[The problem of critical intensity].

We investigated a total of 537 patients (68 men, 469 women) working in the textile industry to ascertain their hearing level in the conventional hearing range as well as in the HF range. The persons tested work at 3 different noise levels (80-84, 85-89 and 90-94 dB (A) Leq. The differences in the hearing thresholds of the three sound level groups mentioned above were checked by means of discrimination analysis. The first hearing level changes noise levels below 90 dB develop mainly in the HF range; in the conventional hearing range, however, the hearing levels remain unchanged even during long exposure times. Hearing level impairment in the conventional range occurs only in the sound level group of 90-94 dB (A) Leq without attaining any social importance. The tests clearly show that if the noise level damage risk criterion of 85 dB (A) Leq at which hearing is impaired, is not exceeded any hearing lesions involving social hearing loss are definitely avoided.