The only difference between it being on and off is that when it is off I can hear a low frequency rumble and some of the ambient low frequency noise can be heard a little bit more, but apart from that there is barely any difference. For earphones touted as being the best noise cancelling I don’t understand it. There is no difference to high frequencies when it is on as well. So if someone is banging a frying pan nearby noise cancelling does absolutely nothing.