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Typically a product's sound absorption capability is defined by three letters: NRC. This abbreviation stands for Noise Reduction Coefficient and is an arithmetic average (rounded off to the nearest 0.05 of the sound absorption capability of a product at only four frequencies: 250, 500, 1000, and 2000 hertz. These frequencies are representative of the center range of human speech. In order to place this important concept in perspective, one might consider a number of interesting pieces of information:

1. Humans can hear sounds from a very low frequency of 20 hertz to an extremely high frequency of 20,000 hertz – far above and below the limited range described by NRC.

2. Because NRC is an average of four values, it is certainly possible that two products could have very different sound absorption performance characteristics, yet the same NRC. 

CertainTeed Ceilings products have a range of Noise Reduction Coefficient NRC values because of the difference in the intended function of each one. SINOCEILING® products have superior sound absorption that is ideal for classrooms where the teacher should be able to be heard by each student. Other products, such as School Board, have a fair NRC, but improved durability for school hallways – where sound absorption may not as important as durability.