I listen using noise canceling and randomly (once every few hours of listening or so) the noise canceling stops working and they make this loud squealing feedback type sound and crackling. This lasts maybe 10-20 seconds and then the Noise canceling comes back on. After hours with apple support chat and doing things I've already done a million times they told me to make a genius bar appt. I did and apple pretty much said they couldn't replicate it in the few minutes of testing so there's nothing they could do. Any suggestions here? Of course it's not going to happen in a few minutes of testing when sometimes it doesn't happen at all for hours.