Alexander A. Menshov
Dept. of Phys. Factors, Inst. for Occupational Diseases, 252033 Kiev, Ukraine
Over 24 h the influence of occupational and nonoccupational noise may be distinguished by three periods: job, rest, and sleep. If the level of noise for each period is described in dBA there is no possibility of summing up these levels and receiving mean arithmetical values (average daily) because dBA is a logarithmic value. But if one describes levels of noise in doses there is a possibility of receiving a ``medium-weighted'' dose of noise load for 24-h because the doses are arithmetical values and it is possible to sum up and divide the total. If the dose level during the work is 1 dose -80 dBA, at rest 1 dose -40 dBA (one dose), and during sleep 1 dose -30 dBA (Ukraine and Russian sanitary standards), then the medium-weighted sanitary standard for the 24-h level of noise is one dose. The increase of the level for each a third 24-h period at 3 dBA above the norm will increase the dose level twice (two doses); at 6 dBA it will increase to four doses; at 9 dBA it will increase to eight doses; at 12 dBA, to sixteen doses, etc. If such high doses for each period are summed up and are then devised in three, a real medium-weighted dose of noise load for 24 h above the standard, which is 1 dose, will be found. This method is simpler than estimating the noise load above the standard for each third period of a 24-h influence of noise.