Every office has one: the conference room where everyone knows the walls are thin. You whisper during HR conversations. You avoid scheduling sensitive client calls. The "Private" label on the booking calendar is a suggestion, not a reality.
Conference room soundproofing addresses two distinct problems: keeping sound IN the room (privacy) and making sound within the room clear (quality). Both matter for productive meetings and confidential conversations.
Sound Privacy vs Sound Quality
Sound privacy means conversations inside the room are not intelligible outside. This is measured by STC (Sound Transmission Class) for the wall and door assemblies, CAC (Ceiling Attenuation Class) for the ceiling, and SPI (Speech Privacy Index) for the overall room.
Sound quality means people in the room can hear each other clearly. This is affected by reverberation time (RT60), background noise level, and surface treatment within the room. A room can be perfectly private (nothing gets out) but acoustically terrible inside (too much echo, poor speech clarity).
Good conference room design addresses both.
The Four Paths Sound Takes
Sound escapes a conference room through four paths. You need to address all of them — the weakest link determines your actual privacy level:
1. Walls
Standard office partitions (single layer drywall each side on metal studs) achieve STC 33-38. That's terrible for privacy — normal speech is easily understood through the wall. For conference rooms, you need STC 50+ minimum. How to get there:
- Double drywall: Two layers of 5/8" drywall on each side of the stud. STC 43-48. Better, but still not great.
- Staggered stud or double stud wall: STC 50-55. The air gap between stud rows breaks the vibration path.
- Resilient channel: Metal channels that decouple drywall from studs. STC 48-52 with single stud wall.
- Sound isolation clips + hat channel: The gold standard for retrofit. Clips decouple the drywall layer from the existing wall. STC improvement of 10-15 points over the existing assembly.
Every wall assembly needs sound insulation (fiberglass batt or mineral wool) in the stud cavity. Without insulation, even a double-stud wall underperforms.
2. Ceiling
In most offices, the wall between the conference room and the adjacent space stops at the ceiling grid — it doesn't extend to the deck above. Sound travels over the wall through the shared ceiling plenum. This is the most common reason conference rooms lack privacy, and it's the easiest to overlook.
Solutions:
- Extend walls to deck: The best solution. Build the wall all the way up to the structural deck above, seal all gaps, and insulate the cavity. This eliminates the plenum path entirely.
- High-CAC ceiling tile: If extending walls isn't possible, use ceiling tiles with CAC 35+ (standard tile is CAC 20-25). Tiles like Armstrong Total Acoustics or USG Halcyon provide CAC 35-40. Our CAC guide explains the ratings.
- Plenum barrier: A sound barrier blanket (mass-loaded vinyl + absorber) laid across the top of the wall in the plenum. Blocks the over-wall path without extending the wall to deck.
3. Doors
A standard hollow-core office door is STC 20-25. You could build STC 60 walls and the door would completely undermine the investment. Conference room doors should be:
- Solid core (minimum STC 30-33)
- Fitted with perimeter seals (jamb gaskets and automatic door bottom)
- No undercut gap at the bottom — use a drop seal or threshold
For high-privacy rooms, acoustic-rated doors (STC 40-50) with factory-installed seals are available. They cost 3-5x a standard door but they're worth it if the room handles truly confidential conversations.
4. Flanking Paths
Sound finds every gap. Common flanking paths in conference rooms:
- Electrical outlets back-to-back on shared walls (sound travels through the open boxes)
- HVAC ducts connecting the conference room to adjacent spaces (duct-borne noise)
- Gaps at wall-floor and wall-ceiling junctions
- Window mullion connections to adjacent spaces
Seal every penetration with acoustical caulk. Offset electrical boxes so they're not back-to-back. Add duct silencers or lined duct elbows on HVAC connections.
Inside the Room: Acoustic Treatment
Once the room is isolated from outside noise, treat the interior for speech clarity:
- Ceiling: NRC 0.70+ acoustical tile or panels. This is the single most important interior surface for controlling reverberation.
- Walls: Fabric-wrapped acoustic panels on 1-2 walls. Target 15-25% wall coverage. Over-treating the room makes it feel dead and uncomfortable.
- Table: Large conference tables reflect sound. A felt pad or blotter surface helps, but this is minor compared to ceiling and wall treatment.
Target RT60 of 0.4-0.6 seconds for conference rooms. That's enough absorption for clear speech and comfortable video calls without making the room feel like an anechoic chamber.
Sound Masking
Sound masking systems emit a low-level, engineered background sound in the spaces outside the conference room. This raises the background noise floor, which reduces the intelligibility of any sound that does leak through. It's not white noise — it's specifically shaped to mask speech frequencies.
Sound masking is particularly effective in open offices where the area outside the conference room has very low background noise. Even a small amount of leakage becomes noticeable in a quiet office. Masking fills that quiet with unobtrusive sound that covers the leakage.