NRC Ratings Explained for Studios

By Priya Nair · October 11, 2026

What Is NRC?

Noise Reduction Coefficient (NRC) measures how much sound a material absorbs. Rated from 0.00 (perfect reflector) to 1.00 (perfect absorber), NRC is the average absorption across frequencies from 250Hz to 2kHz.

How NRC Is Measured

NRC testing follows ASTM C423, using a reverberation room method. A sample of the material is placed in a test chamber, and the decay rate of sound is measured with and without the sample.

NRC Values for Common Materials

Open-cell foam (2 inch): NRC 0.50-0.70
Fiberglass panels (2 inch, 703): NRC 0.85-0.95
Heavy curtains: NRC 0.30-0.50
Carpet on concrete: NRC 0.10-0.20
Mineral wool (4 inch): NRC 0.95-1.10

NRC vs Low Frequency Absorption

A critical limitation of NRC is that it ignores frequencies below 250Hz. A material with NRC 0.90 may absorb almost nothing at 63Hz. For bass control, check individual low-frequency coefficients.

Choosing Materials for Your Studio

For broadband mid/high absorption, fiberglass or mineral wool panels offer the best NRC per dollar. For bass trapping, use thicker panels (4-6 inches) or dedicated membrane absorbers.