If I had a dollar for every time I heard this I would be a millionaire. While a deaf person’s speech may sound normal, it doesn’t mean that their hearing is as well.
I was four years old when I lost much of my hearing. That is significant. We start learning language during the first year of life and I had four years of hearing sounds. My voice patterns were set and my memory of sounds has carried me through. So while I don’t sound deaf, I actually can hear very little even with hearing aids.