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CTS Corporation is a leading designer and manufacturer of sensors, actuators and electronic components to OEMs in the aerospace, communications, defense, industrial, information technology, medical, and transportation markets. Acoustical protection measures and sound masking systems are designed to protect SCI against being inadvertently overheard by the casual passerby, not to protect against deliberate interception of audio.� The ability of a SCIF structure to retain sound within the perimeter is rated using a descriptive value, the Sound Transmission Class (STC). 1.1� The STC Rating: STC is a single number rating used to determine the sound barrier performance of walls, ceilings, floors, windows, and doors. 1.2� Use of Sound Groups: The current edition of Architectural Graphics Standards (AGS) describes various types of sound control, isolation requirements and office planning.� The AGS established Sound Groups I through 4, of which Groups 3 and 4 are considered adequate for specific acoustical security requirements for SCIF construction. 1.2.1� Sound Group I - STC of 30 or better.� Loud speech can be understood fairly well.� Normal speech cannot be easily understood. 1.2.2� Sound Group 2 - STC of 40 or better.� Loud speech can be heard, but is hardly intelligible.� Normal speech can be heard only faintly if at all. 1.2.3� Sound Group 3 - STC of 45 or better.� Loud speech can be faintly heard but not understood.� Normal speech is unintelligible. 1.2.4� Sound Group 4 - STC of 50 or better.� Very loud sounds, such as loud singing, brass musical instruments or a radio at full volume, can be heard only faintly or not at all. 2.0� Sound Reduction for SCIFs: The amount of sound energy reduction may vary according to individual facility requirements.� However, Sound Group ratings shall be used to describe the effectiveness of SCIF acoustical security measures afforded by various wall materials and other building components. 2.1� All SCIF perimeter walls shall meet Sound Group 3, unless additional protection is required for amplified sound. 2.2� If compartmentation is required within the SCIF, the dividing office walls must meet Sound Group 3. 3.0� Sound Masking and Stand-Off Distance: 3.1� When normal construction and baffling measures have been determined to be inadequate for meeting Sound Group 3 or 4, as appropriate, sound masking shall be employed.� Protection against interception of SCI discussions may include use of sound masking devices, structural enhancements, or SCIF perimeter placement. 3.1.1� Sound masking devices may include vibration and noise generating systems located on the perimeter of the SCIF. 3.1.2� Structural enhancements may include the use of high density building materials (i.e.� sound deadening materials) to increase the resistance of the perimeter to vibration at audio frequencies. 3.1.3� SCIF perimeter placement may include construction design of a stand-off distance between the closest point a non-SCI indoctrinated person could be positioned and the point when SCI discussions become available for interception.� Use of a perimeter fence or protective zone between the SCIF perimeter walls and the closest "listening place" is permitted as an alternative to other sound protection measures. 3.2� Masking of sound which emanates from an SCI discussion area is commonly done by a sound masking system.� A sound masking system may utilize a noise generator, tape, disc or record player as a noise source and an amplifier and speakers or transducers for distribution. 4.0� Placement of Speakers and Transducers: To be effective, the masking device must produce sound at a higher volume on the exterior of the SCIF than the voice conversations within the SCIF.� Speakers/transducers should be placed close to or mounted on any paths which would allow audio to leave the area.� These paths may include doors, windows, common perimeter walls, vents/ducts, and any other means by which voice can leave the area. 4.1� For common walls, the speakers/transducers should be placed so the sound optimizes acoustical protection. 4.2� For doors and windows, the speakers/transducers should be close to the aperture of the window or door and the sound projected in a direction facing away from conversations. 4.3� Once the speakers or transducers are optimally placed, the system volume must be set and fixed.� The level for each speaker should be determined by listening to conversations occurring within the SCIF and the masking sound and adjusting the level until conversations are unintelligible from outside the SCIF. 5.1� The sound masking system and all wires and transducers shall be located within the perimeter of the SCIF. 5.2� The sound masking system shall be subject to review during TSCM evaluations to ensure that the system does not create a technical security hazard.