Is your SCIF / SAPF Not Meeting STC Ratings? Sound Leak Issues, Causes, and How to Fix Them
- Cooper Building Services
- 3 days ago
- 5 min read
Sound transmission issues in Sensitive Compartmented Information Facilities (SCIFs) and Special Access Program Facilities (SAPFs) aren’t just a construction problem—they’re a security risk. If a SCIF / SAPF is not meeting the Sound Transmission Class (STC) rating required under ICD 705, it could allow classified conversations or activities to be overheard or intercepted, breaching national security standards.
This post breaks down what STC-rated walls actually mean, how ICD 705 guides sound control in secure environments, common causes of sound leakage in SCIFs and SAPFs, and what best practices help prevent or fix these issues. Whether you're building a new facility or diagnosing a sound leak, here’s what you need to know.
What Are STC-Rated Walls?
STC, or Sound Transmission Class, is a numerical rating of how well a building partition (like a wall or ceiling) attenuates airborne sound. The higher the STC rating, the better the barrier is at blocking sound.
In most SCIF / SAPF environments, the minimum acceptable STC rating is 45, with higher ratings—such as STC 50—commonly required depending on the nature of the facility and its accreditation. Here's a basic idea of what different STC levels mean:
STC 30: Normal speech can be heard clearly through the wall.
STC 45: Loud speech is heard but not intelligible.
STC 50+: Loud speech is barely audible or not heard at all.
But an STC rating is only as good as its real-world performance. Even if the wall design meets the specs on paper, faulty construction or overlooked details can cause the actual performance to fall short—leading to a SCIF / SAPF not meeting STC rating requirements and possibly causing SCIF / SAPF sound leaks.
Understanding ICD 705 and Acoustic Requirements
ICD 705, or Intelligence Community Directive 705, sets the physical and technical security standards for SCIFs and SAPFs. Within it, Technical Specifications for Construction of SCIFs (ICS 705-1) outlines acoustic protection requirements in detail.
Key ICD 705 acoustic protection rules include:
STC Rating Requirements: Interior walls, doors, ceilings, and floors that demarcate the SCIF perimeter must meet the required STC rating to prevent sound transmission.
Acoustic Testing: Facilities must undergo acoustic testing to verify performance, not just rely on construction specs or assumptions.
Visual Inspections: Before accreditation, inspectors will assess for common pathways that could allow sound to leak (e.g., gaps, penetrations, poor seals).
Failure to meet these standards can lead to denial of accreditation, required retrofits, or in worst-case scenarios, classified data exposure.
Common Issues with STC Walls in SCIFs / SAPFs
Even if the design calls for STC 50-rated partitions, the actual construction often falls short due to execution flaws. These are the most common culprits when a SCIF / SAPF is not meeting STC rating requirements or is experiencing a sound leak:
1. Poor Quality Control During Construction
STC performance is highly sensitive to workmanship. Even small deviations can undermine an otherwise solid design:
Incomplete drywall layers
Improper staggered studs
Insufficient or poorly installed insulation
Gaps left at top or bottom tracks
Sound finds the path of least resistance—if there's a weak spot, it will exploit it.
2. Flanking Paths
Flanking is one of the most overlooked problems in SCIF construction. Sound can travel around a wall, not just through it, via:
Shared ceiling plenums
Raised floors
Structural steel framing
Electrical conduits and ductwork
Access flooring or drop ceilings
Even with STC-compliant walls, a sound leak can still occur if the sound bypasses the wall through adjacent construction elements.
3. Unsealed Penetrations
Every penetration in a SCIF or SAPF wall—electrical boxes, HVAC ducts, piping, conduit, etc.—is a potential weak point. If not properly sealed with acoustic-rated putty or caulking, these gaps allow sound to leak through.
Improper sealing is a top reason for a SCIF / SAPF not meeting STC rating during inspection.
4. Doors and Windows
Doors and windows are always acoustic weak points. Hollow-core doors, improperly installed seals, or non-STC-rated window glazing can all significantly reduce the effective STC rating of a wall.
Even with STC-rated doors, lack of perimeter gasketing or drop seals can reduce their effectiveness.
Best Practices to Prevent Sound Transmission in SCIFs / SAPFs
Preventing sound leaks in secure facilities requires detailed attention to both design and execution. Here are some proven best practices:
Use Double-Layered Drywall and Insulation
Use two layers of drywall with staggered seams and a dense acoustic batt insulation (such as mineral wool). This creates mass and decouples the surfaces, significantly improving STC ratings.
Stagger Studs or Use Resilient Channels
Staggered stud walls and resilient channels break the path of vibration, reducing direct sound transmission. These are often necessary for achieving STC ratings of 50 and above.
Isolate Ceilings and Floors
Avoid continuous ceiling plenums or raised floors that run across both secure and non-secure areas. These should be acoustically isolated or have sound-blocking baffles installed.
Seal Every Penetration
Use acoustic putty pads for electrical boxes, backer rods, and acoustical sealants for conduit and pipe penetrations. Every opening must be sealed to maintain acoustic integrity.
Install Acoustic Doors and Seals
Use doors with a tested STC rating, and ensure they’re installed with:
Full perimeter seals
Drop seals at the bottom
Proper door hardware to maintain pressure
Even the best door is only as good as the seal around it.
Conduct Acoustic Testing
Don’t assume your facility is quiet enough—test it. Use a certified professional to conduct field sound tests before accreditation. Many sound issues aren’t apparent until you perform a real-world test.
Diagnosing a SCIF / SAPF Sound Leak: What to Look For
If you're already dealing with a sound leak or failed STC test in a SCIF or SAPF, here's how to approach it:
Start with a Visual Inspection
Look for obvious culprits—gaps in drywall, unsealed penetrations, or missing insulation.
Use Sound Mapping or Acoustic Cameras
These tools help visualize sound movement and pinpoint weak spots, especially around flanking paths.
Check Doors and Ceiling Systems
Verify gasketing, door seals, and ceiling/floor construction. Ceiling plenums and raised floors are common failure points.
Review Construction Documents
Compare the as-built conditions to the original design specs. Any deviations could explain the performance gap.
Bring in SCIF Experts
Professionals with experience in ICD 705 compliance can assess both the construction and acoustics holistically, then recommend remediation.
Why STC Compliance is Critical for National Security
Sound leaks don’t just mean failed tests—they’re potential security breaches. SCIFs and SAPFs exist to protect sensitive conversations and operations. If sound is escaping, adversaries could be listening.
Facilities that don’t meet STC ratings can be denied accreditation, face costly retrofits, or worse—compromise national security operations. Investing in quality soundproofing and expert consultation is not optional; it’s essential.
Don’t Let a Sound Leak Undermine Your Security: Contact Cooper
If your SCIF / SAPF is not meeting STC rating standards, or you suspect a SCIF / SAPF sound leak, don’t wait for a failed inspection or worse—a security incident. Cooper Building Services specializes in secure facility construction and remediation, with deep expertise in meeting and exceeding ICD 705 acoustic requirements.
We’ve helped federal agencies, contractors, and integrators across the country build and repair SCIFs and SAPFs that pass inspection the first time—and stay secure. Contact us today to schedule a site visit or acoustic consultation. We’ll help you identify vulnerabilities, recommend solutions, and deliver peace of mind through secure construction.