Noise Reduction Cofficient

SoftForm Lighting's light forms have an NRC of 0.25. So what exactly does that mean? Be careful what you wish for, but here it goes. To begin with, the Noise Reduction Coefficient (commonly abbreviated NRC) is a scalar representation of the amount of sound energy absorbed upon striking a particular surface. Due to the formulas used, the coefficient is not a percentage and values larger than one are possible.


But from a practical application standpoint, the higher the value the more sound is absorbed. 0 (zero) means all sound is reflected and nothing is absorbed. 1 (one) or greater means all sound is absorbed and nothing is reflected. So for example, if the exposed surface of a light fixture is comprised of hard plastic and metal and has an NRC value of 0, then SoftForm Lighting's fabric diffuser is 25 times better at attenuating sound.


Frequency values for voices and piano.

The NRC testing process determines the arithmetic average, rounded to the nearest multiple of 0.05, of the absorption coefficients for a specific material and mounting condition determined at the octave band center frequencies of 250, 500, 1000 and 2000 Hz. The absorption coefficients of materials were determined through use of standardized testing procedures:

  • ASTM C423-17 - Standard Test Method for Sound Absorption and Sound Absorption Coefficients by the Reverberation Room Method.

  • ASTM E795-16 - Standard Practices for Mounting Test Specimens During Sound Absorption Tests.

SoftForm Lighting's fabric light diffusion material was also evaluated for the newer Sound Absorption Average (SAA) standard. The SAA is also a single-number rating of sound absorption properties of a material similar to NRC, except that the sound absorption values employed in the averaging are taken at the twelve one-third octave bands from 200 Hz to 2500 Hz, inclusive, and rounding is to the nearest multiple of 0.01.


Testing was performed by a laboratory accredited by the U.S. Department of Commerce, National Institute of Standards and Technology (NIST) under the National Voluntary Laboratory Accreditation Program (NVLAP) as an ISO 17025:2005 Laboratory (NVLAP Lab Code: 100227-0).


A graph of the test results are below. Or you can view the entire report here.



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