This study, conducted in 1987 and 1988, has made it possible to quantify exposure to noise among heavy equipment operators, associated laborers, and crane operators. The average daily noise exposure was 84 to 99 dBA for heavy equipment, 90 dBA for the laborer, and 74 to 97 dBA for the crane operator. The main sources of noise to which heavy equipment operators are exposed are vehicle engines and the muffler exhaust system, usually located near the operator. The presence of insulated cabs such as those found on power shovels, backhoes, wheel loaders, and graders help reduce noise exposure. The type of tasks carried out by the laborers, the sources of noise from heavy equipment around which they work, and the manual equipment they use determine the noise levels to which such workers are exposed. In the case of crane operators, an insulated cab significantly reduces the operator's exposure to engine noise.