Having done work on this subject, ANR appears not the panacea it is claimed to be. In many respects it does make you feel better, and certainly improves radio/intercom clarity. However, it does not cover all harmfull frequencies that are generated by helo aviation. Thus ANR could, in some circumstances, accellerate your hearing loss by fooling you into spending longer in a noise-harmful environment. The only way to prevent, or delay, the onset of hearing loss is to physically block out the harmful noise as well as the irritating, ie use F1 style moulded ear plugs (which rock musicians & motorcyclists also swear by).