On Wikipedia, there is a list of phonetic vowels and their average 1st and 2nd formants.


Throughout the web are many more of such charts with varying frequencies.

So obviously some amount of tolerance exists, but I don't know what it is, nor do I think I could really come to a strong conclusion using the data I have.

What is the tolerance on formants?

P.S. if you know of a better formant chart than the one on Wikipedia, please share.

  • 2
    I think this question is more suited to SO Linguistics, in that it doesn't seem to have much to do with English usage in particular. – FumbleFingers Jun 9 '17 at 17:21
  • These are the most common English phonemes, based off English speaking habits. The answer to this question may very well not apply to other languages, especially because many other languages use different timing styles that might emphasize the need for pitch perfection. – Seph Reed Jun 9 '17 at 17:44
  • This depends very much on what dialect of English (or, in general, what language) you are speaking. Generally, the tolerance is around how much you can change the formants without running into another vowel in the same language/dialect. – Peter Shor Jun 9 '17 at 19:25

enter image description here

            Ratio Tolerance
 Phoneme    F1       F2
 /a/        .24      .31
 /e/        .15      .12
 /ɛ/        .15      .11
 /i/        .14      .19
 /o/        .23      .55
 /ɔ/        .16      .51
 /u/        .17      .57

I just found this data, and I think it's enough to extrapolate that the tolerance varies greatly from vowel to vowel, but if the average ratios are put onto the mouth shape chart...

enter image description here

  i .14 .19                   u .17 .57

        e .15 .12             o .23 .55

          ɛ .15 .11           ɔ .15 .51  

              a .24 .31       

it appears that tolerance is partially related to mouth shape, with the second formant having greater variance the more guttural the vowel. Also, it appears that if the /a/ in the tolerance chart had actually been /ä/, the data would make more sense, and hearing the difference between the two it wouldn't be a surprising mistake at all.

So, final answer is:

  • F1 varies on average between 15% and 20% tolerance based off front to back
  • F2 varies on average between 15% and 55% tolerance based off front to back

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