In 1995, Gerald Fabris, the curator of the Edison National Historic Site, discovered a wax cylinder among 43 other recordings that were being catalogued, preserved, and re-recorded. Fabris has concluded that
the voice on the cylinder is Edison’s. This was remarkable because no recordings of Edison’s voice that predated 1906 were thought to exist. Because Edison disliked his voice, he usually destroyed test recordings by scraping the wax off the cylinder.
Fabris sent me a conference paper in which he presented his case, which seemed convincing. Not everyone agrees that the voice is Edison’s, however. That’s all I can tell you about the controversy, until I get some time to research more fully.