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The present study was approved by the Ethics in Research Committee (protocol # 2606/2007).
We studied information concerning the following procedures:
• audiological interview, in which we surveyed identification data and the auditory health history;
• threshold tonal audiometry, in which we assessed tonal thresholds of the subjects (air and bone conduction);
• immittance measures, in which we analyzed data concerning tympanometry, with the aim of studying the functional integrity of the tympanic-ossicular chain in the auditory system.
The audiometry tests were done in a sound-treated booth, using the GSI 61 Grason - Stadler audiometer. For acoustic immittance measures we used the GSI 38 Grason-Stadler immittance metering device.
Audiometric findings were analyzed and classified according to the occupational profile of the hearing loss. In order to study the level of significance between the age of the individual and the time they had been working in that position we used the Student t-test. While the statistical analysis of the comparison of the audiologic results between groups I and II was carried out by the Anova test. In both cases the level of significance was 5% (p < 0.05) and the confidence interval was established at 95% of statistical confidence.
RESULTS
The results from the interview showed that the main complaints from the individuals in Group I were: tinnitus (n = 25 / 52.08%); allergies (n = 13 / 27.08%) and recruitment (n = 10 / 20.83%). In Group II, the main ones were: tinnitus (n = 21 / 58.33%); recruitment (n = 9 / 25 %) and autophonia (n = 6 / 16.66 %). Among the data obtained from the anamneses, we plotted the age and duration of exposure to noise, which can be seen on Table 1. The data analysis show that there was no statistically significant difference between the mean values of age and duration of noise exposure, considering groups I and II.
In assessing the functional integrity of the tympanic-ossicular chain, specifically in the tympanometry, we noticed that in Group I, both in the right ear and in the left ear, 35 (87.5%) individuals had type A curves and 5 (12.5%) had type Ad. While in Group II, 36 (90%) had type A tympanometric curve and 4 (10%) had type Ad, also bilaterally. The results from the threshold tonal audiometries were analyzed from the frequencies of 500 Hz up to 8 kHz. In each frequency we analyzed the right and left ears of Group I compared to the right and left ears of Group II, in order to check whether or not the Anova statistical test would show significant differences between the groups. Analysis of the tonal audiometry results, considering the mean values (dB HL) and the comparison between the groups I and II - Anova Test.
Frequency Ear Group I Group II p value
500 Hz Right 9,87 9,37 0,706
Left 7,0 8,25 0,355
1000 Hz Right 8,62 8,87 0,886
Left 7,25 8,5 0,416
2000 Hz Right 8,5 8,25 0,884
Left 10,87 8,5 0,159
3000 Hz Right 15,75 12,62 0,240
Left 19,5 12,37 0,008b
4000 Hz Right 25,37 16,37 0,007b
Left 25,37 18,87 0,023b
6000 Hz Right 23,75 21,62 0,520
Left 24,25 21,75 0,370
8000 Hz Right 17,12 18,87 0,540
Left 17,62 17,50 0,960
HLNA - hearing level b significant difference for a = 0.05