1.1 An aeroacoustic confound revisited

Ejective fricatives are relatively rare sounds in the world's languages. In the UCLA Phonological Segment Inventory Database (UPSID-PC) (Maddieson & Precoda Reference Maddieson and Precoda1991), only ten of 451 languages (2.2%) are reported to have an ejective fricative. The languages with ejective fricatives reported in this database are:

• Acoma (Keres) – Miller Reference Miller1966

• Berta (Nilo-Saharan) – Triulzi, Dafallah & Bender Reference Triulzi, Dafallah, Bender and Bender1976

• Dakota (Siouan) – Boas & Deloria Reference Boas and Deloria1939

• Kabardian (Caucasian) – Kuipers Reference Kuipers1960

• Koma (Adamawa-Ubangi) – Tucker & Bryan Reference Tucker and Bryan1966

• Mazahua (Oto-Manguean) – Spotts Reference Spotts1953

• Soqotri (South Arabian) – Leslau Reference Leslau1938, Johnstone Reference Johnstone1975

• Tlingit (Na-Dene) – Story & Naish Reference Story and Naish1973, Swanton Reference Swanton and Boas1911

• WichitaFootnote ¹ (Caddoan) – Garvin Reference Garvin1950, Rood Reference Rood1975

• Yuchi – Crawford Reference Crawford1973, Ballard Reference Ballard and Crawford1975

To the UPSID-PC list, one might add the following:

• Adyghe, Bagwali (or Bagwalal), and Karata (Caucasian) – Catford Reference Catford and Paris1992

• HausaFootnote ² (Chadic) – Ladefoged & Maddieson Reference Ladefoged and Maddieson1996, Newman Reference Newman2000, although see Lindsey, Hayward & Haruna Reference Lindsey, Hayward and Haruna1992

• Mehri, Harsusi, Bathari, Hobyot, Jibbali (or Shehri) (SouthArabian) – Simeone-Senelle Reference Simeone-Senelle and Hetzron1997

• Upper Necaxa Totonac (Totonac-Tepehua) – Beck Reference Beck and Kirchner2006

• Yapese (Oceanic) – Jensen Reference Jensen1977, Maddieson Reference Maddieson1998

• Amharic (Ethio-Semitic) – Leslau Reference Leslau1995

• Tigre (Ethio-Semitic) – Palmer Reference Palmer1962, Raz Reference Raz1983

• Tigrinya (Ethio-Semitic) – Leslau Reference Leslau1939, Reference Leslau1941

This additional list is based on a general survey of the literature on ejective fricatives, not on an exhaustive survey of language grammars.

The presence of an ejective fricative in a language seems almost always to imply the presence of at least one other ejective obstruent. In all UPSID-PC languages the presence of an ejective fricative implies the presence of at least one ejective stop. One exception to this generalization is Upper Necaxa Totonac (Beck Reference Beck and Kirchner2006; not reported in UPSID-PC), which has ejective fricatives but no ejective stops or ejective affricates. Like languages with ejective fricatives, UPSID-PC languages with ejective affricates fit neatly within the set of languages with ejective stops. The only exception is Iraqw, a Cushitic language of Tanzania which has two ejective affricates but no ejective stop (nor an ejective fricative) (Whiteley Reference Whiteley1958, see also Mous Reference Mous1993).Footnote ³ Of the ten UPSID-PC languages with ejective fricatives, only three lack ejective affricates: Berta, Koma, and Soqotri. Conversely, of the 59 languages that have ejective affricates, only seven have ejective fricatives (see Figure 1). Thus, the chance of a language having ejective fricatives seems to increase slightly if the language also has ejective affricates. Of the seven languages that have both ejective fricatives and affricates, six (Acoma, Dakota, Mazahua, Tlingit, Wichita, and Yuchi) have affricates and ejectives at the same place of articulation.

Figure 1

Languages with ejective stops in UPSID-PC (Maddieson & Precoda Reference Maddieson and Precoda1991) categorized by the presence/absence of ejective fricatives and/or affricates.

Ejectives are produced by trapping air between the tightly adducted vocal folds and a constriction at an oral place of articulation. To produce an ejective, the larynx should be raised, thereby compressing the air in the supralaryngeal cavity (Ladefoged Reference Ladefoged1993: 130). Upon release, ‘the entrapped high-pressure air will momentarily burst forth in a short sharp explosion’ (Catford Reference Catford2001: 22).

The release of the oral closure results in a sudden outflow of air (a glottalic egressive airstream), along with a characteristic burst of acoustic energy. After this, the laryngeal closure is released, the suprahyoid musculature relaxes, thus lowering the larynx, and pulmonic egressive airflow may course through the glottis.

