[norm1996]

Hi!
I have my S4 since May 2013 with no issues. Thursday, Jan 9 I got a call but couldn't hear the caller nor they me.
1) Rebooted and it didn't help. Tried again and it did until I accessed any app that uses the microphone or speakers.
2) Cleared cache partition and this seemed to help for longer but eventually died out again. For example, I tried to record a voice recorder file and it although the timer on the recording was rolling, it did not record any sound.
3) I did a factory reset after backing everything up. To my surprise It seemed to be working for a while but then I realized that this did not fix the issue entirely. It had slipped into NO sound mode again.
I would say its a hardware issue, but why would it even fix for a short amount of time? And if its a software issue why wouldn't clear cache partition and factory reset resolve it permanently? Any help would be greatly appreciated!

[fatboy97]

It might be just a coincidence... the phone gets a little heated up when you did the factory reset or clearing cache, and then you tried it... just guess work at this point.

Or after you did these things and it worked, then you setup or started an app which is causing your issues... again, just guess work. It sounds like a major issue, since it is a phone first and foremost. Personally, I would just bring it in and get it replaced as soon as possible.