---
kind: "section"
citation: "40 C.F.R. § 211.207"
title: "40"
number: "211.207"
heading: "Computation of the noise reduction rating (NRR)."
url: "https://uscodex.org/cfr/40/211.207"
---

# §211.207. Computation of the noise reduction rating (NRR).


Calculate the NRR for hearing protective devices by substituting the average attenuation values and standard deviations for the pertinent protector category for the sample data used in steps #6 and #7 in Figure 2. The values of −.2, 0, 0, 0, −.2, −.8, −3.0 in Step 2 and −16.1, −8.6, −3.2, 0, + 1.2, + 1.0, −1.1 in Step 4 of Figure 2 represent the standard “C”- and “A”-weighting relative response corrections applied to any sound levels at the indicated octave band center frequencies. (NOTE: The manufacturer may label the protector at values lower than indicated by the test results and this computation procedure, e.g. lower NRR from lower attenuation values. (Ref. [§ 211.211(b)](/cfr/40/211.211.md?p=b).)


## Notes

### Authority

Authority: Sec. 8, Pub. L. 92-574, 86 Stat. 1241 (42 U.S.C. 4907), and additional authority as specified.

### Source

Source: 44 FR 56139, Sept. 28, 1979, unless otherwise noted.

### Source

Source: 44 FR 56127, Sept. 28, 1979, unless otherwise noted.