text presented and synchronized with multimedia to provide not only the speech, but also sound effects and sometimes speaker identification
The term they're looking for here is ""non-speech information, including meaningful sound effects and identification of speakers"" (the latter a slightly different sense than ""speaker identification,"" which seems to require explicitly naming the speaker).
Note: In some countries, the term ""subtitle"" is used to refer to dialogue only and ""captions"" is used as the term for dialogue plus sounds and speaker identification. In other countries, subtitle (or its translation) is used to refer to both.
Those other countries are wrong. Captioning is captioning and subtitling is subtitling. WCAG 2 should not muddy the waters by giving any credibility to errors of nomenclature in other English dialects.
We changed "sound effects and sometimes speaker identification" to "non-speech information conveyed through sound, including meaningful sound effects and identification of speakers"
We kept the note since, although one might consider them wrong, they still do this in both common and official language. The note is therefore accurate and important for people to understand".