Noise Reduction Coefficient (NRC)

Sound Reflection and Absorption

When a sound is produced, it expands through the air in a spherical pressure wave. When the wave reaches a surface, some of its energy is reflected, while the rest is absorbed.

The Noise Reduction Coefficient measures how much energy a surface absorbs, and how much it reflects. An NRC of 0 means that the product absorbs no sound. An NRC of 1 means that the product absorbs all sound. The higher the NRC, the better the product is at soaking up the sound.

Hard surfaces tend to have low NRC ratings; reflecting most of the energy in a sound wave, and absorbing very little. Soft surfaces tend to have high NRC ratings; reflecting less energy, and absorbing more.

The atmosphere also has a damping effect on a sound wave, because the molecules in the air absorb tiny mounts of energy as they move. This effect is called atmospheric absorption.