Indoor cam poor sound quality

Hi there. I've installed today my first indoor camera and I like the quality of the video it streams/record. I do have an issue with the audio though, as the quality is extremely poor. When I stream or play videos on my mobile device, there's a buzz/white sound on the background, even when the room is completely silent. I would understand if it was a quiet noise, but this is so strong I have issues even hearing clearly my partner speaking in the room. I have changed room, reset the cam, unplugged it and plugged it back, turned my mobile volume up and down and the noise is still there. My internet connection is super good, too. The audio works fine the other way round (from mobile to cam) and the siren it's also ok. It seems like an issue with the built in mic of the cam. Does anybody have the same issue? Dues anybody know how to resolve this, please? Thanks guys!