Towards prediction of high-fidelity earplug subjective ratings using acoustic metrics

High-fidelity earplugs are used by musicians and live sound engineers to prevent hearing damage while allowing musical sounds to reach the eardrum without distortion. To determine objective methods for judging earplug fidelity in a similar way to headphones or loudspeakers, a small sample of trained listeners were asked to judge the attenuation level and clarity of music through seven commercially available passive earplugs. These scores were then compared to acoustic/musical metrics measured in a laboratory. It was found that NRR is strongly predictive of both attenuation and clarity scores, and that insertion loss flatness provides no advantage over NRR. A different metric measuring spectral flatness distortion seems to predict clarity independently from attenuation and will be subject to further study.