noise reduction coefficient
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noise reduction coefficient[′nȯiz ri‚dək·shən ‚kō·i′fish·ənt]
The average over the logarithm of frequency, in the frequency range from 256 to 2048 hertz inclusive, of the sound absorption coefficient of a material.
noise reduction coefficient, NRC
The average of the sound absorption coefficients of an acoustical material at frequencies of 250, 500, 1,000, and 2,000 Hz, expressed to the nearest integral multiple of 0.05.