The Tech Spec defines acoustic performance as Sound Groups. SCIFs use Sound Group 3 or Sound Group 4. Attribute Sound Group 3 Sound Group 4 Rating STC 45 or better STC 50 or better Descriptor (Tech Spec, as quoted) "Loud speech from within …
Sound Group assignment is room by room, not just building by building. Most SCIFs have a Sound Group 3 perimeter and one or more Sound Group 4 rooms inside it. Space Sound Group Source SCIF perimeter (default) Sound Group 3: "A minimum of S …
Plain English: Build the room to the right Sound Group first. Sound masking is an AO-approved fix for a specific leak, not a substitute for construction. Decision guide Situation Usual answer Normal SCIF perimeter Sound Group 3 (STC 45 or b …
Most SCIF acoustic confusion comes from two ratings that sound similar but measure different things. Plain English: Sound Transmission Class (STC) is a single number that says how well a wall, door or window blocks airborne sound, measured …
Plain English: A good wall stops speech from getting through. Sound masking lets some speech through, then covers it with steady noise so nobody outside can make out the words. One is a barrier and the other is camouflage. Inspectors expect …
… the Tech Spec (Chapter 9, as quoted by practitioner sources) sets the basic geometry and sound level. Parameter Requirement (as quoted) Who tests "Only those with training on audio testing techniques shall conduct instrumental acoustic test …
Sound systems inside a SCIF create two acoustic problems: loud sound that must be kept in, and wiring that can carry sound out. Keeping amplified sound in. Rooms with amplified audio (VTC, conference audio, presentation systems) need Sound …
The Tech Spec requires the perimeter to be tested so the AO can confirm the Sound Group is met. How that testing is done is an AO decision. The Tech Spec requirement (Ch. 9.C, as quoted). "With all SCIF doors closed, all perimeter walls and …
… lower than the lab rating of the parts. Where performance is lost. Flanking path How sound escapes Deck flutes and top-of-wall gaps Over the wall through open voids above the top track Door perimeter Gaps at the head and jambs, missing or m …
… (Tech Spec Wall A; UFC 3-4.4.2) 7 Rooms later given VTC or amplified audio but built to Sound Group 3 Sound Group 4 for amplified audio (UFC 3-4.3.2) 8 Poor seal application around door frames and inadequate sealant at pipe penetrations and …
… Role in SCIF work ASTM E90 Standard Test Method for Laboratory Measurement of Airborne Sound Transmission Loss of Building Partitions and Elements Transmission loss at each test frequency for a wall, door, window or panel, measured in a lab …
Sometimes a perimeter cannot reach the required Sound Group through construction alone: an existing window that cannot be removed, a duct that cannot be rerouted, or a wall shared with a space the owner does not control. The Tech Spec (Chap …
… devices or other deliberate technical collection Set a measurable performance level (Sound Group 3 or 4) for the perimeter Replace TSCM, TEMPEST countermeasures or PED controls Apply to every discussion area, including conference and VTC ro …
The acoustic level, STC 50 or better, for conference, VTC and other rooms where amplified audio is used. See: Acoustics & Sound Masking
… loud speech inside can be faintly heard but not understood outside. See: Acoustics & Sound Masking
… be protected to meet the acoustic requirements of the SCIF." Tech Spec 3.G.7 "Provide sound baffles (duct silencers) or (Z) Duct Penetrations" UFC 3-4.13 "In lieu of acoustical duct liner, provide double wall acoustic duct" UFC 3-4.13 Z-duc …
… so they are not on the same stud UFC 3-4.4.2; Tech Spec Wall A Insulation 3-1/2 in. sound attenuation material "fastened to prevent sliding"; use fibrous insulation Tech Spec Wall A; UFC 3-4.4.4 Sealant "Seal gaps on both sides with a non-h …
… points in a perimeter. A speaker in the corridor directly outside puts the masking sound where a listener would stand. The rigid conduit protects the one cable that now leaves the SCIF. Installation points (derived from related rules) Treat …
… way it was tested. DoD ratings (UFC 4-010-05). Perimeter target Door assembly lab rating Sound Group 3 (STC 45 perimeter) Factory tested per ASTM E90 to no less than STC 50 (UFC 3-4.6.1) Sound Group 4 (STC 50 perimeter) No less than STC 55 …
… bridges the wall. Trap Why it fails Fix Source type VTC or amplified-audio room built to Sound Group 3 UFC 3-4.3.2 requires Sound Group 4 (STC 50) Design for the room's likely future use UFC Treating a lab STC as the field result Flanking p …
A SCIF masking system has three parts: a sound source, an amplifier, and speakers or transducers that put the sound onto leakage paths. The Tech Spec (Chapter 9.E, public copy) describes them this way: "Sound masking devices, in conjunction …
… open storage; 15-minute vs. 5-minute response Discussion areas and amplified-audio rooms Sound Group 3 vs. Sound Group 4 zoning Electronic processing of classified information TEMPEST Checklist; possible RF protection at CTTA direction The …
… Where a perimeter wall is also a rated wall, the designer must reconcile both. Walls for Sound Group 4. UFC 4-010-05 §3-4.4.2 notes that the standard STC 45 wall has three layers of 5/8 in. GWB and associates STC 50 with four layers (two o …
When the AO approves sound masking, the Tech Spec (Chapter 9.E, as quoted by practitioner and vendor sources) sets rules for where the transducers go, how loud the system runs, and what the sound source may contain. Topic Requirement (as qu …
… FFC F.1–F.2, G Approved instruments; isolation Checklist 24 VTC room built to Sound Group 3 UFC 3-4.3.2 Sound Group 4 UFC 25 No photo record; untracked field changes UFC 4-7 Photo log; SSM and AO concurrence UFC / Practitioner
Knowledge base · public-level
Ask a question the way you would ask a colleague on the jobsite. SCIF Answers covers ICD 705, the IC Tech Spec, UL 2050 Extent 3, doors and locks, acoustics, RED/BLACK and RF shielding: 344 sections across 19 modules, each one citing the public document it relies on.
Built 12 September 2026. Public-level information only: the Accrediting Official, Cognizant Security Authority and CTTA set the requirements for any real facility. Planning a SCIF or SAPF? Talk to LA CCTV Supply or see SCIF Security.
