Voices can be deceiving.
When I hear someone on the radio or just know them as a voice on the phone and then I see what they look like, most of the time I'm wrong, or wrongish. When my mental picture is right on the money I feel I deserve a parade.
Usually I can tell a man from a woman by the voice. Not always. Some voices seem a bit borderline, could go either way, but when I think I know what it is, I am dead certain. There was a large and unattractive woman on the subway recently whom I heard before I saw, and I would bet a good hunk of money that however the person chose to dress or identify or whatever, that person's birth certificate said Boy.
A couple of things can lead to an educated guess. Age is almost always apparent. Sometimes very heavy people's jowls give away their weight. And there are issues of race probably related to timbre, bone structure, and God knows what else that may be indicative. Although we've likely all fallen into same trap as Lt. Zachary Graber in the original Taking of Pelham One Two Three, whose conversations with Inspector Daniels led him to believe the possessor of that deep, authoritative voice (African-American actor Julius Harris) was white. "Oh, I, uh, thought you were, uh, like a shorter guy or---I don't know what I thought."
Some of the scariest women and dumpiest men have the most awesome voices, too. Think of that next time you call your Frisky French Nurses Hotline, boys.
Singing voices can also be weird. Some people with lovely speaking voices can sing like busted trash compactors and vice versa. For decades people wondered how Gomer Pyle could have such an astonishing operatic baritone. Then again, Goober Pyle had a bachelor's in science, so we know TV can be deceiving.
Why do I bring this all up when everyone knows it from childhood? Because it's one of those things that keep shocking us even though we know it so well. We may become accustomed to the idea that a lovely face may hide an evil heart, but never to the idea that a voice and a face may be completely at odds in our imagination. Or as the great baritone Robert Merrill might say, "Well, surprise, surprise, surprise!"