Gretchen McCulloch of All Things Linguistic posted without comment a graphic by Suzy Styles, of the Nanyang Technological University, Singapore, of The Commonest Speech Sounds: Prevalence Rates for Phonemes of the World. Styles, in turn also doesn’t comment on it, beyond stating that she compared the speech sounds of 1672 languages on a certain online database. What follows are my own thoughts about the graphic, primarily as an ESL teacher and not as a linguist.
(There’s a large space under this graphic – keep scrolling.)
(Don’t worry about the technicalities of the IPA charts. I will make this as non-technical as possible.)
Human mouths, ears and brains are approximately the same worldwide, so the sounds of the world’s languages are approximately the same, and almost all of them seek to make the greatest possible use of the shape of the mouth.
For the consonants, the most used cluster around the two lips (English /m/, /p/ and /b/), the front of the tongue at the front of the mouth (English /n/, /t/, /d/, /s/ and /l/) and the back of the tongue at the back of the mouth (English /ŋ/, /k/ and /g/). Indeed, all of those sounds occur in over half of the world’s languages, and, generally speaking*, ESL students have no or little difficulty with them. For the vowels, the three overwhelmingly used are /i/ (high front), /a/ (low central) and /u/ (high back rounded). The next two (/e/ and /o/) fill in the space between those. (*The biggest provisos to that statement concern the unvoiced/voiced pairs, and /s/ and /l/.)
On both sections of the chart, note the large amount of white space: about half the possible sounds are used never or at most in 5 percent of languages, including some English sounds. Not surprisingly, these are sounds which, generally speaking, ESL students great or extreme difficulty with.
Coloured green, blue or purple on the consonant chart are English /m/, /n/, /ŋ/, /p/, /b/, /t/, /d/, /k/, /g/, /s/, /h/, /w/, /l/ and /j/ (yes, not Jess). In red, orange or yellow are /f/, /v/, /z/, /ʒ/, /ʃ/, /tʃ/, /dʒ/, and /r/. In beige is /ð/ and in white is /θ/. These last two are phenomenally rare in the world’s languages. Some varieties of English don’t use them – think of a Jamaican or Irish person saying this and that or thick and thin; it’s more likely to be dis and dat or tick and tin. ESL students or speakers might say zis and zat or sick and sin. (Compare the old joke: Radio operator of ship in distress: ‘Help, I’m sinking!’ Coast guard of unspecified European country: ‘Vat are you sinking about?’)
But /θ/ appears in two of the world’s most commonly spoken languages, English and Spanish. I don’t know how common it is in Spanish, but it English, it occurs in words such as thick and thin (above) as well as think, three etc, thing, through, thought, thousand, thank, throw, earth, month, mouth, growth, health, death, truth, north, south, length, strength, path, both. /ð/ occurs in a large number of function words – this and that (above) as well as the, they, them, their, theirs, these, those, there, then, than, though, other, another, either – as well as the common content words mother, father, brother, clothes and smooth. Because so many of these words are so frequently used, these two sounds are used in total more than some of the sounds in the red-orange-yellow group. (/ʒ/) is, in fact, the least-used English consonant, while /θ/ is the second least used and /ð/ is actually the sixth most used.
Coloured green, blue or purple on the vowel chart are /i/ (peat), /e/ (approx) pet), /a/ (part), /o/ ((approx) boat) and /u/ (boot). English uses approximately all of these: the mid-front vowel might be the slightly lower /ɛ/ (pet) and the mid-back vowel is probably the diphthong /oʊ/ or /əʊ/ (boat) . (I can’t make /əʊ/ but I can recognise it on ESL classroom recordings when an English RP speaker produces it.) Of the remaining pure vowels, /ɪ/ (pit), /ɔ/ (port), /ʊ/ (put) and /ə/ (apart) are red, orange or yellow, /æ/ (pat), /ɒ/ (pot) and /ʌ/ (putt) are beige and /ɜ/ (pert) is white. Styles’s chart does not include diphthongs. I wouldn’t be surprised if many/most of the English diphthongs were very rare worldwide. (In fact, the rarest vowel in English is /ʊə/ (pure), and the next two rarest are also diphthongs.) In my experience, ESL students have the most trouble with the rarer diphthongs, and also distinguishing between a chain of pure vowels around the mouth: /i/ and /ɪ/ (peat and pit), /ɪ/ and /ɛ/ (pit and pet), /ɛ/ and /æ/ (pet and pat) etc.