Two Quantities, Two Tests
Sound insulation has two parts: airborne sound (speech, music) and impact sound (footsteps). Each is measured separately. Airborne insulation yields Transmission Loss (TL) and its ratings STC/Rw; impact insulation yields IIC (or Ln,w in ISO).
Laboratory Measurement — Airborne
- Per ISO 10140 / ASTM E90.
- A sample is installed between a source room and a receiving room.
- Sound is generated in the source room; levels are measured on both sides across frequency bands to obtain TL.
- Laboratory conditions isolate the element from flanking paths.
Field Measurement — Airborne
- Per ISO 16283 / ASTM E336.
- Measures the apparent performance (R′w / FSTC), which includes flanking and installation, so it is usually lower than the laboratory value.
Impact Sound
Impact insulation is measured using a standard tapping machine on the floor; the sound level is measured in the room below. It is rated as IIC (ASTM) or Ln,w (ISO). This is separate from airborne insulation and must not be confused with STC/Rw.
Relevant Standards
- ISO 10140 — laboratory measurement of sound insulation.
- ISO 16283 — field measurement of sound insulation.
- ISO 717-1 / 717-2 — rating (Rw / impact).
- ASTM E90 / E336 — airborne TL laboratory / field.
Limitations
Laboratory values isolate the element; field values include flanking and workmanship. Airborne and impact insulation are different quantities tested differently.
Related Yamamah Solutions
For insulation testing guidance, contact us for a free acoustic consultation.
Frequently Asked Questions
Why is field performance lower than lab? Because field tests include flanking paths, penetrations and installation imperfections that the laboratory isolates.
Is impact sound the same as airborne? No — impact (footsteps) is tested with a tapping machine and rated separately (IIC / Ln,w).
Verified Sources
- ISO 10140 / ISO 16283 / ISO 717-1.
- ASTM E90 / ASTM E336.