BS EN 352-4:2020 pdf free.Hearing protectors一Safety requirements Level-dependent earmuffs. BS EN 352-4 This document is applicable to level-dependent earmuffs. It specifies requirements on construction, design, performance, marking and user information related to the inclusion of the level-dependent functionality.Level-dependent earmuffs are designed to provide restoration of external sounds, while providing attenuation of sounds at high levels. They may be selected for...