Typical relative frequencies of the first four formants measured in dF units
(average spacing between formants, or formant dispersion) above or below
schwa based on estimated VTL in American English, from Hillenbrand (1995),
who measured F1-F4 in ~1.5K recordings (139 speakers, 12 vowels from each).
Audio and formant measurements are freely available online:
https://homepages.wmich.edu/~hillenbr/voweldata.html. The dataset below is
the result of modeling Hillenbrand's data with brms: mvbind(F1rel, F2rel) ~
vowel + (vowel|speaker). It shows the most credible location of each vowel
centroid in the F1Rel-F2Rel space.
Usage
hillenbrand
Arguments
Format
An object of class data.frame with 12 rows and 5 columns.
Details
A dataframe of 12 observations and 5 columns: "vowel" = vowel (American
English), "F1Rel" to "F4Rel" = formant frequencies in dF relative to their
neutral, equidistant positions in a perfectly cylindrical vocal tract. See
schwa - this is what schwa() returns as $ff_relative_dF
References
Hillenbrand, J., Getty, L. A., Clark, M. J., & Wheeler, K.
(1995). Acoustic characteristics of American English vowels. The Journal of
the Acoustical society of America, 97(5), 3099-3111.