Reliability of an extended version of the 3m™ Eargage tool to assess earcanal size and assist earplug selection.

Objective: Evaluate the ability of an extended version of the 3 M^TM Eargage to estimate the earcanal size and assess the likelihood that a particular earplug can fit an individual's earcanal, ultimately serving as a tool for selecting earplugs in the field.

Design: Earcanal morphology, assessed through earcanal earmolds scans, is compared to earcanal size assessed with the extended eargage (EE) via box plots and Pearson linear correlations coefficients. Relations between attenuation measured on participants (for 6 different earplugs) and their earcanal size assessed with the EE are established via comparison tests.

Study sample: 121 participants exposed to occupational noise (103 men, 18 women, mean age 47 years).

Results: The earcanal size assessed with the EE allows for estimating the area of the earcanal's first bend cross-section (correlation coefficient $r$ = 0.533, p < 0.001). Extremely large earcanals (12.7% of earcanals in our sample) lead to significantly lower earplug attenuation (potentially inadequate) than smaller earcanals.

Conclusions: The EE is a simple and inexpensive tool easily deployable in the field to assist earplugs selection. When extended with sizes larger than the maximum size of the commercial tool, it allows for detecting individuals with extremely large earcanals who are most likely to be under-protected.