| STC | What you hear through the wall | Typical use |
|---|---|---|
| 25 | Normal speech clearly understood | Hollow-core door |
| 30 | Loud speech understood | Single glass, poor partition |
| 35 | Loud speech audible, hard to follow | Basic office partition |
| 40 | Loud speech heard as a murmur | Insulated stud wall |
| 45 | Loud speech barely audible | Good office or bedroom wall |
| 50 | Loud music faint; speech inaudible | Code minimum between apartments (IBC) |
| 55 | Loud music barely audible | Theaters, studios, hotel rooms |
| 60+ | Most sound inaudible | Recording studios, cinemas |
Targets by room
| Situation | Target STC |
|---|---|
| Bedroom next to bedroom (house) | 40–45 |
| Office to office | 45 |
| Conference room to corridor | 50 |
| Apartment to apartment (code minimum) | 50 |
| Hotel room to room | 50–55 |
| Home theater to bedroom | 55–60 |
| Recording studio to anything | 60+ |