Abstract
Exposure time of harmful vibrations in case of the forest work using chain-saws was estimated to be 40 to 90% of the actual working time at the level of 100 dB(A) and over. This was ascertained by the use of a type of noise exposure meter designed by the author. On the other hand, from the data of time studies it was estimated to be about 30 to 60%. These great variations in each survey and between surveys may result from difference of personal work capacity, contents of work, various conditions of forests, climate and other working conditions. To evaluate the grade of harmfulness of vibration work and to establish the permissible level of vibration from the viewpoint of epidemiology, a large number of measurements of exposure time is necessary. The noise exposure meter was found to be very efficient for this purpose.
