One of the major health risks for those who maintain military aircraft is the high sound levels. All aircraft use turbine (jet) engines, even if the turbines just spin propellers. Turbines can get very noisy. In some cases, three seconds of unprotected exposure to high sound levels can cause permanent hearing loss. Over the years, the solution had been ear protection in the from of plugs or headsets. The downside here is that all sound is blocked out, and people have to rely on hand signals to communicate. The Department of Defense is paying Adaptive Technologies, Inc., to develop a solution in the form of ear plugs that combine noise cancellation technology (which has been around since the 1980s), with ear plugs and an intercom system. The new equipment will not only cancel out industrial strength engine noises, but also allow users to carry on a conversation via a wireless network at the same time. Aircraft maintenance crews will be more comfortable, safer and productive as a result.