So, hear me out. I am going nuts over this. I hope I can explain myself appropriately: Whenever I hear a female French native speaker, I notice some sort of nasalization of /i/ after certain phonemes such as /d/ as in the word "dire" or even present in the combination /ui/ when saying "aujourd'hui". This may also be true for men--and I may be missing more examples of its occurrence--but I'm positive something is going on there and I can't quite put my finger on it. I've looked up info on French phonology (including some posts on this site) and haven't had any luck. This became even more evident after coming across a Mexican tiktoker who tries to teach people about languages and she herself speaks French but overdoes that "nasalization" and thus, instead of accurately pronouncing it--as her female native counterparts would--she just sounds as if she's got a cold and all sounds nasal AF, so maybe I'm not that wrong, it's a thing. Hope someone can shed some light on it and prove I'm not delusional. Merci d'avance !
So, after some time spent delving into it and analyzing different samples of spoken French, I came up with a hypothesis that still needs to be tested--and I hope you can give me a hand with that.
I'm quite positive that the phoneme I'm talking about occurs in Swedish as well (its incidence may as well be higher). Here's what I found on such phoneme (for Swedish, that is):
One of the varieties of /iː/ is made with a constriction that is more forward than is usual. Peter Ladefoged and Ian Maddieson describe this vowel as being pronounced "by slightly lowering the body of the tongue while simultaneously raising the blade of the tongue (...) Acoustically this pronunciation is characterized by having a very high F3, and an F2 which is lower than that in /eː/." They suggest that this may be the usual Stockholm pronunciation of /iː/. (Ladefoged & Maddieson, 1996, p. 292)
And this as well:
Patterns of diphthongs of long vowels occur in three major dialect groups. In Central Standard Swedish, the high vowels /iː/, /yː/, /ʉː/ and /uː/ are realized as narrow closing diphthongs with fully close ending points: [ɪ̝i ʏ̝y ɵ̝˖ʉ̟ ʊ̝u] (McAllister, Lubker & Carlson, 1974; cited in Ladefoged & Maddieson, 1996, p. 295). According to Engstrand (1999, p. 141), the second element is so close as to become a palatal or bilabial fricative: [ɪ̝ʝ ʏ̝ʝʷ ɵ̝˖βʲ ʊ̝β].
Here's a link to a video of a female French native speaker: https://www.youtube.com/watch?v=5-_EZDKFv7U
I think she realizes that same phoneme when uttering certain words such as "aujourd'hui" (0:37 in the video)--which could be some sort of a diphthong pattern where /i:/ is somehow affected by the preceding phoneme /ɥ/--and then again at 1:02 when she says "traduire" (same mechanics involved as the example above).
I definitely hear more constriction in the realization of that /i/. It may only occur in the phoentic diphthong pattern /ɥi/ that is phonemically realized as /ɥɪ̝ʝ/ (if that even exists, of course); I don't have any other examples at the moment, but I'll share them with you in case I come across any in the future.