STUDIES ON OCCUPATIONAL DEAFNESS

Abstract

Lately, many methods of calculatiing the average hearing loss for occulational deafness are discussed. A new procedure for such a method is proposed and was centered on the tone range impaired and the pattern of the development of hearing impair-ment. A classifing criteria as shown in fig. was basedon the average hearing loss at the middle and hig-her frequency range. The air conduction audiograms in 237 persons (474 ears) working under the noise exposure in a certain factory could be divided in to 0, A and B groups. The chief results were as follow: 1) Occupational deafness was found in 66% of the screening test (1000, 4000 cps 20db).2) 0 group showed slight hearing loss under 20db at the middle and higher frequency range in 16% of 311 audiograms. 3) A group showed hearing loss under 20db at middle frequency range and over 20db at the higherfrequency range, in 57% of all ears. There appea-red in 41% a dip type hearing impairment with peaks around 4000cps in this group.Bad subjective symptom of hard-hearing. Fi-fty percent of this group. A considerable loss of hearing at 2000.--3000cps tone range was formd in many of this group. 4) B gooups showed loss over 20 db at the mid-dle and higher frequency range, in 14% in all ears. The number of afflicted ears increased as the year of service increased and were especially seen most frequently in those with records over 20 years of service. 5) The author found that the decrease of hea-ring tend to become worse in proportion to the nu-mber of working years. However, a significant diff-erence was not noticed in decibel hearing loss among the classfication of age in the group of working years.