Front rounded vowels are somewhat uncommon. If we focus on the high front rounded vowel /y/ and consider cases where it was lost, it seems most likely to shift to /i/ by losing its rounding or to shift to /u/ by changing its backness than it is to shift to any other vowel.
I find /y/ more acoustically similar to /u/ than to /i/. However, I can think of one example of the sound change /y/ > /i/ off the top of my head, namely Greek, but no examples of the sound change /y/ > /u/.
My question is twofold:
- Are there known instances of the sound change /y/ > /u/?
- Is the sound change /y/ > /i/ actually more common than /y/ > /u/?
The immediate motivation for this question is personal experience. I'm trying to square my intuition that
/y/ > /i/ is probably a way more common change than /y/ > /u/ with the observation that
/y/ sounds much closer to /u/ in real life than it does to /i/.
I have studied French and Mandarin to some degree, both of which have the /y/ phoneme. For me, at least, the /y/ sound in both these languages sounds much, much more like /u/ than it does like /i/.
I speak California English natively, so I guess my normal /u/ sound is fairly front.