The production of an ejective fricative involves an aeroacoustic dilemma. Two competing demands, stated here as directives, must be satisfied: (i) Ejectivity: Substantially increase air pressure above the larynx (to a degree greater than expected during pulmonic egressive obstruents); (ii) Frication: Vent air continuously through a narrow constriction. The venting required of a fricative may defeat the increase in pressure required of an ejective.

Maddieson (Reference Maddieson1997, Reference Maddieson1998) has put forward two mechanisms for satisfying these demands. First, he proposes reducing the size of the constriction between oral articulators to increase intraoral pressure. Thus, the fricative can be produced exclusively on the outflow of air trapped above the larynx, albeit at some cost to net flow and therefore duration. The ejective fricatives of Tlingit, with an oral constriction narrower than that of pulmonic fricatives, are of this type. They allow intraoral air pressure to achieve a higher peak than is found during pulmonic fricatives but the duration is reduced, since the supralaryngeal cavity volume is much smaller than the volume of the lungs (Maddieson, Smith & Bessell Reference Maddieson, Smith and Bessell2001).

Maddieson's (Reference Maddieson1997, Reference Maddieson1998) second proposal for resolving the aeroacoustic dilemma is to sequence frication and glottal constriction, as in Yapese. This proposal raises the question of whether such a sound still qualifies as an ejective in the classic sense, e.g. that of Catford (Reference Catford2001). After all, frication is not produced simultaneously with glottal closure, nor is the larynx necessarily raised to increase pressure during the fricative. Indeed, Maddieson (Reference Maddieson1998) concludes that Yapese ejective fricatives are not ejectives at all, but a sequence of e.g. /f/ + /ʔ/ (see Section 1.3.5 for further discussion of Yapese).

Beyond these two mechanisms, another may be posited: Frication may be preceded by a period of oral closure, allowing time for air pressure to build (we will refer to this as the affrication hypothesis). Closure plus frication is characteristic of affricates, not fricatives, and thus raises the question of whether ejective fricatives realized in this way have crossed an ontological boundary. Pre-release closures have been reported in the literature for ejective fricatives in Amharic (Demolin Reference Demolin, Gussenhoven and Warner2002) and Kabardian (Gordon & Applebaum Reference Gordon and Appelbaum2006) with little comment.

The purpose of this paper is to further elaborate the affrication hypothesis through an acoustic study of the alveolar ejective fricative in Tigrinya. The results will suggest that this fricative is often realized as an affricate, thus explaining historical confusion about the transcription of the sound, as well as dialectal variation in its realization. More generally, the results will suggest that affrication is a phonetically natural path in the evolution of ejective fricatives.

1.2 Tigrinya and its ejective fricatives

Tigrinya is a North Ethio-Semitic language spoken in northern Ethiopia and Eritrea. The Ethio-Semitic (also termed Ethiopian Semitic) family is classified as South Semitic, part of the larger West Semitic branch (Faber Reference Faber and Hetzron2007). The consonant inventory for Tigrinya is shown in Table 1. There are five ejectives: /t’ k’ k^ʷ’ s’ ʧ’/,

Table 1

Phonemic obstruents in Tigrinya.

All consonants in Tigrinya, including the ejectives, may be geminate/long, although the ‘guttural’ sounds /h ħ ʔ ʕ/ appear as geminate in limited circumstances (Berhane Reference Berhane1991).Footnote ⁴ The sounds [p] and [ʧ] appear in loanwords, primarily from Italian and English, whereas the sound [p’] appears in Greek loanwords. [ʒ] is uncommon and varies with /ʤ/. The voiceless velar stop /k/ is realized as [x] in post-vocalic position, and the ejective /k’/ has a post-vocalic allophone commonly transcribed as [x’] (Leslau Reference Leslau1941, Schein Reference Schein, Borer and Aoun1981, Kenstowicz Reference Kenstowicz1982, Denais Reference Denais1990, Fitzgerald Reference Fitzgerald and Uhlig2006). The actual production of this sound is reported as uvular (Fre Woldu Reference Fre Woldu1985), but whether it is ejective is unclear. An acoustic and aerodynamic investigation of its properties is being undertaken by the current authors.

