PNC - Preferred Noise Criterion

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

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.

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 : 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.

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