Earplug‐Type Earphone with Built‐in Microphone Improves Monosyllable Intelligibility in Noisy Environments

1 , Headsets (earphones or headphones equipped with a microphone) are widely used at work sites such as call centers or manufacturing facilities. Among workers using these headsets in noisy environments, adverse health effects may result not just from exposure to environmental noise, but to loud voice signals from the apparatus itself 1-3). A device composed of a bone-conduction microphone and a speaker-equipped earmuff has been developed. Although the device effectively reduces the noise-induced temporary threshold shift, its weight makes it impractical for real-world use 3). We undertook an extensive search of breakthrough technologies in the areas of hearing protectors, microphones, speakers, and headsets, including earphones developed for portable audio-players, then incorporated a newly available earplug-type earphone with built-in microphone (EM) as a telecommunication device for workers required to engage in communications tasks at noisy work sites. The effectiveness of the EM was evaluated as a dual- function device providing both communication functions and hearing protection in noisy work environments. Materials and Methods We used an EM (inCore, NAP Enterprise Co., Ltd.) incorporating a minute microphone-loudspeaker capsule inserted into the external ear canal and shielded from the exterior environment by a five-layer silicon rubber ear pad. These ear pads are available in three sizes: small,