Question: Is there a matrix or table showing how audibly similar the different sounds from the IPA are? I'm looking for a scalar value that somehow measures the oral distance between two phonemes.

Example: The following sounds are "close"

ɑ (father) ɛ (dress)

while the following sounds are "distant"

b (buy) n (can)

Nomenclature: I'm putting quotes around "close" and "distant" since I don't know the proper term to quantify the oral similarity between two phonemes. Please edit or correct any mistakes I've made.

Motivation: I'm actually looking for this similarity matrix with a reduced set of the IPA, namely those sounds coming from the ARPABET.

  • You probably want a metric based on a featural characterisation of the sounds.
    – Colin Fine
    Sep 23, 2015 at 14:56
  • 2
    "Similar" is absolutely subjective, in fact any two objects in the Universe have somethings in common and are similar in something, e.g. b and n are also 'close' because both are voiced and both are consonants. You need to define what you mean by 'similar'.
    – Yellow Sky
    Sep 23, 2015 at 14:56
  • @YellowSky I wish I could, but as I noted in my answer I lack the terminology. In a very ambiguous way, "similar" would be the average ranking provided by thousands of listeners. There will be a lot of variance, but there should be some features that are universal (I think?). Perhaps something mentioned by Colin, the "featural characterisation" would suffice.
    – Hooked
    Sep 23, 2015 at 15:05
  • 2
    For consonants, the similarity is the hamming distance (# of bits different) of the feature matrix. For vowels, it's the distance in the vowel trapezium (plus some features like rounding).
    – Mitch
    Sep 23, 2015 at 15:10
  • 3
    There are no speakers of IPA so the question is meaningless. One could ask specifically about confusability in English; or Spanish. There are multiple IPA transcriptions of English, so this will not tell you much about IPA.
    – user6726
    Sep 24, 2015 at 16:11

1 Answer 1


As described (empirical similarity from many listeners), I think you want confusability, e.g. a ‘confusion matrix'. Here’s an example, from Munson et al. (2003): https://doi.org/10.1121/1.1536630

Full reference:
Munson, B., Donaldson, G. S., Allen, S. L., Collison, E. A., & Nelson, D. A. (2003). Patterns of phoneme perception errors by listeners with cochlear implants as a function of overall speech perception ability. The Journal of the Acoustical Society of America, 113(2), 925-935.


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