The mining industry recognizes the importance of engineering controls as a primary means of preventing hearing loss. The noise-control treatments most commonly observed on drills and bolters during this study were windshields, sound-absorbing material and hydraulic motor covers. These controls were evaluated on machines at underground metal mines to determine the amount of noise reduction achieved by each control. The results indicate that absorbing material has very little effect on the noise level. The noise reduction attributable to the motor covers was dependent on the material used to create the cover. Properly installed windshields were the most consistent control.