I had the iphone 5 and now a new 6 and both did this. The sounds just simply stop at random. When it happens, there are no clicks from the keyboard, there is no volume in videos I'm playing online.....its just totally mute. If I power off and then re-start the device, its fine and back working normally. Verizon tried telling me its likely pocket lint getting in the headphone jack, so I purchased a plug and cleaned it out good. It makes no difference at all, it still randomly stops and once I restart its totally fine. I cant find anything on this and this is the second phone its done it to me on. Any help?? Thanks!!