This European Standard is concerned with ear-plugs fitted with an electronic level-dependent sound restoration function. It specifies additional constructional, design and performance requirements, methods of test, marking requirements and user information relating to the incorporation of the level-dependency facility. The performance of the ear-plug in impulsive noise is not addressed. 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)