Towards a "global" definition of the comfort of earplugs

Many workers are exposed on a daily basis to noise levels that can cause hearing problems. The risk of hearing loss then depends on both the level and the duration of exposure. Although it should ideally remain the last choice in terms of noise exposure reduction, hearing protection devices (HPDs) are the most commonly used noise control solution. Nevertheless, practically, discontinuous use, misuse or refusal to wear are frequently observed. Thus, while the "comfort" dimension (even though this notion for HPDs still turns out to be unclear and plural in the literature) may a priori seem to be secondary compared to the provided attenuation, it impacts the effective protection by influencing the HPD consistent and correct use. This paper focuses on earplugs which are the most commonly used category of HPDs. Despite the fact that the question of their use (and consequently of the protection) cannot be dissociated from the comfort one, they still remain exclusively characterized by the acoustic attenuation they provide. In a general way, it raises the question of identifying and understanding the comfort attributes and therefore, more fundamentally, the question of the definition of the comfort of earplugs itself. This last point proves to be major because this definition will finally impact the protocol of any research dedicated to comfort. Consequently, in order to progress on this crucial point, this paper presents different comfort attributes identified in a recent literature review (from the 1950s to the present) and proposes a "global" definition of comfort which includes the following four dimensions: physiological (irritation, pain, etc.), auditory (attenuation, occlusion effect, etc.), functional (ergonomics, easy-to-fit, etc.) and psychological (habituation, acceptance, etc.)