Is iPhone 5 rear microphone replaceable?

I have an iPhone 5 that will not pick up sound through the small microphone between the main camera and flash. Mostly I don't notice it unless I am taking a video. Phone works fine, speakerphone seems ok, but when I record video using the main camera, its all white noise. I can speak right into it or even tap the mic opening itself and I get nothing.

I've looked at all the teardown pics and I do not see a microphone as part of the camera/flash assembly. I also don't see it as a standalone part. The only part I see nearby is the power button/volume control ribbon cable. Is it integrated into that? I think I can do the repair myself, but I do not know where that tiny little mic is located. Can anyone help?