Four machines contribute the following noise levels in db to a worker's exposure:

machine 1 80 dba

machine 2 86 dba

machine 3 93 dba

machine 4 70 dba

(a) calculate the combined noise-level exposure for this worker.

(b) the offending machine is obviously machine 3. suppose that machine 3 was at a distance of 5 feet away from the worker when the 93 dba level was measured. determine how far away would machine 3 have to be moved to bring the worker's continuous 8-hour combined exposure from all machines down to the osha pel