Answer to: The volume bar has disappeared. There's no sound in apps.If you can't fix it on the hardware side, there is a way you can do in the program side. Install iFile or other compatible apps. go to /System/Library/LaunchDaemons find com.apple.iapd.plist delete it. There you go. you should get back you volume bar again. Thanks to a dude from the web that found the solution. Hope it will help you beside hard working on your iphone's hardwares without any solution.