It includes German, Italian, Polish, Slovak, Hungarian, French and other nationalities that emigrated to the region. They require much more of the tongue being put forward under the teeth. Regional speech has a lot to do with the way facial muscles are used, according to Eatman. In Texas and the Midwest, the tendency is to spread the muscles very wide. They're not necessarily all that nice, but they have been trained, for whatever cultural reasons, to smile.
People pick up what they are around.
Anybody who ever left the area, even for a short time, would probably tend to assimilate what they were around. Every variant on idealized American speech does something to the vowel sounds, according to Eatman. Western Pennsylvanians tend to pinch their vowels. The speaker comes right up to the point of fusion, and then there is a grab that shortens the word. But to anybody who is not used to that it is kind of a shock.