[Referential value of auditory threshold depending on age].

The value of "normal hearing" intended as the "base value of reference" to be used also for preventive as well as medical-legal purposes, is still subject of study and discussion. The Authors present the results relative to the definition of the hearing threshold in a vast "scrupulously screened" group of subjects between the ages of 15 and 65 (divided into 10 year bands), resident in industrial city areas and made up a homogeneous group of industrial workers with the same socioenvironmental characteristics. Distribution is calculated in hundreds of values relative to the average bilateral threshold for frequencies between 500 and 4000 Hz considering the 90th percentile the reference value.