PNC - the Preferred Noise Criterion
A noise measurement system for continuous or ambient noise in indoor environments.
Preferred Noise Criterion Curves - PNC - is a noise measurement system for continuous or ambient noise in indoor environments proposed by Leo Beranek in 1971.
PNC is often used to judge the acceptability of ventilation and other background broad band noise sources.
Preferred Noise Criterion Curves - PNC - was introduced as a modification of the Noise Criterion - NC due to unacceptable low frequency noise in air-conditioning systems. The PNC at lower frequencies is more stringent than NC.
| 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.
Example - Estimating PNC - Preferred Noise Criterion
The Preferred Noise Criterion - PNC - of a noise spectrum like
- 31.5 Hz : 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.
