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Noise Rating (NR) |
A method for rating the acceptability of indoor environments for the purposes of hearing preservation, speech communication and annoyance, based on curves developed by Kosten and van Os (1962).
Sound Pressure Levels measured in octave bands are compared with these curves from which a Noise Rating (NR) is obtained. It will be seen that higher frequencies (where the ear is more sensitive) are given heavier Noise Ratings than lower ones, information not taken into consideration in strict decibel measurements.
Compare: Equal Loudness Contours, Sound Level, Sound Level Meter.
Acceptable NR values for various environmental situations have also been obtained, along with correction factors for variations.
Compare: Community Noise Equivalent Level, Noise and Number Index, Noise Criterion, Noise Exposure Forecast, Noise Level, Noise Pollution Level, Perceived Noise Level, Speech Communication Criterion, Speech Interference Level.
Noise rating curves. The individual Noise Rating (NR) curves are identified by the numerals along the 1000 Hz line (from Kosten and van Os, "Community reaction criteria for external noises," National Physical Laboratory Symposium, No. 12, 1962, p. 377, London H.M.S.O., used by permission).
|
Area |
Criterion |
Correction for dwellings |
Correction in dB |
| Broadcasting studio | 15 | Pure tone, easily perceptible | - 5 |
| Concert hall, legitimate theatre, 500 seats | 20 | Impulsive and/or intermittent | - 5 |
| Classroom, music room, TV studio, conference room | 25 | Noise only during working hours | + 5 |
| Sleeping room (see corrections at right) | 25 | Noise during 25% of the time | + 5 |
| Conference room, 20 seats or with public address system; cinema, hospital, church, courtroom, library | 30 | Noise during 6% of the time | + 10 |
| Living room (see corrections at right) | 30 | Noise during 1.5% of the time | + 15 |
| Private office | 40 | Noise during 0.5% of the time | + 20 |
| Restaurant | 45 | Noise during 0.1% of the time | + 25 |
| Gymnasium | 50 | Noise during 0.02% of the time | + 30 |
| Office (typewriters) | 55 | Economic tie | + 5 |
| Workshop | 65 | Very quiet suburban | - 5 |
| Suburban | 0 | ||
| Residential urban | + 5 | ||
| Urban, near some industry | + 10 | ||
| Area of heavy industry | + 15 |