Influência da vibração de corpo inteiro e/ou ruído na audição de indivíduos sentados

Abstract

The physical risks, noise and whole body vibration (WBV) are often found in occupational environment. However, the effects of WBV isolated and the combination (WBV+ noise) on human hearing are poorly studied and unclear. Therefore, the main objective of this study was to investigate the effects of WBV and noise, isolated and combined, on human hearing. Besides, as secondary objectives, to verify also what hearing and non-hearing symptoms can occur after these exposures; if there are differences between the hearing of male and female or between right and left ears. Nineteen volunteers (10 males and 9 females) healthy young adults underwent all the following test conditions: 1) only noise (two exposures of 18 minutes each to high Sound Pressure Levels (SPL) (white noise at 96 dB(A)); 2) only vibration (two exposures of 18 minutes each to WBV (z-axis, 5 Hz at 2.12 m/s2 rms) and 3) noise + vibration (two exposures of 18 minutes each to WBV + SPL simultaneously, with the same previous characteristics). There was a 10-12 minutes interval between the 1st and 2nd exposure to each stimulus. The volunteers hearing was assessed by the audiometry and the otoacoustic emission distortion product (DPOAE) exams. The exams carried out before the tests were used as reference ones. A comparison of the exams performed before and after the exposures aimed at verifying the occurrence of temporary hearing changes. The results were analyzed statistically using the T-Student, Wilcoxon and Mann-Whitney tests, according to the study objective. The results indicated that WBV alone did not cause significant temporary hearing shift, whereas both noise and the combination (WBV+SPL) caused such shift, particularly at high frequencies between 2000 Hz - 8000 Hz. The combination was not significantly worse than the noise exposure alone, in other words, there was no synergic effect of the combination (WBV+SPL). After the exposures to WBV it was not observed hearing symptoms, only extra-auditory ones, such as fatigue, back pain and inattention. After the exposures to SPL it was noted the presence of the auditory symptoms tinnitus, ear fullness and hearing worsening feeling, and the extra-auditory symptoms fatigue, irritability, nervousness, anxiety and inattention. After the exposures to WBV+SPL the same hearing symptoms found after the SPL exposures were present and the same extra-auditory symptoms detected after the WBV exposures were present. There was no difference between male and female hearing, as there was no difference between right and left ear hearing by audiometry. However for the DPOAE it was observed that at 3984 Hz the left ear was better than the right ear and at 6000 Hz the right ear was better than the left. Therefore, this result was useful for the data selection for the statistical analysis, althoughunreliable as to whether there is difference between the amplitudes of responses the DPOAE, needing a larger sample to achieve a conclusion of such magnitude.