The study of temporary threshold shift(TTS) caused by noise 103-105dB) exposure was performed for 76 ears of 76 female workers who were 18-25 years old and had normal hearing at the spinnery located in Daejeon. They were divided into three groups as the first noise-exposure from 30 minutes to one and half an hour, the second, from two to two and a half hours, the third, from three to four hours. The study has demonstrated. several significant facts as follows
1. The incidence of TTS had not significant correlation with noise-exposure time. On the whole, the incidence was higher at high frequencies than lower ones. The highest incidences were 52.9,°o and 53.9% at 4000 Hz and 6000 Hz respectively, the lowest 36. 8% at 1000 Hz.
2. The temporary shift of auditory threshold which results from 30 minutes to 4 hours
to noise levels of 103-105 dB varied from no shift to 35 dB.
But most of them were belonged to the categories of the shifts over 5 dB and 10 dB.
3. The amount of temporary loss occurred the first half an hour or one and half an hour of exposure and was not significantly correlated with exposure time.
4. The degree of TTS was larger at high frequencies than ?lower ones. The largest degree was 9.5 dB at 4000 Hz and the smallest 5. 2 dB at 1000 Hz.
|