Development and validation of the North American COmfort of hearing PROtection Device questionnaire (COPROD-NAQ)

The use of hearing protection devices (HPDs), such as earplugs, is essential for mitigating occupational noise-induced hearing loss. However, earplug discomfort often hinders consistent and proper usage. This international and multidisciplinary study is based on a comfort model of HPD use, and considers four comfort dimensions (physical, functional, acoustical, psychological) and the influence of the triad environment/person/earplugs” components on overall comfort. Addressing shortcomings in defining and measuring comfort, the study aims to enrich understanding of the multifaceted aspects of earplug (dis)comfort and the role played by the triad. Specific objectives include developing and validating the “North American COmfort of Hearing PROtection Device Questionnaire (COPROD-NAQ),” proposing a latent overall comfort (LOC) model and comparing earplug families regarding (dis)comfort dimensions. Longitudinal data were collected over a 7-week from 173 workers testing 998 pairs of earplugs in three Canadian manufacturing companies. Factor analyses identified 51 items across 11 conceptual sub-dimensions with satisfactory reliability coefficients. Statistical analyses confirmed the COPROD-NAQ's validity as well. All its sub-dimensions significantly contributed to the LOC, with psychological and functional comfort exerting greater influence. Certain triad component characteristics (e.g., working during weekdays with a day shift, being right-handed, Custom 1 earplug model) enhanced the LOC. Finally, custom earplugs were perceived as most comfortable. The COPROD-NAQ emerges as a powerful tool for assessing earplug comfort and its interaction with triad characteristics, beneficial for occupational health and safety stakeholders. It will aid in prevention programs and help manufacturers design more comfortable earplugs to prevent hearing impairment.