"As a side thought, and thinking out loud, i do wonder if there has been any research into the use of noise canceling headsets instead of hearing protection headsets, and if there is any long term effect on hearing as a result? I am assuming that the noise canceling variety introduce the an opposing sound to the ambient ones that are being picked up and therefore canceling out that sound, but does that have an effect on the ear?" I couldn't find anything interesting. Nausea and disorientation seem quite common, with suggestions that the cancellation at low frequencies affects balance. And, of course, widespread expectation that the reduction in volume will protect hearing. Jonathan