[Noise-induced hearing loss and the sisi test. on the assessment of noise-induced hearing loss (author's transl)].

In the assessment of noise-induced hearing loss problems arise mainly in those cases where the middle frequencies are involved in the hearing defects at a proportionally high degree, because this strongly impairs the speech discrimination and because such a hearing defect cannot be regarded as a typical case of noise-induced hearing loss. A recruitment test must be carried out in the middle or lower frequency range in order to diagnose any possible multifactorial genesis of the hearing defect. As concerns the widely used SISI test the result is shown to depend not only on the test intensity but also on the test frequency. Since the hearing threshold in the middle under discussion is usually better in the middle and lower frequency ranges than in the higher ones and since, as a consequence, the test intensity in the SISI test is lower, frequently lower SISI values can be observed here than in the case of higher frequencies. Since the test of the lower frequencies results in lower SISI values than for higher frequencies also in those cases where the hearing threshold in the lower frequency range is the same or even worse, we must assume that the results of the SISI test depend on the frequency. In the examination of patients with a hearing defect where the hearing threshold curve flattens obliquely, intensity dependence and frequency dependence are added in the lower frequency range; negative SISI values are not infrequent. It is not admissible to conclude from that a retrocochlear defect in the middle and lower frequency ranges in cases of noise-induced hearing loss in the high-tone range.