This morning when my alarm was supposed to go off, it didn't. I happened to wake up. I could see the alarm icon flashing on the screen. Later I set a new alarm and no sound. I tried dialing my phone and got no ring tone. I checked on the settings and everything was correct. No silent mode, etc. So then i shut the phone down and restarted it. Then everything was working fine. But..the alarm sound not working or phone sound not working is not good. You could not tell its not working until its too late.