I get so many complaints from people thinking that something is wrong. In fact, I made a "Sound Check" layout that comes up to tell the user to unmute their device and turn their ringer on - along with a button to check the sound. But I STILL get emails (as well as negative reviews on iTunes).
My apps are to help teach kids to read and I use them all the time when I tutor kids, and even I start playing with no sound and then I remember - oh yes - ringer on... This is not an issue from other apps that I use made by other people.
Maybe there's a way I can ignore the ringer and mute?