Discrete sensors: New sensors to track head acceleration during possible injurious events

Endevco/Meggitt has developed a new miniature tri-axial accelerometer that is small enough to be placed in the ear canal portion of communication earplugs (earpieces) used by race-car drivers. This system improves coupling to the driver’s head and reliability of recordings during multi-axial crash events.


Instrumented earplugs were first introduced in 2000 by the Air Force Research Lab (AFRL) 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 (IRL) and Championship Auto Race Teams (CART) in 2003.
In 2006, researchers 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. This led to the development of a new miniature tri-axial accelerometer that is small enough to be placed in the ear canal portion of communication earplugs (earpieces), thereby improving the coupling and, thus, reliability of recordings from drivers undergoing multi-axial crash events.
The first part of the effort involved developing design specifications for the next generation earplugs. These came from Andrew Mellor at the Federation Internationale de l'Automobile (FIA) Safety Center who developed these specifications with a view toward using the new earplugs in the F1 race series.
Endevco/Meggitt proposed to develop mini-triax sensors to this specification, and secured congressional funding to support development of a manufacturing process to reliably produce them. The AFRL team collaborated with Endevco/Meggitt to build the new sensors and provide the validation testing and comparison with the currently operational sensors.
The new 7273GT sensors were mounted in molded earplugs and subjected to impacts as high as 300 g with very short durations in multiple axes. The earplugs were mounted in artificial ears which were mounted on rigid blocks. The sensors showed good correlation with reference sensors and demonstrated improved coupling to the head over the current generation of earplug accelerometers.
Edited by C.G. Masi , senior editor
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