the stops, that vowel length is phonemic in Central Bavarian, and the consonant duration contributes to marking the vowel length contrast. On Washo, Yu (2008) acknowledges that his analysis rests on an assumption of vowel length being contrastive and that the issue is still under debate.

As mentioned in Section 1, an inverse duration relationship is reported for other Yolŋu languages, with longer vowels being followed by shorter consonants, and vice versa. This type of durational relationship is proposed to be a phonetic feature of most Australian languages that have contrastive vowel length (Dixon, 2002, p. 591). When contrastive vowel length, which had historically been more commonly observed around Australia (Dixon, 2002, p. 639), is lost, consonant duration is hypothesised to be phonologised as being contrastive (Dixon, 2002, pp. 591, 595). Though, for a number of Yolŋu languages, two series of stops are attested, as well as contrastive vowel length (the historical conditions that could account for this are discussed by Dixon, 2002, pp. 604, 611). It appears that this has contributed in part to the diverse analyses for the similar phonetic outcomes in Yolŋu languages, the details for which are discussed here.

Of the varieties and languages discussed below, Djambarrpuyŋu is most closely related to Djapu—both are within the same language group of Dhuwal—while it is more distantly related to Ritharrŋu, Djinang, and Gälpu which are in different language groups (Bowern, 2023; Wilkinson, 2012). In some descriptions, sonorants are the focus of lengthening processes, while in others, obstruents are primarily discussed.

Morphy (1983) reports for Djapu that in disyllabic words where the first/stressed syllable is open, the duration of the following consonant varies according to the length of the stressed vowel. The relationship is predictable and complementary, with short vowels being followed by longer consonants, and long vowels followed by shorter consonants. She illustrates this with the pair waŋa /wɐŋɐ/ “to talk/speak” and wäŋa /wɐːŋɐ/ “home/place” (Morphy, 1983, p. 25). It is argued that the lengthening or “gemination” of the consonant following the long vowel occurs to ensure that the stressed syllable is heavy. In Morphy’s analysis, a syllable is heavy as the result of either a long vowel in the stressed syllable, due to a coda consonant, or, when the following consonant is the onset in the next syllable, the lengthening of that consonant which is consequentially analysed as being ambisyllabic (to fulfil the requirement that all syllables are consonant initial). So, in the above examples, waŋa /wɐŋɐ/ [wɐŋːɐ] is syllabified as [wɐŋ.ŋɐ], while wäŋa /wɐːŋɐ/ [wɐːŋɐ] is syllabified as [wɐː.ŋɐ]. Morphy notes that the durational difference could be analysed as originating from either the vowel or the consonant, but argues that to motivate the lengthening of the consonant is simpler. She suggests there would be no way to motivate lengthening of vowels in words like yolŋu /jʊːlŋʊ/ “person,” which would be a heavy syllable by nature of being closed.

Heath (1980) posits a length contrast for vowels in stressed syllables in Ritharrŋu, though notes that there is a tendency for long vowels to be phonetically shortened in words of three or more syllables as well as in reduplicants (p. 12), as Wilkinson (2012) has also reported for Djambarrpuyŋu (Section 1.1). Lengthened consonants, specifically liquids and nasals, are reported to occur intervocalically when following short vowels. Heath (1980, p. 12) had originally posited a length contrast for consonants in addition to vowels. He provides a discussion of his changing analysis, citing the occurrence of long vowels before consonant clusters, and gives examples such as the word yalu “nest” which was originally transcribed as [jɐlːʊ] (orig. [yallu] in text), explaining consonant duration varies phonetically, without phonological implications. Ritharrŋu is analysed as having fortis and lenis stop series though the effect of vowel length on those consonants is not discussed.

