I'm not too sure about the pronunciation that is given here. I'm not French, but I learned French in school and I've been in France about three times. Ay-TYEN seems to me like somebody is trying to pronounce it correctly but does not succeed. (Sorry, if this sounds too harsh, I don't mean to offend anybody) It is hard to translate the E in Étienne into a phoneme that also exists in English, but I think "Eh-TYEN" would be closer, with the "Eh" pronounced like the first "e" in "gender" only a bit lighter.
Maybe the example I gave ('gender') wasn't the best one, but ay-TYEN is definitely wrong. It isn't the correct French spelling. I have never heard any French pronounce the name like that. And I know about the difference between é and è. I learned this language for four years. And though my own pronunciation might be very German, I have met a lot of French people. My teacher was French, too. So I know what the language is supposed to sound like. ;)