[Occupational hearing loss as probability diagnosis (author's transl)].

The paper discusses the question of which factors that are to be taken into consideration are of relevance to the expert in making his differential diagnosis in cases of occupational hearing loss. On the basis of the medical literature and earlier investigations the discussion is concerned with the proof of recruitment as well as with the effects of the exposure level and the exposure duration. Special reference is made to the "typical" hearing-threshold curve. The result of the examination with factor-analysis of 14,684 pure tone audiograms suggests that a small involvement of low and medium frequencies in the hearing loss is especially typical of occupational hearing losses. Not even this method permits delineating the effects of age on hearing from those of exposure to noise. The varying (pathogenetic) exposure level has a strikingly low influence on the extent of the occupational hearing loss. The entire data resulting from 25.544 pure tone audiograms are furthermore used for the computation of hearing-loss curves of different tail probability (supposing a normal distribution). The expert has thus a means available to estimate the probability of whether or not a concrete case is still a typical example of occupational hearing loss.