A shaped acoustic foam insert for use in improving the performance of circumaural hearing protectors is described. A foam block having a cross-section and shape is adapted to occupy the entire interior volume of an earcup of a circumaural hearing protector. The insert has no folds or open acoustic cavities. The surface of the insert that faces the ear of the user of the circumaural hearing protector comprises a curvilinear groove. The groove has no sharp angles and accommodates the average human pinna. A system and method of manufacturing the attenuating foam insert are provided.