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ACOUSTICS at Large

NRC is more than just a value, you must its component structure to recognize its by Keith Peterson

W

ow, what can I say? I am so grateful for the near full house turnout for my presentation at the convention. It was truly a pleasure to speak and have fun with the group that attended. There were more great questions asked about acoustics, and I will be fielding some of them in more detail in the upcoming articles. After my presentation someone asked me if I would share a slide, and more importantly, what this side represents.

frequencies to demonstrate how dramatically values can change. As I described in the lecture, just because they all have the same NRC value does not mean that they behave the same at all frequencies.

The slide says it all, but the bottom line is that NRC is a single number representing a lot of information. Sometimes it is necessary to review the full acoustical test report from which the NRC is derived to get a full understanding. For example, in the chart we have panel types that are all a .85 NRC based on their absorption coefficient averages at 250, 500, 1000, and 2000 Hertz. In the graph I have included 125 Hz and 4000 Hz, which are the next octave bands above and below the range we use to determine NRC. I have included these

Type 1 has a very typical drop in the lower frequency range, which is common with most standard acoustical tiles, and these products can work very well for controlling speech frequencies despite the lack of lower frequency absorption.

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SPRING 2015 | Acoustical INTERIOR CONSTRUCTION

Type 2 has the most evenly distributed absorption values, which make it the best choice for most applications.

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Acoustical Interior Construction magazine  

Ceiling & Interior Systems Construction Association

Acoustical Interior Construction magazine  

Ceiling & Interior Systems Construction Association

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