Abstract
1)People who are exposed to heavy noises with quick variations of intensity (2 or 3 per second) between 80 and 110 Db, acquire easely perception deafness in low frequencies (15 to 20 Db./500 to 2000 c./sec.)
2)There are not 3 parameters for caracteristics of the noise (intensity - frequency - duration) but four (in addition quick transitory variations of intensity).