Noise Reduction Coefficient is a parameter used to quantify the sound absorption capacity of a material. Its specific meaning and characteristics are as follows:
Definition and Calculation Method: NRC is an arithmetic mean of the sound absorption coefficients of a material in the mid to high frequency range of 250Hz, 500Hz, 100 Hz, and 200 Hz. Results rounded to the nearest 0.05.
Value range and significance:
0 ≤ NRC ≤ 1:
NRC=0: The material completely absorbs sound energy (e.g., smooth concrete walls) and sound is fully reflected.
NRC=1: The material absorbs almost all of sound energy (e.g., high-efficiency sound-absorbing cotton) and sound is almost never reflected.
The higher the NRC value, the better the sound absorption and noise reduction performance:
For example, materials with NRC=0.8 absorb more sound and reduce indoor reverberation and background noise than materials with NRC = 0.4.
Application Scenarios
NRC is commonly used to evaluate the acoustic performance of the following materials to control noise levels and improve acoustic comfort:
Ceilings: Mineral cotton insulation (NRC 0.8 -0.95), fiberglass insulation (NRC 0.9 -1.0).
Wall: Acoustic panels, insulation, fabric wall coverings.
Floor: Thick carpet (NRC 0.6 -0.8) or carpet + cushion combination.
Other: Studios, home theaters, meeting rooms, classrooms, open-plan offices, etc., requiring noise control.
Differences Other Acoustic Parameters
STC: Measuring the material's ability to block sound transmission (e.g. soundproofing of walls), which is different from the NRC NRC the "absorption" function.
Sound Absorption Coefficient: represents the sound absorption capacity of a single frequency, while NRC is an average of four frequencies, providing a more comprehensive assessment.
Important Note:
Low-frequency neglect: NRC does not include low-frequency (e.g., 125Hz) sound absorption performance and must be evaluated in conjunction with low-frequency data (e.g., in theaters or low-frequency spaces).
Laboratory data: Tests are usually conducted in ideal idealized laboratory environments; actual installation results may vary according to construction techniques and environment.
Material impact: The values of visual fatigue signatures in the NRC are influenced by factors such as material thickness, density, pore size, and method of installation (e.g. depth of cavity behind material).