[s’] is described as an alveolar ejective fricative in the standard linguistic and grammatical literature on Tigrinya and usually transcribed with the letter 〈s〉 and a diacritic to indicate glottalization (Leslau Reference Leslau1941, Pam Reference Pam1973, Denais Reference Denais1990, Berhane Reference Berhane1991, Kogan Reference Kogan and Hetzron1997, Tewolde Reference Tewolde2002. However, Denais (Reference Denais1990: 32) notes that /s’/ is a fricative but has a free variant [^ts’]. The sound is also transcribed as [ts’] without comment by Palmer (Reference Palmer1966) and Walther (Reference Walther1999). Finally, Fre Woldu (Reference Fre Woldu1985: 4), a native Tigrinya speaker, uses a fricative transcription, but places the sound in the affricate section of the obstruent chart. Berhane (Reference Berhane1991), another native speaker of Tigrinya, calls it a fricative. These variable transcriptions lend credence to the hypothesis that Tigrinya's ejective fricative may be realized with initial closure.

Alternation of [s’] with [ts’] is reported for other languages. In Hausa, the digraph 〈ts〉 is used in the standard orthography for what Jaggar (Reference Jaggar2001) describes as an ejective alveolar sibilant, but it is listed as an affricate in the consonant chart. Leslau (Reference Leslau1957: 156) reports that in the Amharic dialect of Godjam, [s’] is ‘often definitely pronounced as affricate [ts’]’. Bender (Reference Bender and Bright1992) reports that [s’] alternates with [ts’], but also tends to be realized as [t’] in the Shewa dialect of Amharic. Indeed, Amharic cognates of Tigrinya words containing [s’] generally show [t’] or its palatalized version [ʧ’] (Leslau Reference Leslau1987), and some words show variation, e.g. [s’omə] ~ [t’omə] ‘he fasted’ (Tadesse Reference Tadesse1992, Leslau Reference Leslau1995). In Dime (Fleming Reference Fleming and Hayward1990), [s’] and [ts’] pronunciations cannot be distinguished, at least in initial position (although Seyoum (Reference Seyoum2008) does not mention this variation). Savà (Reference Savà2005: 23) reports that the ejective affricate /ts’/ in Ts'amakko has an ejective fricative [s’] as a free variant. In Lowland Oaxaca Chontal (Maddieson, Avelino & O'Connor Reference Maddieson, Avelino and O'Connor2009), /s’/ is realized as [ts’] or [tsʔ] with a few tokens of [sʔ] or [ʔs] (see Section 1.3.6 for more discussion).

There is also historical and dialectal evidence which may support the affrication hypothesis for Tigrinya. First, Steiner (Reference Steiner1982) proposes that West Semitic *Ṣ (Ṣade) should be reconstructed as a glottalized affricate [ts^ˀ] rather than a fricative, and Faber (Reference Faber1985) supports and extends this position to Proto-Semitic. Reflexes of this sound appear as [ts] in Modern Hebrew, as [sˤ] in Arabic, and as [s’] in Tigrinya, e.g. [ħisˤaːr] (Arabic) ‘enclosure’ [xatsər] (Modern Hebrew) ‘enclosure, courtyard’, [ħas’ərə] (Tigrinya) ‘make a fence’. Arabic acquired secondary pharyngealization, whereas Hebrew lost glottalization. These variable reflexes could stem from an affricate pronunciation of an ejective fricative. Second, rural dialects of Tigrinya favor a palato-alveolar affricate [ʧ’] instead of [s’] in some lexical items: e.g. [ħas’ərə] ~ [ħaʧ’ərə] ‘become short’, [k’^ʷɨns’i] ~ [k’^ʷɨnʧ’i] ‘flea’ or [s’əmmərə] ~ [ʧ’əmmərə] ‘add, unite’. Tigre cognates also occasionally have [ʧ’]: [ʧ’amraː] ‘unite’ or [k’ars’aː] ~ [k’arʧ’aː] ‘slice, cut off’ (Tigrinya [k’ərəs’ə]) (Leslau Reference Leslau1987). Ullendorff (Reference Ullendorff1955) and Voigt (Reference Voigt1988) propose that this alternation is a type of palatalization due to influence from rounded vowels by way of labial consonants, parallel to a [s ~ ʃ] alternation. Although the viability of the rounding trigger may be questioned, it is clear that [s’] alternates not with [ʃ’], but with an affricate.

Fre Woldu (Reference Fre Woldu1985) analyzed the properties of voiceless, voiced and ejective stops in Tigrinya, but not the ejective fricative /s’/. He found that the main characteristic of ejective stops, in relation to pulmonics, was a longer burst release followed by a period of silence preceding the vowel. In perceptual experiments, native listeners reliably cued into this long silent period in order to distinguish ejective and plain voiceless stops.

