Noise Criterion - NC - level is a standard describing relative loudness of a space with a range of frequenciesNoise Criterion -
NC - were established in the U.S. for rating indoor noise like noise from air-conditioning equipment and similar. In Europe it is common to use the alternative
Noise Rating Curve - NR.
The method is based on a measurement of
sound pressures levels and a set of sound pressure criteria curves ranging frequencies from
63 to 8000 Hz - and a tangent rating procedure. The criteria curves defines the limits of the octave band spectra that must not be exceeded to meet the occupants acceptance in the actual spaces.
The NC rating can be determined by plotting the measured sound pressure at each octave band. The noise spectrum is specified as having a NC rating same as the lowest NC curve which is not exceeded by the spectrum.
Noise CriterionOctave Band Center Frequency (Hz)
631252505001000200040008000
Sound Pressure Levels (dB)
NC-15
47
36
29
22
17
14
12
11
NC-20
51
40
33
26
22
19
17
16
NC-25
54
44
37
31
27
24
22
21
NC-30
57
48
41
35
31
29
28
27
NC-35
60
52
45
40
36
34
33
32
NC-40
64
56
50
45
41
39
38
37
NC-45
67
60
54
49
46
44
43
42
NC-50
71
64
58
54
51
49
48
47
NC-55
74
67
62
58
56
54
53
52
NC-60
77
71
67
63
61
59
58
57
NC-65
80
75
71
68
66
64
63
62
NC-70
83
79
75
72
71
70
69
68
Related Mobile Apps from The Engineering ToolBox- free apps for offline use on mobile devices.
Recommended Noise Criterion - NCNC rated noise should not exceed the limits listed below:
Type of Room - Space TypeRecommended NC Level
NC CurveEquivalent Sound Level
dBA
Residences
Apartment Houses25-3535-45
Assembly Halls25-3035-40
Churches, Synagogues, Mosques30-3540-45
Courtrooms30-4040-50
Factories40-6550-75
Private Homes, rural and suburban20-3030-38
Private Homes, urban25-3034-42
Hotels/Motels
- Individual rooms or suites25-3535-45
- Meeting or banquet rooms25-3535-45
- Service and Support Areas40-4545-50
- Halls, corridors, lobbies35-4050-55
Offices
- Conference rooms25-3035-40
- Private30-3540-45
- Open-plan areas35-4045-50
- Business machines/computers40-4550-55
Hospitals and Clinics
- Private rooms25-3035-40
- Operating rooms25-3035-40
- Wards30-3540-45
- Laboratories35-4045-50
- Corridors30-3540-45
- Public areas35-4045-50
Schools
- Lecture and classrooms25-3035-40
- Open-plan classrooms35-4045-50
Movie motion picture theaters30-3540-45
Libraries35-4040-50
Legitimate theaters20-2530-65
Private Residences25-3535-45
Restaurants40-4550-55
TV Broadcast studies15-2525-35
Recording Studios15-2025-30
Concert and recital halls15-2025-30
Sport Coliseums45-5555-65
Sound broadcasting15-2025-30
Example - Estimate Rated Noise by using the Noise Criterion- 62.5 Hz : 40 dB
- 125 Hz : 50 dB
- 250 Hz : 55 dB
- 500 Hz : 60 dB
- 1000 Hz : 50 dB
- 2000 Hz : 55 dB
- 4000 Hz : 45 dB
- 8000 Hz : 45 dB
The Noise Criterion can be estimated to
NC = 57 dB
as indicated in the spreadsheet diagram below.
NC - Noise Criterion - Interactive Spreadsheet
NCB CurvesBalanced Noise Criteria (NCB) curves are used to specify acceptable background noise levels in occupied spaces and include noise from air-conditioning systems and any other ambient noise. They are intended to replace the NC curves.
Related Topics- Acoustics - Room acoustics and acoustic properties - decibel A, B and C - Noise Rating (NR) curves, sound transmission, sound pressure, sound intensity and sound attenuation
Related DocumentsTag Search- en: noise criterion nc
- es: ruido criterio nc
- de: Lärmkriterium nc
发表于 2019-8-27 15:12:16