In Djinang (Waters, 1979, 1989), a similar phonetic pattern is described, though the phonological analysis and underlying mechanism differs to Djapu and Ritharrŋu. Waters proposes that vowel length is not contrastive. Rather, vowels optionally lengthen in stressed syllables, especially when the syllable is open (see discussion in Ryan, 2019, p. 36), and that consonants, specifically voiceless stops (i.e., fortis stops in other analyses), geminate following stressed syllables when the stressed vowel is phonetically short.

Wood (1978), on the other hand, proposes for Gälpu (also Gaalpu) that vowel length is determined by a “syllable feature” of length—short or long. Long vowels occur in syllables with the long feature, while short vowels occur in short syllables. Stops lengthen in intercontinuant environments, and lengthening is especially “pronounced” when the vowel is short and the consonant is the onset to the second syllable (i.e., is intervocalic) (Wood, 1978, p. 64). He terms the analysis “a prosodic solution” in contrast to a segmental solution in which vowel length would be analysed as contrastive (i.e., as in Morphy, 1983). These two options are both considered valid analyses by Wood, but he argues that the prosodic solution is better supported as it reflects the analysis of the glottal stop as syllable feature (first proposed by Bernhard Schebeck in a paper in 1974, cited in Wood, 1978), possibly historically associated with stress (Wood, 1978, p. 98).

For Djambarrpuyŋu, Wilkinson (2012) posits contrastive vowel length, but does not mention a durational relationship with the following consonant. Jepson and Stoakes (2015) examined intervocalic consonants in CV.CV Djambarrpuyŋu words spoken in isolation, and found that their duration differed significantly depending on whether they occurred following a phonemically (and durationally) short or long vowel, with consonants following short vowels being 236 ms in duration and consonants following long vowels being 191 ms. This study, also discussed in Section 1.1, supported the phonetic facts of what has been reported for Yolŋu languages: that the vowel in the first syllable of words varies in duration, that the duration of the following consonant varies too, and these are often in a complementary relationship. However, as only CV.CV words were examined, the analysis of segments in words with different syllable structures is necessary to understand the segment duration patterns of Djambarrpuyŋu.

All of these analyses rely to a degree on stress, and a requirement for stressed syllables to be a certain weight (i.e., heavy), or privileged to some degree. That is, contrastive length occurring only in stressed syllables could be interpreted as showing positional prominence, with more segmental contrasts maintained in stressed syllables than unstressed syllables in these languages (Hyman, 2014). On the other hand, as mentioned above (Section 2.2), it is generally assumed that stress is not quantity sensitive in most Australian languages, with most systems having fixed stress either to a word or root morpheme boundary (Baker, 2014; Fletcher & Butcher, 2014; Jepson & Ennever, 2023). The preference for heavy stressed syllables could suggest that some version of a Weight-to-Stress principle, which specifies heavy syllables are stressed, could be at play (Gordon, 2011; Prince, 1990). It is noted that this principle is violated in so much as unstressed syllables can also be heavy (e.g., /ˈɹɐj.mɐl/ “temple, side of head”; /ˈn̪ʊ.mɐn/ “smell, give off smell”), but it could motivate a preference for phonetically heavy stressed syllables. Djambarrpuyŋu allows monosyllabic words of the structure CV, for example /kɐ/ “and,” or the present and today future form of the imperfective auxiliary (Wilkinson, 2012, p. 44). However, there is a preference for minimally bimoraic roots in Djambarrpuyŋu, and from descriptions of other languages with prosodic minimality constraints, function words are observed to be prosodically deficient such as Ixtayutla Mixtec (Penner, 2019). So, it may be that minimality constraints related to word structure apply in Djambarrpuyŋu, and a similar minimum may also apply specifically to stressed syllables in Djambarrpuyŋu.

