Modeling individual noise-induced hearing loss risk with proxy measurements of external-ear amplification

Significant variability in noise-induced hearing loss (NIHL) susceptibility suggests there are factors beyond sound level and duration of exposure that contribute to individual susceptibility. External-ear amplification (EEA) from external-ear structures varies significantly due to ear size and shape, potentially influencing NIHL susceptibility. This study tested the hypothesis that EEA can be predicted using non-technical proxy measurements including pinna height (cm), body height (m), and earcanal volume (cm³). 158 participants (4-78 years) completed otoscopy, tympanometry, pinna measurements, body height measurements, and two EEA measurements: (1) total real-ear unaided gain (REUG) of the open ear and (2) real-ear to coupler difference (RECD), representing unaided gain from the earcanal. Participants' individual noise doses were compared in hypothetical exposures. REUG ranged from 5 to 19 dBA and was correlated with pinna height. High-REUG participants were estimated to accrue noise doses at least 5 times higher than low-REUG participants. RECD ranged from 7 to 24 dBA and was correlated with earcanal volume and body height. The results support the hypothesis that EEA measurement could significantly improve estimation of an individual's position along the NIHL risk spectrum. Non-technical proxy measurements of EEA (pinna height, body height, earcanal volume) were statistically significant but yielded high variability in individual EEA prediction.