Noise Rating Curves
Developed by the International Standards Organisation in 1971 to rate noisiness with the 1000 Hz octave band as reference point.
The noise rating (NR) system was introduced by Kosten and van Os in 1962.
Numerically, the NR rating is equal to the sound level in decibels at a frequency of 1000 hertz, but the rating requires lower levels at the more objectionable higher frequencies.
See also: Community Noise Criteria.
Subjects: Noise & Vibration