Such "secret" rooms, intended to keep sensitive confidential or even classified information out of the earshot of unauthorized listeners, might meet DOD standards, but they offer less protection against snooping than is found in a luxury condo, Marlund Hale of Advanced Engineering Acoustics in Simi Valley, Calif., says.
Hale evaluated the acoustic security of several classified spaces, including a supposedly secure conference room at a U.S. military installation and several classified spaces at a National Guard base. The facilities complied with DOD acoustical design criteria and passed acoustical standard field tests, but "failed to provide the desired secret-level acoustical performance," he said.
A common problem, he said, is that some contractors fail to adhere to specific design details during a secure room's construction. While the individual components of such spaces -- floors, walls, doors, windows, air ducts -- proved secure in laboratory testing, they didn't retain that level of security when pieced together to make a room, Hale said.
The root problem is that DOD design criteria are not stringent enough, he said.
"The minimum acceptable performance standards for secret military facilities should be adequate to prevent secret information from being understood in adjacent non-classified spaces," Hale told a meeting of the Acoustical Society of America in San Francisco Wednesday. "It is interesting that DOD design standards only require sufficient acoustical isolation to prevent a casual passerby from understanding classified information, but do not need to be adequate to prevent a deliberate effort by someone to understand that information."