An extensive set of measurements has been made on various type of ear protection devices, generally consisting of a hard-shelled volume coupled to the head by an annular pad filled with various materials. Attenuation measurements were made with a miniature pressure microphone. Accelerometers were used to measure the motion of the shells and head. Attenuations as high as 40 db at 20 cps have been obtained using volumes of the order of 2000 cc coupled to the head with a liquid-filled pad. (This work has been supported by Contract AF 33(600)-33172.)