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Instrumented earplugs were first introduced in 2000 by the Air Force Research Lab as a means of measuring head accelerations in race car drivers after it was shown that instrumented helmets slipped on the head during impact events. A version of these earplugs was adopted by the Indy Racing League and Championship Auto Race Teams (CART) in 2003. In 2006, Begeman, Melvin, Troxel and Mellor reported that signals from earplugs mounted in cadavers showed a phase shift at 50 and 100 Hz vibration indicating less than perfect coupling with the head. A new miniature tri-axial accelerometer has been developed that is small enough to be placed in the ear canal portion of communication earplugs (earpieces) as a way of improving the coupling and thus the reliability of the recordings from drivers undergoing multi-axial crash events. The first part of the effort involved developing design specifications for the next generation earplugs.