This code of practice provides guidance on achieving effective sound insulation in buildings. It covers the fundamental principles of airborne and impact sound transmission, and provides recommended insulation ratings and acceptable indoor noise levels for various building types like dwellings, offices, and schools.
Provides guidance on achieving adequate sound insulation in buildings to control noise transmission.
Quick Reference Values
Recommended minimum STC for party wall between apartments50
Recommended minimum STC for wall between office and corridor40
Recommended maximum Impact Insulation Class (IIC) for floor between apartments50
Recommended indoor noise level (NC) for bedrooms25-35
Recommended indoor noise level (NC) for general offices35-45
Approximate sound insulation increase per doubling of mass (Mass Law)6 dB
Key Formulas
R ≈ 20 log(m) + 20 log(f) - 47.5 — Mass Law approximation for Sound Reduction Index (R in dB, m in kg/m², f in Hz)
Practical Notes
A common design failure is ignoring flanking transmission, where sound bypasses a partition via adjacent structures like floors, ceilings, and side walls, severely compromising insulation.
The overall acoustic performance is limited by the weakest element. A high-STC wall's performance can be ruined by a low-performance door, window, or unsealed penetrations.
For floors, both airborne (STC) and impact (IIC) sound insulation are critical. Neglecting impact insulation from footfalls is a frequent cause of noise complaints in multi-storey residential buildings.