Speech rhythm

It has been suggested that NigE has a syllable-timed rather than stress-timed rhythm. The languages of the world have traditionally been divided into stress-timed and syllable-timed. Speech rhythm was understood to be a periodic recurrence of events such as syllables in the case of the so-called “syllable-timed” languages and feet in the case of the so-called “stress-timed” languages. In syllable-timed languages such as Yoruba, syllables are assumed to be equal in length. Stress-timed languages such as English, in contrast, are supposed to have regular recurring stress beats. Since the number of syllables between two stress beats varies, their length is adjusted to fit into the stress interval – syllable length, hence is very variable in stress-timed languages. No acoustic basis for either isochrony of feet in stress-timed languages or equal length of syllables in syllable-timed languages has ever been found. Eka (1985) proposes that NigE speech rhythm is ‘inelastic’ insofar as the durational adjustment of unstressed syllables does not occur.

Recent approaches of measuring speech rhythm are based on the assumption that speech rhythm is a multidimensional concept which includes various phonological properties of languages. Accordingly, languages are not classified into distinct rhythmic classes anymore but are assumed to be located along a continuum. Dauer (1983: 55), for example, suggested that “rhythmic differences […] between languages […] are more a result of phonological, phonetic, lexical, and syntactic facts about that language than any attempt on the part of the speaker to equalize interstress or intersyllable intervals”. In Dauer’s view, speech rhythm reflects variety of syllable structures, phonological vowel length distinctions, absence/presence of vowel reduction and lexical stress. Whereas languages formerly classified as stress-timed such as English show a variety of different syllable structures, languages formerly classified as syllable-timed have a majority of CV syllables. Equally, differences in rhythm between languages reflect whether a language has vowel reduction or not; those classified as stress-timed usually do. In addition, languages with a tendency to syllable-timing either do not have lexical stress or accent is realized by variations in pitch contour. Conversely, languages with a tendency to stress-timing realize word level stress by a combination of length, pitch, loudness and quality changes, which result in clearly discernible beats.

This approach is reflected in recent measurements of the acoustic correlates of speech rhythm, which are based on phonetic cues such as successive vowel and syllable durations. Experimental studies employing these acoustic measurements of the phonetic correlates of speech rhythm confirmed the impression of a tendency to “syllable-timing” in NigE. Vowel reduction does not occur in NigE, which results in a more equal duration of syllables (Udofot 2003; Gut 2003). Subsequent syllables in NigE are more similar in length than in British English but less similar than in West African languages. Compared to other languages classified with Ramus, Nespor and Mehler’s (1999) measurement of rhythm, NigE groups with Spanish, Catalan, Italian and French, all of which are presumed to be syllabletimed, in terms of the vowel percentage, but shows a higher standard deviation of consonantal intervals than those languages.

In general, the overall speech tempo in NigE is slower than in British English, and NigE speakers divide their utterances into more and shorter intonation phrases than British English speakers (Udofot 2003; Gut 2003).