The Grain Mill's Noise Budget: Daily Dose by Task Rotation, and What Distance, a Mud-Brick Enclosure, and a Shorter Rotation Each Buy

A small grain-milling workshop exposes one worker, in rotation, to a hammer mill at 102 dBA, a power loom at 92 dBA, a forge blower at 90 dBA, and quiet sorting and packing at 78 dBA. This study computes the worker's daily noise dose with a 3 dB exchange rate against an 85 dBA 8-hour criterion. A baseline rotation of 3 hours on the mill, 2 hours on the loom, 2 hours on the blower, and 1 hour on quiet work gives a dose of 2112.7 percent and a time-weighted average of 98.25 dBA; the mill alone contributes 1904.9 percent. Moving the mill operator from 1 m to 2 m lowers the mill level to 95.98 dBA and the total dose to 681.8 percent, and to 4 m lowers it to 89.96 dBA and 325.8 percent. A partial mud-brick enclosure around the mill, with a stated insertion loss of 12 dB, lowers the mill level to 90.0 dBA and the total dose to 326.9 percent at the baseline rotation. Neither distance nor the enclosure alone brings the baseline rotation to the criterion, because the loom and blower also contribute substantially. A schedule that does meet the criterion combines the enclosure with short spells: 0.5 hours on the enclosed mill, 0.5 hours on the loom, 0.5 hours on the blower, and 6.5 hours on quiet work, giving a dose of 87.3 percent and a time-weighted average of 84.41 dBA. The enclosure requires 480 mud bricks and is priced at $156.00 in total. SIMULATED, NOT MEASURED.