all sound intermittant on phone

hi

my I phone 4s suddenly stopped all sound

front speaker,earpiece,headphone jack just all silent and no vibration

if you click the power /sleep button a few times it suddenly all comes back.... for a few minutes then goes.

I have noticed b4 it goes there is an electrical 'POP'

I HAVE CHANGED DOCK PORT , FRONT SPEAKER AND EARPIECE. still the same

any ideas would be helpful. thanks