By CATHERINE CLABBY, Staff Writer Rural African-Americans increasingly speak the urban-sounding dialect called ebonics, even when their grandparents sound like their white neighbors.That helps explain how the distinctive tongue is spreading nationwide, two N.C. State University linguists say.NCSU researchers Walt Wolfram and Erik Thomas analyzed interviews with working-class blacks and whites born in coastal Hyde County, where regional speech long has reigned. Two generations back, members of both groups shared the distinctive Pamlico Sound dialect that calls a "high tide" a "hoi toide," the linguists found. But as younger black men and women are exposed by travel, television and pop...