1951 Revision
The 1951 chart was identical to that of 1932. There were a few changes in the descriptions. Apart from dropping the couple words noted above, these were,
Substitutions:
- ɼ fricative trill.
- ɩ, ʏ, ɷ (lowered varieties of i, y, u).
Additions:
- ƞ Japanese syllabic nasal.
- ɧ (combination of x and ʃ).
- r-coloured vowels : eɹ, aɹ, ɔɹ, etc., or eʴ, aʴ, ɔʴ, etc., or ᶒ, ᶏ, ᶗ, etc.; r-coloured ə : əɹ or əʴ or ɹ or ᶕ or ɚ.
In addition, the diacritics ⟨◌̘⟩ and ⟨◌̙⟩ had been used for advanced and retracted vowels since the 1900s, but not included in IPA charts. They were now replaced by
- ˖ tongue advanced (u˖ or u̟ = an advanced u, t̟ = t̪). ˗ or - tongue retracted (i˗ or i̠ = ɨ˖, t̠ = alveolar t).
Read more about this topic: History Of The International Phonetic Alphabet