Koss plugs have no active nc. Just good old passive isolation (they are good comfy plugs) and great sound. No active nc phone can help without putting some music on. Otherwise they have the dreaded his. And if you do play some music, the sound quality from the Koss ones can be surpassed (not isolation) only by the etymotic ones (for much more $$$$$$$). Otherwise, this are the ones. Forget Bose, Sony, Aiwa, Senss etc....After too much research and try ons......for sound isolation in planes (active and passive nc heaphones) Koss plugs ended up being THE best and surprisingly the cheapest solution too with only passive isolation. The only better solution is Etymotic that (while providing the same isolation) will give you super audiopfile quality for around $300.00. Koss audio quality is simply excellent for me (and yes, I am quite fussy about audio quality). I hope I have helped some other souls with this thing.