Development of a biofidelic acoustic test fixture and evaluation in impulsive noise

Here, we describe the development and use of a novel biofiedlic head surrogate for evaluating head and hearing protection devices against impulsive, shock, and blast insults. The head surrogate, derived from biomedical imagery, includes biofidelic pinnea, ear canals, and skull. In addition to microphones positioned at the ear canal terminus, the surrogate includes accelerometers and a hydrophone to provide an estimate of sound propagation through the bone-conduction pathways. This allows use of the surrogate to estimate a device's ability to attenuate bone-conducted pressure waves. We discuss the tradeoffs between biofidelity, manufacturability, instrumentation, and cost. We will show example data from various test campaigns, including the estimating the attenuation of the bone-conduction pathway afforded by different helmet systems during a 178 dB SPL (peak) shock insult. We will conclude with a look towards the future, including potentially updating the underlying three dimensional models to align with modern biomedical models and databases.