Observations on the Noise Analysis and the Hearing Survey of Employees in a Brass Stick Manufacturing Factory

Abstract

The Noise analysis and the hearing survey of employees were made in a brass stick manufacturing factory. The results obtained were as follows. 1) The hearing loss of C⁵-dip type was most frequently observed in this group getting more distinct with prolongation of exposure time. 2) The hearing loss of workers exposed low- and middle frequency noise (noise of rolling machine and oil-burner with over-all sound pressure level between 96-104db and with intense energy concentration between 50-1000cps) was more severe than that of workers exposed middle- and high-frequency noise (noise of drawing machine with Over-all sound pressure level between 97-102db and with intense energy concentration between 1000-6000cps). 3) Within 1 year exposure, the pattern of hearing loss was different between workers exposed low-and middle-frequency noise and those exposed middle- and high-frequency noise, the former showed C⁵-dip type and the latter C⁶-dip type. This difference in patterns becomes gradually obscure with prolongation of exposure time, and at last the both show the same C⁵-dip typO.