The authors show how drill noise was attenuated 13 to 18 dB(A) with no loss in drilling rate. Long-term reliability is currently being evaluated through in-mine-testing. In controlled laboratory tests, the prototype jumbo drill noise control treatment has achieved a 19 dB(A) reduction in the radiated sound power level, with no significant reduction in the drilling rate. Field tests (underground as well as on the surface) have indicated that the treatment is capable of providing a 13 to 18 dB reduction in the A-weighted sound level, measured at the operator's position, under actual drilling conditions. While these tests are not complete, the preliminary results are encouraging in that the treatment is not prone to excessive exhaust icing, docs not materially degrade drilling performance, and is durable.