Considering other motives for lengthening, Solé and Ohala (2010, pp. 608, 611, inter alia) suggest that language-specific secondary properties that covary with a contrastive dimension could serve to enhance the contrast (see also Schertz & Clare, 2020). That could be the case for compensatory lengthening of the type proposed for Yolŋu and other Australian languages, to enhance the contrast between short and long vowels. This too is in conflict with the prevailing understanding of the phonetics of Australian languages. The large consonant inventories with many places of articulation that are found in most Australian languages, it is argued, require a maximisation of acoustic cues to consonant place at the expense of vowel contrasts (Butcher, 2006). This tendency for preserving or enhancing the place information of consonants over enhancing vowels has been termed the “Place of Articulation Imperative” by Butcher (2006) and is phonetically realised as the “lengthening and strengthening” of, in particular, post-tonic consonants in some Australian languages, serving dual purposes of maintaining and possibly enhancing paradigmatic consonant contrasts on the one hand and signalling prosodic prominence on the other (Butcher, 2006; Fletcher & Butcher, 2014). This preference is not observed across the board in Djambarrpuyŋu, but is found in words of two syllables (Jepson et al., 2021).

In Jepson et al. (2021), the duration of intervocalic consonants was measured in words of two to six syllables in length, and post-tonic consonants (i.e., following the stressed vowel) in disyllabic words were found to be significantly longer than post-tonic consonants in words with more syllables and non-post-tonic consonants. The words analysed in Jepson et al. (2021) contained only short stressed vowels. Therefore, it is not entirely clear if the duration of the consonant was conditioned by post-tonic lengthening (a focus of Jepson et al., 2021) or due to following a short vowel, as explored in this paper (for more on post-tonic consonant lengthening in other Australian languages see Butcher & Harrington, 2003a; Butcher & Harrington, 2003b; Fletcher et al., 2010; Fletcher et al., 2015). Disyllabic words are mentioned explicitly in Morphy’s (1983) analysis of vowel length in Djapu, and because they partake in other segment duration processes in Djambarrpuyŋu, it appears that two syllable words could present an interesting and distinct word structure in Yolŋu languages, which may show processes that are otherwise not observed in words of other structures.

Vowel duration is the primary cue used by listeners cross-linguistically when categorising vowels as “short” or “long” in perception studies (e.g., German: Lehnert-LeHouillier, 2007, 2010; Tomaschek et al., 2011; Thai: Abramson & Ren, 1990; Lehnert-LeHouillier, 2007, 2010; Roengpitya, 2001; Japanese: Arai et al., 1999; Behne et al., 1999; Kinoshita et al., 2002; Lehnert-LeHouillier, 2007, 2010). Listeners of languages with a phonemic vowel length contrast use their knowledge of the sounds in their language to categorise stimuli into existing categories in categorisation experiments (Holt & Lotto, 2010; Liberman et al., 1957).

However, vowel duration can be one of many cues that lead to the categorisation of the phone to a length category. A cue, albeit the primary one, is neither independent of the influence of other cues on the perception of a phone, nor solely responsible for it. (Repp, 1982). Further, in perception studies (and in day-to-day speech), there are also stimuli with duration values that fall between the typical durational range of “short” and “long” categories found in the production data for a language. Stimuli within this range are ambiguous as they do not provide durational cues that are sufficient for listeners to categorise the phone. In vowel length perception, stimuli containing vowels in the language-specific ambiguous region can be more difficult for listeners to process, which has been reflected in reaction times (Eerola et al., 2012, for Finnish listeners). Further, vowels that are between duration categories are subject to the influence of secondary cues.

Covarying of secondary features may be used as reliable indicators of the primary contrast (Solé & Ohala, 2010, p. 611), and when the primary acoustic cue is ambiguous, secondary cues can influence listeners’ perception (Hillenbrand & Clark, 2000, pp. 3020–3021; Lehnert-LeHouillier, 2010; Whalen et al., 1993). Secondary features are not ignored by listeners when the primary cue is not ambiguous; these cues are used by listeners even when phonologically redundant (Whalen et al., 1993). This type of effect can alter the location of the crossover point between categories. In vowel length perception, spectral information and f0 are most commonly investigated as secondary cues. These cues are used differently across languages in perception, as they are in production (Lehnert-LeHouillier, 2010). Language-specific formant quality changes can also result in varying crossover points in the perception of length contrasts (Abramson & Ren, 1990). This is to say, altering of one cue can be compensated for by altering another cue, thus maintaining the original phonetic percept in a cue trading relation (see Raphael, 2005; Repp, 1982).

