I think it still makes the sound even when muted, or at least with the volume down to zero, is there a difference? I use the slide switch for rotation lock, is there another way to mute other than the slide switch?
I have just the opposite question... My plugged in sound has disappeared and I can't figure out why or how to get it back. Sounds are on, volume is up. Even tried a different cable. Found another forum with same question but no answers. Now I always have to check the little battery charging icon to see if the iPad is really charging. Any thoughts on how to get the sound back? NEVER MIND... Discovered in another forum to check the Mute Slide button above the Volume button on the side of the iPad, and sure enough it somehow got turned off. All set.