Repeated noise overexposure converts temporary threshold shifts into permanent hearing loss

Evidence

Overexposure of our hearing system to sound initially produces temporary threshold shifts. After too many exposures this temporary threshold shift leads to a permanent shift, i.e. to a hearing loss. In this case, threshold in quiet is no longer normal but is shifted towards higher sound pressure levels and will never recover. — Professor Dr.-Ing. Hugo Fastl, Professor Dr.-Ing. Eberhard, Psychoacoustics- Facts and Models, 161