Why is “c'est un” pronounced /sɛ tœ̃ /, but “c'est une” /sɛ tʃyn/?

Question

I'm learning French, and from what I've heard, it seems that:* _c'est un_ is pronounced /sɛ tœ̃ /, but* _c'est une_ is pronounced /sɛ tʃyn/,with a /tʃ/ as in *cheese*. I heard this difference both in Duolingo and Forvo ([un](http://sv.forvo.com/word/c%27est_un/), [une](http://sv.forvo.com/word/c%27est_une/)).Is this the case in standard Parisian dialect? Why does it happen, and when?

Answer 1

In my experience with French speakers from the Paris area, as well as francophone Africa, I've heard only /sɛ tyn/ for 'c'est une.'

That's not to negate the existence of /sɛ tʃyn/, or rather, /sɛ tsyn/. Maybe this pronunciation is a feature of how people speak French in northeastern France, or I don't know, Quebec?

On this latter note, here's an interesting summary on Wikipedia (in the section "Consonants" about how /ty/ sometimes turns into /tsy/ in Quebecois: en.m.wikipedia.org/wiki/Quebec_French_phonology