Posted by Mark Liberman
https://languagelog.ldc.upenn.edu/nll/?p=70850&utm_source=rss&utm_medium=rss&utm_campaign=intonation-units-form-low-frequency-rhythms
https://languagelog.ldc.upenn.edu/nll/?p=70850
Several people have asked me about this paper — Maya Inbar, Eitan Grossman, and Eyelet Landau, "A universal of speech timing: Intonation units form low-frequency rhythms", PNAS 8/19/2025:
Intonation units (IUs) are a hypothesized universal building block of human speech [W. Chafe, Discourse, Consciousness and Time: The Flow and Displacement of Conscious Experience in Speaking and Writing (1994); N. P. Himmelmann et al., Phonology 35, 207–245 (2018)). Linguistic research suggests they are found across languages and that they fulfill important communicative functions such as the pacing of ideas in discourse and swift turn-taking. We study the rate of IUs in 48 languages from every continent and from 27 distinct language families. Using an analytic method to annotate natural speech recordings, we identify a low-frequency rate of IUs across the sample, with a peak at 0.6 Hz, and little variation between sexes or across the life span. We find that IU rate is only weakly related to speech rate quantified at the syllable level, and crucially, that cross-linguistic variation in IU rate does not stem from cross-linguistic variation in syllable rate.
Note that 0.6 Hz is 1/0.6 ≈ 1.7 seconds in the time domain.
Here's the chapter on "Intonation Units" in Wally Chafe's 1994 monograph (annotations are not mine…). N. P. Himmelmann's Google Scholar page offers the cited 2018 paper "On the universality of intonational phrases: A cross-linguistic interrater study", as well as other relevant references. Both citations make it clear that the issue is a complex one, with "phrases" in (various aspects of phonological and syntactic) message structure and "phrases" in (various aspects of phonetic) speech production being often quite different, especially in spontaneous speech. In addition, both "phonological" and "phonetic" phrasing have generally been regarded as hierarchical., so that I'm skeptical of the view that a single well-defined series of "intonation units" makes descriptive or cognitive sense. And in any case, it's obvious that individual speakers differ from one another, and also from their own performances in different settings — which doesn't mean that there are no typical or average values, but …
Maya Inbar has put relevant links to data and code on OSF, but I won't have time for a while to examine that material and evaluate their analyses. So for now I'll just list some relevant past posts, with brief associated comments.
"Speech rhythm in Visible Speech", 12/18/2013 — describes the section in Visible Speech (the 1947 book by Potter, Koop and Green) on "Rhythm in Speech", where the authors use a syllable-scale spectral analysis to look for phrase-scale rhythms.
"My poster for the 'Prosody Visualization Challenge'", 6/14/2018 — various ways to visualize relations among pitch, ampitude, and time,
"Towards automated babble metrics", 5/26/2019 — I replicate the 1947 method digitally, taking infant babble recordings as input, showing a spectral peak at 2.25 Hz (= 445 msec in the time domain), as well as other spectro-temporal structure.
"Cumulative syllable-scale power spectra", 6/11/2019 — I look at the syllable-scale power spectra of a car commercial and the associated rapid disclaimer:
"Political sound and silence", 2/8/2016 — compares two-dimensional density plots of speech-segment duration and (adjacent) silence-segment duration in the weekly radio addresses of Barack Obama and George W. Bush. The patterns are quite different, illustrating the point that things are not necessarily the same within the same genre and language:
"Poetic sound and silence", 2/12/2016 — offers similar plots for poetry readings by W.C. Williams, Wallace Stevens, Sylvia Plath, W.H. Auden, Gertrude Stein, Charles Bernstein, Carl Sandburg, Y.B. Yeats, John Ashbery, and Allen Ginsberg. Also adding Ronald Reagan, though he was not reading poetry.
"Some phonetic dimensions of speech style", 4/9/2016 — differences in speech-segment and silence-segment distributions for various sources of read and spontaneous speech.
"Political sound and silence II", 5/30/2017 — adds Donald Trump…
"Inter-syllable intervals", 9/13/2023 — What the distribution of inter-syllable time intervals looks like, in a range of examples at different speaking rates, along with the T-SNE analysis of a simple 4-parameter model…
"Read vs. spontaneous speech", 10/16/2023 — press briefings offer a useful local contrast between the reading of a prepared statement and the spontaneous reponses to questions about it.
Note that all of the above posts deal with phonetic aspects of phrase-level patterns — the spectrum of syllable-scale oscillations, or the distribution of speech segment and silence segment durations — not the spectrum of "intonation units", whatever they turn out to be…
https://languagelog.ldc.upenn.edu/nll/?p=70850&utm_source=rss&utm_medium=rss&utm_campaign=intonation-units-form-low-frequency-rhythms
https://languagelog.ldc.upenn.edu/nll/?p=70850
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