Durational information beyond the vocalic element has also been shown to be a cue to vowel length in perception. This can operate between the vowel and the following consonant. For example, in Thai, longer post-vocalic consonant duration was found to condition a higher proportion of short vowel responses than post-vocalic consonants with shorter durations (Roengpitya, 2001). Similarly, van Dommelen (1999) found for Norwegian that the boundary between the categories of long and short for vowels was influenced by the duration of the following consonant. Overall, there was a shift in where the boundary occurred, such that a longer consonant resulted in a later boundary between the vowel categories than a shorter consonant, suggesting longer consonants resulted in perceptual shortening of the vowel.

This study is based on a dataset drawn from a larger database produced as part of the author’s doctoral research (in the process of being archived in PARADISEC). The project had ethics approval from the University of Melbourne Human Research Ethics Committee (HREC number: 1544581). Further details of data collection and the database can be found in Jepson (2019a) and Jepson et al. (2021).

As hypothesised, vowel duration varied consistently with respect to the length categories of short and long. Long vowels, overall, where twice as long as short vowels. The third hypothesis, that intervocalic consonants would vary with the phonological length of the preceding vowel, was also confirmed. The ratio between the two consonant categories following short and long vowels was relatively similar, though overall, obstruents had longer duration than sonorants. One might have thought the putative fortis/lenis contrast would have resulted in less durational variation for obstruents, due to duration most likely being used as a means for distinguishing between the two stop series (Round, 2023). However, it could have also been the case that these fortis stops were lengthened to an even greater degree, as there would be no upper duration limit that could result in an overlap in categories. As lenis stops were not examined here, comments on their behaviour cannot be made. The finding that vowels are, overall, shorter before obstruents than sonorants may reflect a broader segment duration relationship in the language (see Section 4.2.1).

Overall, consonant duration varied to a lesser degree than vowel duration. For both consonant categories, the lengthening does not wholly make up for the shorter duration of short vowels; on average, short vowels were 97 ms and long vowels were 194 ms, while consonants were 155 ms after short vowels and 107 ms after long vowels. That is to say, as in the Shetland variety of English and Washo (van Leyden, 2004; Yu, 2008), while consonant duration is longer after short vowels by approximately 45% (see Table 7, overall ratio), this does not account for short vowels being only half the duration of long vowels. These findings contribute to the conclusion that contrastive vowel length, and not consonant length, remains the most plausible phonological explanation for the observed segment duration values.

The lengthening of the C2 consonant appears to result in the main stressed syllable in Djambarrpuyŋu being heavy, irrespective of the phonological analysis of consonants or vowels (as in Swedish, Thai, Washo, and the Shetland variety of English (Schaeffler, 2005; van Leyden, 2004; Yu, 2008)). The consonant lengthening pattern also does not appear to be conditioned by another word-level requirement, for example, bimoraic minimum, as the minimum was already met in this dataset because all the words were disyllabic. It could be, however, that there is a phonetic bimoraic minimum requirement for stressed syllables. The complementarity between vowel and consonant duration is taken up in the perception study, presented in Section 5.

With respect to the second hypothesis, formants were affected by vowel length; long vowels were more peripheral than short vowels. Close vowels varied in F2 (higher values for /ɪː/ than /ɪ/, lower values for /ʊː/ than /ʊ/), and the open vowel varied in F1 (higher values for /ɐː/ than /ɐ/), reflecting findings reported for Gupapuyŋu (Graetzer, 2012) and tendencies for the relationship between duration and formant structure cross-linguistically (Cho, 2004; Lehiste, 1970, p. 31; Lindblom, 1963, p. 1780).3 The relatively compressed vowel spaces with considerable overlap between short/long pairs is observed in many Australian languages (Fletcher & Butcher, 2014).

