Why can't I hear audio when my volume is turned up?

Your device may be on silent mode, which would prevent you from hearing audio.  To resolve this, go to "Settings", then select "Sounds". Turn the "Vibrate on Silent" setting to "Off". When you want the phone to be silent, slide the mute switch – that's the small slider located just above the volume buttons – toward the back of the phone. There is also a mute button on the side of the iPhone/iPad that needs to be switched off.