This European Standard is concerned with ear-muffs whose passive acoustic performance may be supplemented by an electrical audio input facility or circuit for essential safety-related purposes. It specifies additional constructional, design and performance requirements, methods of test, marking requirements and user information relating to the incorporation of the electrical audio input facility. The requirements of this standard are intended to take account of the ergonomic interaction between the wearer, the device and, where possible, the working environment in which the device is likely to be used (see Annex ZA of this standard and EN 458)