Well, call me ignorant, but the first vowel is not there at all. It has been taken over by the following ‘r’ which has become syllabic in my dialect.
The first syllable, ‘sur-’, sounds just like the word ‘sir’, with which I still address my father and the few remaing men who are older than me.
The other two vowels I pronounce as shwa!
I have heard people pronouce the first syllable with a shwa, a short ‘u’ (as in ‘but’) or even a long ‘u’ (like in ‘mule’).
These sound a bit affected to my ear!
Sitran
Sitran