The eartips seal on the body of the earplugs when being pushed inside your ear and when air can make it again between the seal, they make a low and loud pop sound. The fit of the eartips of any size is also not great and I had to go for aftermarket tips. This poor fit is probably related to the pop that happens that loosens the tips from your ear and you end up having to push for an oversize with the extra pressure and discomforts that comes with it. Additionally, the ANC is fiddly and if you dont get the perfect fit it backs out very quckly. It is hard to get them to run consistently at the max ANC. Finally, When you are in a loud ish enviroment and the ANC is fighting it, the ANC introduces a high frequency hiss sounds that is annoying and can get very distracting. They are fantasticly loaded with features and fantastic sound. I just feel like the ANC is trying too hard and becomes annoying.