Why do I hear a crackling noise whenever I record video or audio?

My iPhone 5c videos that I record using the camera on my phone will record but on playback, I hear no sound at all, just an annoying static or crackling sound but no audio that was recording from the video itself. This has happened to me twice so far and I have absolutely no idea what is going on. I cant even record voice memos because it comes out flat and there's no sound recorded. What could be the issue? This has never happened before in the past when creating videos or recording from voice memos. If i try to listen to music or watch a video using my headphones or without them, I can hear the sound perfectly but when I record a video on my phone through the camera itself I will not hear any sound at all. Just static please help me I don't know what to do, this is upsetting  me???

Ps: i called someone from my neighborhood who knows about my phone issues and he says there’s either water clogged in or because my phone is of old age but it really isn’t. He says he has no parts to fix it and if he did I would cost 60$. And the other day I was able to record a video with the audio recorded and it came out just fine with no problems .