If you're reading this sentence, chances are you're reading it silently (if you're reading it out loud, hey, that's cool too). Your lips aren't moving, you're not making any sound that other people can hear. But are you making "sound" in your head? Many people who read silently do so by imagining a voice speaking the words they are reading (and often, it's your own voice, so there's even a specific "tone." I wonder if this is what makes people react so strongly to some blog posts).
Scicurious looks at whether we're hearing what we're seeing when we're reading without speaking.