Electroacoustic validation of a neck-based field attenuation estimation system

Many commercially available hearing protector fit testing (HPFT) systems are able to measure personal attenuation rating (PAR) values for earplugs, but only a few are capable of measuring PAR with over-the-ear protectors and even fewer are able to estimate PAR values with double hearing protection. One approach that could potentially be used with any type of hearing protection is to modify the real-ear attenuation at threshold method to use an occluded threshold that is measured with circumaural headphones worn around the neck rather than over the ears. However, this method would only be valid if the neck-to-ear transfer function of the headphones is stable across a variety of headphone fittings. This study evaluated the validity of a neck-based HPFT approach by (1) measuring the transfer function from headphones worn around the neck to the ear across a variety of headphone positions and head and ear geometries; and (2) using an acoustic test fixture to compare PAR values measured with a neck-based sound source to those obtained with more conventional HPFT approaches. The results indicate that the neck-based HPFT system has a relatively consistent neck-to-ear transfer function and produced PAR values comparable to those obtained with other HPFT systems.