THE SCIENCE AND APPLICATIONS OF ACOUSTICS - H. H. Arnold ...

326 13. Criteria and Regulations for Noise ControlFigure 13.2. Noise criterion (NC) curves.Example Problem 2A noise generator in a room was found to yield 50 dB straight across the octaveband from center frequencies 63–8000 Hz. What is the RC rating for that room?SolutionDraw a horizontal line at the 50 dB level. The highest NC curve penetrated is 50.The NC value is therefore NC 50.Noise Rating CurvesThe noise rating (NR) curves of Figure 13.3 are very similar to the NC curves.Their original purpose was to determine whether noise heard from industrial plantsis acceptable at nearby apartments and houses. As with the NC curves, the noisespectrum is also measured at the affected locations and plotted in Figure 13.3. TheNR curves differ in that they include corrections for time of day, fraction of thetime the noise is heard, and the type of neighborhood. In the range between 20 and50 for NR or NC, there is little difference between results obtained from the twosets of calculated procedures.