Noise rating
BG 87/2024, Useful Information Guide, written by Chin Hang “Kay” Lam and published by BSRIA in 2024, defines noise rating (NR) as: ‘A criterion, often used in building specifications, for acceptable noise levels. A noise rating gives sound pressure levels (in decibels – dB) which must not be exceeded for a range of octave bands.’
'Noise ratings are a means of specifying acceptable indoor noise levels. Each noise rating (NR) curve gives sound pressure levels which must not be exceeded for a range of octave bands. This acknowledges that higher-frequency sound is considered more intrusive than lower-frequency sound. The graph below shows the maximum allowable sound pressure levels at each octave band for each noise rating. It also illustrates that for NR30, the maximum is 40 dB at 250 Hz, 34 dB at 500 Hz, and 30 dB at 1,000 Hz. Typical noise ratings for a variety of spaces can be found in BG 85 (BG 85/2024 Mechanical Criteria).'
--BSRIA
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