A Triaxial Accelerometer Small Enough to Fit in Your Ear

Crash testing injury calculations have historically been based on measurements of forces and accelerations on cadavers subjected to crashes. For example, the Head Injury Criteria (HIC) was developed by bolting accelerometers to the skulls of cadavers and comparing the actual damage to the head and brain to the measured acceleration. These calculations are currently being improved by evaluating the injuries sustained by race car drivers involved in crashes during races. Biomechanics researchers have installed accelerometers to measure the race car accelerations during a crash. To further improve the injury assessment capabilities, the researchers would like to measure the actual acceleration of the driver’s head. Unfortunately race drivers, unlike cadavers, object to having accelerometers bolted to their skulls. Mounting accelerometers on the racing helmets gives some data, but the drivers head can move within the helmet during a crash. To resolve this problem, a miniature triaxial accelerometer is being designed to fit inside a radio earpiece that the drivers wear during the race. This paper describes the design of the accelerometer, specifications, and results of proof-of-concept testing of the first prototypes.