NRC / Sound Absorption Rating

Our Cumulus cloud has an NRC rating of .45 for sound absorption. A sample was tested in accordance with the American Society for Testing and Materials, a method that measures the sound absorption by analyzing the decay rate of sound in a reverberation room.

Due to the nature of the freeform shape, our other cloud models are not NRC rated. The Stratus and Cirrus are available using the same sound dampening materials, and thus should compare similarly to our Cumulus model.

The NRC rating is based on the absorption coefficient, or the absorption over a specific surface area. The surface area of a relatively flat and uniform specimen (such as the Cumulus) is easy to determine and will have minimal acoustic change from the shape of the sample. However, a non-flat object (such as the Stratus and Cirrus) is more difficult to rate as the shape and angle vary. The 3D shapes have more effective surface area but the absorption between the two samples is nearly the same.

The Noise Reduction Coefficient (NRC) is a single number rating obtained by taking the arithmetic average of the absorption coefficients at 250, 500, 1000, and 2000 Hz rounded to the nearest multiple of 0.05.

Absorption Coefficients -- Sabins/m.2-- One-Third Octave Band Center Frequency, Hz

Hz 125 250 500 1000 2000 4000 AVE
**NRC Rating .10 .29 .42 .48 .58 .59 .45
**Our Cumulus cloud has an NRC rating of .45 for sound absorption. A sample was tested in accordance with the American Society for Testing and Materials, a method that measures the sound absorption by analyzing the decay rate of sound in a reverberation room. 

The Sound Absorption Average (SAA) is a single number rating obtained by taking the arithmetic average of the one-third octave bands from 200 through 2500 Hz rounded to the nearest 0.01.

Sound Absorption Hz per ASTM Designation E795-16
Hz 125 250 500 1000 2000 4000 AVE
**Absorption 1.035 4.185 5.625 7.129 8.508 9.07 5.925
**Absorption Rating applicable only to Clouds with Acoustical Element 

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