Abstract: The thresholds of hearing for pure tones from 125 Hz to 8000 Hz of more thantwo thousand workers after exposures for different number of years to various noiselevels were measured and their speech hearing ability under everyday life conditionswere questioned simultaneously. On the basis of these data, the thresholds of impair-ment for hearing of standard colloquial Chinese were evaluated by means of psycho-physical statistical analysis. They were 20db, 27db and 30db for three differentfrequency combinations of 500, 1000 and 2000 Hz; 1000, 2000 and 6000 Hz; and of sixfrequencies from 500 Hz to 6000 Hz respectively. In comparison with the recommendation of 25db of ISOR 1999, our result was about 5db lower.

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