STC, Sound Transmission Class, is the single number you will see on every soundproofing product, from drywall assemblies to acoustic doors. It measures how much airborne sound a partition blocks. Higher is better. But the number alone does not tell you what you will actually hear.
What the numbers feel like
| STC | What you hear through it | Typical construction |
|---|---|---|
| 25 | Normal speech clearly understood | Hollow-core door, single pane glass |
| 35 | Loud speech audible but muffled | Standard drywall wall, solid door |
| 45 | Loud speech barely audible | Insulated double drywall, acoustic door |
| 55 | Shouting barely audible | Decoupled wall systems, commercial doors |
| 60+ | Most sounds inaudible | Room-within-room, studio door systems |
A wall is only as strong as its weakest opening. An STC 50 wall with a standard door performs like an STC 25 wall.
Why doors decide the outcome
Sound leaks through gaps first. A typical interior door leaves a 15–20 mm gap at the threshold and unsealed edges all around, which is why upgrading the door is usually the highest-impact single improvement in a room.
Our Silent Guard acoustic door series covers the full range: SG-35 for bedrooms and home offices ($1,900–$2,900), SG-45 for speech privacy in offices ($3,500–$4,800), up to the SG-60 PRO studio system ($12,000–$20,000+).
How to choose your target STC
- Bedrooms & home offices: STC 35–40, everyday quiet
- Offices, therapy & consultation rooms: STC 45–50, full speech privacy
- Studios, theaters, critical listening: STC 55+, engineered isolation
Not sure what your space needs? That is exactly what our free acoustic assessment answers. We measure, listen and give you a target number with a plan to reach it.
