Possible faulty audio IC

The audio on my iPhone 4 CDMA sometimes will randomly cut out for 10-15 minutes. Hitting/impacting the phone seems to cause this problem, although it sometimes occurs while its sitting on a table. Bluetooth audio always works. I have already changed the dock port, speaker, and volume flex, and power flex. From what I know, it seems that some IC dealing with audio needs to be replaced. Does this sound like the correct move or something else? If so, which IC should I replace and where do I get it?