My German professor (Dr. Tolk) would have pronounced it as shurn. The umlauted letter is spoken as a "ur". Back in the 50's, Chemical Engineering students were advised to take two years of German - I wound upped taking 4 years of it.
You are the closet yet

umlauts are a b1tch

There is a reason we call Munchen (with umlaut) by the name Munich


Again, most folks in Chicago just call it "Shown".. no umlaut.. and everyone and his brother know exactly what you are talking about...