[ New NORM v. 1.1 | original version (v. 0.9) ] The Vowel Normalization and Plotting Suite


About NORM

NORM is a web-based software package designed to aid sociophoneticians, phoneticians, and sociolinguists in normalizing and plotting their vowel formant data. (See our page About Normalization if you're not sure what "normalization" is or why you should do it.) Our motivation for NORM stems from the fact that there are a large and growing number of different techniques available for normalizing formant data. Some are better than others, though all have disadvantages as well as advantages. While there have been a few good comparisons of vowel normalization techniques (e.g., Disner 1980 and Adank et al. 2004), it's not always clear which method is best to use or even the exact formulae one should use for a given method.

NORM allows you run a number of the methods and quickly compare the results, determining which may be best and most suited for your dataset. However, please be sure you understand the specifics of each method - not all will be equally appropriate for all datasets. In addition to developing the NORM software, we have also compiled information on each method - on the Methods page - which discuss the specifics (and our implementation) of each method and their advantages and disadvantages as we've discovered them.

How NORM Works

NORM, this software, works by processing a spreadsheet of your raw vowel measurements through your choice from a variety of the published normalization techniques.

The processing is conducted by using a combination of PHP, the open-source web-oriented scripting language (see, and R, the open-source statistics and graphing language (see Most of the actual processing of the vowel data is done through an R script. PHP is used primarily to build the webpages - to retrieve your data and to present your results back to you. In the spirit of the open-source movement, the main processing script is available, under the GNU General Public License, here:

R script: xls icon vowel_normalize.R [ 50 kb; Last Mod: 11/18/2015 ]

(This is the actual script that processes your data when you upload them.) You are welcome to modify the script or re-use it as you like. We ask that you let us know if you find errors and that you share with us any improvements you make to the script. Of course, we recommend that you confirm the output of the script before publishing your results. We'll periodically make changes to the script, so check back for updates, new normalization methods, and possible bug fixes.

About NORM's Scaling

A number of the normalization methods implemented in NORM (namely, the Lobanov, Nearey, and Watt & Fabricius methods) result in vowel data that are not in Hertz or Bark values. In order to "translate" the resultant values into Hertz-like values, we provide the Scale normalized results to Hz? option on the NORM Form. The formulas for the scaling algorithm are:

F'1 = 250 + 500 (FN1 - FN1MIN) / (FN1MAX - FN1MIN)
F'2 = 850 + 1400 (FN2 - FN2MIN) / (FN2MAX - FN2MIN)

Where FNi is a normalized value for formant i and FNiMIN and FNiMAX are the minimum and maximum normalized formant values for formant i.

IMPORTANT: It is imperative that the MIN and MAX values for the formants are determined speaker extrinsically, that is from ALL speakers' normalized formant values together. If this is not done, the scaling will, in effect, undo much of the work of the normalization procedure! In fact, it will do something equivalent to Gerstman's (1968) normalization technique - simply scaling each vowel to the relative position it occupies in the speaker's vowel space - a technique which has been out-performed and out-dated since Lobanov (1971) and Nearey (1977) (n.b. we don't even provide a NORM option for it). In short, DO NOT scale your normalized data, UNLESS you have submitted all of the speakers you are comparing to NORM at the same time. Otherwise, it is recommended that you scale your results manually, using the above formulas, when you have finished normalizing all of your data.

How to Cite NORM

To cite the vowels R package:

You can cite NORM by one of the following:

  • Thomas, Erik R. and Tyler Kendall. 2007. NORM: The vowel normalization and plotting suite. [ Online Resource: ]

  • Thomas, Erik R., Tyler Kendall, Malcah Yeager-Dror, and William Kretzschmar. 2007. Two things sociolinguists should know: Software packages for vowel normalization, and accessing linguistic atlas data. [ Workshop at New Ways of Analyzing Variation (NWAV) 36, University of Pennsylvania, PA ]

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Last Mod: 11/18/2015
© Erik R. Thomas & Tyler Kendall 2007-2015
erthomas [at] & tsk [at]