A typical security requirement for an area might be 45db attenuation or reduction of audible conversations within the area. To achieve this level of attenuation, the requirement forces some construction- specific details to be incorporated. For example, the door or doors into the area will have specialized weather stripping sweeps that minimize sound transmission. The doors must be solid core to minimize sound transmission and add to the physical security.
The walls that enclose the area will often incorporate double 5/8-inch sheetrock that is overlapped so that the seams do not line up on the second layer. Often, 9-gauge expanded metal is welded to the studs prior to applying the sheetrock.
Sound emission or Sound Transmission Criteria (STC) control often includes some electronics that are used for sound masking.
Manufacturers make a sound transducer device - basically an electromagnet for a speaker that is mounted to the walls, doors, ductwork, etc. An amplifier is used to drive the sound masking devices. A CD player is added to allow music to be played, which is transmitted to the walls, doors or other surfaces via the electromagnetic devices. In addition to music, random noise also called pink noise is played over the system to help mask conversations.
Limited access is controlled both physically and electronically. To enable a person access to a high-security area, that person must have access to the front gate, the building entrance, and finally, to the area itself.
There are several checkpoints or layers of access. At the entrance to the classified area, typically there will be a spin dial lock that requires a combination. This lock is a high-security lock that is opened when the area is to be occupied and locked when it is not. There is also an electronic security system to gain entry. This electronic security alarm system can be set up to require one or two people entering security codes to access the area - referred to as a one- or two-man rule.
If the government agency allows, a badge reader can be added to the door locking hardware that will allow access after the spin dial lock has been opened. This means that occupants only have to unlock the combination lock once at the start of the day. Normal operation should occur in a specific order: The combination lock is opened; and then the electronic security alarm system is accessed, which activates the electronic access control badge reader. At the close of working hours, the electronic security alarm system is secured, which deactivates the electronic access control badge reader, and the combination lock is secured again.
This approach assumes that the database for the area electronic access control badge reader system resides in the classified area and has proper approval levels to ensure only authorized personnel have access. The computer that this badge reader database resides on can be considered classified to the same level of the area itself. It enables flexibility and ease of access while providing a high level of security.
Documentation of Personnel Movement
An area that is not entered often or has few personnel gaining access can be largely controlled by "sign in" logs that are in the area - one for employees and one for visitors.
In most high-traffic applications, however, documentation of the various personnel entering the area is accomplished electronically. The electronic access control badge reader can add a level of documentation, indicating who was in and out at a certain time.
Each person with approval to access the area will have his or her own code number for the security alarm keypad. If a badge read is also required to access and secure the alarm system, there is additional assurance that the person controlling the system is who they say they are. This approach is referred to as two-credential verification.
Detection of Unauthorized Access
For the most part, unauthorized access is handled via the electronic security alarm and electronic access control system. The access control system controls entry after the area has been accessed, but when the area is secured, the electronic security alarm system will detect unauthorized entry.
The alarm system should include door sensors, motion detectors and specialty sensors. Any doors into or out of the secure area should have door sensors which will be deactivated when the electronic security alarm system has been accessed. If there is a second door at the end of the vestibule, the second door sensor will remain active, but will be shunted once there is a valid badge read.