Silence

Mrs H was moaning that her iPhone had never actually played a ringtone since she got it, it only vibrated.  I asked if she'd checked the settings - she had.  I suggested turning it on and off again (maybe an ex-Microsoft engineer made that particular one).  That didn't work.

I said I'd take a look and sure enough the settings looked OK.  So I checked the mute switch, and asked her if it had been on since she got it.

"What mute switch?"

RTFM