Development of resistance to noise.

Recent investigations have demonstrated that in animal models repeated exposures to mid-intensity noise induce a progressive reduction of the temporary threshold shift (TTS) following the exposures. This phenomenon is named "conditioning" and it is actually able to reduce the permanent threshold shift (PTS) following exposure to high intensity noise; this finding is named "toughening". In the present work the fundamental steps of the research concerning the toughening are reviewed and the biological mechanisms supposed to be underlying this phenomenon discussed. The few preliminary results of the studies on humans are also reported.