Noise reduction coefficient

The noise reduction coefficient (commonly abbreviated NRC) is a single number value ranging from 0.0 to 1.0 that describes the average sound absorption performance of a material.

The NRC is a logarithmic representation of the decay rate (dB/s) due to a panel or object with a defined surface area absorbing energy compared to the decay rate in a standard reverberant room without the panel or object Wallace Clement Sabine was the first scientist to study the sound-absorbing characteristics of materials in a scientifically rigorous manner.

Paul Sabine, a distant cousin of Wallace, studied the repeatability of sound absorption coefficient measurements in reverberation chambers.

There is potential for greater error or overemphasizing the acoustic efficacy of a material if tested sample sizes are smaller than the standardized 8-by-9-foot (2.4 m × 2.7 m) modules.

Thicker materials also have larger surface area at the sides, resulting in increased sound absorption due to edge effects.

NRC is a useful rating for general purpose rooms where speech noise build-up is the major concern: lobbies, open offices, reception areas, etc.