PNC - Preferred Noise Criterion

A noise measurement system for continuous or ambient noise in indoor environments proposed by Leo Beranek in 1971

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Preferred Noise Criterion curves (PNC) are often used to judge the acceptability of ventilation and other background broad band noise.

Noise Criterion - NC - curves are generally preferred over PNC curves, because the PNC criteria at lower frequencies are more stringent than that of the NC curves.

Maximum Sound Pressure Level (dB)
PNC
Preferred Noise Criterion 		Center frequency (Hz)
31.5 63.0 125 250 500 1000 2000 4000 8000
PNC - 15 58 43 35 28 21 15 10 8 8
PNC - 20 59 46 39 32 26 20 15 13 13
PNC - 25 60 49 43 37 31 25 20 18 18
PNC - 30 61 52 46 41 35 30 25 23 23
PNC - 35 62 55 50 45 40 35 30 28 28
PNC - 40 64 59 54 50 45 40 35 33 33
PNC - 45 67 63 58 54 50 45 41 38 38
PNC - 50 70 66 62 58 54 50 46 43 43
PNC - 55 73 70 66 62 59 55 51 48 48
PNC - 60 76 73 69 66 63 59 56 53 53
PNC - 65 79 76 73 70 67 64 61 58 58

PNC-type criteria provide no protection for low frequency sound exposure, and further, tend to rely on the public's increasing toleration of background noise and what seems to be decreasing auditory skills.

pnc preferred noise criteria diagram

Example - Estimating PNC - Preferred Noise Criterion

The Preferred Noise Criterion - PNC - of a noise spectrum like

  • 31.5 : 40 dB
  • 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

can be estimated to PNC = 57 dB as indicated in the diagram below.

pnc - preferred noise criteria - example

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Related Topics

  • Acoustics - Room acoustics, acoustic properties - decibel A, B and C - Noise Rating (NR) curves, sound transmission, sound pressure, sound intensity, attenuation and more ..

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