I think there's some confusion about what is a Kindle Touch. That was the name, as I recall, of the Kindle 5. Amazon called it the Kindle Touch. When they came out with the newer non-lit Kindle that somewhat resembles a Paperwhite a lot of people called it the Kindle Touch but I'm not sure that was an official name. Probably people who are describing a Kindle Touch without sound are referring to that one.
This is all from memory and I'm not 100% sure I'm right about any of it. But I think I mostly have it right. I'm sure if I don't someone will let me know.
Barry