The final hypothesis, that syllable structure would affect vowel and consonant duration, was supported. Long vowels were shorter in closed syllables than in open syllables, while short vowels remained relatively constant in duration. This suggests there may be a threshold beyond which vowels cannot be further compressed (Siddins et al., 2013; see also Nooteboom, 1997, pp. 656–658). The effect of syllable structure on long and short vowels consequently affected the ratio between categories (see Table 2). The duration of intervocalic C2 consonants varied inversely with the length of the preceding vowel, while the duration of coda C2 consonants did not vary significantly due to vowel length. In Lebanese Arabic, it has been found that only long vowel duration is affected by following geminate consonants; they have shorter duration compared to when they are followed by singleton consonants, while short vowels remain the same duration in both conditions (Khattab & Al-Tamimi, 2014). That finding, while conditioned by a different process, echoes the Djambarrpuyŋu findings. Syllable association also operates in a different way in Dutch: C2 in CV1C2.CVC words was found to be of significantly longer duration when the V1 was short than when it was long, but in CV1.C2VC words C2 duration did not differ significantly (Jongman, 1998). Jongman argued that the status of the C2 consonant as ambisyllabic or tautosyllabic determines whether lengthening occurs, with only tautosyllabic consonants participating in the lengthening pattern. If the duration variation of the consonants was to enhance the vowel length contrast in Djambarrpuyŋu (in a way described by e.g., Solé & Ohala, 2010), we might expect that consonant duration values in Djambarrpuyŋu followed the Dutch pattern, as there is considerably more overlap in duration between the short and long vowel categories in closed syllables. However, we see no significant duration relationship between vowel and consonant duration when the consonant is coda to the first syllable. The opposing results agree that syllable structure “has a direct influence on the … acoustic realization of individual segments” (Jongman, 1998, p. 219); however, it does not necessarily have the same influence.

Figure 7 shows the proportion of /wɐŋɐ/ and /wɐːŋɐ/ responses to each stimulus, pooled for the 19 participants. Along the x-axis is vowel step, and on the y-axis is the nasal step. Each cell represents one stimulus. The colour of the cell represents the count of /wɐːŋɐ/ responses: A lighter colour reflects more /wɐːŋɐ/ responses, the darker the cell, the fewer /wɐːŋɐ/ responses (i.e., more /wɐŋɐ/ responses). Each stimulus has maximally 76 responses.

Of the 3,718 total valid responses, 1,378 were /wɐŋɐ/ and 2,340 were /wɐːŋɐ/. The responses, therefore, are skewed towards /wɐːŋɐ/ (63%). Possible reasons for this are discussed further in Section 5.3. Overall, participants selected /wɐːŋɐ/ less frequently when a stimulus contained a vowel at step 1 or 2 in the continuum, and more frequently when a stimulus contained a vowel at step 4, 5, 6 or 7 in the continuum. As can be seen in Figure 7, stimuli with vowel step 3 form an intermediate group for which /wɐŋɐ/ and /wɐːŋɐ/ are selected with relatively equal frequency. Nasal step, on the other hand, does not appear to have a consistent effect on listeners’ responses.

It was hypothesised that vowel length perception is categorical in the pair of words /wɐŋɐ/ and /wɐːŋɐ/. The results from the analysis show that listeners’ selection in this forced-choice task were strongly influenced by vowel duration. There was a shift between /wɐŋɐ/ and /wɐːŋɐ/ at around vowel step 3 when considering data pooled across the 19 participants. Vowels at step 3 were ambiguous as to their length category as evidenced by participants performing at chance for stimuli containing those vowels (Lehnert-LeHouillier, 2010). Recall that in the corpus, the duration of the short vowel in /wɐŋɐ/ ranged from 102 to 158 ms (median = 127), and 132 to 286 ms (median = 214 ms) in /wɐːŋɐ/. Therefore, the location for the crossover point between short and long vowel words in perception, around vowel step 3 in the vowel continuum (160 ms), is in line with the production data in terms of the durational ranges for short and long categories.

