Studies were made of the results of audiometry, the state of recovery of hearing impairment, and the relationship between personal character and hearing impairment of female workers in a cotton spinning mill, and the following results were obtained.
1.Practically no hearing impairment was demonstrable in the spinning department up to the end of one year after employment, but after this period the impairment began to appear.The characteristics of the audiograms obtained were found to have tendencies for a diphasic fall to occur with peaks at 250, 500 and 5000 cps.
2.In those engaged in the weaving department the impairment of hearing in the high tone range began to appear after one month.This was followed by a transitory recovery at 5_??_6 months, but from about the 9th month permanent impairment began to appear which was chara-cterized mainly by falls in air and bone conduction hearing in the high tone range.With the passage of time the grade of impairment became increased, and after about5 to 10 years there appears a dip-type lowering at between 2, 000 to 10, 000 cps with maximum of 27.5db (at 5.000cps).
3.In both spinning and weaving departments workers with average hearing loss in the speech frequency range of more than 30 db, namely with difficulty in ordinary conversation were not encountered in this investigation.
4.The grades of hearing recovery brought about by taking leave (average 12_??_13 days) were examined on workers in the weaving department who were divided into two groups one of which was under 5 year employment, the other 5_??_10 year employment.Cases with hearing impairment of more than 10 db ( 500cp s + 1, 000cps +2, 000cps +5, 000cps/4)were found in 55% of the former group and 62% of the latter before leave, but on returning to work at the end of the leave the figures were 3% for the former and 19% for the latter, indicating the poorer recovery in those engaged for longer periods.
5.The relationship between personal character and incidence of hearing impairment was examined in the second place.It was found that epileptic character was seen in 43%, hysterical character in 41%, schizoid character in 35%, nervousness in 32%, and cyclical character in 32 o, indicating the tendency for hearing impairment to occur in the epileptical and hysterical types.