I always had this view that noise cancellation demands doubling the energy in the system, to effect the cancellation. It may manifest as heat in the noise cancellation speakers, but also as pressure. In other words the eardrum system is exposed to "more" load, not less, it's just that it hears less.<p>However, the articles have been about neurological changes because of sound isolation which is different.<p>I'd be interested if the prior cohort of e.g. helicopter crew can show functional changes, deficits.
If you don't like (loud) noise, being able to escape from it via noise-cancelling headphones makes you like it even less.<p>I wonder how many people actually use noise-cancelling headphones _that_ much. And wouldn't someone that lives in a quiet environment suffer the same thing _without_ having to use a noise-cancelling headphone?