I know that the diacritic ̈ is for centralization and ̞ for lowered. So when [e] is centralized, it becomes [ɘ] and when lowered it becomes [ə]. See the diagram:
If someone gives me the transcription [ë̞] (centralized and lowered [e]), how should I know which sound it is? I saw this in a textbook. The book said "anyone who is well-versed in IPA will know what sound [ë̞] is" I read the whole chapter but they didn't tell what sound it was.
When someone gives [ë̞], how do linguists pronounce it? Is it [ə]? I know that mixing diacritics can get you another sound for which IPA already has another symbol.
- is [ï] another symbol for [ɨ]? and
- [ɛ̈] for [ɜ]?