(An) audiological survey of noise induced hearing loss of coal miners
With the development of modern culture and industry, environmental noises are growing claiming more attention.
Grossly, there are three main categories of hazard to man from noise, and are; a) objective physiological responses, b) efficiency of job performance and c) objective verbal response to stimuli. To measure the damage risk from noise, it has been used to measure the noise induced hearing loss for its objectivity and
The coal mine have much hazardous noise due to explosion drilling machine, heavy train and other heavy mechines is considered to be one of the most hazardous place for noise induced hearing loss. For prevention of damage from noise, it is required to clarify the environmental noise of work shop and the resulting damage at present.
Author have stuided 2716 coal miners in audiologically and had following results;
1) The over-all noise level of work-shop was highest at drilling shop with 115-122 dB and machine repaireing shops, coal lumbering shop and coal selection place, etc. ware over 98dB.
2) The over-all incidence of noise induced hearing loss was 9.7% with the criteria of early loss index and the relation between environmental noise level and incidence of noise induced hearing loss was parallel. The incidence of hearing loss with categories of speech communication handicaps of AAOO was 1& of all coal miner.
3) The form of hearing loss on pure tone audiogram was highest in C^^5 dip with 54.2% which was considered to be the earliest form of noise induced hearing loss and then abrupt form; 27.7%, divided dip form; 11.2%, and other form; 6.5%, in that order.
4) The relationship between age and noise induced hearing loss showed that the incidence of hearing loss grew progressively from 20th to 40th year of age but thereafter it diminished suddenly at 50th year of age. This trend was considered to be due to the progressive increase of age presbycusis.
5) The relationship between duration of working and noise induced hearing loss showed that the incidence of hearing loss were; up to 5 years group; 7.7%, 6 to 10 years group; 9.0% and 11 to 15 years group; 27.8% with tendency of paralell increase and then showed some diminished incidence in over 15 years group with
The relation between degree of noise induced hearing loss and the duration of working showed that the degree of hearing loss increase sharply up to 3 to 4 years and then gradually increase up to 9 years but there after it was stabilize without any further changes.
6) The side preference of noise induced hearing, impairement shows bilateral symetric loss were 48.5% and left side poorers were more common than the right with the ratio of 27.3% to 24.2%.
7) Among 2716 coal miner, there was only 9 cases(0.3%) who were evaluated to be the candidate for compensation low.