What exact iPhone 4 part contains the lower Microphone?

The iPhone did have a water damage and since then the lower Microphone does not seem to be working. I confirm this because the upper mic works on speaker but the lower does not when I turn of speaker phone. I also confirmed then when taking apart the iPhone and finding liquid near the bottom of the phone.

My question is this:

What actual part do I need to swap out if the lower Mic is blown. I do not see it anywhere in the parts guides? My guess is that is part of the doc connector, however can someone confirm this?