Why can I not fix my sound on my iPhone 4?

I have replaced everything i can think of! the speaker, the headphone jack, and the charging port! I did just recently notice this one spot though and i have it circled in red. Can someone please tell me what this piece on the mother board does? mine is damaged and im not sure if it has anything to do with the sound or not. on a side note i do have sound if my headphones are plugged in and this device has been dropped in mountain dew about a year ago. the sound issue didn't occour until about 5 months ago when i completly cleaned my motherboard with alcohol to remove any sugar or anything