On the quantal nature of speech timing

This is a review of regularities which we have observed in the analysis of text reading, mostly Swedish, directed to the timing of vowels and consonants, syllables, inter-stress intervals and pauses. We have found tendencies of quantal aspects of temporal structure, superimposed on more gradual variations, which add quasi-rhythmical elements to speech. A local average of inter-stress intervals of the order of 0.5 sec. appears to function as a reference quantum for the planning of pause durations. A recent study, confirming our previous findings of multiple peaks with about 0.5 sec. spacing in histograms of pause durations, provides support for this model. It is well established that pause durations tend to increase with increasing syntactic level of boundaries. However, these variations tend to be quantally scaled, even within a specific boundary category, e.g. between sentences or between paragraphs. Relatively short pauses, as between phrases or clauses, show durations in complementary relation to terminal lengthening. There are indications of approximately 1, 1/2, 1/4 and 1/8 ratios of the average durations of inter-stress intervals, stressed syllables, unstressed syllables and phoneme segments, which add to the observed regularities. The timing of syllables and phonetic segments, with due regard to relative distinctiveness and reading speed, is discussed, and also tempo variations within a sentence.