Use of Instrumented Earplugs to Measure Driver Head Accelerations 2002-01-3303

This paper reports on cooperative research between the Air Force Research Laboratory (AFRL) and motorsports to establish a relationship between multi-axis impact acceleration and injury for improving pilot/driver protection concepts Problem: The particular problem addressed by this paper is to establish how well head accelerations recorded by accelerometers mounted in molded earplugs inserted in manikin ears correlate with head accelerations measured by internal accelerometers. Method: Very small (0.4 gm) Endevco model 7269-500 tri-axial accelerometers were mounted in molded earplugs. In the laboratory, the earplugs were inserted into artificial ears glued to a Hybrid III manikin head. The headform was covered with artificial “skin” shaped to match a 3D scan of a human head. The headform, wore an instrumented (6 DOF) race helmet (reported on last conference), was instrumented internally with accelerometers (6 DOF), was attached to a sled and dropped on a Monterey Vertical Impact Device at from 12.5 G to 100 G in various (x, y, z, Rx, Ry, Rz) directions. Results: In 80 drops there was a progressive increase in acceleration recorded at the sled, then the base of the neck and finally the earplug. These differences were most probably due to the behavior of the headform mounting structure. Earplugs mounted directly on the sled replicated the sled acceleration within 5%. Conclusion: Since these results represent the behavior of a mechanical head and “rubber” ears, they need to be confirmed by using human volunteers up to 10 G (safe level) accelerations. Application to Racing: By monitoring drivers during crashes, it should be possible to calculate neck loads for correlation with injury data collected by medical personnel, and to revise impact tolerance criteria pertinent to racing, military and commercial crash protection.