The duration of complex speech units obviously depends on the duration of their constituents. The duration of units described in section 1.1 depends on a number of factors, some of them universal, others — language specific. This section points out the main determinants of speech unit duration focussing on those which show different influence on timing in English and Polish. These factors will be considered in accounting for the timing problems of Polish learners of English demonstrated by the results of the empirical study.
Universal factors will remain outside the focus of this study as they are irrelevant in FL acquisition process.
1.2.1 Intrinsic segmental length
The length of individual segments depends on their intrinsic characteristics and extrinsic factors, operating on higher levels of the utterance structure. The latter will be discussed in the subsequent sections of this chapter, devoted to the higher-level units.
1.2.1.1 Universal segmental duration determinants
Among the universal principles, connected with the anatomy and physiology of speech, Waniek-Klimczak (2005) mentions the following:
1. Tongue height in vowel articulation (referring to studies by Lehiste 1970, cf. also House and Fairbanks 1953, Peterson and Lehiste 1960, Delattre 1962, Elert 1964) is inversely proportional to vowel length.
2. The place of articulation of consonants is an important duration determinant: Labial consonants are longer than alveolars and velars (Waniek-Klimczak 2005: 25, after Lehiste 1970, Klatt 1976, Maddieson 1997, Luce and Charles-Luce 1985), while VOT duration is proportional to the degree of backness (Lisker and Abramson 1964, Cho and Ladefoged 1999), which suggests duration balance, e.g. between /p/ (longer closure, shorter VOT) and /k/ (shorter closure, longer VOT — cf. Docherty 1992).
3. Voiced consonants are shorter than voiceless consonants (Chen 1970, Klatt 1976, Port 1979, Lisker 1986), also in languages which do not exploit tense/lax opposition, e.g. Polish (Keating 1985).
The above relations are claimed to be universal and as such they do not influence segmental length in the pronunciation of native speakers and FL learners in dissimilar ways. Still, different L1 backgrounds may result in duration discrepancies between the two groups as a consequence of the following interference processes:
1. Non-native vowel quality may lead to additional uncontrollable length variation.
2. VOT is generally shorter in Polish and, arguably, phonologically less relevant than in English, which may affect the length of prosodic units unless longer VOT is offset by vowel shortening.
3. The regularity comprises contexts where voicing contrast is neutralised in Polish, hence voicing inconsistencies may also affect timing relations within speech units.
Therefore, despite acknowledging the universal character of the intrinsic temporal characteristics of segments, we must allow for other L1-related processes, which make the conditions for the application of the above rules different in the performance of Polish and English speakers.
1.2.1.2 Language-specific intrinsic segmental length
English, unlike Polish, is a language that uses vowel quantity as a phonologically relevant feature. Although all English vowel contrasts are
1.2. Segmental length and its determinants 23
reflected in the sound quality, most classifications mention intrinsically long and short vowels and even the most popular transcription systems used for pedagogical purposes mark that feature explicitly (e.g. Wells 2008, Hornby 2000). Moreover, studies have been carried out to establish regular duration relations between short and long vowels by Wiik (1965) (quoted by Cruttenden 2001: 96), Gonet (1997), Peterson and Lehiste (1960), Lehiste (1970).
Waniek-Klimczak (2005: 25), referring to the latter two sources, mentions a mean of 50% difference in length between the two vocalic classes. This difference can be increased to 100% or even more if the shortest and longest vowels are compared (e.g. Umeda 1975, Van Santen 1992). This typological discrepancy between English and Polish must be treated as a potential source of non-native timing in the learners’ English pronunciation.
Although consonant quantity contrasts are not used in English, studies of speech timing must take into account the length of consonants as well. Jassem et al. (1984) measured vocalic and consonantal segments and their duration variability in recorded study units of A Course in Spoken English: Intonation (Halliday 1970) and distinguished 18 phone classes, then grouped into 6 duration categories based on the principle of minimum within-group variation and maximum between group variation (Table 1.3).
Table 1.3. The duration of phone classes (Jassem et al. 1984)
Rank Class Mean (ms) FOOT NRU ANA FOOT (rel) ANA (rel)
1. F 16.6 16.8 18.5 14.5 .907 .785
Abbreviations:F — flaps, lenis stops /r/, /b/, /d/, /g/; D — weak-friction lenis fricatives /¶/, /v/; G — non-syllabic vocoids /w/, /j/, /r/; E — checked non-open vowels /e/, /ö/, /¬/, /Ã/; B — non-initial lenis stops /b/, /d/, /g/; N — non-syllabic nasals /m/, /n/; H — the aspirate and initial voiceless fortis aspirated stops /pú/, /tú/, /kú/; K — fortis unaspirated stops /p/, /t/, /k/;
Z — heavy-friction lenis fricatives /z/, /½/; SC — syllabic contoids /l/, /n/, /m/; KH — aspirated unaccented fortis stops /pú/, /tú/, /kú/; S — fortis fricatives /f/, / /, /s/, /§/; AFV — lenis affricates /d½/, /dr/; O — close unchecked and the open checked vowels /iÉ/, /uÉ/, /¾(É)/, //; KHA — accented fortis stops /pú/, /tú/, /kú/; AF — fortis affricates /t§/, /tr/; A — mid and open unchecked monophthongs /±É/, /É/, /¿É/ and diphthongs; FTH — aspirated final fortis stops /pú/, /tú/, /kú/.