Kingston (Reference Kingston1985) analyzed larynx movement for Tigrinya stops. He observed 4–6 mm of laryngeal displacement during the ejective consonants but commented that larynx elevation is variable across speakers and is too slow and ill-timed with oral closure and release to fully explain the decreased volume of the oral cavity necessary for ejectives. No data on the ejective fricatives of Tigrinya were reported.

1.3 The phonetics of ejective fricatives: A cross-linguistic perspective

In this section we present observations about ejective fricatives in those languages where the sounds have been described instrumentally.

1.3.2 Tlingit

Tlingit, a Na-Dene language spoken in the Pacific Northwest coast of North America has six ejective fricatives, /s’ ɬ’ x’ x^ʷ’ χ’ χ^ʷ’/, five ejective stops, /t’ k’ k^ʷ’ q’ q^ʷ’/, and three ejective affricates, /ts’ ʧ’ tɬ’/ (Maddieson et al. Reference Maddieson, Smith and Bessell2001). All of these sounds have plain pulmonic counterparts. Maddieson et al. (Reference Maddieson, Smith and Bessell2001) present both acoustic and aerodynamic data for the ejective fricatives. Word-initial ejective fricatives are characterized by an approximately 46 ms silent interval following a word-initial fricative, punctuated by a release (of glottal closure) into the vowel. Word-final fricatives are flanked by silent intervals, and there is a detectable release burst approximately 39 ms after the silent period. The noisy portion of the fricative is significantly shorter in an ejective fricative than a pulmonic fricative (word-initial 148 ms vs. 222 ms and word-final 127 ms vs. 301 ms, respectively), and the noise is ‘scrapy’ (broken into a series of pulses). Maddieson et al. (Reference Maddieson, Smith and Bessell2001: 159) postulate that this scrapy quality (which they did not observe in /s’/) occurs due to intermittent closures of the oral channel, possibly related to the presence of saliva in a very narrow constriction. The scrapy quality may also be caused by friction at the aryepiglottic folds (Esling Reference Esling1996, Moisik Reference Moisik2008). Maddieson et al. (Reference Maddieson, Smith and Bessell2001: 172) explicitly reject the possibility that the scrapy quality is a glottal phenomenon. Given the high intraoral pressure observed during ejective fricatives, they argue that glottal pulsing would require an ‘improbably high’ level of subglottal pressure. Although pulmonic fricatives undergo final lengthening in Tlingit, ejective fricatives do not.

Intraoral air pressure data was recorded by speakers holding a narrow plastic tube positioned between the lips with the open end resting against the center of the hard palate. Pressure behind the constriction was detected through the tube and recorded using Macquirer hardware and software. A series of calibration recordings were then made using a U-tube manometer. The intraoral pressure trace for Tlingit ejective fricatives is parabolic, with a high peak level between 14 hPa and 17 hPa, but without a sustained peak, compared with between 5.2 hPa and 8.6 hPa for pulmonic fricatives. Air pressure is presumably maintained by forcing air through a narrower supraglottal constriction, which could also explain the scrapy, pulsing quality of the fricative noise. Maddieson et al. (Reference Maddieson, Smith and Bessell2001) propose that the silent periods flanking frication are due to glottal closure overlapping the entire fricative. The silent interval before frication appears to occur variably, as illustrated by a word with a word-medial ejective fricative uttered by two different native speakers (Dauenhauer & Dauenhauer Reference Dauenhauer and Dauenhauer1991; see Figure 2). It is not clear why the closure preceding frication is interpreted as glottal rather than oral. No data on the ejective affricates were reported to test how contrast is realized between the fricative/affricate pairs [s’] and [ts’] or [ɬ’] and [tɬ’].

Figure 2

The Tlingit word ús'aa ‘soap’ produced by a female speaker (left) and a male (right), taken from audio files in Dauenhauer & Dauenhauer (Reference Dauenhauer and Dauenhauer1991). The second token is marked by a nearly silent closure before the onset of frication [(t)]. Both are marked by a period of irregular vibration or near silence after the frication, transcribed here as [ʔ].

