J.K. Rowling has gone on record a few times that she pronounces Voldemort with a silent T, so like vol-de-more.

Are there any hints in the book that basically the entire world is mispronouncing He-who-must-not-be-named's name? The original audio books read by Jim Dale, he pronounced it with a silent T, and then changed to saying the T after the first movie, which annoyed audio book fans.

Did J.K. Rowling tell Jim Dale how it should be pronounced with a silent T? Did the movies know the J.K. Rowling way of saying it, but went with the vastly more popular pronounced T?