The study shows considerable differences in duration means and variability depending on the type of a segment. Obviously in many cases the duration of particular phones might have been influenced by their phonetic environment since often particular positional allophones of one phoneme are classified in different groups. The general influence of phonetic context on segmental duration is discussed in the next section.
The results obtained by Jassem et al. (1984) will later be considered in discussing the results of the present research.
1.2.2 Phonetic context as a segmental duration determinant
The intrinsic duration properties of speech sounds are modified by a number of contextual factors addressed in this section, including the phonetic characteristics of adjacent segments and the position of the segment within utterance structure. Another important factor, prominence, is discussed separately in Chapter 2.
One important segmental factor influencing speech timing is consonant elision. It may strongly influence syllable duration because a whole segment is deleted. This is not always the case, though, because elision may invoke
“compensatory” lengthening of the adjacent segments. The process is more widespread in unstressed positions (to be discussed in Chapter 2 as well), but Cruttenden (2001: 237) mentions a lot of examples of consonant (especially alveolar stop) elision typical mainly of colloquial speech, but independent of stress. These include segments occurring between other consonants, e.g.
“facts,” “exactly,” “handsome,” also before a word boundary, e.g. “next day,”
“old man,” “looked fine,” and in negations, e.g. “mustn’t lose.”
Otherwise, little significant length modification has been reported in consonants, although Lisker and Abramson (1967), Flege et al. (1998) report evidence for longer VOT duration before high vowels, a regularity that is physiologically (cf. Waniek-Klimczak 2005: 27) rather than phonologically motivated.
More contextual variability is visible in vocalic segments. Whereas the influence of the preceding consonant on vowel duration is considered negligible (Peterson and Lehiste 1960), the consonant that follows is significant. The fact that English vowels are longer before voiced than voiceless consonants has been documented in numerous publications, e.g. House and Fairbanks (1953), House (1961), Chen (1970), Klatt (1973), Lisker (1974).
A difference of 50% was reported by Peterson and Lehiste (1960).
This regularity was also found in other languages (Chen 1970), even those which neutralise word-final voicing contrast, including Polish. Slowiaczek and Dinnsen (1985) observed a 10% vowel lengthening before underlyingly
1.2. Segmental length and its determinants 25
voiceless consonants. However, Jassem and Richter (1989) only found a mean 4ms difference in vowel length. Likewise, House (1961) and Keating (1985) did not observe that process in Spanish, Czech or Polish. Considering the research by Delattre (1962), Chen (1970), Mack (1982), and Laeufer (1992), who argued for language-specific range of pre-voice lengthening, and studies of the acquisition of vowel duration by children (e.g. Krause 1982, Ko 2007), we may consider vowel length effect a universal tendency, manifested to varying degrees cross-linguistically.
The fact that English actually uses vowel length variation as the main cue for coda phonological voicing contrast perception (Raphael 1972, Gimson 1974, Hogan and Rozsypal 1980), especially word-finally (Docherty 1992: 120), while Polish shows little variation in that respect, may become a source of potential timing problems that Polish learners of English face.
1.2.3 The effect of syllable structure
The structure of syllable, the smallest prosodic unit, comprising an optional onset and an obligatory rhyme (Fudge 1969, Blevins 1995), can influence the duration of its segmental constituents. In open syllables, ones with no coda, vowels are reported to be longer (Maddieson 1985, Nowak 2006). This tendency has been observed in many languages, but it is not obvious in Polish.
Jassem (1962) found no vowel lengthening in open syllables, unlike Klessa and Śledziński (2007), who reported considerable lengthening, magnified in prepausal positions.
Syllable nucleus duration is strongly modified by the type of coda, as indicated in the previous section, but also by the onset. The main cue to syllable onset voicing, VOT, is enhanced by length modification of the vowel.
The reduced vowel portion is shorter than VOT (Allen and Miller 1999), which indicates that the process does not only involve vowel devoicing without changing length proportions. A similar compensatory process adjusts the temporal relations between the nucleus and coda (e.g. Jassem 1971, Waniek-Klimczak 2005). According to Cunningham (2008: 3), “[i]n English, for example, the durations of vowels and of the stops which follow them have an inverse durational relationship.” If this statement, besides for the fortis/lenis contrast, also holds true for intrinsic vowel length effects, it broadens the scope of Lehiste’s (1977) claim that longer duration of fortis consonants and their shortening effect on the preceding vowel reflects a tendency for syllable rhyme isochrony.
Vowel duration differences before fortis and lenis codas (cf. section 1.2.2) are most significant in stressed syllables and nonexistent or negligible in unstressed ones (de Jong 1991). With respect to speaking style, Crystal and
House (1988c) found more evident length differences depending on coda voicing in clear speech in comparison to normal speech.
The structure of higher level units influences the duration of its constituents in a more complex way. The lengthening or shortening processes seldom affect single segments, and their influence may exceed even higher-level unit boundaries. This problem will be discussed in section 1.3.