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Noise Criterion vs. Noise Rating and dB(A)

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Noise Criterion - NC - were established in U.S. for rating indoor noise, noise from air-conditioning equipment etc.

In Europe it is common to use Noise Rating Curves - NR.

dB(A) - LA - is a weighted method compensating for the human hearing of sound pressure at different frequencies.

Choosing appropriate noise criteria is important when specifying acceptable levels of noise. Most organizations use a particular index based upon practical experience. Recommended maximum noise levels for different types of rooms and standards are indicated in the table below

Noise Criterion vs. Noise Rating and dB(A)
Type of Room - OccupancyMaximum Level (dB)
Noise Criterion
- NC, NCB, RNC -
Noise Rating
- NR -
Very quiet Concert and opera halls, recording studios, theaters, etc. 10 - 20 20 25 - 30 20
Private bedrooms, live theaters, television and radio studios, conference and lecture rooms, cathedrals and large churches, libraries, etc. 20 - 25 25 25 - 30 25
Private living rooms, board rooms, conference and lecture rooms, hotel bedrooms 30 - 40 30 30 - 35 30
Quiet Public rooms in hotels, small offices classrooms, courtrooms 30 - 40 35 40 - 45 35
Moderate noisy Drawing offices, toilets, bathrooms, reception areas, lobbies, corridors, department stores, etc. 35 - 45 40 45 - 55 40
Noisy Kitchens in hospitals and hotels, laundry rooms, computer rooms, canteens, supermarkets, office landscape, etc. 40 - 50 45 45 - 55 45
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Related Topics


Room acoustics and acoustic properties. decibel A, B and C calculations. Noise Rating (NR) curves. Sound transmission through walls. Calculate sound pressure, sound intensity and sound attenuation.

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The Noise Rating (NR) Curve used to determine acceptable indoor environments for hearing preservation, speech communication and annoyance.

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Shift in hearing threshold for men and women vs. age.

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Satisfactory, difficult and impossible noise levels for telephone use in noisy areas.

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