Santiago Barreda
Postdoctoral Researcher, Dept. of Physiology, University of Arizona

# Main Research Vignettes CV phonTools Statistics Links

## normalize [phonTools]

This function normalizes vowel data using several different methods in order to facilitate the comparison of vowels produced by different speakers. The figures show normalized vowels from the Peterson & Barney data, plotted using the vowelplot() function included on this package. The methods currently supported are Nearey intrinsic (NeareyI) and extrinsic (NeareyE) log-mean normalization, Lobanov and Watt and Fabricius (wandf). Normalizing vowel data can greatly reduce between-category overlap relative to raw formant-data. Code used to generate examples:

```
library (phonTools)

## normalize all Peterson & Barney (1952) vowels using each method.
data (pb52)

neareyE = normalize (pb52[,7:9], pb52\$speaker, pb52\$vowel, method = 'neareyE')
lobanov = normalize (pb52[,7:9], pb52\$speaker, pb52\$vowel, method = 'lobanov')
wandf = normalize (pb52[,7:9], pb52\$speaker, pb52\$vowel, method = 'wandf', corners =  c('i','A'))

## compare normalization methods using vowelplot().
par (mfrow = c(2,2), mar = c(4,4,3,1))

vowelplot (pb52[,7], pb52[,8], pb52\$vowel, alternateAxes = TRUE, pointType = 16,
main = 'Raw data', ellipses = TRUE, logaxes = 'xy')

vowelplot (neareyI[,1], neareyI[,2], neareyI\$vowel, alternateAxes = TRUE, pointType = 16,
main = 'neareyI', ellipses = TRUE)

vowelplot (lobanov[,1], lobanov[,2], lobanov\$vowel, alternateAxes = TRUE, pointType = 16,
main = 'lobanov', ellipses = TRUE)

vowelplot (wandf[,1], wandf[,2], wandf\$vowel, alternateAxes = TRUE, pointType = 16,
main = 'wandf', ellipses = TRUE)

```