Abstract
In engine rooms, the noise level is considerably high compared with other work places on shore. This has been accelerated by the employment of medium-speed geard diesel engines. Judging by the permissible criteria for noise exposure from the viewpoint of hearing conservation, it can be seen clearly that engine room crews are in danger of having their hearing impaired. The results of hearing tests of engine-room crews show clearly the occurrence of noise-induced permanent threshold shift centered at 4, 000 Hz. Moreover, it was recognized that the longer the noise exposure history becomes, the further hearing loss develops. However, in according to the hearing impairment evaluation through the speech average loss method, there were found very few crews suffering from “mild” hearing impairment who have frequent difficulty with normal speech. “Slight” hearing impairment among crews of pelagic fishing boats and trading ships belonging to the 6 major companies was approximately 17% and was smaller than expected.
However, in the comparative studies of ferries with engine semi-control room and ferries without one, many crews of ships which do not have a semi-control room were observed to be suffering from hearing impairment. Further comparative studies must be conducted on the basis of differences in the conditions which affect hearing impairment.