The duration of the nasal in C2 affected listeners responses in two ways. Firstly, it was hypothesised that the consonant’s duration would have the strongest effect when the vowel’s duration was ambiguous. Figure 7 suggests that consonant duration is used by listeners as a secondary cue to vowel length when vowel duration is in the durationally ambiguous region between short and long (vowel step 3). Secondly, an overall effect of consonant duration on vowel length perception was hypothesised, which is observed by the leftwards and rightwards shift in the vowel category crossover points in Figure 10 for the nasal step 1 and 7 data. Specifically, shorter consonant duration conditioned an earlier crossover between the length categories, while longer consonant duration conditioned a later crossover. There were also fewer /wɐːŋɐ/ responses to stimuli with nasal step 7, even when the vowel was at its longest. Together, these findings suggest listeners made use of secondary cues when the primary cue was ambiguous (Lehnert-LeHouillier, 2010), as well as phonologically redundant phonetic information in their perception of the vowel length contrast in this minimal pair (Whalen et al., 1993). The pattern observed in the figures corresponds to results for Thai (Roengpitya, 2001; see also Abramson & Ren, 1990, on formants) and Norwegian (van Dommelen, 1999), which showed similar movement in the crossover point in vowel categorisation due to the duration of the following consonant.

Because nasal duration did not have a strong effect on listeners’ responses whereas vowel duration showed a pattern consistent with categorical perception, the results of the perception study support the analysis that only vowel length is contrastive in the language. The results from this study do suggest that the inverse lengthening of consonants may perceptually enhance the vowel length contrast for this minimal pair and possibly other words. It is possible that this finding would not be observed in a study comparing words with obstruents. That is because the nasal steps are shorter in duration than the vowel steps in the perception task, and sonorants overall are shorter than obstruents in the language. Both of these factors might mean that the nasal (i.e., sonorant) duration is more of a secondary perceptual cue than if there had been a perceptual comparison between words with obstruents.

With respect to block, recall that it also had a significant effect. One possibility for this result is that listeners became more familiar with the range of durational values contained in the data over time. Inspection of the data showed that listeners’ decisions became more consistent throughout the blocks, especially so for stimuli containing vowel step 1. Overall, responses in block 1 were significantly different from blocks 2, 3, and 4, while blocks 2, 3, and 4 did not differ significantly.

The overall greater proportion of /wɐːŋɐ/ responses may be due to a number of factors, some of which are discussed here. It could be that the continuum did not include vowels of short enough duration. This is supported in the lack of a level state at the lower end of the vowel continuum in Figure 8. Another possibility is that because the original token contained a long vowel and listeners had access to a range of acoustic cues other than duration, these cues conditioned more /wɐːŋɐ/ responses. For example, the small difference in formants may have affected listeners, at least in the trials in block 1, though the manipulated token was within the overlapped areas for short and long vowels (Figure 5). An additional factor that could be utilised by listeners that may be examined in the future is the f0 contour (see e.g., Lehnert-LeHouillier, 2010; Sanker, 2019), which has been found to differ between short and long vowels in Djambarrpuyŋu, but has not been subject to thorough investigation (Jepson, 2019a, pp. 104–109). The presentation of the stimuli could have also been a factor in the skewed responses as the keyboard responses and on-screen images were not counter-balanced throughout the trials or between participants. This may have led to a bias to select the right-side response button (i.e., selecting the long vowel word /wɐːŋɐ/) (Richardson, et al., 2020). These factors will be taken into account in future perception studies with Yolŋu listeners.