1.3.7 Summary

In conclusion, ejective fricatives are characterized by shorter frication duration than pulmonic fricatives (except for Upper Necaxa Totonac), with a following (near-)silent lag before vowel onset, presumably associated with the time that it takes for the larynx to drop and regular vocal fold vibration to initiate under an egressive pulmonic airflow regime. The frication itself is often described as ‘scrapy’ or ‘pulsing’, perhaps indicative of an oral constriction that opens and closes quickly. Ejective fricatives generally show higher intraoral pressure peaks, typically occurring earlier than they do during pulmonics. High supralaryngeal cavity pressure is of course a hallmark of ejectives. The timing of the peak suggests that pressure builds more slowly in pulmonic fricatives, a difference that is likely to have acoustic consequences as well. Upper Necaxa Totonac is an exception to this intraoral pressure pattern. Palatograms reveal wider contact and narrower constriction, and in some cases evidence of total alveolar or alveopalatal occlusion, particularly in Amharic. Silence preceding frication is sporadically reported and was interpreted as glottal closure (without further comment) for Tlingit (Maddieson et al. Reference Maddieson, Smith and Bessell2001). This can be seen on the right-hand side of Figure 2. A summary of these characteristics for four languages, excluding Yapese and Lowland Oaxaca Chontal (because their so-called ejective fricatives have been interpreted as a sequence of fricative plus glottal stop), is shown in Table 2. None of the languages surveyed had geminate ejective fricatives.

Table 2

Characteristics of ejective fricatives compared to pulmonic fricatives (n/r = not recorded or reported).

1.4 The problem

The motivation for our study is based on several observations: (i) most languages that have ejective fricatives also have ejective affricates (see Figure 1); (ii) Tigrinya ejective fricatives do not contrast with homorganic affricates, but the fricatives are occasionally transcribed or described as affricates and dialectal variation along these lines is reported; (iii) linguopalatal occlusion has been reported for the ejective fricative of Amharic, a related language; and (iv) the buildup of intraoral pressure during ejective consonants can be achieved most effectively by creating a complete supralaryngeal occlusion while raising the larynx. Thus, our study will investigate the affrication hypothesis, i.e. there is a complete supralaryngeal occlusion before the onset of frication in Tigrinya ejective fricatives. If this hypothesis is correct, we expect that ejective fricative /s’/ will manifest a silent interval preceding fricative release and that pulmonic fricative /s/ will not. We will report measures of this pre-release silent interval as ‘closure duration’ throughout the paper.

We also hypothesize that closure duration will be longer in the geminate ejective fricative than the singleton. Longer closure duration is the expected measure of phonological length contrast for affricates (Pycha Reference Pycha2009).

As mentioned above, there is abundant dialectal and transcriptional evidence suggesting that the ejective fricative of Tigrinya varies with an affricate. Furthermore, Demolin's (Reference Demolin, Gussenhoven and Warner2002, Reference Demolin2004) aerodynamic and EPG measures of /s’/ in Amharic, a closely-related language, are indicative of complete linguopalatal closure. In addition, if closure is manipulated to convey length differences for the /s’/ vs. /sː’/ contrast as it does for affricates, then this further reinforces our interpretation of the closure as linguopalatal. Nevertheless, there is the possibility that the closure could be interpreted as glottal. Maddieson et al. (Reference Maddieson, Smith and Bessell2001) assume this intepretation for Tlingit /s’/ where increased intraoral pressure is interpreted as evidence of increased supraglottal constriction but not full linguopalatal closure. Despite the absence of aerodynamic or physiological data for Tigrinya /s’/, we believe that the facts are more in line with a supralaryngeal closure interpretation.

We will investigate other acoustic properties (besides closure duration) that differentiate the two types of fricatives from each other and which also differentiate Tigrinya's ejective fricative from its ejective affricate. These are release duration, preceding and following vowel duration, presence and duration of post-release laryngealization, amplitude rise slope, and rise time.Footnote ⁷ These measurements will allow us to present a full acoustic profile of intervocalic /s’/ in comparison to the pulmonic fricative and assess its properties as characteristic of either fricative or affricate. We predict that release duration will be shorter for the ejective fricative than the pulmonic fricative, and we anticipate that the presence of laryngealization and perhaps longer laryngealized intervals will signal ejectivity. We make no strong predictions concerning vowel duration. On the one hand, the presence of predicted closure in ejective fricatives may correlate with a shorter preceding vowel. On the other hand, if release duration is shorter for ejective fricatives, then the preceding vowel may be longer. Following vowel duration may adjust for a longer laryngealization period, with shorter vowels following ejectives. The affrication hypothesis predicts that, apart from properties associated with alveolar versus palato-alveolar place of articulation differences, /s’/ should share characteristics with /ʧ’/: similar release duration, high amplitude rise slope, and long rise time. Finally, we will discuss the likelihood that affrication is a viable strategy for satisfying the competing aeroacoustic demands involved in the production of simultaneous frication and ejectivity, particularly in languages that lack a corresponding ejective affricate.