The audiometric evaluation is crucial to the success of the Hearing Conservation Programs in industries. Sequential audiograms have been compared with baseline ones made at the beginning of the employment. Preventive actions are taken as soon as a progressive occupational hearing loss occurs. However, many workers achieve better thresholds during the first five years by a learning effect. AIM: To identify the occurrence of the learning effect in the first five-year periodical audiograms in industries and evaluate its implications, particularly upon the true validity of the baseline audiogram. STUDY DESIGN: Clinical retrospective. MATERIAL AND METHOD: 835 audiograms of 167 workers were studied comparing five periodical audiometric tests with the respective baseline one. Better shifts of 5 dB or more, in one or more frequencies from 500 to 6.000 Hz were considered as "learning effect". RESULTS: From 92 to 96% of the workers presented better shifts in one or more frequencies. From 31 to 37% of the workers presented better shifts in one or more frequencies, comparing the second with the first test and from 23 to 35%, comparing the fifth with the first test. Comparing the average thresholds in 500, 1000 and 2000 Hz and in 3000, 4000 and 6000 Hz, from 16 to 23% of the workers presented better shifts, comparing the second with the first test and from 11 to 15%, comparing the fifth with the first test. CONCLUSION: The learning effect produced better shifts over more than one third of the studied population. So, the baseline audiogram may not be considered the best reference to be compared with the others tests.
noise induced hearing loss; hearing conservation programs; learning effect; industrial audiometry
