The previous sections of this chapter were devoted to prominence and accentual lengthening. In many languages, the effect of accentual lengthening is further enhanced by the reduction of unstressed speech units. Reduction may be observed both in the spectral qualities of the signal and its shorter duration.
2.7.1 The locus of reduction
Qualitative and quantitative reduction of speech units is a universal phenomenon connected with informal speech and lack of prominence. In English phonetics textbooks (e.g. Clark and Yallop 1990, Cruttenden 2001), vowel reduction is presented as an important feature of the language.
Although less research has been done on consonant reduction, there is evidence that, to a degree depending on their type, consonants are also reduced in unstressed contexts (eg. Byrd 1994, Keating et al. 1994, Schmidt and Flege 1995, Van Son and Van Pols 1996).
Consonantal reduction may consist only in shorter articulation of a segment, but it may also comprise phonological processes generally described as lenitions, such as spirantisation, vocalisation, debuccalisation and the ultimate lenition — elision. Consonant elision (apart from examples presented in section 1.2.2) is commonplace in weak forms of English function
words, affecting those beginning with /w/ and /h/, i.e. “will/would,” all forms of auxiliary verb “have” and many personal and possessive pronouns. This kind of reduction normally occurs in postconsonantal positions.
Quantitative consonant reduction is a result of less articulatory space taken by consecutive gestures and more gesture overlap in prosodically weak positions (cf. Lindblom 1990, Cole et al. 2007). The scale of duration differences, apart from position and prominence level, depends on the type of consonant. Jassem et al. (1984 — cf. Table 1.3) distinguished separate phone classes with respect to prominence and position-related features, i.e.
“aspirated/unaspirated,” “accented/unaccented,” “initial/non-initial/final,” and
“syllabic/non-syllabic.”
The complex relations between prominence level and consonant duration, including such phenomena as Voice Onset Time or the articulation of consonant clusters, are especially difficult to grasp if native and non-native speech samples are to be compared. It is probably the multitude of factors governing the timing of consonants and the lesser efficiency of conscious control of consonant length in foreign language learners that makes textbook authors concentrate more on vowel duration and syllable duration. For the same reasons, the focus of this study, apart from higher prosodic level units, is upon vowel duration and syllable duration, with only some indirect references to consonant length, where differences between native English speakers and Polish learners appear evident.
2.7.2 Reasons for vowel reduction
The motivation for vowel reduction is explained in terms of modulating attention to consecutive parts of the speech signal. Information-light weak syllables (cf. Harris 2005) are reduced in order to enhance the prominence of strong positions (de Jong 2000). Harris (2005) treats reduction as planned behaviour. Alternatively, it is regarded as a failure to achieve hypothetical articulatory targets in shorter time (Flemming 1995, Kirchner 1998). This idea of articulatory undershoot was proposed by Lindblom (1963), who also suggested “hyperarticulation” and “hypoarticulation” (Lindblom 1990) as alternate stages of speech production, invoking the hearer’s “hyperperception”
and “hypoperception” (cf. Cole et al. 1978). One argument for regarding vowel reduction as planned behaviour is the fact that although it is a universal tendency (e.g. Van Son and Van Pols 1996), it is not used in the same way in all languages. It may be realised by qualitative centrifugal (Russian) and centripetal (English) reduction or the magnitude of reduction may be very small (Polish).
2.7 Lack of prominence as a duration determinant 45
2.7.3 Vowel reduction in English and Polish
Vowel reduction mainly consists in shortening the segment and centralising it.
The strong tendency to reduce unstressed vowels in English very often results in complete vowel elision. Because it occurs in information light syllables, the vowel schwa, the most frequent result of the process, may be regarded as having no articulatory target (Keating 1988). Even if the reduced vowel disappears altogether, it usually prevents assimilation processes between onset and coda consonants, which take place in underlying consonant clusters.
Catford (1988) describes the two types of consonant interaction as open (onset-coda) and closed (cluster) transitions.
As mentioned above, the scale of reduction in English and Polish differs considerably. According to Lindblom’s (1990) undershoot theory, languages which show little positive correlation between stress and vowel duration do not reduce their unstressed vowels significantly. Polish may be regarded as an example of that language type (e.g. Crosswhite 2001), if we consider studies of stressed and unstressed vowel duration. Jassem (1959) claims that Polish stressed vowels in citation forms are 17% longer. He also concludes that there is little correlation between stress and vowel reduction in Polish. Nowak (2006) finds 22% difference in a more extensive study comprising various speech styles, while Rojczyk (2010b) observes a 30% difference in reiterant speech.
Dogil (1999) claims that vowel duration is not a word stress correlate in Polish, but even Rojczyk’s results for reiterant speech do not approach the ratio of 2:1 for English monophthongs and 1.5:1 for diphthongs reported by Crystal and House (1988b).
In conclusion, considering the research presented above, it must be acknowledged that the durational “flexibility” of Polish vowels is rather low in comparison with such languages as English. According to Nowak (2006: 378), the lack of vowel reduction in Polish may be “constrained by the admittedly limited durational variation of Polish vowels (vis-à-vis many other languages).”
This statement, supported by Dogil’s (1995, 1999) observations of the effects of word stress on (among other things) vowel duration, is a basic assumption for the formulation of the research hypotheses investigated in the present study.
C
HAPTER3
S PEECH TIMING AND THE NOTION OF RHYTHM
3.1 Introduction
Similar to many basic notions related to language structure, the existence of rhythm in speech is a controversial issue. If we assume that the impression of rhythm depends on the distribution of prominence to selected speech units in an utterance and the durational relations between alternating prominent and non-prominent elements, then we must acknowledge the existence of
“rhythmisation” mechanisms which assign prominence to particular speech units according to certain “global” patterns. Indeed, as signalled in the introduction to Chapter 2, it is claimed that a universal human preference for rhythm in perception and motor behaviour is an important factor motivating regular patterns of alternating stronger and weaker elements. The importance of this preference is reflected, for instance, in metrical stress theory (Liberman 1975, Liberman and Prince 1977, Hayes 1995), where stress is understood as a manifestation of the rhythmic structure of language.
Such an approach is not necessarily in conflict with the statement that the distribution of prominent elements primarily depends on their informational value. The analysis of syntactic structures characteristic of particular languages yields evidence that the arrangement of important lexical items is highly regular and predictable (cf. the notions of the Nuclear Stress Rule or “normal stress” discussed in section 2.4).
The description of rhythm requires distinguishing a basic organisation unit, serving the purpose of durational regularisation of speech, naturally connected with the general utterance structure described in Chapter 1. The selection of such a basic rhythm unit depends on the type of language, as it has been generally accepted that rhythmic organisation of speech forms a basis for a classification of languages.