How do I stop the screeching noise that happens when Im video chatting?

[iWrite]

My gf and I video chat through our apple laptops. I have a mac book and she has the air. For a while she was using her sisters mac book same as mine and everything was fine. Once she got her air the video would start screeching constantly. I searched for possible reasons and I found something about our phones being to close to the compute because of the magnets or whatever. So I tried putting our phones far away from our lap tops while video chatting and still we get that horrible screech noise. Can someone please help its very irritating.. Thanks