A Statistical approach to the problem of isochrony in spoken British english

Date
1978-01-01
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Abstract
In another paper (Hill, Witten and Jassem, 1978) we reported a preliminary study of rhythm in Spoken British English which, among other things, showed that there was a tendency for segments to be of shorter duration, on average, in rhythmic units containing more segments than in rhythmic units containing fewer segments. Such an effect would tend to make rhythmic units more nearly equal in duration than would be expected from a straight segment count and is referred to as "a tendency towards isochrony". Much recent research in acoustic phonetics, especially in the US< has tended to discount the importance of such an effect. In view of our finding that it forms the third most important factor in accounting for segment duration variation, we wished to go further and to try to produce some reasonable measure of the isochrony effect, partly as a useful descriptor for the rhythmic character of utterances and partly to provide a more objective basis for comparing different theories of rhythm that incorporated notions of such a tendency. In this paper we go some way towards a measure of isochrony which expresses the percentage of the mean duration of rhythmic units that may be regarded as fixed, regardless of rhythmic unit size (segment count). A figure of 0% would suggest no tendency towards isochrony whilst a figure of 100% would suggest strictly isochronous speech. We applied this measure to the body of speech data resulting from the analysis of exercises recorded for M.A.K. Halliday's book written for students of spoken British English (Halliday, 1970), on the basis of two different frameworks for rhythmic description, one commonly associated with the names of Jones, Abercrombie, Halliday and Ladefoged and based on what Halliday calls "feet", the due to Jassem, based on "rhythm units". The differences between the two frameworks were marginal as far as goodness of fit between data and theory was concerned, the latter theory leading to somewhat less scatter of the data and actually excluding just those portions of speech exhibiting the least tendency towards isochrony. The measure did, however, show very clearly another effect that was intuitively obvious in the data, namely that marked rhythmic units showed a far greater tendency towards isochrony than unmarked units. The work is continuing. (Work supported by the National Research Council of Canada).
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Computer Science
Citation
Hill, D.R., Jassem, W. & Witten, I. H. (1978) "A statistical approach to the problem of isochrony in spoken British English." Research Report 78/27/6 January 1978 (Published as: Current Issues in Linguistic Theory 9 (eds. H. & P. Hollien), 285-294, Amsterdam: John Benjamins B.V. 1979).