Iphone 3gs sound cuts out, then reboots itself

[Stevea83]

Ok I have a 3gs 16gb that the sound is randomly cutting out. I get a loud static sound from speaker and then the sound cuts out. The phone then either reboots or just has no sound from speaker,mic, or earpiece. When I make a phone call the phone will connect but I cant hear them and they cant hear me.
I have since restored phone to factory and the phone still made same noise and reboot itself. I have updated software to latest version 4.3.5 but was occurring on 4.3.3 as well. I have opened phone to check connection of ribbon cables and all appear to be good. I checked for the two capacitors above the #4 cable and they dont appear damaged.
I've seen multiple posts with similar problems but no answers. As far as phone being opened replaced battery about 9 months earlier and had no problems with phone till recently. Phone was not dropped or wet. Thanks in advance, Steve

[Mes]

Sorry, can't offer any suggestions. There may be no solution.
It sounds like a hardware ... the motherboard

[Cowboy]

Yeah sounds like the logic board.
the only way to know for sure tho is by replacing all parts that are acting up