no sound whatsoever on phone (on calls, or while playing a video or mp3)

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http://android.stackexchange.com – I have adoogee dg500 running android 4.2.2 . Apart from automatic updates for installed applications , no other applications have been changed recently. Problem is I switched my phone to silent audio profile, so that I could sleep. Then the next day I set the audio profile to general again, but no sound can be heard from the phone. The phone has not been dropped or misused in any way. I have tried turning the phone off, removing the battery for a few seconds and re-assembling everything together again but I had no luck. how can I fix the sound??? (HowTos)