A prosodic difference

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In "Political sound and silence II" I noted a large difference in measures of speaking rate across the Weekly Addresses of the past three American presidents:

 N Speech
% Speech Words WPM
(excl. silence)
Bush 2008  48  8262  1976  10237 213  0.807  24483  166.9  206.9
Obama 2010  50  9840  2884  12724 254  0.773  38253  180.4  233.3
Trump 2017  14  2417  480  2898 207  0.834  7131  147.6  177.0

And in "Trends in presidential speaking rate", I showed that

… across the first few months of Weekly Addresses, President Trump is tending to talk somewhat faster as well as using a higher range of pitches.

I wondered about the causes:

This might simply reflect a choice to use more words per pause group — pre-pausal lengthening would thus be amortized over a large number of words, and similarly for phrase-final lowering. Or perhaps the distribution of words per pause group is stable, with the speaking rate and pitch range increasing for phrases of a given length. Or both. I’ll test these hypothesis another morning.

As a start —  for this morning's Breakfast Experiment™, I calculated mean syllable duration as a function of the number of syllables in the pause group (defined simply as a speech segment without internal silent pauses), across 13 comparable Weekly Addresses for Donald Trump (January to May 2017) and Barack Obama (January to May 2009):

[For why this general sort of relationship is expected, see "The shape of a LibriVox phrase", 3/5/2017.]

There are two differences here.

  1. Trump is speaking more slowly in the body of longer phrases than Obama is. His average syllable duration in phrases between 7 and 15 syllables long is 221 msec., compared to Obama's 176 msec., 20% less.
  2. Obama uses relatively little pre-pausal lengthening, so that his plot of mean syllable duration by the number of syllables in the phrase is relatively flat. This gives his performance a somewhat clipped character, which I've mentioned before, e.g. in "Tunes, political and geographical".

It's logical to wonder whether a difference in the type of words used might be involved, but in this case I doubt it. The mean number of syllables per word in (this sample of) Obama's Weekly Addresses was 1.59, while in Trump's Weekly Addresses it was 1.64.

Anyhow, I'm now ready to look into the nature of Trump's overall rate speed-up across his first few months of Weekly Addresses.


1 Comment

  1. Clive Moss said,

    June 2, 2017 @ 4:13 pm

    Some indication of variance (Standard Deviations or whatever) would be nice.

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