What would cause video recording and audio recording for voice memos to be filled with static or silent?, What would cause video recording and audio recording for voice memos to be filled with static or silent?

I have a white iPhone5 16G and I use it regularly to shoot video using ProCamera app, with iMovie for editing. For about a week, the only audio it will pick up while recording video is static or silence. Same goes for when I use the native Voice Memos app. It doesn't affecting phone calling, which makes me suspect it's a software and not hardware issue. I had trouble earlier with an iPhone 5 that didn't want to make calls or produced the same static and had it replaced by Verizon only two weeks ago.

For the record, my case does not cover either microphone; the problem occurs whether the case is on or not. I've tried restoring twice, changing up with airplane mode, turning bluetooth off or on, turning wifi off or on ... no luck.

I called Verizon and was told they'd send another replacement and that Apple is investigating this.