CIA Directive DCID 1/21 provides general guidance, as does the Defense Intelligence Agency Manual 50-3. Designing rooms for speech security requires consideration of the category of eavesdropper, the highest level of voices within the room, the eavesdropping locations, the attenuation of voice levels, and the level of background noise. The designer can directly control only two items, the sound attenuation and the background sound level of sound attenuation. A two-step design method can be used to determine the design requirements and protect against eavesdroppers of different levels of sophistication. Figures and detailed instructions