[Effect of noise, exertion and thermal load on temporary auditory threshold shift (TTS) and on fatigue].

Temporary threshold shifts were determined in 14 voluntary subjects who were exposed during one hour to noise levels 70, 85 and 100 dB(A) accompanied by physical exercise (30% VO2max), thermal load (TE = 32.0 +/- 0.8 degrees C), and after combined exposure to these three factors. Before and after each exposure, temporary were measured threshold shifts (TTS2) at frequencies 3, 4 and 6 kHz. The psychophysical fatigue was determined using flicker and blinking tests. The results showed that exposure to noise, noise and thermal load, noise and exercise, and combined noise-exercise -thermal load exposure induced statistically significant increases of TTS values, especially at 85 and 100 dB(A) noise levels. Noise and thermal load, noise and exercise, and the combination of the three did not cause psychophysical fatigue, probably on account of the short duration of exposure. The results of this work show that estimation of exposure to noise, performed by measuring noise levels at workplaces and comparing them with the current standards without considering the effects of exercise and/or thermal load is not sufficient to evaluate occupational exposure and the risk of permanent hearing loss.