Noise Rating Levels

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Noise Rating Levels or NR Level Curves are developed by the International Organization for Standardization (ISO) and specify an indoor acoustic environment for different requirements of hearing preservation, speech communication and annoyance, in different applications.

Noise Rating values for different sound pressure levels are tabulated below and are the established sound pressure levels at different frequencies. Noise Ratings are then used to specify the maximum permissable sound power level at each frequency by selecting a single Noise Rating (NR) number. The use of Noise Rating – NR – is widespread across Europe.

Noise Criterion or NC levels are a different set of values developed for the same purpose, the use of Noise Criterion (NC) is mainly used in North America.

Noise Rating Values (dB)

NR Level 63 HZ 125 HZ 250 HZ 500 HZ 1000 HZ 2000 HZ 4000 HZ 8000 HZ
NR 20 51 39 31 24 20 17 14 13
NR 25 55 44 35 29 25 22 20 18
NR 30 59 48 40 34 30 27 20 18
NR 35 63 52 45 39 35 32 30 28
NR 40 67 57 49 44 40 37 35 33
NR 45 71 61 54 48 45 42 40 38
NR 50 75 65 59 53 50 47 45 43
NR 55 79 70 63 58 55 52 50 49
NR 60 83 74 68 63 60 57 55 54
NR 65 87 78 72 68  65 62 61 59
NR 70 91 83 77 73 70 68 66 64
NR 75 95 87 82 78 75 72 71 69
NR 80 99 91 86 82 80 78 76 74

Recommended Noise Ratings

The table indicates recommended Noise Rating specifications for some common interior room applications.
For advice on how to specify or achieve the recommendations please contact us.

Room Application NR Level Room Application NR Level
Sound, Broadcast & Recording Studio 20 Reception 30-35
Concert Hall 20-25 Open Plan 35
Lecture Theatre, Cinema 25-30 Assembly Hall 25-35
Operating Theatre 30-35 Library, Museum 30-35
Multi Bed Ward 35 Wash Room, Toilet 35-45
Wash Room, Kitchen 35-40 Swimming Pool / Sports Arena 40-45
Individual Room 20-30 Garage / Car Park 55
Ballroom, Banquet Room 30-35 Church 25-30
Corridor, Lobby 35-40 Classroom & Lecture Theatre 25-35
Kitchen 40-45 Laboratory 35-40
Restaurant 35-40 Warehouse & Garage 45-50
Night Club, Public House, Cafe 35-40 Workshop 50-65
Large Retail Space, Supermarket 40-45 Bedroom 25
Boardroom, Single Office 25-30 Living Room 30



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